/* pngpriv.h - private declarations for use inside libpng
 *
 * Copyright (c) 2018-2025 Cosmin Truta
 * Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
 * Copyright (c) 1996-1997 Andreas Dilger
 * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
 *
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 */

/* The symbols declared in this file (including the functions declared
 * as extern) are PRIVATE.  They are not part of the libpng public
 * interface, and are not recommended for use by regular applications.
 * Some of them may become public in the future; others may stay private,
 * change in an incompatible way, or even disappear.
 * Although the libpng users are not forbidden to include this header,
 * they should be well aware of the issues that may arise from doing so.
 */


/* pngpriv.h must be included first in each translation unit inside libpng.
 * On the other hand, it must not be included at all, directly or indirectly,
 * by any application code that uses the libpng API.
 */
#ifndef PNGPRIV_H
#  define PNGPRIV_H
#else
#  error Duplicate inclusion of pngpriv.h; please check the libpng source files
#endif

#if defined(PNG_H) || defined(PNGCONF_H) || defined(PNGLCONF_H)
#  error This file must not be included by applications; please include <png.h>
#endif

/* Feature Test Macros.  The following are defined here to ensure that correctly
 * implemented libraries reveal the APIs libpng needs to build and hide those
 * that are not needed and potentially damaging to the compilation.
 *
 * Feature Test Macros must be defined before any system header is included (see
 * POSIX 1003.1 2.8.2 "POSIX Symbols."
 *
 * These macros only have an effect if the operating system supports either
 * POSIX 1003.1 or C99, or both.  On other operating systems (particularly
 * Windows/Visual Studio) there is no effect; the OS specific tests below are
 * still required (as of 2011-05-02.)
 */
#ifndef _POSIX_SOURCE
#  define _POSIX_SOURCE 1 /* Just the POSIX 1003.1 and C89 APIs */
#endif

#ifndef PNG_VERSION_INFO_ONLY
/* Standard library headers not required by png.h: */
#  include <stdlib.h>
#  include <string.h>
#endif

#define PNGLIB_BUILD /*libpng is being built, not used*/

/* If HAVE_CONFIG_H is defined during the build then the build system must
 * provide an appropriate "config.h" file on the include path.  The header file
 * must provide definitions as required below (search for "HAVE_CONFIG_H");
 * see configure.ac for more details of the requirements.  The macro
 * "PNG_NO_CONFIG_H" is provided for maintainers to test for dependencies on
 * 'configure'; define this macro to prevent the configure build including the
 * configure generated config.h.  Libpng is expected to compile without *any*
 * special build system support on a reasonably ANSI-C compliant system.
 */
#if defined(HAVE_CONFIG_H) && !defined(PNG_NO_CONFIG_H)
#  include <config.h>
   /* Pick up the definition of 'restrict' from config.h if it was read: */
#  define PNG_RESTRICT restrict
#endif

/* To support symbol prefixing it is necessary to know *before* including png.h
 * whether the fixed point (and maybe other) APIs are exported, because if they
 * are not internal definitions may be required.  This is handled below just
 * before png.h is included, but load the configuration now if it is available.
 */
#include "pnglibconf.h"
#include "pngtarget.h"

/* Local renames may change non-exported API functions from png.h */
#ifdef PNG_PREFIX
#  include "pngprefix.h"
#endif

#ifdef PNG_USER_CONFIG
#  include "pngusr.h"
   /* These should have been defined in pngusr.h */
#  ifndef PNG_USER_PRIVATEBUILD
#    define PNG_USER_PRIVATEBUILD "Custom libpng build"
#  endif
#  ifndef PNG_USER_DLLFNAME_POSTFIX
#    define PNG_USER_DLLFNAME_POSTFIX "Cb"
#  endif
#endif

/* Is this a build of a DLL where compilation of the object modules requires
 * different preprocessor settings to those required for a simple library?  If
 * so PNG_BUILD_DLL must be set.
 *
 * If libpng is used inside a DLL but that DLL does not export the libpng APIs
 * PNG_BUILD_DLL must not be set.  To avoid the code below kicking in build a
 * static library of libpng then link the DLL against that.
 */
#ifndef PNG_BUILD_DLL
#  ifdef DLL_EXPORT
      /* This is set by libtool when files are compiled for a DLL; libtool
       * always compiles twice, even on systems where it isn't necessary.  Set
       * PNG_BUILD_DLL in case it is necessary:
       */
#     define PNG_BUILD_DLL
#  else
#     ifdef _WINDLL
         /* This is set by the Microsoft Visual Studio IDE in projects that
          * build a DLL.  It can't easily be removed from those projects (it
          * isn't visible in the Visual Studio UI) so it is a fairly reliable
          * indication that PNG_IMPEXP needs to be set to the DLL export
          * attributes.
          */
#        define PNG_BUILD_DLL
#     else
#        ifdef __DLL__
            /* This is set by the Borland C system when compiling for a DLL
             * (as above.)
             */
#           define PNG_BUILD_DLL
#        else
            /* Add additional compiler cases here. */
#        endif
#     endif
#  endif
#endif /* Setting PNG_BUILD_DLL if required */

/* See pngconf.h for more details: the builder of the library may set this on
 * the command line to the right thing for the specific compilation system or it
 * may be automagically set above (at present we know of no system where it does
 * need to be set on the command line.)
 *
 * PNG_IMPEXP must be set here when building the library to prevent pngconf.h
 * setting it to the "import" setting for a DLL build.
 */
#ifndef PNG_IMPEXP
#  ifdef PNG_BUILD_DLL
#     define PNG_IMPEXP PNG_DLL_EXPORT
#  else
      /* Not building a DLL, or the DLL doesn't require specific export
       * definitions.
       */
#     define PNG_IMPEXP
#  endif
#endif

/* No warnings for private or deprecated functions in the build: */
#ifndef PNG_DEPRECATED
#  define PNG_DEPRECATED
#endif
#ifndef PNG_PRIVATE
#  define PNG_PRIVATE
#endif

/* Symbol preprocessing support.
 *
 * To enable listing global, but internal, symbols the following macros should
 * always be used to declare an extern data or function object in this file.
 */
#ifndef PNG_INTERNAL_DATA
#  define PNG_INTERNAL_DATA(type, name, array) PNG_LINKAGE_DATA type name array
#endif

#ifndef PNG_INTERNAL_FUNCTION
#  define PNG_INTERNAL_FUNCTION(type, name, args, attributes)\
      PNG_LINKAGE_FUNCTION PNG_FUNCTION(type, name, args, PNG_EMPTY attributes)
#endif

#ifndef PNG_INTERNAL_CALLBACK
#  define PNG_INTERNAL_CALLBACK(type, name, args, attributes)\
      PNG_LINKAGE_CALLBACK PNG_FUNCTION(type, (name), args,\
         PNG_EMPTY attributes)
#endif

/* If floating or fixed point APIs are disabled they may still be compiled
 * internally.  To handle this make sure they are declared as the appropriate
 * internal extern function (otherwise the symbol prefixing stuff won't work and
 * the functions will be used without definitions.)
 *
 * NOTE: although all the API functions are declared here they are not all
 * actually built!  Because the declarations are still made it is necessary to
 * fake out types that they depend on.
 */
#ifndef PNG_FP_EXPORT
#  ifndef PNG_FLOATING_POINT_SUPPORTED
#     define PNG_FP_EXPORT(type, name, args)\
         PNG_INTERNAL_FUNCTION(type, name, args, PNG_EMPTY);
#     ifndef PNG_VERSION_INFO_ONLY
         typedef struct png_incomplete png_double;
         typedef png_double*           double *;       /* [Deprecated] */
         typedef const png_double*     const double *; /* [Deprecated] */
         typedef png_double**          double **;      /* [Deprecated] */
#     endif
#  endif
#endif
#ifndef PNG_FIXED_EXPORT
#  ifndef PNG_FIXED_POINT_SUPPORTED
#     define PNG_FIXED_EXPORT(type, name, args)\
         PNG_INTERNAL_FUNCTION(type, name, args, PNG_EMPTY);
#  endif
#endif

#include "png.h"

/* pngconf.h does not set PNG_DLL_EXPORT unless it is required, so: */
#ifndef PNG_DLL_EXPORT
#  define PNG_DLL_EXPORT
#endif

/* This is a global switch to set the compilation for an installed system
 * (a release build).  It can be set for testing debug builds to ensure that
 * they will compile when the build type is switched to RC or STABLE, the
 * default is just to use PNG_LIBPNG_BUILD_BASE_TYPE.  Set this in CPPFLAGS
 * with either:
 *
 *   -DPNG_RELEASE_BUILD Turns on the release compile path
 *   -DPNG_RELEASE_BUILD=0 Turns it off
 * or in your pngusr.h with
 *   #define PNG_RELEASE_BUILD=1 Turns on the release compile path
 *   #define PNG_RELEASE_BUILD=0 Turns it off
 */
#ifndef PNG_RELEASE_BUILD
#  define PNG_RELEASE_BUILD (PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC)
#endif

/* SECURITY and SAFETY:
 *
 * libpng is built with support for internal limits on image dimensions and
 * memory usage.  These are documented in scripts/pnglibconf/pnglibconf.dfa of
 * the source and recorded in the machine generated header file pnglibconf.h.
 */

/* If you are running on a machine where you cannot allocate more
 * than 64K of memory at once, uncomment this.  While libpng will not
 * normally need that much memory in a chunk (unless you load up a very
 * large file), zlib needs to know how big of a chunk it can use, and
 * libpng thus makes sure to check any memory allocation to verify it
 * will fit into memory.
 *
 * zlib provides 'MAXSEG_64K' which, if defined, indicates the
 * same limit and pngconf.h (already included) sets the limit
 * if certain operating systems are detected.
 */
#if defined(MAXSEG_64K) && !defined(PNG_MAX_MALLOC_64K)
#  define PNG_MAX_MALLOC_64K
#endif

#ifndef PNG_UNUSED
/* Unused formal parameter warnings are silenced using the following macro
 * which is expected to have no bad effects on performance (optimizing
 * compilers will probably remove it entirely).  Note that if you replace
 * it with something other than whitespace, you must include the terminating
 * semicolon.
 */
#  define PNG_UNUSED(param) (void)param;
#endif

/* Just a little check that someone hasn't tried to define something
 * contradictory.
 */
#if (PNG_ZBUF_SIZE > 65536L) && defined(PNG_MAX_MALLOC_64K)
#  undef PNG_ZBUF_SIZE
#  define PNG_ZBUF_SIZE 65536L
#endif

/* If warnings or errors are turned off the code is disabled or redirected here.
 * From 1.5.4 functions have been added to allow very limited formatting of
 * error and warning messages - this code will also be disabled here.
 */
#ifdef PNG_WARNINGS_SUPPORTED
#  define PNG_WARNING_PARAMETERS(p) png_warning_parameters p;
#else
#  define png_warning_parameter(p,number,string) ((void)0)
#  define png_warning_parameter_unsigned(p,number,format,value) ((void)0)
#  define png_warning_parameter_signed(p,number,format,value) ((void)0)
#  define png_formatted_warning(pp,p,message) ((void)(pp))
#  define PNG_WARNING_PARAMETERS(p)
#endif
#ifndef PNG_ERROR_TEXT_SUPPORTED
#  define png_fixed_error(s1,s2) png_err(s1)
#endif

#ifndef PNG_VERSION_INFO_ONLY
/* Other defines specific to compilers can go here.  Try to keep
 * them inside an appropriate ifdef/endif pair for portability.
 */

/* C allows up-casts from (void*) to any pointer and (const void*) to any
 * pointer to a const object.  C++ regards this as a type error and requires an
 * explicit, static, cast and provides the static_cast<> rune to ensure that
 * const is not cast away.
 */
#ifdef __cplusplus
#  define png_voidcast(type, value) static_cast<type>(value)
#  define png_constcast(type, value) const_cast<type>(value)
#  define png_aligncast(type, value) \
   static_cast<type>(static_cast<void*>(value))
#  define png_aligncastconst(type, value) \
   static_cast<type>(static_cast<const void*>(value))
#else
#  define png_voidcast(type, value) (value)
#  define png_constcast(type, value) ((type)(void*)(const void*)(value))
#  define png_aligncast(type, value) ((void*)(value))
#  define png_aligncastconst(type, value) ((const void*)(value))
#endif /* __cplusplus */

#if defined(PNG_FLOATING_POINT_SUPPORTED) ||\
    defined(PNG_FLOATING_ARITHMETIC_SUPPORTED)
   /* png.c requires the following ANSI-C constants if the conversion of
    * floating point to ASCII is implemented therein:
    *
    *  DBL_DIG  Maximum number of decimal digits (can be set to any constant)
    *  DBL_MIN  Smallest normalized fp number (can be set to an arbitrary value)
    *  DBL_MAX  Maximum floating point number (can be set to an arbitrary value)
    */
#  include <float.h>

#  include <math.h>

#  if defined(_AMIGA) && defined(__SASC) && defined(_M68881)
   /* Amiga SAS/C: We must include builtin FPU functions when compiling using
    * MATH=68881
    */
#    include <m68881.h>
#  endif
#endif

/* This provides the non-ANSI (far) memory allocation routines. */
#if defined(__TURBOC__) && defined(__MSDOS__)
#  include <mem.h>
#  include <alloc.h>
#endif

#if defined(_WIN32) || defined(__WIN32__) || defined(__NT__)
#  include <windows.h>
#endif
#endif /* PNG_VERSION_INFO_ONLY */

/* Moved here around 1.5.0beta36 from pngconf.h */
/* Users may want to use these so they are not private.  Any library
 * functions that are passed far data must be model-independent.
 */

/* Platform-independent functions */
#ifndef PNG_ABORT
#  define PNG_ABORT() abort()
#endif

/* These macros may need to be architecture dependent. */
#define PNG_ALIGN_NONE      0 /* do not use data alignment */
#define PNG_ALIGN_ALWAYS    1 /* assume unaligned accesses are OK */
#ifdef offsetof
#  define PNG_ALIGN_OFFSET  2 /* use offsetof to determine alignment */
#else
#  define PNG_ALIGN_OFFSET -1 /* prevent the use of this */
#endif
#define PNG_ALIGN_SIZE      3 /* use sizeof to determine alignment */

#ifndef PNG_ALIGN_TYPE
   /* Default to using aligned access optimizations and requiring alignment to a
    * multiple of the data type size.  Override in a compiler specific fashion
    * if necessary by inserting tests here:
    */
#  define PNG_ALIGN_TYPE PNG_ALIGN_SIZE
#endif

#if PNG_ALIGN_TYPE == PNG_ALIGN_SIZE
   /* This is used because in some compiler implementations non-aligned
    * structure members are supported, so the offsetof approach below fails.
    * Set PNG_ALIGN_SIZE=0 for compiler combinations where unaligned access
    * is good for performance.  Do not do this unless you have tested the
    * result and understand it.
    */
#  define png_alignof(type) (sizeof(type))
#else
#  if PNG_ALIGN_TYPE == PNG_ALIGN_OFFSET
#    define png_alignof(type) offsetof(struct{char c; type t;}, t)
#  else
#    if PNG_ALIGN_TYPE == PNG_ALIGN_ALWAYS
#      define png_alignof(type) 1
#    endif
     /* Else leave png_alignof undefined to prevent use thereof */
#  endif
#endif

/* This implicitly assumes alignment is always a multiple of 2. */
#ifdef png_alignof
#  define png_isaligned(ptr, type) \
   (((type)(size_t)((const void*)(ptr)) & (type)(png_alignof(type)-1)) == 0)
#else
#  define png_isaligned(ptr, type) 0
#endif

/* End of memory model/platform independent support */
/* End of 1.5.0beta36 move from pngconf.h */

/* CONSTANTS and UTILITY MACROS
 * These are used internally by libpng and not exposed in the API
 */

/* Various modes of operation.  Note that after an init, mode is set to
 * zero automatically when the structure is created.  Three of these
 * are defined in png.h because they need to be visible to applications
 * that call png_set_unknown_chunk().
 */
/* #define PNG_HAVE_IHDR            0x01U (defined in png.h) */
/* #define PNG_HAVE_PLTE            0x02U (defined in png.h) */
#define PNG_HAVE_IDAT               0x04U
/* #define PNG_AFTER_IDAT           0x08U (defined in png.h) */
#define PNG_HAVE_IEND               0x10U
                   /*               0x20U (unused) */
                   /*               0x40U (unused) */
                   /*               0x80U (unused) */
#define PNG_HAVE_CHUNK_HEADER      0x100U
#define PNG_WROTE_tIME             0x200U
#define PNG_WROTE_INFO_BEFORE_PLTE 0x400U
#define PNG_BACKGROUND_IS_GRAY     0x800U
#define PNG_HAVE_PNG_SIGNATURE    0x1000U
#define PNG_HAVE_CHUNK_AFTER_IDAT 0x2000U /* Have another chunk after IDAT */
#define PNG_WROTE_eXIf            0x4000U
#define PNG_IS_READ_STRUCT        0x8000U /* Else is a write struct */
#ifdef PNG_APNG_SUPPORTED
#define PNG_HAVE_acTL            0x10000U
#define PNG_HAVE_fcTL            0x20000U
#endif

/* Flags for the transformations the PNG library does on the image data */
#define PNG_BGR                 0x0001U
#define PNG_INTERLACE           0x0002U
#define PNG_PACK                0x0004U
#define PNG_SHIFT               0x0008U
#define PNG_SWAP_BYTES          0x0010U
#define PNG_INVERT_MONO         0x0020U
#define PNG_QUANTIZE            0x0040U
#define PNG_COMPOSE             0x0080U    /* Was PNG_BACKGROUND */
#define PNG_BACKGROUND_EXPAND   0x0100U
#define PNG_EXPAND_16           0x0200U    /* Added to libpng 1.5.2 */
#define PNG_16_TO_8             0x0400U    /* Becomes 'chop' in 1.5.4 */
#define PNG_RGBA                0x0800U
#define PNG_EXPAND              0x1000U
#define PNG_GAMMA               0x2000U
#define PNG_GRAY_TO_RGB         0x4000U
#define PNG_FILLER              0x8000U
#define PNG_PACKSWAP           0x10000U
#define PNG_SWAP_ALPHA         0x20000U
#define PNG_STRIP_ALPHA        0x40000U
#define PNG_INVERT_ALPHA       0x80000U
#define PNG_USER_TRANSFORM    0x100000U
#define PNG_RGB_TO_GRAY_ERR   0x200000U
#define PNG_RGB_TO_GRAY_WARN  0x400000U
#define PNG_RGB_TO_GRAY       0x600000U /* two bits, RGB_TO_GRAY_ERR|WARN */
#define PNG_ENCODE_ALPHA      0x800000U /* Added to libpng-1.5.4 */
#define PNG_ADD_ALPHA        0x1000000U /* Added to libpng-1.2.7 */
#define PNG_EXPAND_tRNS      0x2000000U /* Added to libpng-1.2.9 */
#define PNG_SCALE_16_TO_8    0x4000000U /* Added to libpng-1.5.4 */
                       /*    0x8000000U unused */
                       /*   0x10000000U unused */
                       /*   0x20000000U unused */
                       /*   0x40000000U unused */
/* Flags for png_create_struct */
#define PNG_STRUCT_PNG   0x0001U
#define PNG_STRUCT_INFO  0x0002U

/* Flags for the png_ptr->flags rather than declaring a byte for each one */
#define PNG_FLAG_ZLIB_CUSTOM_STRATEGY     0x0001U
#define PNG_FLAG_ZSTREAM_INITIALIZED      0x0002U /* Added to libpng-1.6.0 */
                                  /*      0x0004U    unused */
#define PNG_FLAG_ZSTREAM_ENDED            0x0008U /* Added to libpng-1.6.0 */
                                  /*      0x0010U    unused */
                                  /*      0x0020U    unused */
#define PNG_FLAG_ROW_INIT                 0x0040U
#define PNG_FLAG_FILLER_AFTER             0x0080U
#define PNG_FLAG_CRC_ANCILLARY_USE        0x0100U
#define PNG_FLAG_CRC_ANCILLARY_NOWARN     0x0200U
#define PNG_FLAG_CRC_CRITICAL_USE         0x0400U
#define PNG_FLAG_CRC_CRITICAL_IGNORE      0x0800U
/*      PNG_FLAG_ASSUME_sRGB unused       0x1000U  * Added to libpng-1.5.4 */
#define PNG_FLAG_OPTIMIZE_ALPHA           0x2000U /* Added to libpng-1.5.4 */
#define PNG_FLAG_DETECT_UNINITIALIZED     0x4000U /* Added to libpng-1.5.4 */
/* #define PNG_FLAG_KEEP_UNKNOWN_CHUNKS      0x8000U */
/* #define PNG_FLAG_KEEP_UNSAFE_CHUNKS      0x10000U */
#define PNG_FLAG_LIBRARY_MISMATCH        0x20000U
                                  /*     0x40000U    unused */
#define PNG_FLAG_STRIP_ERROR_TEXT        0x80000U
#define PNG_FLAG_BENIGN_ERRORS_WARN     0x100000U /* Added to libpng-1.4.0 */
#define PNG_FLAG_APP_WARNINGS_WARN      0x200000U /* Added to libpng-1.6.0 */
#define PNG_FLAG_APP_ERRORS_WARN        0x400000U /* Added to libpng-1.6.0 */
                                  /*    0x800000U    unused */
                                  /*   0x1000000U    unused */
                                  /*   0x2000000U    unused */
                                  /*   0x4000000U    unused */
                                  /*   0x8000000U    unused */
                                  /*  0x10000000U    unused */
                                  /*  0x20000000U    unused */
                                  /*  0x40000000U    unused */

#define PNG_FLAG_CRC_ANCILLARY_MASK (PNG_FLAG_CRC_ANCILLARY_USE | \
                                     PNG_FLAG_CRC_ANCILLARY_NOWARN)

#define PNG_FLAG_CRC_CRITICAL_MASK  (PNG_FLAG_CRC_CRITICAL_USE | \
                                     PNG_FLAG_CRC_CRITICAL_IGNORE)

#define PNG_FLAG_CRC_MASK           (PNG_FLAG_CRC_ANCILLARY_MASK | \
                                     PNG_FLAG_CRC_CRITICAL_MASK)

/* Save typing and make code easier to understand */

#define PNG_COLOR_DIST(c1, c2) (abs((int)((c1).red) - (int)((c2).red)) + \
   abs((int)((c1).green) - (int)((c2).green)) + \
   abs((int)((c1).blue) - (int)((c2).blue)))

/* Added to libpng-1.6.0: scale a 16-bit value in the range 0..65535 to 0..255
 * by dividing by 257 *with rounding*.  This macro is exact for the given range.
 * See the discourse in pngrtran.c png_do_scale_16_to_8.  The values in the
 * macro were established by experiment (modifying the added value).  The macro
 * has a second variant that takes a value already scaled by 255 and divides by
 * 65535 - this has a maximum error of .502.  Over the range 0..65535*65535 it
 * only gives off-by-one errors and only for 0.5% (1 in 200) of the values.
 */
#define PNG_DIV65535(v24) (((v24) + 32895) >> 16)
#define PNG_DIV257(v16) PNG_DIV65535((png_uint_32)(v16) * 255)

/* Added to libpng-1.2.6 JB */
#define PNG_ROWBYTES(pixel_bits, width) \
    ((pixel_bits) >= 8 ? \
    ((size_t)(width) * (((size_t)(pixel_bits)) >> 3)) : \
    (( ((size_t)(width) * ((size_t)(pixel_bits))) + 7) >> 3) )

/* This returns the number of trailing bits in the last byte of a row, 0 if the
 * last byte is completely full of pixels.  It is, in principle, (pixel_bits x
 * width) % 8, but that would overflow for large 'width'.  The second macro is
 * the same except that it returns the number of unused bits in the last byte;
 * (8-TRAILBITS), but 0 when TRAILBITS is 0.
 *
 * NOTE: these macros are intended to be self-evidently correct and never
 * overflow on the assumption that pixel_bits is in the range 0..255.  The
 * arguments are evaluated only once and they can be signed (e.g. as a result of
 * the integral promotions).  The result of the expression always has type
 * (png_uint_32), however the compiler always knows it is in the range 0..7.
 */
#define PNG_TRAILBITS(pixel_bits, width) \
    (((pixel_bits) * ((width) % (png_uint_32)8)) % 8)

#define PNG_PADBITS(pixel_bits, width) \
    ((8 - PNG_TRAILBITS(pixel_bits, width)) % 8)

/* PNG_OUT_OF_RANGE returns true if value is outside the range
 * ideal-delta..ideal+delta.  Each argument is evaluated twice.
 * "ideal" and "delta" should be constants, normally simple
 * integers, "value" a variable. Added to libpng-1.2.6 JB
 */
#define PNG_OUT_OF_RANGE(value, ideal, delta) \
   ( (value) < (ideal)-(delta) || (value) > (ideal)+(delta) )

/* Conversions between fixed and floating point, only defined if
 * required (to make sure the code doesn't accidentally use float
 * when it is supposedly disabled.)
 */
#ifdef PNG_FLOATING_POINT_SUPPORTED
/* The floating point conversion can't overflow, though it can and
 * does lose accuracy relative to the original fixed point value.
 * In practice this doesn't matter because png_fixed_point only
 * stores numbers with very low precision.  The png_ptr and s
 * arguments are unused by default but are there in case error
 * checking becomes a requirement.
 */
#define png_float(png_ptr, fixed, s) (.00001 * (fixed))

/* The fixed point conversion performs range checking and evaluates
 * its argument multiple times, so must be used with care.  The
 * range checking uses the PNG specification values for a signed
 * 32-bit fixed point value except that the values are deliberately
 * rounded-to-zero to an integral value - 21474 (21474.83 is roughly
 * (2^31-1) * 100000). 's' is a string that describes the value being
 * converted.
 *
 * NOTE: this macro will raise a png_error if the range check fails,
 * therefore it is normally only appropriate to use this on values
 * that come from API calls or other sources where an out of range
 * error indicates a programming error, not a data error!
 *
 * NOTE: by default this is off - the macro is not used - because the
 * function call saves a lot of code.
 */
#ifdef PNG_FIXED_POINT_MACRO_SUPPORTED
#define png_fixed(png_ptr, fp, s) ((fp) <= 21474 && (fp) >= -21474 ?\
    ((png_fixed_point)(100000 * (fp))) : (png_fixed_error(png_ptr, s),0))
#define png_fixed_ITU(png_ptr, fp, s) ((fp) <= 214748 && (fp) >= 0 ?\
    ((png_uint_32)(10000 * (fp))) : (png_fixed_error(png_ptr, s),0))
#endif
/* else the corresponding function is defined below, inside the scope of the
 * cplusplus test.
 */
#endif

/* Constants for known chunk types.  If you need to add a chunk, define the name
 * here.  For historical reasons these constants have the form png_<name>; i.e.
 * the prefix is lower case.  Please use decimal values as the parameters to
 * match the ISO PNG specification and to avoid relying on the C locale
 * interpretation of character values.
 *
 * Prior to 1.5.6 these constants were strings, as of 1.5.6 png_uint_32 values
 * are computed and a new macro (PNG_STRING_FROM_CHUNK) added to allow a string
 * to be generated if required.
 *
 * PNG_32b correctly produces a value shifted by up to 24 bits, even on
 * architectures where (int) is only 16 bits.
 *
 * 1.6.47: PNG_32b was made into a preprocessor evaluable macro by replacing the
 * static_cast with a promoting binary operation using a guaranteed 32-bit
 * (minimum) unsigned value.
 */
#define PNG_32b(b,s) (((0xFFFFFFFFU)&(b)) << (s))
#define PNG_U32(b1,b2,b3,b4) \
   (PNG_32b(b1,24) | PNG_32b(b2,16) | PNG_32b(b3,8) | PNG_32b(b4,0))

/* Chunk name validation.  When using these macros all the arguments should be
 * constants, otherwise code bloat may well occur.  The macros are provided
 * primarily for use in #if checks.
 *
 * PNG_32to8 produces a byte value with the right shift; used to extract the
 * byte value from a chunk name.
 */
#define PNG_32to8(cn,s) (((cn) >> (s)) & 0xffU)
#define PNG_CN_VALID_UPPER(b) ((b) >= 65 && (b) <= 90) /* upper-case ASCII */
#define PNG_CN_VALID_ASCII(b) PNG_CN_VALID_UPPER((b) & ~32U)
#define PNG_CHUNK_NAME_VALID(cn) (\
   PNG_CN_VALID_ASCII(PNG_32to8(cn,24)) && /* critical, !ancillary */\
   PNG_CN_VALID_ASCII(PNG_32to8(cn,16)) && /* public, !privately defined */\
   PNG_CN_VALID_UPPER(PNG_32to8(cn, 8)) && /* VALID, !reserved */\
   PNG_CN_VALID_ASCII(PNG_32to8(cn, 0))   /* data-dependent, !copy ok */)

/* Constants for known chunk types.
 *
 * MAINTAINERS: If you need to add a chunk, define the name here.
 * For historical reasons these constants have the form png_<name>; i.e.
 * the prefix is lower case.  Please use decimal values as the parameters to
 * match the ISO PNG specification and to avoid relying on the C locale
 * interpretation of character values.  Please keep the list sorted.
 *
 * Notice that PNG_U32 is used to define a 32-bit value for the 4 byte chunk
 * type.  In fact the specification does not express chunk types this way,
 * however using a 32-bit value means that the chunk type can be read from the
 * stream using exactly the same code as used for a 32-bit unsigned value and
 * can be examined far more efficiently (using one arithmetic compare).
 *
 * Prior to 1.5.6 the chunk type constants were expressed as C strings.  The
 * libpng API still uses strings for 'unknown' chunks and a macro,
 * PNG_STRING_FROM_CHUNK, allows a string to be generated if required.  Notice
 * that for portable code numeric values must still be used; the string "IHDR"
 * is not portable and neither is PNG_U32('I', 'H', 'D', 'R').
 *
 * In 1.7.0 the definitions will be made public in png.h to avoid having to
 * duplicate the same definitions in application code.
 */
#define png_IDAT PNG_U32( 73,  68,  65,  84)
#define png_IEND PNG_U32( 73,  69,  78,  68)
#define png_IHDR PNG_U32( 73,  72,  68,  82)
#define png_PLTE PNG_U32( 80,  76,  84,  69)
#define png_acTL PNG_U32( 97,  99,  84,  76) /* PNGv3: APNG */
#define png_bKGD PNG_U32( 98,  75,  71,  68)
#define png_cHRM PNG_U32( 99,  72,  82,  77)
#define png_cICP PNG_U32( 99,  73,  67,  80) /* PNGv3 */
#define png_cLLI PNG_U32( 99,  76,  76,  73) /* PNGv3 */
#define png_eXIf PNG_U32(101,  88,  73, 102) /* registered July 2017 */
#define png_fcTL PNG_U32(102,  99,  84,  76) /* PNGv3: APNG */
#define png_fdAT PNG_U32(102, 100,  65,  84) /* PNGv3: APNG */
#define png_fRAc PNG_U32(102,  82,  65,  99) /* registered, not defined */
#define png_gAMA PNG_U32(103,  65,  77,  65)
#define png_gIFg PNG_U32(103,  73,  70, 103)
#define png_gIFt PNG_U32(103,  73,  70, 116) /* deprecated */
#define png_gIFx PNG_U32(103,  73,  70, 120)
#define png_hIST PNG_U32(104,  73,  83,  84)
#define png_iCCP PNG_U32(105,  67,  67,  80)
#define png_iTXt PNG_U32(105,  84,  88, 116)
#define png_mDCV PNG_U32(109,  68,  67,  86) /* PNGv3 */
#define png_oFFs PNG_U32(111,  70,  70, 115)
#define png_pCAL PNG_U32(112,  67,  65,  76)
#define png_pHYs PNG_U32(112,  72,  89, 115)
#define png_sBIT PNG_U32(115,  66,  73,  84)
#define png_sCAL PNG_U32(115,  67,  65,  76)
#define png_sPLT PNG_U32(115,  80,  76,  84)
#define png_sRGB PNG_U32(115,  82,  71,  66)
#define png_sTER PNG_U32(115,  84,  69,  82)
#define png_tEXt PNG_U32(116,  69,  88, 116)
#define png_tIME PNG_U32(116,  73,  77,  69)
#define png_tRNS PNG_U32(116,  82,  78,  83)
#define png_zTXt PNG_U32(122,  84,  88, 116)

#ifdef PNG_APNG_SUPPORTED

/* For png_struct.apng_flags: */
#define PNG_FIRST_FRAME_HIDDEN       0x0001U
#define PNG_APNG_APP                 0x0002U
#endif

/* The following will work on (signed char*) strings, whereas the get_uint_32
 * macro will fail on top-bit-set values because of the sign extension.
 */
#define PNG_CHUNK_FROM_STRING(s)\
   PNG_U32(0xff & (s)[0], 0xff & (s)[1], 0xff & (s)[2], 0xff & (s)[3])

/* This uses (char), not (png_byte) to avoid warnings on systems where (char) is
 * signed and the argument is a (char[])  This macro will fail miserably on
 * systems where (char) is more than 8 bits.
 */
#define PNG_STRING_FROM_CHUNK(s,c)\
   (void)(((char*)(s))[0]=(char)(((c)>>24) & 0xff), \
   ((char*)(s))[1]=(char)(((c)>>16) & 0xff),\
   ((char*)(s))[2]=(char)(((c)>>8) & 0xff), \
   ((char*)(s))[3]=(char)((c & 0xff)))

/* Do the same but terminate with a null character. */
#define PNG_CSTRING_FROM_CHUNK(s,c)\
   (void)(PNG_STRING_FROM_CHUNK(s,c), ((char*)(s))[4] = 0)

/* Test on flag values as defined in the spec (section 5.4): */
#define PNG_CHUNK_ANCILLARY(c)   (1 & ((c) >> 29))
#define PNG_CHUNK_CRITICAL(c)     (!PNG_CHUNK_ANCILLARY(c))
#define PNG_CHUNK_PRIVATE(c)      (1 & ((c) >> 21))
#define PNG_CHUNK_RESERVED(c)     (1 & ((c) >> 13))
#define PNG_CHUNK_SAFE_TO_COPY(c) (1 & ((c) >>  5))

/* Known chunks.  All supported chunks must be listed here.  The macro PNG_CHUNK
 * contains the four character ASCII name by which the chunk is identified.  The
 * macro is implemented as required to build tables or switch statements which
 * require entries for every known chunk.  The macro also contains an index
 * value which should be in order (this is checked in png.c).
 *
 * Notice that "known" does not require "SUPPORTED"; tables should be built in
 * such a way that chunks unsupported in a build require no more than the table
 * entry (which should be small.)  In particular function pointers for
 * unsupported chunks should be NULL.
 *
 * At present these index values are not exported (not part of the public API)
 * so can be changed at will.  For convenience the names are in lexical sort
 * order but with the critical chunks at the start in the order of occurrence in
 * a PNG.
 *
 * PNG_INFO_ values do not exist for every one of these chunk handles; for
 * example PNG_INFO_{IDAT,IEND,tEXt,iTXt,zTXt} and possibly other chunks in the
 * future.
 */
#define PNG_KNOWN_CHUNKS\
   PNG_CHUNK(IHDR,  0)\
   PNG_CHUNK(PLTE,  1)\
   PNG_CHUNK(IDAT,  2)\
   PNG_CHUNK(IEND,  3)\
   PNG_CHUNK(acTL,  4)\
   PNG_CHUNK(bKGD,  5)\
   PNG_CHUNK(cHRM,  6)\
   PNG_CHUNK(cICP,  7)\
   PNG_CHUNK(cLLI,  8)\
   PNG_CHUNK(eXIf,  9)\
   PNG_CHUNK(fcTL, 10)\
   PNG_CHUNK(fdAT, 11)\
   PNG_CHUNK(gAMA, 12)\
   PNG_CHUNK(hIST, 13)\
   PNG_CHUNK(iCCP, 14)\
   PNG_CHUNK(iTXt, 15)\
   PNG_CHUNK(mDCV, 16)\
   PNG_CHUNK(oFFs, 17)\
   PNG_CHUNK(pCAL, 18)\
   PNG_CHUNK(pHYs, 19)\
   PNG_CHUNK(sBIT, 20)\
   PNG_CHUNK(sCAL, 21)\
   PNG_CHUNK(sPLT, 22)\
   PNG_CHUNK(sRGB, 23)\
   PNG_CHUNK(tEXt, 24)\
   PNG_CHUNK(tIME, 25)\
   PNG_CHUNK(tRNS, 26)\
   PNG_CHUNK(zTXt, 27)

/* Gamma values (new at libpng-1.5.4): */
#define PNG_GAMMA_MAC_OLD 151724  /* Assume '1.8' is really 2.2/1.45! */
#define PNG_GAMMA_MAC_INVERSE 65909
#define PNG_GAMMA_sRGB_INVERSE 45455

/* gamma sanity check.  libpng cannot implement gamma transforms outside a
 * certain limit because of its use of 16-bit fixed point intermediate values.
 * Gamma values that are too large or too small will zap the 16-bit values all
 * to 0 or 65535 resulting in an obvious 'bad' image.
 *
 * In libpng 1.6.0 the limits were changed from 0.07..3 to 0.01..100 to
 * accommodate the optimal 16-bit gamma of 36 and its reciprocal.
 *
 * These are png_fixed_point integral values:
 */
#define PNG_LIB_GAMMA_MIN 1000
#define PNG_LIB_GAMMA_MAX 10000000

/* Almost everything below is C specific; the #defines above can be used in
 * non-C code (so long as it is C-preprocessed) the rest of this stuff cannot.
 */
#ifndef PNG_VERSION_INFO_ONLY

#include "pngstruct.h"
#include "pnginfo.h"

/* Validate the include paths - the include path used to generate pnglibconf.h
 * must match that used in the build, or we must be using pnglibconf.h.prebuilt:
 */
#if PNG_ZLIB_VERNUM != 0 && PNG_ZLIB_VERNUM != ZLIB_VERNUM
#  error The include path of <zlib.h> is incorrect
   /* When pnglibconf.h was built, the copy of zlib.h that it used was not the
    * same as the one being used here.  Considering how libpng makes decisions
    * to use the zlib API based on the zlib version number, the -I options must
    * match.
    *
    * A possible cause of this mismatch is that you passed an -I option in
    * CFLAGS, which is unlikely to work.  All the preprocessor options, and all
    * the -I options in particular, should be in CPPFLAGS.
    */
#endif

/* Added to libpng-1.5.7: sRGB conversion tables */
#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
   defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)
#ifdef PNG_SIMPLIFIED_READ_SUPPORTED
PNG_INTERNAL_DATA(const png_uint_16, png_sRGB_table, [256]);
   /* Convert from an sRGB encoded value 0..255 to a 16-bit linear value,
    * 0..65535.  This table gives the closest 16-bit answers (no errors).
    */
#endif

PNG_INTERNAL_DATA(const png_uint_16, png_sRGB_base, [512]);
PNG_INTERNAL_DATA(const png_byte, png_sRGB_delta, [512]);

#define PNG_sRGB_FROM_LINEAR(linear) \
  ((png_byte)(0xff & ((png_sRGB_base[(linear)>>15] \
   + ((((linear) & 0x7fff)*png_sRGB_delta[(linear)>>15])>>12)) >> 8)))
   /* Given a value 'linear' in the range 0..255*65535 calculate the 8-bit sRGB
    * encoded value with maximum error 0.646365.  Note that the input is not a
    * 16-bit value; it has been multiplied by 255! */
#endif /* SIMPLIFIED_READ/WRITE */


/* Inhibit C++ name-mangling for libpng functions but not for system calls. */
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

/* Internal functions; these are not exported from a DLL however because they
 * are used within several of the C source files they have to be C extern.
 *
 * All of these functions must be declared with PNG_INTERNAL_FUNCTION.
 */
/* Zlib support */
#define PNG_UNEXPECTED_ZLIB_RETURN (-7)
PNG_INTERNAL_FUNCTION(void, png_zstream_error,
   (png_struct *png_ptr, int ret),
   PNG_EMPTY);
   /* Used by the zlib handling functions to ensure that z_stream::msg is always
    * set before they return.
    */

#ifdef PNG_WRITE_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_free_buffer_list,
   (png_struct *png_ptr, png_compression_buffer **list),
   PNG_EMPTY);
   /* Free the buffer list used by the compressed write code. */
#endif

#if defined(PNG_FLOATING_POINT_SUPPORTED) && \
   !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
   (defined(PNG_gAMA_SUPPORTED) || defined(PNG_cHRM_SUPPORTED) || \
   defined(PNG_sCAL_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED) || \
   defined(PNG_mDCV_SUPPORTED) || \
   defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)) || \
   (defined(PNG_sCAL_SUPPORTED) && \
   defined(PNG_FLOATING_ARITHMETIC_SUPPORTED))
PNG_INTERNAL_FUNCTION(png_fixed_point, png_fixed,
   (const png_struct *png_ptr, double fp, const char *text),
   PNG_EMPTY);
#endif

#if defined(PNG_FLOATING_POINT_SUPPORTED) && \
   !defined(PNG_FIXED_POINT_MACRO_SUPPORTED) && \
   (defined(PNG_cLLI_SUPPORTED) || defined(PNG_mDCV_SUPPORTED))
PNG_INTERNAL_FUNCTION(png_uint_32, png_fixed_ITU,
   (const png_struct *png_ptr, double fp, const char *text),
   PNG_EMPTY);
#endif

/* Check the user version string for compatibility, returns false if the version
 * numbers aren't compatible.
 */
PNG_INTERNAL_FUNCTION(int, png_user_version_check,
   (png_struct *png_ptr, const char *user_png_ver),
   PNG_EMPTY);

#ifdef PNG_READ_SUPPORTED /* should only be used on read */
/* Security: read limits on the largest allocations while reading a PNG.  This
 * avoids very large allocations caused by PNG files with damaged or altered
 * chunk 'length' fields.
 */
#ifdef PNG_SET_USER_LIMITS_SUPPORTED /* run-time limit */
#  define png_chunk_max(png_ptr) ((png_ptr)->user_chunk_malloc_max)

#elif PNG_USER_CHUNK_MALLOC_MAX > 0 /* compile-time limit */
#  define png_chunk_max(png_ptr) ((void)png_ptr, PNG_USER_CHUNK_MALLOC_MAX)

#elif (defined PNG_MAX_MALLOC_64K)  /* legacy system limit */
#  define png_chunk_max(png_ptr) ((void)png_ptr, 65536U)

#else                               /* modern system limit SIZE_MAX (C99) */
#  define png_chunk_max(png_ptr) ((void)png_ptr, PNG_SIZE_MAX)
#endif
#endif /* READ */

/* Internal base allocator - no messages, NULL on failure to allocate.  This
 * does, however, call the application provided allocator and that could call
 * png_error (although that would be a bug in the application implementation.)
 */
PNG_INTERNAL_FUNCTION(void *, png_malloc_base,
   (const png_struct *png_ptr, png_alloc_size_t size),
   PNG_ALLOCATED);

#if defined(PNG_TEXT_SUPPORTED) || defined(PNG_sPLT_SUPPORTED) ||\
   defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED)
/* Internal array allocator, outputs no error or warning messages on failure,
 * just returns NULL.
 */
PNG_INTERNAL_FUNCTION(void *, png_malloc_array,
   (const png_struct *png_ptr, int nelements, size_t element_size),
   PNG_ALLOCATED);

/* The same but an existing array is extended by add_elements.  This function
 * also memsets the new elements to 0 and copies the old elements.  The old
 * array is not freed or altered.
 */
PNG_INTERNAL_FUNCTION(void *, png_realloc_array,
   (const png_struct *png_ptr,
    const void *array, int old_elements, int add_elements,
    size_t element_size),
   PNG_ALLOCATED);
#endif /* text, sPLT or unknown chunks */

/* Magic to create a struct when there is no struct to call the user supplied
 * memory allocators.  Because error handling has not been set up the memory
 * handlers can't safely call png_error, but this is an obscure and undocumented
 * restriction so libpng has to assume that the 'free' handler, at least, might
 * call png_error.
 */
PNG_INTERNAL_FUNCTION(png_struct *, png_create_png_struct,
   (const char *user_png_ver,
    void *error_ptr, png_error_ptr error_fn, png_error_ptr warn_fn,
    void *mem_ptr, png_malloc_ptr malloc_fn, png_free_ptr free_fn),
   PNG_ALLOCATED);

/* Free memory from internal libpng struct */
PNG_INTERNAL_FUNCTION(void, png_destroy_png_struct,
   (png_struct *png_ptr),
   PNG_EMPTY);

/* Free an allocated jmp_buf (always succeeds) */
PNG_INTERNAL_FUNCTION(void, png_free_jmpbuf,
   (png_struct *png_ptr),
   PNG_EMPTY);

/* Function to allocate memory for zlib. */
PNG_INTERNAL_FUNCTION(voidpf, png_zalloc,
   (voidpf png_ptr, uInt items, uInt size),
   PNG_ALLOCATED);

/* Function to free memory for zlib. */
PNG_INTERNAL_FUNCTION(void, png_zfree,
   (voidpf png_ptr, voidpf ptr),
   PNG_EMPTY);

/* Internal callback. */
PNG_INTERNAL_FUNCTION(void, png_default_read_data,
   (png_struct *png_ptr, png_byte *data, size_t length),
   PNG_EMPTY);

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
/* Internal callback. */
PNG_INTERNAL_FUNCTION(void, png_push_fill_buffer,
   (png_struct *png_ptr, png_byte *buffer, size_t length),
   PNG_EMPTY);
#endif

/* Internal callback. */
PNG_INTERNAL_FUNCTION(void, png_default_write_data,
   (png_struct *png_ptr, png_byte *data, size_t length),
   PNG_EMPTY);

#ifdef PNG_WRITE_FLUSH_SUPPORTED
#  ifdef PNG_STDIO_SUPPORTED
/* Internal callback. */
PNG_INTERNAL_FUNCTION(void, png_default_flush,
   (png_struct *png_ptr),
   PNG_EMPTY);
#  endif
#endif

/* Reset the CRC variable */
PNG_INTERNAL_FUNCTION(void, png_reset_crc,
   (png_struct *png_ptr),
   PNG_EMPTY);

/* Write the "data" buffer to whatever output you are using */
PNG_INTERNAL_FUNCTION(void, png_write_data,
   (png_struct *png_ptr, const png_byte *data, size_t length),
   PNG_EMPTY);

/* Read and check the PNG file signature */
PNG_INTERNAL_FUNCTION(void, png_read_sig,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);

/* Read the chunk header (length + type name) */
PNG_INTERNAL_FUNCTION(png_uint_32, png_read_chunk_header,
   (png_struct *png_ptr),
   PNG_EMPTY);

/* Read data from whatever input you are using into the "data" buffer */
PNG_INTERNAL_FUNCTION(void, png_read_data,
   (png_struct *png_ptr, png_byte *data, size_t length),
   PNG_EMPTY);

/* Read bytes into buf, and update png_ptr->crc */
PNG_INTERNAL_FUNCTION(void, png_crc_read,
   (png_struct *png_ptr, png_byte *buf, png_uint_32 length),
   PNG_EMPTY);

/* Read "skip" bytes, read the file crc, and (optionally) verify png_ptr->crc */
PNG_INTERNAL_FUNCTION(int, png_crc_finish,
   (png_struct *png_ptr, png_uint_32 skip),
   PNG_EMPTY);

/* Calculate the CRC over a section of data.  Note that we are only
 * passing a maximum of 64K on systems that have this as a memory limit,
 * since this is the maximum buffer size we can specify.
 */
PNG_INTERNAL_FUNCTION(void, png_calculate_crc,
   (png_struct *png_ptr, const png_byte *ptr, size_t length),
   PNG_EMPTY);

#ifdef PNG_WRITE_FLUSH_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_flush,
   (png_struct *png_ptr),
   PNG_EMPTY);
#endif

/* Write various chunks */

/* Write the IHDR chunk, and update the png_struct with the necessary
 * information.
 */
PNG_INTERNAL_FUNCTION(void, png_write_IHDR,
   (png_struct *png_ptr,
    png_uint_32 width, png_uint_32 height, int bit_depth, int color_type,
    int compression_method, int filter_method, int interlace_method),
   PNG_EMPTY);

PNG_INTERNAL_FUNCTION(void, png_write_PLTE,
   (png_struct *png_ptr,
    const png_color *palette, png_uint_32 num_pal),
   PNG_EMPTY);

PNG_INTERNAL_FUNCTION(void, png_compress_IDAT,
   (png_struct *png_ptr,
    const png_byte *row_data, png_alloc_size_t row_data_length, int flush),
   PNG_EMPTY);

PNG_INTERNAL_FUNCTION(void, png_write_IEND,
   (png_struct *png_ptr),
   PNG_EMPTY);

#ifdef PNG_WRITE_gAMA_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_gAMA_fixed,
   (png_struct *png_ptr, png_fixed_point file_gamma),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_sBIT_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_sBIT,
   (png_struct *png_ptr, const png_color_8 *sbit, int color_type),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_cHRM_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_cHRM_fixed,
   (png_struct *png_ptr, const png_xy *xy),
   PNG_EMPTY);
   /* The xy value must have been previously validated */
#endif

#ifdef PNG_WRITE_cICP_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_cICP,
   (png_struct *png_ptr,
    png_byte colour_primaries, png_byte transfer_function,
    png_byte matrix_coefficients, png_byte video_full_range_flag),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_cLLI_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_cLLI_fixed,
   (png_struct *png_ptr, png_uint_32 maxCLL, png_uint_32 maxFALL),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_mDCV_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_mDCV_fixed,
   (png_struct *png_ptr,
    png_uint_16 red_x, png_uint_16 red_y,
    png_uint_16 green_x, png_uint_16 green_y,
    png_uint_16 blue_x, png_uint_16 blue_y,
    png_uint_16 white_x, png_uint_16 white_y,
    png_uint_32 maxDL, png_uint_32 minDL),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_sRGB_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_sRGB,
   (png_struct *png_ptr, int intent),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_eXIf_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_eXIf,
   (png_struct *png_ptr, png_byte *exif, int num_exif),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_iCCP_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_iCCP,
   (png_struct *png_ptr,
    const char *name, const png_byte *profile, png_uint_32 proflen),
   PNG_EMPTY);
   /* Writes a previously 'set' profile.  The profile argument is **not**
    * compressed.
    */
#endif

#ifdef PNG_WRITE_sPLT_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_sPLT,
   (png_struct *png_ptr, const png_sPLT_t *palette),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_tRNS_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_tRNS,
   (png_struct *png_ptr,
    const png_byte *trans, const png_color_16 *values, int number,
    int color_type),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_bKGD_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_bKGD,
   (png_struct *png_ptr, const png_color_16 *values, int color_type),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_hIST_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_hIST,
   (png_struct *png_ptr, const png_uint_16 *hist, int num_hist),
   PNG_EMPTY);
#endif

/* Chunks that have keywords */
#ifdef PNG_WRITE_tEXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_tEXt,
   (png_struct *png_ptr,
    const char *key, const char *text, size_t text_len),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_zTXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_zTXt,
   (png_struct *png_ptr,
    const char *key, const char *text, int compression),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_iTXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_iTXt,
   (png_struct *png_ptr,
    int compression, const char *key, const char *lang,
    const char *lang_key, const char *text),
   PNG_EMPTY);
#endif

#ifdef PNG_TEXT_SUPPORTED  /* Added at version 1.0.14 and 1.2.4 */
PNG_INTERNAL_FUNCTION(int, png_set_text_2,
   (const png_struct *png_ptr,
    png_info *info_ptr, const png_text *text_ptr, int num_text),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_oFFs_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_oFFs,
   (png_struct *png_ptr,
    png_int_32 x_offset, png_int_32 y_offset, int unit_type),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_pCAL_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_pCAL,
   (png_struct *png_ptr,
    char *purpose, png_int_32 X0, png_int_32 X1,
    int type, int nparams, const char *units, char **params),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_pHYs_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_pHYs,
   (png_struct *png_ptr,
    png_uint_32 x_pixels_per_unit, png_uint_32 y_pixels_per_unit,
    int unit_type),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_tIME_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_tIME,
   (png_struct *png_ptr, const png_time *mod_time),
   PNG_EMPTY);
#endif

#ifdef PNG_WRITE_sCAL_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_sCAL_s,
   (png_struct *png_ptr,
    int unit, const char *width, const char *height),
   PNG_EMPTY);
#endif

/* Called when finished processing a row of data */
PNG_INTERNAL_FUNCTION(void, png_write_finish_row,
   (png_struct *png_ptr),
   PNG_EMPTY);

/* Internal use only.   Called before first row of data */
PNG_INTERNAL_FUNCTION(void, png_write_start_row,
   (png_struct *png_ptr),
   PNG_EMPTY);

/* Combine a row of data, dealing with alpha, etc. if requested.  'row' is an
 * array of png_ptr->width pixels.  If the image is not interlaced or this
 * is the final pass this just does a memcpy, otherwise the "display" flag
 * is used to determine whether to copy pixels that are not in the current pass.
 *
 * Because 'png_do_read_interlace' (below) replicates pixels this allows this
 * function to achieve the documented 'blocky' appearance during interlaced read
 * if display is 1 and the 'sparkle' appearance, where existing pixels in 'row'
 * are not changed if they are not in the current pass, when display is 0.
 *
 * 'display' must be 0 or 1, otherwise the memcpy will be done regardless.
 *
 * The API always reads from the png_struct row buffer and always assumes that
 * it is full width (png_do_read_interlace has already been called.)
 *
 * This function is only ever used to write to row buffers provided by the
 * caller of the relevant libpng API and the row must have already been
 * transformed by the read transformations.
 *
 * The PNG_USE_COMPILE_TIME_MASKS option causes generation of pre-computed
 * bitmasks for use within the code, otherwise runtime generated masks are used.
 * The default is compile time masks.
 */
#ifndef PNG_USE_COMPILE_TIME_MASKS
#  define PNG_USE_COMPILE_TIME_MASKS 1
#endif
PNG_INTERNAL_FUNCTION(void, png_combine_row,
   (const png_struct *png_ptr, png_byte *row, int display),
   PNG_EMPTY);

#ifdef PNG_READ_INTERLACING_SUPPORTED
/* Expand an interlaced row: the 'row_info' describes the pass data that has
 * been read in and must correspond to the pixels in 'row', the pixels are
 * expanded (moved apart) in 'row' to match the final layout, when doing this
 * the pixels are *replicated* to the intervening space.  This is essential for
 * the correct operation of png_combine_row, above.
 */
PNG_INTERNAL_FUNCTION(void, png_do_read_interlace,
   (png_row_info *row_info,
    png_byte *row, int pass, png_uint_32 transformations),
   PNG_EMPTY);
#endif

/* GRR TO DO (2.0 or whenever):  simplify other internal calling interfaces */

#ifdef PNG_WRITE_INTERLACING_SUPPORTED
/* Grab pixels out of a row for an interlaced pass */
PNG_INTERNAL_FUNCTION(void, png_do_write_interlace,
   (png_row_info *row_info, png_byte *row, int pass),
   PNG_EMPTY);
#endif

/* Unfilter a row: check the filter value before calling this, there is no point
 * calling it for PNG_FILTER_VALUE_NONE.
 */
PNG_INTERNAL_FUNCTION(void, png_read_filter_row,
   (png_struct *pp, png_row_info *row_info,
    png_byte *row, const png_byte *prev_row, int filter),
   PNG_EMPTY);

#ifdef PNG_TARGET_CODE_IMPLEMENTATION
/* png_struct::target_state contains a cache of these flags and updates
 * it as required during read.  The hardware implementation may also do
 * this, for example if it determines that hardware optimization is not
 * available for this image.
 */
#define png_target_filters 1 /* MASK: hardware support for filters */
#define png_target_expand_palette 2 /* MASK: hardware support for palettes */

PNG_INTERNAL_FUNCTION(void, png_target_init,
   (png_struct *),
   PNG_EMPTY);
   /* Initialize png_struct::target_state if required. */

PNG_INTERNAL_FUNCTION(void, png_target_free_data,
   (png_struct *),
   PNG_EMPTY);
   /* Free any data allocated in the png_struct::target_data.
    */

PNG_INTERNAL_FUNCTION(void, png_target_init_filter_functions,
   (png_struct *png_ptr, unsigned int bpp),
   PNG_EMPTY);
   /* The filter function initializer that selects the specific hardware
    * implementation.  Called once before the first row needs to be defiltered.
    */

/* Handlers for specific transforms (currently only 'expand_palette').  These
 * are implemented in pngsimd.c to call the actual SIMD implementation if
 * required.
 *
 * The handlers return "false" if nothing was done and the C code will then be
 * called.  The implementations must do everything or nothing.
 */
PNG_INTERNAL_FUNCTION(int, png_target_do_expand_palette,
   (png_struct *, png_row_info *),
   PNG_EMPTY);
   /* Expand the palette and return true or do nothing and return false. */
#endif /* TARGET_CODE */

/* Choose the best filter to use and filter the row data */
PNG_INTERNAL_FUNCTION(void, png_write_find_filter,
   (png_struct *png_ptr, png_row_info *row_info),
   PNG_EMPTY);

#ifdef PNG_SEQUENTIAL_READ_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_read_IDAT_data,
   (png_struct *png_ptr, png_byte *output, png_alloc_size_t avail_out),
   PNG_EMPTY);
   /* Read 'avail_out' bytes of data from the IDAT stream.  If the output buffer
    * is NULL the function checks, instead, for the end of the stream.  In this
    * case a benign error will be issued if the stream end is not found or if
    * extra data has to be consumed.
    */
PNG_INTERNAL_FUNCTION(void, png_read_finish_IDAT,
   (png_struct *png_ptr),
   PNG_EMPTY);
   /* This cleans up when the IDAT LZ stream does not end when the last image
    * byte is read; there is still some pending input.
    */

PNG_INTERNAL_FUNCTION(void, png_read_finish_row,
   (png_struct *png_ptr),
   PNG_EMPTY);
   /* Finish a row while reading, dealing with interlacing passes, etc. */
#endif /* SEQUENTIAL_READ */

/* Initialize the row buffers, etc. */
PNG_INTERNAL_FUNCTION(void, png_read_start_row,
   (png_struct *png_ptr),
   PNG_EMPTY);

PNG_INTERNAL_FUNCTION(int, png_zlib_inflate,
   (png_struct *png_ptr, int flush),
   PNG_EMPTY);

#ifdef PNG_READ_TRANSFORMS_SUPPORTED
/* Optional call to update the users info structure */
PNG_INTERNAL_FUNCTION(void, png_read_transform_info,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
#endif

/* Shared transform functions, defined in pngtran.c */
#if defined(PNG_WRITE_FILLER_SUPPORTED) || \
    defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
PNG_INTERNAL_FUNCTION(void, png_do_strip_channel,
   (png_row_info *row_info, png_byte *row, int at_start),
   PNG_EMPTY);
#endif

#ifdef PNG_16BIT_SUPPORTED
#if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
PNG_INTERNAL_FUNCTION(void, png_do_swap,
   (png_row_info *row_info, png_byte *row),
   PNG_EMPTY);
#endif
#endif

#if defined(PNG_READ_PACKSWAP_SUPPORTED) || \
    defined(PNG_WRITE_PACKSWAP_SUPPORTED)
PNG_INTERNAL_FUNCTION(void, png_do_packswap,
   (png_row_info *row_info, png_byte *row),
   PNG_EMPTY);
#endif

#if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
PNG_INTERNAL_FUNCTION(void, png_do_invert,
   (png_row_info *row_info, png_byte *row),
   PNG_EMPTY);
#endif

#if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
PNG_INTERNAL_FUNCTION(void, png_do_bgr,
   (png_row_info *row_info, png_byte *row),
   PNG_EMPTY);
#endif

/* The following decodes the appropriate chunks, and does error correction,
 * then calls the appropriate callback for the chunk if it is valid.
 */
typedef enum
{
   /* Result of a call to png_handle_chunk made to handle the current chunk
    * png_struct::chunk_name on read.  Always informational, either the stream
    * is read for the next chunk or the routine will call png_error.
    *
    * NOTE: order is important internally.  handled_saved and above are regarded
    * as handling the chunk.
    */
   handled_error = 0,  /* bad crc or known and bad format or too long */
   handled_discarded,  /* not saved in the unknown chunk list */
   handled_saved,      /* saved in the unknown chunk list */
   handled_ok          /* known, supported and handled without error */
} png_handle_result_code;

PNG_INTERNAL_FUNCTION(png_handle_result_code, png_handle_unknown,
   (png_struct *png_ptr, png_info *info_ptr, png_uint_32 length, int keep),
   PNG_EMPTY);
   /* This is the function that gets called for unknown chunks.  The 'keep'
    * argument is either non-zero for a known chunk that has been set to be
    * handled as unknown or zero for an unknown chunk.  By default the function
    * just skips the chunk or errors out if it is critical.
    */

PNG_INTERNAL_FUNCTION(png_handle_result_code, png_handle_chunk,
   (png_struct *png_ptr, png_info *info_ptr, png_uint_32 length),
   PNG_EMPTY);
   /* This handles the current chunk png_ptr->chunk_name with unread
    * data[length] and returns one of the above result codes.
    */

#if defined(PNG_READ_UNKNOWN_CHUNKS_SUPPORTED) ||\
    defined(PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
PNG_INTERNAL_FUNCTION(int, png_chunk_unknown_handling,
   (const png_struct *png_ptr, png_uint_32 chunk_name),
   PNG_EMPTY);
   /* Exactly as the API png_handle_as_unknown() except that the argument is a
    * 32-bit chunk name, not a string.
    */
#endif /* READ_UNKNOWN_CHUNKS || HANDLE_AS_UNKNOWN */

/* Handle the transformations for reading and writing */
#ifdef PNG_READ_TRANSFORMS_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_do_read_transformations,
   (png_struct *png_ptr, png_row_info *row_info),
   PNG_EMPTY);
#endif
#ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_do_write_transformations,
   (png_struct *png_ptr, png_row_info *row_info),
   PNG_EMPTY);
#endif

#ifdef PNG_READ_TRANSFORMS_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_init_read_transformations,
   (png_struct *png_ptr),
   PNG_EMPTY);
#endif

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_push_read_chunk,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_read_sig,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_check_crc,
   (png_struct *png_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_save_buffer,
   (png_struct *png_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_restore_buffer,
   (png_struct *png_ptr, png_byte *buffer, size_t buffer_length),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_read_IDAT,
   (png_struct *png_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_process_IDAT_data,
   (png_struct *png_ptr, png_byte *buffer, size_t buffer_length),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_process_row,
   (png_struct *png_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_have_info,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_have_end,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_have_row,
   (png_struct *png_ptr, png_byte *row),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_push_read_end,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_process_some_data,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_read_push_finish_row,
   (png_struct *png_ptr),
   PNG_EMPTY);
#endif /* PROGRESSIVE_READ */

#ifdef PNG_APNG_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_ensure_fcTL_is_valid,
   (png_struct *png_ptr,
    png_uint_32 width, png_uint_32 height,
    png_uint_32 x_offset, png_uint_32 y_offset,
    png_uint_16 delay_num, png_uint_16 delay_den,
    png_byte dispose_op, png_byte blend_op),
   PNG_EMPTY);

#ifdef PNG_READ_APNG_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_handle_acTL,
   (png_struct *png_ptr, png_info *info_ptr, png_uint_32 length),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_handle_fcTL,
   (png_struct *png_ptr, png_info *info_ptr, png_uint_32 length),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_handle_fdAT,
   (png_struct *png_ptr, png_info *info_ptr, png_uint_32 length),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_have_info,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_ensure_sequence_number,
   (png_struct *png_ptr, png_uint_32 length),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_read_reset,
   (png_struct *png_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_read_reinit,
   (png_struct *png_ptr, png_info *info_ptr),
   PNG_EMPTY);
#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_progressive_read_reset,
   (png_struct *png_ptr),
   PNG_EMPTY);
#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */
#endif /* PNG_READ_APNG_SUPPORTED */

#ifdef PNG_WRITE_APNG_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_write_acTL,
   (png_struct *png_ptr, png_uint_32 num_frames, png_uint_32 num_plays),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_write_fcTL,
   (png_struct *png_ptr,
    png_uint_32 width, png_uint_32 height,
    png_uint_32 x_offset, png_uint_32 y_offset,
    png_uint_16 delay_num, png_uint_16 delay_den,
    png_byte dispose_op, png_byte blend_op),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_write_fdAT,
   (png_struct *png_ptr, const png_byte *data, png_size_t length),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_write_reset,
   (png_struct *png_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_write_reinit,
   (png_struct *png_ptr, png_info *info_ptr,
    png_uint_32 width, png_uint_32 height),
   PNG_EMPTY);
#endif /* PNG_WRITE_APNG_SUPPORTED */
#endif /* PNG_APNG_SUPPORTED */

#ifdef PNG_iCCP_SUPPORTED
/* Routines for checking parts of an ICC profile. */
#ifdef PNG_READ_iCCP_SUPPORTED
PNG_INTERNAL_FUNCTION(int, png_icc_check_length,
   (const png_struct *png_ptr,
    const char *name, png_uint_32 profile_length),
   PNG_EMPTY);
#endif /* READ_iCCP */
PNG_INTERNAL_FUNCTION(int, png_icc_check_header,
   (const png_struct *png_ptr,
    const char *name, png_uint_32 profile_length,
    const png_byte *profile /* first 132 bytes only */, int color_type),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(int, png_icc_check_tag_table,
   (const png_struct *png_ptr,
    const char *name, png_uint_32 profile_length,
    const png_byte *profile /* header plus whole tag table */),
   PNG_EMPTY);
#endif /* iCCP */

#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_set_rgb_coefficients,
   (png_struct *png_ptr),
   PNG_EMPTY);
   /* Set the rgb_to_gray coefficients from the cHRM Y values (if unset) */
#endif /* READ_RGB_TO_GRAY */

/* Added at libpng version 1.4.0 */
PNG_INTERNAL_FUNCTION(void, png_check_IHDR,
   (const png_struct *png_ptr,
    png_uint_32 width, png_uint_32 height, int bit_depth, int color_type,
    int interlace_type, int compression_type, int filter_type),
   PNG_EMPTY);

/* Added at libpng version 1.5.10 */
#if defined(PNG_READ_CHECK_FOR_INVALID_INDEX_SUPPORTED) || \
    defined(PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED)
PNG_INTERNAL_FUNCTION(void, png_do_check_palette_indexes,
   (png_struct *png_ptr, png_row_info *row_info),
   PNG_EMPTY);
#endif

#if defined(PNG_FLOATING_POINT_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
PNG_INTERNAL_FUNCTION(void, png_fixed_error,
   (const png_struct *png_ptr, const char *name),
   PNG_NORETURN);
#endif

/* Puts 'string' into 'buffer' at buffer[pos], taking care never to overwrite
 * the end.  Always leaves the buffer nul terminated.  Never errors out (and
 * there is no error code.)
 */
PNG_INTERNAL_FUNCTION(size_t, png_safecat,
   (char *buffer, size_t bufsize, size_t pos, const char *string),
   PNG_EMPTY);

/* Various internal functions to handle formatted warning messages, currently
 * only implemented for warnings.
 */
#if defined(PNG_WARNINGS_SUPPORTED) || defined(PNG_TIME_RFC1123_SUPPORTED)
/* Utility to dump an unsigned value into a buffer, given a start pointer and
 * an end pointer (which should point just *beyond* the end of the buffer!).
 * Returns the pointer to the start of the formatted string.  This utility only
 * does unsigned values.
 */
PNG_INTERNAL_FUNCTION(char *, png_format_number,
   (const char *start, char *end, int format, png_alloc_size_t number),
   PNG_EMPTY);

/* Convenience macro that takes an array: */
#define PNG_FORMAT_NUMBER(buffer,format,number) \
   png_format_number(buffer, buffer + (sizeof buffer), format, number)

/* Suggested size for a number buffer (enough for 64 bits and a sign!) */
#define PNG_NUMBER_BUFFER_SIZE 24

/* These are the integer formats currently supported, the name is formed from
 * the standard printf(3) format string.
 */
#define PNG_NUMBER_FORMAT_u     1 /* chose unsigned API! */
#define PNG_NUMBER_FORMAT_02u   2
#define PNG_NUMBER_FORMAT_d     1 /* chose signed API! */
#define PNG_NUMBER_FORMAT_02d   2
#define PNG_NUMBER_FORMAT_x     3
#define PNG_NUMBER_FORMAT_02x   4
#define PNG_NUMBER_FORMAT_fixed 5 /* choose the signed API */
#endif

#ifdef PNG_WARNINGS_SUPPORTED
/* New defines and members adding in libpng-1.5.4 */
#  define PNG_WARNING_PARAMETER_SIZE 32
#  define PNG_WARNING_PARAMETER_COUNT 8 /* Maximum 9; see pngerror.c */

/* An l-value of this type has to be passed to the APIs below to cache the
 * values of the parameters to a formatted warning message.
 */
typedef char png_warning_parameters[PNG_WARNING_PARAMETER_COUNT][
   PNG_WARNING_PARAMETER_SIZE];

PNG_INTERNAL_FUNCTION(void, png_warning_parameter,
   (png_warning_parameters p, int number, const char *string),
   PNG_EMPTY);
   /* Parameters are limited in size to PNG_WARNING_PARAMETER_SIZE characters,
    * including the trailing '\0'.
    */
PNG_INTERNAL_FUNCTION(void, png_warning_parameter_unsigned,
   (png_warning_parameters p, int number, int format, png_alloc_size_t value),
   PNG_EMPTY);
   /* Use png_alloc_size_t because it is an unsigned type as big as any we
    * need to output.  Use the following for a signed value.
    */
PNG_INTERNAL_FUNCTION(void, png_warning_parameter_signed,
   (png_warning_parameters p, int number, int format, png_int_32 value),
   PNG_EMPTY);

PNG_INTERNAL_FUNCTION(void, png_formatted_warning,
   (const png_struct *png_ptr,
    png_warning_parameters p, const char *message),
   PNG_EMPTY);
   /* 'message' follows the X/Open approach of using @1, @2 to insert
    * parameters previously supplied using the above functions.  Errors in
    * specifying the parameters will simply result in garbage substitutions.
    */
#endif

#ifdef PNG_BENIGN_ERRORS_SUPPORTED
/* Application errors (new in 1.6); use these functions (declared below) for
 * errors in the parameters or order of API function calls on read.  The
 * 'warning' should be used for an error that can be handled completely; the
 * 'error' for one which can be handled safely but which may lose application
 * information or settings.
 *
 * By default these both result in a png_error call prior to release, while in a
 * released version the 'warning' is just a warning.  However if the application
 * explicitly disables benign errors (explicitly permitting the code to lose
 * information) they both turn into warnings.
 *
 * If benign errors aren't supported they end up as the corresponding base call
 * (png_warning or png_error.)
 */
PNG_INTERNAL_FUNCTION(void, png_app_warning,
   (const png_struct *png_ptr, const char *message),
   PNG_EMPTY);
   /* The application provided invalid parameters to an API function or called
    * an API function at the wrong time, libpng can completely recover.
    */

PNG_INTERNAL_FUNCTION(void, png_app_error,
   (const png_struct *png_ptr, const char *message),
   PNG_EMPTY);
   /* As above but libpng will ignore the call, or attempt some other partial
    * recovery from the error.
    */
#else
#  define png_app_warning(pp,s) png_warning(pp,s)
#  define png_app_error(pp,s) png_error(pp,s)
#endif

PNG_INTERNAL_FUNCTION(void, png_chunk_report,
   (const png_struct *png_ptr, const char *message, int error),
   PNG_EMPTY);
   /* Report a recoverable issue in chunk data.  On read this is used to report
    * a problem found while reading a particular chunk and the
    * png_chunk_benign_error or png_chunk_warning function is used as
    * appropriate.  On write this is used to report an error that comes from
    * data set via an application call to a png_set_ API and png_app_error or
    * png_app_warning is used as appropriate.
    *
    * The 'error' parameter must have one of the following values:
    */
#define PNG_CHUNK_WARNING     0 /* never an error */
#define PNG_CHUNK_WRITE_ERROR 1 /* an error only on write */
#define PNG_CHUNK_ERROR       2 /* always an error */

/* ASCII to FP interfaces, currently only implemented if sCAL
 * support is required.
 */
#if defined(PNG_sCAL_SUPPORTED)
/* MAX_DIGITS is actually the maximum number of characters in an sCAL
 * width or height, derived from the precision (number of significant
 * digits - a build time settable option) and assumptions about the
 * maximum ridiculous exponent.
 */
#define PNG_sCAL_MAX_DIGITS (PNG_sCAL_PRECISION+1/*.*/+1/*E*/+10/*exponent*/)

#ifdef PNG_FLOATING_POINT_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_ascii_from_fp,
   (const png_struct *png_ptr,
    char *ascii, size_t size, double fp, unsigned int precision),
   PNG_EMPTY);
#endif /* FLOATING_POINT */

#ifdef PNG_FIXED_POINT_SUPPORTED
PNG_INTERNAL_FUNCTION(void, png_ascii_from_fixed,
   (const png_struct *png_ptr,
    char *ascii, size_t size, png_fixed_point fp),
   PNG_EMPTY);
#endif /* FIXED_POINT */
#endif /* sCAL */

#if defined(PNG_sCAL_SUPPORTED) || defined(PNG_pCAL_SUPPORTED)
/* An internal API to validate the format of a floating point number.
 * The result is the index of the next character.  If the number is
 * not valid it will be the index of a character in the supposed number.
 *
 * The format of a number is defined in the PNG extensions specification
 * and this API is strictly conformant to that spec, not anyone else's!
 *
 * The format as a regular expression is:
 *
 * [+-]?[0-9]+.?([Ee][+-]?[0-9]+)?
 *
 * or:
 *
 * [+-]?.[0-9]+(.[0-9]+)?([Ee][+-]?[0-9]+)?
 *
 * The complexity is that either integer or fraction must be present and the
 * fraction is permitted to have no digits only if the integer is present.
 *
 * NOTE: The dangling E problem.
 *   There is a PNG valid floating point number in the following:
 *
 *       PNG floating point numbers are not greedy.
 *
 *   Working this out requires *TWO* character lookahead (because of the
 *   sign), the parser does not do this - it will fail at the 'r' - this
 *   doesn't matter for PNG sCAL chunk values, but it requires more care
 *   if the value were ever to be embedded in something more complex.  Use
 *   ANSI-C strtod if you need the lookahead.
 */
/* State table for the parser. */
#define PNG_FP_INTEGER    0  /* before or in integer */
#define PNG_FP_FRACTION   1  /* before or in fraction */
#define PNG_FP_EXPONENT   2  /* before or in exponent */
#define PNG_FP_STATE      3  /* mask for the above */
#define PNG_FP_SAW_SIGN   4  /* Saw +/- in current state */
#define PNG_FP_SAW_DIGIT  8  /* Saw a digit in current state */
#define PNG_FP_SAW_DOT   16  /* Saw a dot in current state */
#define PNG_FP_SAW_E     32  /* Saw an E (or e) in current state */
#define PNG_FP_SAW_ANY   60  /* Saw any of the above 4 */

/* These three values don't affect the parser.  They are set but not used.
 */
#define PNG_FP_WAS_VALID 64  /* Preceding substring is a valid fp number */
#define PNG_FP_NEGATIVE 128  /* A negative number, including "-0" */
#define PNG_FP_NONZERO  256  /* A non-zero value */
#define PNG_FP_STICKY   448  /* The above three flags */

/* This is available for the caller to store in 'state' if required.  Do not
 * call the parser after setting it (the parser sometimes clears it.)
 */
#define PNG_FP_INVALID  512  /* Available for callers as a distinct value */

/* Result codes for the parser (boolean - true means ok, false means
 * not ok yet.)
 */
#define PNG_FP_MAYBE      0  /* The number may be valid in the future */
#define PNG_FP_OK         1  /* The number is valid */

/* Tests on the sticky non-zero and negative flags.  To pass these checks
 * the state must also indicate that the whole number is valid - this is
 * achieved by testing PNG_FP_SAW_DIGIT (see the implementation for why this
 * is equivalent to PNG_FP_OK above.)
 */
#define PNG_FP_NZ_MASK (PNG_FP_SAW_DIGIT | PNG_FP_NEGATIVE | PNG_FP_NONZERO)
   /* NZ_MASK: the string is valid and a non-zero negative value */
#define PNG_FP_Z_MASK (PNG_FP_SAW_DIGIT | PNG_FP_NONZERO)
   /* Z MASK: the string is valid and a non-zero value. */
   /* PNG_FP_SAW_DIGIT: the string is valid. */
#define PNG_FP_IS_ZERO(state) (((state) & PNG_FP_Z_MASK) == PNG_FP_SAW_DIGIT)
#define PNG_FP_IS_POSITIVE(state) (((state) & PNG_FP_NZ_MASK) == PNG_FP_Z_MASK)
#define PNG_FP_IS_NEGATIVE(state) (((state) & PNG_FP_NZ_MASK) == PNG_FP_NZ_MASK)

/* The actual parser.  This can be called repeatedly. It updates
 * the index into the string and the state variable (which must
 * be initialized to 0).  It returns a result code, as above.  There
 * is no point calling the parser any more if it fails to advance to
 * the end of the string - it is stuck on an invalid character (or
 * terminated by '\0').
 *
 * Note that the pointer will consume an E or even an E+ and then leave
 * a 'maybe' state even though a preceding integer.fraction is valid.
 * The PNG_FP_WAS_VALID flag indicates that a preceding substring was
 * a valid number.  It's possible to recover from this by calling
 * the parser again (from the start, with state 0) but with a string
 * that omits the last character (i.e. set the size to the index of
 * the problem character.)  This has not been tested within libpng.
 */
PNG_INTERNAL_FUNCTION(int, png_check_fp_number,
   (const char *string, size_t size, int *statep, size_t *whereami),
   PNG_EMPTY);

/* This is the same but it checks a complete string and returns true
 * only if it just contains a floating point number.  As of 1.5.4 this
 * function also returns the state at the end of parsing the number if
 * it was valid (otherwise it returns 0.)  This can be used for testing
 * for negative or zero values using the sticky flag.
 */
PNG_INTERNAL_FUNCTION(int, png_check_fp_string,
   (const char *string, size_t size),
   PNG_EMPTY);
#endif /* pCAL || sCAL */

#if defined(PNG_READ_GAMMA_SUPPORTED) ||\
    defined(PNG_COLORSPACE_SUPPORTED) ||\
    defined(PNG_INCH_CONVERSIONS_SUPPORTED) ||\
    defined(PNG_READ_pHYs_SUPPORTED)
/* Added at libpng version 1.5.0 */
/* This is a utility to provide a*times/div (rounded) and indicate
 * if there is an overflow.  The result is a boolean - false (0)
 * for overflow, true (1) if no overflow, in which case *res
 * holds the result.
 */
PNG_INTERNAL_FUNCTION(int, png_muldiv,
   (png_fixed_point *res, png_fixed_point a,
    png_int_32 multiplied_by, png_int_32 divided_by),
   PNG_EMPTY);

/* Calculate a reciprocal - used for gamma values.  This returns
 * 0 if the argument is 0 in order to maintain an undefined value;
 * there are no warnings.
 */
PNG_INTERNAL_FUNCTION(png_fixed_point, png_reciprocal,
   (png_fixed_point a),
   PNG_EMPTY);
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED
/* The same but gives a reciprocal of the product of two fixed point
 * values.  Accuracy is suitable for gamma calculations but this is
 * not exact - use png_muldiv for that.  Only required at present on read.
 */
PNG_INTERNAL_FUNCTION(png_fixed_point, png_reciprocal2,
   (png_fixed_point a, png_fixed_point b),
   PNG_EMPTY);

/* Return true if the gamma value is significantly different from 1.0 */
PNG_INTERNAL_FUNCTION(int, png_gamma_significant,
   (png_fixed_point gamma_value),
   PNG_EMPTY);

/* PNGv3: 'resolve' the file gamma according to the new PNGv3 rules for colour
 * space information.
 *
 * NOTE: this uses precisely those chunks that libpng supports.  For example it
 * doesn't use iCCP and it can only use cICP for known and manageable
 * transforms.  For this reason a gamma specified by png_set_gamma always takes
 * precedence.
 */
PNG_INTERNAL_FUNCTION(png_fixed_point, png_resolve_file_gamma,
   (const png_struct *png_ptr),
   PNG_EMPTY);

/* Internal fixed point gamma correction.  These APIs are called as
 * required to convert single values - they don't need to be fast,
 * they are not used when processing image pixel values.
 *
 * While the input is an 'unsigned' value it must actually be the
 * correct bit value - 0..255 or 0..65535 as required.
 */
PNG_INTERNAL_FUNCTION(png_uint_16, png_gamma_correct,
   (png_struct *png_ptr, unsigned int value, png_fixed_point gamma_value),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(png_uint_16, png_gamma_16bit_correct,
   (unsigned int value, png_fixed_point gamma_value),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(png_byte, png_gamma_8bit_correct,
   (unsigned int value, png_fixed_point gamma_value),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_destroy_gamma_table,
   (png_struct *png_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void, png_build_gamma_table,
   (png_struct *png_ptr, int bit_depth),
   PNG_EMPTY);
#endif /* READ_GAMMA */

#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
/* Set the RGB coefficients if not already set by png_set_rgb_to_gray */
PNG_INTERNAL_FUNCTION(void, png_set_rgb_coefficients,
   (png_struct *png_ptr),
   PNG_EMPTY);
#endif

#if defined(PNG_cHRM_SUPPORTED) || defined(PNG_READ_RGB_TO_GRAY_SUPPORTED)
PNG_INTERNAL_FUNCTION(int, png_XYZ_from_xy,
   (png_XYZ *XYZ, const png_xy *xy),
   PNG_EMPTY);
#endif /* cHRM || READ_RGB_TO_GRAY */

#ifdef PNG_COLORSPACE_SUPPORTED
PNG_INTERNAL_FUNCTION(int, png_xy_from_XYZ,
   (png_xy *xy, const png_XYZ *XYZ),
   PNG_EMPTY);
#endif

/* SIMPLIFIED READ/WRITE SUPPORT */
#if defined(PNG_SIMPLIFIED_READ_SUPPORTED) ||\
    defined(PNG_SIMPLIFIED_WRITE_SUPPORTED)

/* The internal structure that png_image::opaque points to. */
struct png_control_def
{
   png_struct *png_ptr;
   png_info   *info_ptr;
   void       *error_buf;           /* Currently this can only be jmp_buf */

   const png_byte *memory;          /* Memory buffer */
   size_t          size;            /* Size of the memory buffer */

   unsigned int for_write       :1; /* Otherwise it is a read structure */
   unsigned int owned_file      :1; /* We own the file in io_ptr */
};

/* Return the pointer to the jmp_buf from a png_control: necessary because C
 * does not reveal the type of the elements of jmp_buf.
 */
#ifdef __cplusplus
#  define png_control_jmp_buf(pc) (((jmp_buf*)((pc)->error_buf))[0])
#else
#  define png_control_jmp_buf(pc) ((pc)->error_buf)
#endif

/* Utility to safely execute a piece of libpng code catching and logging any
 * errors that might occur.  Returns true on success, false on failure (either
 * of the function or as a result of a png_error.)
 */
PNG_INTERNAL_CALLBACK(void, png_safe_error,
   (png_struct *png_ptr, const char *error_message),
   PNG_NORETURN);

#ifdef PNG_WARNINGS_SUPPORTED
PNG_INTERNAL_CALLBACK(void, png_safe_warning,
   (png_struct *png_ptr, const char *warning_message),
   PNG_EMPTY);
#else
#  define png_safe_warning 0/*dummy argument*/
#endif

PNG_INTERNAL_FUNCTION(int, png_safe_execute,
   (png_image *image, int (*function)(void *), void *arg),
   PNG_EMPTY);

/* Utility to log an error; this also cleans up the png_image; the function
 * always returns 0 (false).
 */
PNG_INTERNAL_FUNCTION(int, png_image_error,
   (png_image *image, const char *error_message),
   PNG_EMPTY);

#ifndef PNG_SIMPLIFIED_READ_SUPPORTED
/* png_image_free is used by the write code but not exported */
PNG_INTERNAL_FUNCTION(void, png_image_free,
   (png_image *image),
   PNG_EMPTY);
#endif /* !SIMPLIFIED_READ */

#endif /* SIMPLIFIED READ/WRITE */

PNG_INTERNAL_FUNCTION(png_uint_32, png_check_keyword,
   (png_struct *png_ptr, const char *key, png_byte *new_key),
   PNG_EMPTY);

/* Maintainer: Put new private prototypes here ^ */

#include "pngdebug.h"

#ifdef __cplusplus
}
#endif

#endif /* PNG_VERSION_INFO_ONLY */