jmemsys.h - third_party/libjpeg-turbo - Git at Google

 /*
  * jmemsys.h
  *
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1992-1997, Thomas G. Lane.
  * It was modified by The libjpeg-turbo Project to include only code and
  * information relevant to libjpeg-turbo.
  * For conditions of distribution and use, see the accompanying README.ijg
  * file.
  *
  * This include file defines the interface between the system-independent
  * and system-dependent portions of the JPEG memory manager.  No other
  * modules need include it.  (The system-independent portion is jmemmgr.c;
  * there are several different versions of the system-dependent portion.)
  *
  * This file works as-is for the system-dependent memory managers supplied
  * in the IJG distribution.  You may need to modify it if you write a
  * custom memory manager.  If system-dependent changes are needed in
  * this file, the best method is to #ifdef them based on a configuration
  * symbol supplied in jconfig.h.
  */


 /*
  * These two functions are used to allocate and release small chunks of
  * memory.  (Typically the total amount requested through jpeg_get_small is
  * no more than 20K or so; this will be requested in chunks of a few K each.)
  * Behavior should be the same as for the standard library functions malloc
  * and free; in particular, jpeg_get_small must return NULL on failure.
  * On most systems, these ARE malloc and free.  jpeg_free_small is passed the
  * size of the object being freed, just in case it's needed.
  */

 EXTERN(void *) jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject);
 EXTERN(void) jpeg_free_small (j_common_ptr cinfo, void * object,
                               size_t sizeofobject);

 /*
  * These two functions are used to allocate and release large chunks of
  * memory (up to the total free space designated by jpeg_mem_available).
  * These are identical to the jpeg_get/free_small routines; but we keep them
  * separate anyway, in case a different allocation strategy is desirable for
  * large chunks.
  */

 EXTERN(void *) jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject);
 EXTERN(void) jpeg_free_large (j_common_ptr cinfo, void * object,
                               size_t sizeofobject);

 /*
  * The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
  * be requested in a single call to jpeg_get_large (and jpeg_get_small for that
  * matter, but that case should never come into play).  This macro was needed
  * to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
  * On machines with flat address spaces, any large constant may be used.
  *
  * NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
  * size_t and will be a multiple of sizeof(align_type).
  */

 #ifndef MAX_ALLOC_CHUNK         /* may be overridden in jconfig.h */
 #define MAX_ALLOC_CHUNK  1000000000L
 #endif

 /*
  * This routine computes the total space still available for allocation by
  * jpeg_get_large.  If more space than this is needed, backing store will be
  * used.  NOTE: any memory already allocated must not be counted.
  *
  * There is a minimum space requirement, corresponding to the minimum
  * feasible buffer sizes; jmemmgr.c will request that much space even if
  * jpeg_mem_available returns zero.  The maximum space needed, enough to hold
  * all working storage in memory, is also passed in case it is useful.
  * Finally, the total space already allocated is passed.  If no better
  * method is available, cinfo->mem->max_memory_to_use - already_allocated
  * is often a suitable calculation.
  *
  * It is OK for jpeg_mem_available to underestimate the space available
  * (that'll just lead to more backing-store access than is really necessary).
  * However, an overestimate will lead to failure.  Hence it's wise to subtract
  * a slop factor from the true available space.  5% should be enough.
  *
  * On machines with lots of virtual memory, any large constant may be returned.
  * Conversely, zero may be returned to always use the minimum amount of memory.
  */

 EXTERN(size_t) jpeg_mem_available (j_common_ptr cinfo, size_t min_bytes_needed,
                                    size_t max_bytes_needed,
                                    size_t already_allocated);


 /*
  * This structure holds whatever state is needed to access a single
  * backing-store object.  The read/write/close method pointers are called
  * by jmemmgr.c to manipulate the backing-store object; all other fields
  * are private to the system-dependent backing store routines.
  */

 #define TEMP_NAME_LENGTH   64   /* max length of a temporary file's name */


 #ifdef USE_MSDOS_MEMMGR         /* DOS-specific junk */

 typedef unsigned short XMSH;    /* type of extended-memory handles */
 typedef unsigned short EMSH;    /* type of expanded-memory handles */

 typedef union {
   short file_handle;            /* DOS file handle if it's a temp file */
   XMSH xms_handle;              /* handle if it's a chunk of XMS */
   EMSH ems_handle;              /* handle if it's a chunk of EMS */
 } handle_union;

 #endif /* USE_MSDOS_MEMMGR */

 #ifdef USE_MAC_MEMMGR           /* Mac-specific junk */
 #include <Files.h>
 #endif /* USE_MAC_MEMMGR */


 typedef struct backing_store_struct * backing_store_ptr;

 typedef struct backing_store_struct {
   /* Methods for reading/writing/closing this backing-store object */
   void (*read_backing_store) (j_common_ptr cinfo, backing_store_ptr info,
                               void * buffer_address, long file_offset,
                               long byte_count);
   void (*write_backing_store) (j_common_ptr cinfo, backing_store_ptr info,
                                void * buffer_address, long file_offset,
                                long byte_count);
   void (*close_backing_store) (j_common_ptr cinfo, backing_store_ptr info);

   /* Private fields for system-dependent backing-store management */
 #ifdef USE_MSDOS_MEMMGR
   /* For the MS-DOS manager (jmemdos.c), we need: */
   handle_union handle;          /* reference to backing-store storage object */
   char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
 #else
 #ifdef USE_MAC_MEMMGR
   /* For the Mac manager (jmemmac.c), we need: */
   short temp_file;              /* file reference number to temp file */
   FSSpec tempSpec;              /* the FSSpec for the temp file */
   char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
 #else
   /* For a typical implementation with temp files, we need: */
   FILE * temp_file;             /* stdio reference to temp file */
   char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
 #endif
 #endif
 } backing_store_info;


 /*
  * Initial opening of a backing-store object.  This must fill in the
  * read/write/close pointers in the object.  The read/write routines
  * may take an error exit if the specified maximum file size is exceeded.
  * (If jpeg_mem_available always returns a large value, this routine can
  * just take an error exit.)
  */

 EXTERN(void) jpeg_open_backing_store (j_common_ptr cinfo,
                                       backing_store_ptr info,
                                       long total_bytes_needed);


 /*
  * These routines take care of any system-dependent initialization and
  * cleanup required.  jpeg_mem_init will be called before anything is
  * allocated (and, therefore, nothing in cinfo is of use except the error
  * manager pointer).  It should return a suitable default value for
  * max_memory_to_use; this may subsequently be overridden by the surrounding
  * application.  (Note that max_memory_to_use is only important if
  * jpeg_mem_available chooses to consult it ... no one else will.)
  * jpeg_mem_term may assume that all requested memory has been freed and that
  * all opened backing-store objects have been closed.
  */

 EXTERN(long) jpeg_mem_init (j_common_ptr cinfo);
 EXTERN(void) jpeg_mem_term (j_common_ptr cinfo);
	/*
	* jmemsys.h
	*
	* This file was part of the Independent JPEG Group's software:
	* Copyright (C) 1992-1997, Thomas G. Lane.
	* It was modified by The libjpeg-turbo Project to include only code and
	* information relevant to libjpeg-turbo.
	* For conditions of distribution and use, see the accompanying README.ijg
	* file.
	*
	* This include file defines the interface between the system-independent
	* and system-dependent portions of the JPEG memory manager. No other
	* modules need include it. (The system-independent portion is jmemmgr.c;
	* there are several different versions of the system-dependent portion.)
	*
	* This file works as-is for the system-dependent memory managers supplied
	* in the IJG distribution. You may need to modify it if you write a
	* custom memory manager. If system-dependent changes are needed in
	* this file, the best method is to #ifdef them based on a configuration
	* symbol supplied in jconfig.h.
	*/


	/*
	* These two functions are used to allocate and release small chunks of
	* memory. (Typically the total amount requested through jpeg_get_small is
	* no more than 20K or so; this will be requested in chunks of a few K each.)
	* Behavior should be the same as for the standard library functions malloc
	* and free; in particular, jpeg_get_small must return NULL on failure.
	* On most systems, these ARE malloc and free. jpeg_free_small is passed the
	* size of the object being freed, just in case it's needed.
	*/

	EXTERN(void *) jpeg_get_small (j_common_ptr cinfo, size_t sizeofobject);
	EXTERN(void) jpeg_free_small (j_common_ptr cinfo, void * object,
	size_t sizeofobject);

	/*
	* These two functions are used to allocate and release large chunks of
	* memory (up to the total free space designated by jpeg_mem_available).
	* These are identical to the jpeg_get/free_small routines; but we keep them
	* separate anyway, in case a different allocation strategy is desirable for
	* large chunks.
	*/

	EXTERN(void *) jpeg_get_large (j_common_ptr cinfo, size_t sizeofobject);
	EXTERN(void) jpeg_free_large (j_common_ptr cinfo, void * object,
	size_t sizeofobject);

	/*
	* The macro MAX_ALLOC_CHUNK designates the maximum number of bytes that may
	* be requested in a single call to jpeg_get_large (and jpeg_get_small for that
	* matter, but that case should never come into play). This macro was needed
	* to model the 64Kb-segment-size limit of far addressing on 80x86 machines.
	* On machines with flat address spaces, any large constant may be used.
	*
	* NB: jmemmgr.c expects that MAX_ALLOC_CHUNK will be representable as type
	* size_t and will be a multiple of sizeof(align_type).
	*/

	#ifndef MAX_ALLOC_CHUNK /* may be overridden in jconfig.h */
	#define MAX_ALLOC_CHUNK 1000000000L
	#endif

	/*
	* This routine computes the total space still available for allocation by
	* jpeg_get_large. If more space than this is needed, backing store will be
	* used. NOTE: any memory already allocated must not be counted.
	*
	* There is a minimum space requirement, corresponding to the minimum
	* feasible buffer sizes; jmemmgr.c will request that much space even if
	* jpeg_mem_available returns zero. The maximum space needed, enough to hold
	* all working storage in memory, is also passed in case it is useful.
	* Finally, the total space already allocated is passed. If no better
	* method is available, cinfo->mem->max_memory_to_use - already_allocated
	* is often a suitable calculation.
	*
	* It is OK for jpeg_mem_available to underestimate the space available
	* (that'll just lead to more backing-store access than is really necessary).
	* However, an overestimate will lead to failure. Hence it's wise to subtract
	* a slop factor from the true available space. 5% should be enough.
	*
	* On machines with lots of virtual memory, any large constant may be returned.
	* Conversely, zero may be returned to always use the minimum amount of memory.
	*/

	EXTERN(size_t) jpeg_mem_available (j_common_ptr cinfo, size_t min_bytes_needed,
	size_t max_bytes_needed,
	size_t already_allocated);


	/*
	* This structure holds whatever state is needed to access a single
	* backing-store object. The read/write/close method pointers are called
	* by jmemmgr.c to manipulate the backing-store object; all other fields
	* are private to the system-dependent backing store routines.
	*/

	#define TEMP_NAME_LENGTH 64 /* max length of a temporary file's name */


	#ifdef USE_MSDOS_MEMMGR /* DOS-specific junk */

	typedef unsigned short XMSH; /* type of extended-memory handles */
	typedef unsigned short EMSH; /* type of expanded-memory handles */

	typedef union {
	short file_handle; /* DOS file handle if it's a temp file */
	XMSH xms_handle; /* handle if it's a chunk of XMS */
	EMSH ems_handle; /* handle if it's a chunk of EMS */
	} handle_union;

	#endif /* USE_MSDOS_MEMMGR */

	#ifdef USE_MAC_MEMMGR /* Mac-specific junk */
	#include <Files.h>
	#endif /* USE_MAC_MEMMGR */


	typedef struct backing_store_struct * backing_store_ptr;

	typedef struct backing_store_struct {
	/* Methods for reading/writing/closing this backing-store object */
	void (*read_backing_store) (j_common_ptr cinfo, backing_store_ptr info,
	void * buffer_address, long file_offset,
	long byte_count);
	void (*write_backing_store) (j_common_ptr cinfo, backing_store_ptr info,
	void * buffer_address, long file_offset,
	long byte_count);
	void (*close_backing_store) (j_common_ptr cinfo, backing_store_ptr info);

	/* Private fields for system-dependent backing-store management */
	#ifdef USE_MSDOS_MEMMGR
	/* For the MS-DOS manager (jmemdos.c), we need: */
	handle_union handle; /* reference to backing-store storage object */
	char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
	#else
	#ifdef USE_MAC_MEMMGR
	/* For the Mac manager (jmemmac.c), we need: */
	short temp_file; /* file reference number to temp file */
	FSSpec tempSpec; /* the FSSpec for the temp file */
	char temp_name[TEMP_NAME_LENGTH]; /* name if it's a file */
	#else
	/* For a typical implementation with temp files, we need: */
	FILE * temp_file; /* stdio reference to temp file */
	char temp_name[TEMP_NAME_LENGTH]; /* name of temp file */
	#endif
	#endif
	} backing_store_info;


	/*
	* Initial opening of a backing-store object. This must fill in the
	* read/write/close pointers in the object. The read/write routines
	* may take an error exit if the specified maximum file size is exceeded.
	* (If jpeg_mem_available always returns a large value, this routine can
	* just take an error exit.)
	*/

	EXTERN(void) jpeg_open_backing_store (j_common_ptr cinfo,
	backing_store_ptr info,
	long total_bytes_needed);


	/*
	* These routines take care of any system-dependent initialization and
	* cleanup required. jpeg_mem_init will be called before anything is
	* allocated (and, therefore, nothing in cinfo is of use except the error
	* manager pointer). It should return a suitable default value for
	* max_memory_to_use; this may subsequently be overridden by the surrounding
	* application. (Note that max_memory_to_use is only important if
	* jpeg_mem_available chooses to consult it ... no one else will.)
	* jpeg_mem_term may assume that all requested memory has been freed and that
	* all opened backing-store objects have been closed.
	*/

	EXTERN(long) jpeg_mem_init (j_common_ptr cinfo);
	EXTERN(void) jpeg_mem_term (j_common_ptr cinfo);