include/freetype/internal/ftvalid.h

/****************************************************************************
 *
 * ftvalid.h
 *
 *   FreeType validation support (specification).
 *
 * Copyright (C) 2004-2022 by
 * David Turner, Robert Wilhelm, and Werner Lemberg.
 *
 * This file is part of the FreeType project, and may only be used,
 * modified, and distributed under the terms of the FreeType project
 * license, LICENSE.TXT.  By continuing to use, modify, or distribute
 * this file you indicate that you have read the license and
 * understand and accept it fully.
 *
 */


#ifndef FTVALID_H_
#define FTVALID_H_

#include <ft2build.h>
#include FT_CONFIG_STANDARD_LIBRARY_H   /* for ft_jmpbuf */

#include "compiler-macros.h"

FT_BEGIN_HEADER


  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/
  /****                                                                 ****/
  /****                                                                 ****/
  /****                    V A L I D A T I O N                          ****/
  /****                                                                 ****/
  /****                                                                 ****/
  /*************************************************************************/
  /*************************************************************************/
  /*************************************************************************/

  /* handle to a validation object */
  typedef struct FT_ValidatorRec_ volatile*  FT_Validator;


  /**************************************************************************
   *
   * There are three distinct validation levels defined here:
   *
   * FT_VALIDATE_DEFAULT ::
   *   A table that passes this validation level can be used reliably by
   *   FreeType.  It generally means that all offsets have been checked to
   *   prevent out-of-bound reads, that array counts are correct, etc.
   *
   * FT_VALIDATE_TIGHT ::
   *   A table that passes this validation level can be used reliably and
   *   doesn't contain invalid data.  For example, a charmap table that
   *   returns invalid glyph indices will not pass, even though it can be
   *   used with FreeType in default mode (the library will simply return an
   *   error later when trying to load the glyph).
   *
   *   It also checks that fields which must be a multiple of 2, 4, or 8,
   *   don't have incorrect values, etc.
   *
   * FT_VALIDATE_PARANOID ::
   *   Only for font debugging.  Checks that a table follows the
   *   specification by 100%.  Very few fonts will be able to pass this level
   *   anyway but it can be useful for certain tools like font
   *   editors/converters.
   */
  typedef enum  FT_ValidationLevel_
  {
    FT_VALIDATE_DEFAULT = 0,
    FT_VALIDATE_TIGHT,
    FT_VALIDATE_PARANOID

  } FT_ValidationLevel;


#if defined( _MSC_VER )      /* Visual C++ (and Intel C++) */
  /* We disable the warning `structure was padded due to   */
  /* __declspec(align())' in order to compile cleanly with */
  /* the maximum level of warnings.                        */
#pragma warning( push )
#pragma warning( disable : 4324 )
#endif /* _MSC_VER */

  /* validator structure */
  typedef struct  FT_ValidatorRec_
  {
    ft_jmp_buf          jump_buffer; /* used for exception handling      */

    const FT_Byte*      base;        /* address of table in memory       */
    const FT_Byte*      limit;       /* `base' + sizeof(table) in memory */
    FT_ValidationLevel  level;       /* validation level                 */
    FT_Error            error;       /* error returned. 0 means success  */

  } FT_ValidatorRec;

#if defined( _MSC_VER )
#pragma warning( pop )
#endif

#define FT_VALIDATOR( x )  ( (FT_Validator)( x ) )


  FT_BASE( void )
  ft_validator_init( FT_Validator        valid,
                     const FT_Byte*      base,
                     const FT_Byte*      limit,
                     FT_ValidationLevel  level );

  /* Do not use this. It's broken and will cause your validator to crash */
  /* if you run it on an invalid font.                                   */
  FT_BASE( FT_Int )
  ft_validator_run( FT_Validator  valid );

  /* Sets the error field in a validator, then calls `longjmp' to return */
  /* to high-level caller.  Using `setjmp/longjmp' avoids many stupid    */
  /* error checks within the validation routines.                        */
  /*                                                                     */
  FT_BASE( void )
  ft_validator_error( FT_Validator  valid,
                      FT_Error      error );


  /* Calls ft_validate_error.  Assumes that the `valid' local variable */
  /* holds a pointer to the current validator object.                  */
  /*                                                                   */
#define FT_INVALID( _error )  FT_INVALID_( _error )
#define FT_INVALID_( _error ) \
          ft_validator_error( valid, FT_THROW( _error ) )

  /* called when a broken table is detected */
#define FT_INVALID_TOO_SHORT \
          FT_INVALID( Invalid_Table )

  /* called when an invalid offset is detected */
#define FT_INVALID_OFFSET \
          FT_INVALID( Invalid_Offset )

  /* called when an invalid format/value is detected */
#define FT_INVALID_FORMAT \
          FT_INVALID( Invalid_Table )

  /* called when an invalid glyph index is detected */
#define FT_INVALID_GLYPH_ID \
          FT_INVALID( Invalid_Glyph_Index )

  /* called when an invalid field value is detected */
#define FT_INVALID_DATA \
          FT_INVALID( Invalid_Table )


FT_END_HEADER

#endif /* FTVALID_H_ */


/* END */