libpng/pngpriv.h

/* pngpriv.h - private declarations for use inside libpng
 *
 * For conditions of distribution and use, see copyright notice in png.h
 * Copyright (c) 1998-2012 Glenn Randers-Pehrson
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
 * Last changed in libpng 1.6.0 [(PENDING RELEASE)]
 *
 * 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.
 */

#ifndef PNGPRIV_H
#define PNGPRIV_H

/* 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.)
 */
#define _POSIX_SOURCE 1 /* Just the POSIX 1003.1 and C89 APIs */

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

#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

#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

#include "png.h"
#include "pnginfo.h"
#include "pngstruct.h"
#if defined PNG_PREFIX && !defined PNGPREFIX_H
#  include "pngprefix.h"
#endif

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

/* This is used for 16 bit gamma tables -- only the top level pointers are
 * const; this could be changed:
 */
typedef const png_uint_16p * png_const_uint_16pp;

/* Moved to pngpriv.h at libpng-1.5.0 */
/* NOTE: some of these may have been used in external applications as
 * these definitions were exposed in pngconf.h prior to 1.5.
 */

/* 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

/* PNG_STATIC is used to mark internal file scope functions if they need to be
 * accessed for implementation tests (see the code in tests/?*).
 */
#ifndef PNG_STATIC
#   define PNG_STATIC static
#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(s1,s2) ((void)(s1))
#  define png_chunk_warning(s1,s2) ((void)(s1))
#  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_error(s1,s2) png_err(s1)
#  define png_chunk_error(s1,s2) png_err(s1)
#  define png_fixed_error(s1,s2) png_err(s1)
#endif

/* 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)
#else
#  define png_voidcast(type, value) (value)
#  define png_constcast(type, value) ((type)(value))
#endif /* __cplusplus */

/* Some fixed point APIs are still required even if not exported because
 * they get used by the corresponding floating point APIs.  This magic
 * deals with this:
 */
#ifdef PNG_FIXED_POINT_SUPPORTED
#  define PNGFAPI PNGAPI
#else
#  define PNGFAPI /* PRIVATE */
#endif

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

#  if (defined(__MWERKS__) && defined(macintosh)) || defined(applec) || \
    defined(THINK_C) || defined(__SC__) || defined(TARGET_OS_MAC)
     /* We need to check that <math.h> hasn't already been included earlier
      * as it seems it doesn't agree with <fp.h>, yet we should really use
      * <fp.h> if possible.
      */
#    if !defined(__MATH_H__) && !defined(__MATH_H) && !defined(__cmath__)
#      include <fp.h>
#    endif
#  else
#    include <math.h>
#  endif
#  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(_Windows) || defined(_WINDOWS) || \
    defined(_WIN32) || defined(__WIN32__)
#  include <windows.h>  /* defines _WINDOWS_ macro */
#endif

/* 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.
 */

/* Memory model/platform independent fns */
#ifndef PNG_ABORT
#  ifdef _WINDOWS_
#    define PNG_ABORT() ExitProcess(0)
#  else
#    define PNG_ABORT() abort()
#  endif
#endif

/* Prior to 1.6.0 if _WINDOWS_ was defined 'lstrlenA' and 'CopyMemory' were used
 * in place of the ISOC90 functions; this is no longer done in 1.6.0, however
 * the use of png_foo as a macro defined to the C function is retained.
 */
#define png_strlen  strlen
#define png_memcmp  memcmp
#define png_memcpy  memcpy
#define png_memset  memset

/* 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_TO_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 to a power of 2. */
#ifdef png_alignof
#  define png_isaligned(ptr, type)\
   ((((const char*)ptr-(const char*)0) & (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 */

/* 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) extern type name array
#endif

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

/* 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            0x01 (defined in png.h) */
/* #define PNG_HAVE_PLTE            0x02 (defined in png.h) */
#define PNG_HAVE_IDAT               0x04
/* #define PNG_AFTER_IDAT           0x08 (defined in png.h) */
#define PNG_HAVE_IEND               0x10
#define PNG_HAVE_gAMA               0x20
#define PNG_HAVE_cHRM               0x40
#define PNG_HAVE_sRGB               0x80
#define PNG_HAVE_CHUNK_HEADER      0x100
#define PNG_WROTE_tIME             0x200
#define PNG_WROTE_INFO_BEFORE_PLTE 0x400
#define PNG_BACKGROUND_IS_GRAY     0x800
#define PNG_HAVE_PNG_SIGNATURE    0x1000
#define PNG_HAVE_CHUNK_AFTER_IDAT 0x2000 /* Have another chunk after IDAT */

/* Flags for the transformations the PNG library does on the image data */
#define PNG_BGR                 0x0001
#define PNG_INTERLACE           0x0002
#define PNG_PACK                0x0004
#define PNG_SHIFT               0x0008
#define PNG_SWAP_BYTES          0x0010
#define PNG_INVERT_MONO         0x0020
#define PNG_QUANTIZE            0x0040
#define PNG_COMPOSE             0x0080     /* Was PNG_BACKGROUND */
#define PNG_BACKGROUND_EXPAND   0x0100
#define PNG_EXPAND_16           0x0200     /* Added to libpng 1.5.2 */
#define PNG_16_TO_8             0x0400     /* Becomes 'chop' in 1.5.4 */
#define PNG_RGBA                0x0800
#define PNG_EXPAND              0x1000
#define PNG_GAMMA               0x2000
#define PNG_GRAY_TO_RGB         0x4000
#define PNG_FILLER              0x8000
#define PNG_PACKSWAP           0x10000
#define PNG_SWAP_ALPHA         0x20000
#define PNG_STRIP_ALPHA        0x40000
#define PNG_INVERT_ALPHA       0x80000
#define PNG_USER_TRANSFORM    0x100000
#define PNG_RGB_TO_GRAY_ERR   0x200000
#define PNG_RGB_TO_GRAY_WARN  0x400000
#define PNG_RGB_TO_GRAY       0x600000 /* two bits, RGB_TO_GRAY_ERR|WARN */
#define PNG_ENCODE_ALPHA      0x800000 /* Added to libpng-1.5.4 */
#define PNG_ADD_ALPHA         0x1000000 /* Added to libpng-1.2.7 */
#define PNG_EXPAND_tRNS       0x2000000 /* Added to libpng-1.2.9 */
#define PNG_SCALE_16_TO_8     0x4000000 /* Added to libpng-1.5.4 */
                       /*   0x8000000 unused */
                       /*  0x10000000 unused */
                       /*  0x20000000 unused */
                       /*  0x40000000 unused */
/* Flags for png_create_struct */
#define PNG_STRUCT_PNG   0x0001
#define PNG_STRUCT_INFO  0x0002

/* Scaling factor for filter heuristic weighting calculations */
#define PNG_WEIGHT_FACTOR (1<<(PNG_WEIGHT_SHIFT))
#define PNG_COST_FACTOR (1<<(PNG_COST_SHIFT))

/* Flags for the png_ptr->flags rather than declaring a byte for each one */
#define PNG_FLAG_ZLIB_CUSTOM_STRATEGY     0x0001
#define PNG_FLAG_ZLIB_CUSTOM_LEVEL        0x0002
#define PNG_FLAG_ZLIB_CUSTOM_MEM_LEVEL    0x0004
#define PNG_FLAG_ZLIB_CUSTOM_WINDOW_BITS  0x0008
#define PNG_FLAG_ZLIB_CUSTOM_METHOD       0x0010
#define PNG_FLAG_ZLIB_FINISHED            0x0020
#define PNG_FLAG_ROW_INIT                 0x0040
#define PNG_FLAG_FILLER_AFTER             0x0080
#define PNG_FLAG_CRC_ANCILLARY_USE        0x0100
#define PNG_FLAG_CRC_ANCILLARY_NOWARN     0x0200
#define PNG_FLAG_CRC_CRITICAL_USE         0x0400
#define PNG_FLAG_CRC_CRITICAL_IGNORE      0x0800
#define PNG_FLAG_ASSUME_sRGB              0x1000  /* Added to libpng-1.5.4 */
#define PNG_FLAG_OPTIMIZE_ALPHA           0x2000  /* Added to libpng-1.5.4 */
#define PNG_FLAG_DETECT_UNINITIALIZED     0x4000  /* Added to libpng-1.5.4 */
#define PNG_FLAG_KEEP_UNKNOWN_CHUNKS      0x8000
#define PNG_FLAG_KEEP_UNSAFE_CHUNKS       0x10000
#define PNG_FLAG_LIBRARY_MISMATCH         0x20000
#define PNG_FLAG_STRIP_ERROR_NUMBERS      0x40000
#define PNG_FLAG_STRIP_ERROR_TEXT         0x80000
                                  /*      0x100000  unused */
                                  /*      0x200000  unused */
                                  /*      0x400000  unused */
#define PNG_FLAG_BENIGN_ERRORS_WARN       0x800000  /* Added to libpng-1.4.0 */
#define PNG_FLAG_ZTXT_CUSTOM_STRATEGY    0x1000000  /* 5 lines added */
#define PNG_FLAG_ZTXT_CUSTOM_LEVEL       0x2000000  /* to libpng-1.5.4 */
#define PNG_FLAG_ZTXT_CUSTOM_MEM_LEVEL   0x4000000
#define PNG_FLAG_ZTXT_CUSTOM_WINDOW_BITS 0x8000000
#define PNG_FLAG_ZTXT_CUSTOM_METHOD      0x10000000
                                  /*     0x20000000  unused */
                                  /*     0x40000000  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)

/* zlib.h declares a magic type 'uInt' that limits the amount of data that zlib
 * can handle at once.  This type need be no larger than 16 bits (so maximum of
 * 65535), this define allows us to discover how big it is, but limited by the
 * maximuum for png_size_t.  The value can be overriden in a library build
 * (pngusr.h, or set it in CPPFLAGS) and it works to set it to a considerably
 * lower value (e.g. 255 works).  A lower value may help memory usage (slightly)
 * and may even improve performance on some systems (and degrade it on others.)
 */
#ifndef ZLIB_IO_MAX
#  define ZLIB_IO_MAX ((uInt)-1)
#endif

/* 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-1.5.7: 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)((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 /* PNG_SIMPLIFIED_READ/WRITE */

/* 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 ? \
    ((png_size_t)(width) * (((png_size_t)(pixel_bits)) >> 3)) : \
    (( ((png_size_t)(width) * ((png_size_t)(pixel_bits))) + 7) >> 3) )

/* 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))
#endif
/* else the corresponding function is defined below, inside the scopt 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.
 */
#define PNG_32b(b,s) ((png_uint_32)(b) << (s))
#define PNG_CHUNK(b1,b2,b3,b4) \
   (PNG_32b(b1,24) | PNG_32b(b2,16) | PNG_32b(b3,8) | PNG_32b(b4,0))

#define png_IHDR PNG_CHUNK( 73,  72,  68,  82)
#define png_IDAT PNG_CHUNK( 73,  68,  65,  84)
#define png_IEND PNG_CHUNK( 73,  69,  78,  68)
#define png_PLTE PNG_CHUNK( 80,  76,  84,  69)
#define png_bKGD PNG_CHUNK( 98,  75,  71,  68)
#define png_cHRM PNG_CHUNK( 99,  72,  82,  77)
#define png_gAMA PNG_CHUNK(103,  65,  77,  65)
#define png_hIST PNG_CHUNK(104,  73,  83,  84)
#define png_iCCP PNG_CHUNK(105,  67,  67,  80)
#define png_iTXt PNG_CHUNK(105,  84,  88, 116)
#define png_oFFs PNG_CHUNK(111,  70,  70, 115)
#define png_pCAL PNG_CHUNK(112,  67,  65,  76)
#define png_sCAL PNG_CHUNK(115,  67,  65,  76)
#define png_pHYs PNG_CHUNK(112,  72,  89, 115)
#define png_sBIT PNG_CHUNK(115,  66,  73,  84)
#define png_sPLT PNG_CHUNK(115,  80,  76,  84)
#define png_sRGB PNG_CHUNK(115,  82,  71,  66)
#define png_sTER PNG_CHUNK(115,  84,  69,  82)
#define png_tEXt PNG_CHUNK(116,  69,  88, 116)
#define png_tIME PNG_CHUNK(116,  73,  77,  69)
#define png_tRNS PNG_CHUNK(116,  82,  78,  83)
#define png_zTXt PNG_CHUNK(122,  84,  88, 116)

/* 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_CHUNK(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), ((char*)(s))[1]=(char)((c)>>16),\
   ((char*)(s))[2]=(char)((c)>>8), ((char*)(s))[3]=(char)((c)))

/* 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_ANCILLIARY(c)   (1 & ((c) >> 29))
#define PNG_CHUNK_CRITICAL(c)     (!PNG_CHUNK_ANCILLIARY(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))

/* 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


/* 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.
 */

#if defined PNG_FLOATING_POINT_SUPPORTED &&\
   !defined PNG_FIXED_POINT_MACRO_SUPPORTED
PNG_INTERNAL_FUNCTION(png_fixed_point,png_fixed,(png_const_structrp png_ptr,
   double fp, png_const_charp 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_structrp png_ptr,
   png_const_charp user_png_ver),PNG_EMPTY);

/* 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(png_voidp,png_malloc_base,(png_const_structrp png_ptr,
   png_alloc_size_t size),PNG_ALLOCATED);

/* 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_structp,png_create_png_struct,
   (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn,
    png_error_ptr warn_fn, png_voidp 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_structrp png_ptr),
   PNG_EMPTY);

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

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

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

/* Next four functions are used internally as callbacks.  PNGCBAPI is required
 * but not PNG_EXPORT.  PNGAPI added at libpng version 1.2.3, changed to
 * PNGCBAPI at 1.5.0
 */

PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_default_read_data,(png_structp png_ptr,
    png_bytep data, png_size_t length),PNG_EMPTY);

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_push_fill_buffer,(png_structp png_ptr,
    png_bytep buffer, png_size_t length),PNG_EMPTY);
#endif

PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_default_write_data,(png_structp png_ptr,
    png_bytep data, png_size_t length),PNG_EMPTY);

#ifdef PNG_WRITE_FLUSH_SUPPORTED
#  ifdef PNG_STDIO_SUPPORTED
PNG_INTERNAL_FUNCTION(void PNGCBAPI,png_default_flush,(png_structp png_ptr),
   PNG_EMPTY);
#  endif
#endif

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

/* Write the "data" buffer to whatever output you are using */
PNG_INTERNAL_FUNCTION(void,png_write_data,(png_structrp png_ptr,
    png_const_bytep data, png_size_t length),PNG_EMPTY);

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

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

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

/* Read bytes into buf, and update png_ptr->crc */
PNG_INTERNAL_FUNCTION(void,png_crc_read,(png_structrp png_ptr, png_bytep buf,
    png_size_t length),PNG_EMPTY);

/* Decompress data in a chunk that uses compression */
#if defined(PNG_READ_COMPRESSED_TEXT_SUPPORTED)
PNG_INTERNAL_FUNCTION(void,png_decompress_chunk,(png_structrp png_ptr,
   int comp_type, png_size_t chunklength, png_size_t prefix_length,
   png_size_t *data_length),PNG_EMPTY);
#endif

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

/* Read the CRC from the file and compare it to the libpng calculated CRC */
PNG_INTERNAL_FUNCTION(int,png_crc_error,(png_structrp png_ptr),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_structrp png_ptr,
   png_const_bytep ptr, png_size_t length),PNG_EMPTY);

#ifdef PNG_WRITE_FLUSH_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_flush,(png_structrp 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_structrp 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_structrp png_ptr,
   png_const_colorp palette, png_uint_32 num_pal),PNG_EMPTY);

PNG_INTERNAL_FUNCTION(void,png_write_IDAT,(png_structrp png_ptr, png_bytep data,
   png_size_t length),PNG_EMPTY);

PNG_INTERNAL_FUNCTION(void,png_write_IEND,(png_structrp png_ptr),PNG_EMPTY);

#ifdef PNG_WRITE_gAMA_SUPPORTED
#  ifdef PNG_FLOATING_POINT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_gAMA,(png_structrp png_ptr, double file_gamma),
   PNG_EMPTY);
#  endif
#  ifdef PNG_FIXED_POINT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_gAMA_fixed,(png_structrp png_ptr,
    png_fixed_point file_gamma),PNG_EMPTY);
#  endif
#endif

#ifdef PNG_WRITE_sBIT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_sBIT,(png_structrp png_ptr,
    png_const_color_8p sbit, int color_type),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_cHRM_SUPPORTED
#  ifdef PNG_FLOATING_POINT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_cHRM,(png_structrp png_ptr,
    double white_x, double white_y,
    double red_x, double red_y, double green_x, double green_y,
    double blue_x, double blue_y),PNG_EMPTY);
#  endif
PNG_INTERNAL_FUNCTION(void,png_write_cHRM_fixed,(png_structrp png_ptr,
    png_fixed_point int_white_x, png_fixed_point int_white_y,
    png_fixed_point int_red_x, png_fixed_point int_red_y, png_fixed_point
    int_green_x, png_fixed_point int_green_y, png_fixed_point int_blue_x,
    png_fixed_point int_blue_y),PNG_EMPTY);
#endif

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

#ifdef PNG_WRITE_iCCP_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_iCCP,(png_structrp png_ptr,
    png_const_charp name, int compression_type,
    png_const_charp profile, int proflen),PNG_EMPTY);
   /* Note to maintainer: profile should be png_bytep */
#endif

#ifdef PNG_WRITE_sPLT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_sPLT,(png_structrp png_ptr,
    png_const_sPLT_tp palette),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_tRNS_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_tRNS,(png_structrp png_ptr,
    png_const_bytep trans, png_const_color_16p values, int number,
    int color_type),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_bKGD_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_bKGD,(png_structrp png_ptr,
    png_const_color_16p values, int color_type),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_hIST_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_hIST,(png_structrp png_ptr,
    png_const_uint_16p hist, int num_hist),PNG_EMPTY);
#endif

/* Chunks that have keywords */
#if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_pCAL_SUPPORTED) || \
    defined(PNG_WRITE_iCCP_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
PNG_INTERNAL_FUNCTION(png_size_t,png_check_keyword,(png_structrp png_ptr,
    png_const_charp key, png_charpp new_key),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_tEXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_tEXt,(png_structrp png_ptr, png_const_charp key,
    png_const_charp text, png_size_t text_len),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_zTXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_zTXt,(png_structrp png_ptr, png_const_charp key,
    png_const_charp text, png_size_t text_len, int compression),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_iTXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_iTXt,(png_structrp png_ptr,
    int compression, png_const_charp key, png_const_charp lang,
    png_const_charp lang_key, png_const_charp 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,(png_const_structrp png_ptr,
    png_inforp info_ptr, png_const_textp text_ptr, int num_text),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_oFFs_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_oFFs,(png_structrp 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_structrp png_ptr, png_charp purpose,
    png_int_32 X0, png_int_32 X1, int type, int nparams,
    png_const_charp units, png_charpp params),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_pHYs_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_pHYs,(png_structrp 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_structrp png_ptr,
    png_const_timep mod_time),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_sCAL_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_write_sCAL_s,(png_structrp png_ptr,
    int unit, png_const_charp width, png_const_charp height),PNG_EMPTY);
#endif

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

/* Internal use only.   Called before first row of data */
PNG_INTERNAL_FUNCTION(void,png_write_start_row,(png_structrp 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 png_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,(png_const_structrp png_ptr,
    png_bytep 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_infop row_info,
    png_bytep 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_infop row_info,
    png_bytep 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_structrp pp, png_row_infop row_info,
    png_bytep row, png_const_bytep prev_row, int filter),PNG_EMPTY);

PNG_INTERNAL_FUNCTION(void,png_read_filter_row_up_neon,(png_row_infop row_info,
    png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_read_filter_row_sub3_neon,(png_row_infop row_info,
    png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_read_filter_row_sub4_neon,(png_row_infop row_info,
    png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_read_filter_row_avg3_neon,(png_row_infop row_info,
    png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_read_filter_row_avg4_neon,(png_row_infop row_info,
    png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_read_filter_row_paeth3_neon,(png_row_infop row_info,
    png_bytep row, png_const_bytep prev_row),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_read_filter_row_paeth4_neon,(png_row_infop row_info,
    png_bytep row, png_const_bytep prev_row),PNG_EMPTY);

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

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

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

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

/* These are the functions that do the transformations */
#ifdef PNG_READ_FILLER_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_read_filler,(png_row_infop row_info,
    png_bytep row, png_uint_32 filler, png_uint_32 flags),PNG_EMPTY);
#endif

#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_read_swap_alpha,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_write_swap_alpha,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_read_invert_alpha,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_write_invert_alpha,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#if defined(PNG_WRITE_FILLER_SUPPORTED) || \
    defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
PNG_INTERNAL_FUNCTION(void,png_do_strip_channel,(png_row_infop row_info,
    png_bytep 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_infop row_info,
    png_bytep 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_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
PNG_INTERNAL_FUNCTION(int,png_do_rgb_to_gray,(png_structrp png_ptr,
    png_row_infop row_info, png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_gray_to_rgb,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_READ_PACK_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_unpack,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_READ_SHIFT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_unshift,(png_row_infop row_info,
    png_bytep row, png_const_color_8p sig_bits),PNG_EMPTY);
#endif

#if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
PNG_INTERNAL_FUNCTION(void,png_do_invert,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_scale_16_to_8,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_chop,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_READ_QUANTIZE_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_quantize,(png_row_infop row_info,
    png_bytep row, png_const_bytep palette_lookup,
    png_const_bytep quantize_lookup),PNG_EMPTY);

#  ifdef PNG_CORRECT_PALETTE_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_correct_palette,(png_structrp png_ptr,
    png_colorp palette, int num_palette),PNG_EMPTY);
#  endif
#endif

#if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
PNG_INTERNAL_FUNCTION(void,png_do_bgr,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_PACK_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_pack,(png_row_infop row_info,
   png_bytep row, png_uint_32 bit_depth),PNG_EMPTY);
#endif

#ifdef PNG_WRITE_SHIFT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_shift,(png_row_infop row_info,
    png_bytep row, png_const_color_8p bit_depth),PNG_EMPTY);
#endif

#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
    defined(PNG_READ_ALPHA_MODE_SUPPORTED)
PNG_INTERNAL_FUNCTION(void,png_do_compose,(png_row_infop row_info,
    png_bytep row, png_structrp png_ptr),PNG_EMPTY);
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_gamma,(png_row_infop row_info,
    png_bytep row, png_structrp png_ptr),PNG_EMPTY);
#endif

#ifdef PNG_READ_ALPHA_MODE_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_encode_alpha,(png_row_infop row_info,
   png_bytep row, png_structrp png_ptr),PNG_EMPTY);
#endif

#ifdef PNG_READ_EXPAND_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_expand_palette,(png_row_infop row_info,
    png_bytep row, png_const_colorp palette, png_const_bytep trans,
    int num_trans),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_do_expand,(png_row_infop row_info,
    png_bytep row, png_const_color_16p trans_color),PNG_EMPTY);
#endif

#ifdef PNG_READ_EXPAND_16_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_expand_16,(png_row_infop row_info,
    png_bytep 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.
 */

/* Decode the IHDR chunk */
PNG_INTERNAL_FUNCTION(void,png_handle_IHDR,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_handle_PLTE,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_handle_IEND,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);

#ifdef PNG_READ_bKGD_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_bKGD,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_cHRM_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_cHRM,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_gAMA_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_gAMA,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_hIST_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_hIST,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_iCCP_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_iCCP,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif /* PNG_READ_iCCP_SUPPORTED */

#ifdef PNG_READ_iTXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_iTXt,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_oFFs_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_oFFs,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_pCAL_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_pCAL,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_pHYs_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_pHYs,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_sBIT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_sBIT,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_sCAL_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_sCAL,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_sPLT_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_sPLT,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif /* PNG_READ_sPLT_SUPPORTED */

#ifdef PNG_READ_sRGB_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_sRGB,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_tEXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_tEXt,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_tIME_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_tIME,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_tRNS_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_tRNS,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_READ_zTXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_zTXt,(png_structrp png_ptr, png_inforp info_ptr,
    png_uint_32 length),PNG_EMPTY);
#endif

#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_handle_unknown,(png_structrp png_ptr,
    png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
#endif

PNG_INTERNAL_FUNCTION(void,png_check_chunk_name,(png_structrp png_ptr,
    png_uint_32 chunk_name),PNG_EMPTY);

#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
/* Exactly as png_handle_as_unknown() except that the argument is a 32-bit chunk
 * name, not a string.
 */
PNG_INTERNAL_FUNCTION(int,png_chunk_unknown_handling,(png_structrp png_ptr,
    png_uint_32 chunk_name),PNG_EMPTY);
#endif

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

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

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_push_read_chunk,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_read_sig,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_check_crc,(png_structrp png_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_crc_skip,(png_structrp png_ptr,
    png_uint_32 length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_crc_finish,(png_structrp png_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_save_buffer,(png_structrp png_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_restore_buffer,(png_structrp png_ptr,
    png_bytep buffer, png_size_t buffer_length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_read_IDAT,(png_structrp png_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_process_IDAT_data,(png_structrp png_ptr,
    png_bytep buffer, png_size_t buffer_length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_process_row,(png_structrp png_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_handle_unknown,(png_structrp png_ptr,
   png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_have_info,(png_structrp png_ptr,
   png_inforp info_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_have_end,(png_structrp png_ptr,
   png_inforp info_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_have_row,(png_structrp png_ptr, png_bytep row),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_read_end,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_process_some_data,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_read_push_finish_row,(png_structrp png_ptr),PNG_EMPTY);
#  ifdef PNG_READ_tEXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_push_handle_tEXt,(png_structrp png_ptr,
    png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_read_tEXt,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
#  endif
#  ifdef PNG_READ_zTXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_push_handle_zTXt,(png_structrp png_ptr,
    png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_read_zTXt,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
#  endif
#  ifdef PNG_READ_iTXt_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_push_handle_iTXt,(png_structrp png_ptr,
    png_inforp info_ptr, png_uint_32 length),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_push_read_iTXt,(png_structrp png_ptr,
    png_inforp info_ptr),PNG_EMPTY);
#  endif

#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */

#ifdef PNG_MNG_FEATURES_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_do_read_intrapixel,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_do_write_intrapixel,(png_row_infop row_info,
    png_bytep row),PNG_EMPTY);
#endif

/* Added at libpng version 1.4.0 */
#ifdef PNG_CHECK_cHRM_SUPPORTED
PNG_INTERNAL_FUNCTION(int,png_check_cHRM_fixed,(png_const_structrp png_ptr,
    png_fixed_point int_white_x, png_fixed_point int_white_y,
    png_fixed_point int_red_x, png_fixed_point int_red_y, png_fixed_point
    int_green_x, png_fixed_point int_green_y, png_fixed_point int_blue_x,
    png_fixed_point int_blue_y),PNG_EMPTY);
#endif

#ifdef PNG_CHECK_cHRM_SUPPORTED
/* Added at libpng version 1.2.34 and 1.4.0 */
/* Currently only used by png_check_cHRM_fixed */
PNG_INTERNAL_FUNCTION(void,png_64bit_product,(long v1, long v2,
    unsigned long *hi_product, unsigned long *lo_product),PNG_EMPTY);
#endif

#ifdef PNG_cHRM_SUPPORTED
/* Added at libpng version 1.5.5 */
typedef struct png_xy
{
   png_fixed_point redx, redy;
   png_fixed_point greenx, greeny;
   png_fixed_point bluex, bluey;
   png_fixed_point whitex, whitey;
} png_xy;

typedef struct png_XYZ
{
   png_fixed_point redX, redY, redZ;
   png_fixed_point greenX, greenY, greenZ;
   png_fixed_point blueX, blueY, blueZ;
} png_XYZ;

/* The conversion APIs return 0 on success, non-zero on a parameter error. They
 * allow conversion between the above representations of a color encoding.  When
 * converting from XYZ end points to chromaticities the absolute magnitude of
 * the end points is lost, when converting back the sum of the Y values of the
 * three end points will be 1.0
 */
PNG_INTERNAL_FUNCTION(int,png_xy_from_XYZ,(png_xy *xy, png_XYZ XYZ),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(int,png_XYZ_from_xy,(png_XYZ *XYZ, png_xy xy),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(int,png_XYZ_from_xy_checked,(png_const_structrp png_ptr,
   png_XYZ *XYZ, png_xy xy),PNG_EMPTY);
#endif

/* Added at libpng version 1.4.0 */
PNG_INTERNAL_FUNCTION(void,png_check_IHDR,(png_const_structrp 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);

#if defined(PNG_FLOATING_POINT_SUPPORTED) && defined(PNG_ERROR_TEXT_SUPPORTED)
PNG_INTERNAL_FUNCTION(void,png_fixed_error,(png_const_structrp png_ptr,
   png_const_charp 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,(png_charp buffer, size_t bufsize,
   size_t pos, png_const_charp 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
 * and 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(png_charp,png_format_number,(png_const_charp start,
   png_charp 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, png_const_charp 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,(png_const_structrp png_ptr,
   png_warning_parameters p, png_const_charp 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 simple result in garbage substitutions.
    */
#endif

/* ASCII to FP interfaces, currently only implemented if sCAL
 * support is required.
 */
#if defined(PNG_READ_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,(png_const_structrp png_ptr,
   png_charp ascii, png_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,(png_const_structrp png_ptr,
   png_charp ascii, png_size_t size, png_fixed_point fp),PNG_EMPTY);
#endif /* FIXED_POINT */
#endif /* READ_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 elses!
 *
 * 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 numb1.ers 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 meants 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 initialzed 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+ 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,(png_const_charp string,
   png_size_t size, int *statep, png_size_tp 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,(png_const_charp string,
   png_size_t size),PNG_EMPTY);
#endif /* pCAL || sCAL */

#if defined(PNG_READ_GAMMA_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_p res, png_fixed_point a,
   png_int_32 multiplied_by, png_int_32 divided_by),PNG_EMPTY);
#endif

#if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)
/* Same deal, but issue a warning on overflow and return 0. */
PNG_INTERNAL_FUNCTION(png_fixed_point,png_muldiv_warn,
   (png_const_structrp png_ptr, png_fixed_point a, png_int_32 multiplied_by,
   png_int_32 divided_by),PNG_EMPTY);
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED
/* 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);

/* 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.
 */
PNG_INTERNAL_FUNCTION(png_fixed_point,png_reciprocal2,(png_fixed_point a,
   png_fixed_point b),PNG_EMPTY);
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED
/* 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_structrp png_ptr,
   unsigned int value, png_fixed_point gamma_value),PNG_EMPTY);
PNG_INTERNAL_FUNCTION(int,png_gamma_significant,(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_structrp png_ptr),
   PNG_EMPTY);
PNG_INTERNAL_FUNCTION(void,png_build_gamma_table,(png_structrp png_ptr,
   int bit_depth),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. */
typedef struct png_control
{
   png_structp png_ptr;
   png_infop   info_ptr;
   png_voidp   error_buf;           /* Always a jmp_buf at present. */

   png_const_bytep memory;          /* Memory buffer. */
   png_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 */
} png_control;

/* 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_FUNCTION(void,png_safe_error,(png_structp png_ptr,
   png_const_charp error_message),PNG_NORETURN);

#ifdef PNG_WARNINGS_SUPPORTED
PNG_INTERNAL_FUNCTION(void,png_safe_warning,(png_structp png_ptr,
   png_const_charp warning_message),PNG_EMPTY);
#else
#  define png_safe_warning 0/*dummy argument*/
#endif

PNG_INTERNAL_FUNCTION(int,png_safe_execute,(png_imagep image,
   int (*function)(png_voidp), png_voidp 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_imagep image,
   png_const_charp error_message),PNG_EMPTY);

#endif /* SIMPLIFIED READ/WRITE */

/* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */

#include "pngdebug.h"

#ifdef __cplusplus
}
#endif

#endif /* PNGPRIV_H */