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src/Source/LibPNG/pngpriv.h  view on Meta::CPAN

/* 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 */

#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.
 */
#ifndef PNGLCONF_H
#  include "pnglibconf.h"
#endif

/* Local renames may change non-exported API functions from png.h */
#if defined(PNG_PREFIX) && !defined(PNGPREFIX_H)
#  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

/* Compile time options.
 * =====================
 * In a multi-arch build the compiler may compile the code several times for the
 * same object module, producing different binaries for different architectures.
 * When this happens configure-time setting of the target host options cannot be
 * done and this interferes with the handling of the ARM NEON optimizations, and
 * possibly other similar optimizations.  Put additional tests here; in general
 * this is needed when the same option can be changed at both compile time and
 * run time depending on the target OS (i.e. iOS vs Android.)
 *
 * NOTE: symbol prefixing does not pass $(CFLAGS) to the preprocessor, because
 * this is not possible with certain compilers (Oracle SUN OS CC), as a result
 * it is necessary to ensure that all extern functions that *might* be used
 * regardless of $(CFLAGS) get declared in this file.  The test on __ARM_NEON__
 * below is one example of this behavior because it is controlled by the
 * presence or not of -mfpu=neon on the GCC command line, it is possible to do
 * this in $(CC), e.g. "CC=gcc -mfpu=neon", but people who build libpng rarely
 * do this.
 */
#ifndef PNG_ARM_NEON_OPT
   /* ARM NEON optimizations are being controlled by the compiler settings,
    * typically the target FPU.  If the FPU has been set to NEON (-mfpu=neon
    * with GCC) then the compiler will define __ARM_NEON__ and we can rely
    * unconditionally on NEON instructions not crashing, otherwise we must
    * disable use of NEON instructions.
    *
    * NOTE: at present these optimizations depend on 'ALIGNED_MEMORY', so they
    * can only be turned on automatically if that is supported too.  If
    * PNG_ARM_NEON_OPT is set in CPPFLAGS (to >0) then arm/arm_init.c will fail
    * to compile with an appropriate #error if ALIGNED_MEMORY has been turned
    * off.
    *
    * Note that gcc-4.9 defines __ARM_NEON instead of __ARM_NEON__, so we
    * check both variants.
    */
#  if (defined(__ARM_NEON__) || defined(__ARM_NEON)) && \
   defined(PNG_ALIGNED_MEMORY_SUPPORTED)
#     define PNG_ARM_NEON_OPT 2
#  else
#     define PNG_ARM_NEON_OPT 0
#  endif
#endif

#if PNG_ARM_NEON_OPT > 0
   /* NEON optimizations are to be at least considered by libpng, so enable the