pngio.c - third_party/libpng - Git at Google


 /* pngio.c - stub functions for i/o and memory allocation

    libpng 1.0 beta 2 - version 0.88
    For conditions of distribution and use, see copyright notice in png.h
    Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
    January 25, 1996

    This file provides a location for all input/output.  Users which need
    special handling are expected to write functions which have the same
    arguments as these, and perform similar functions, but possibly have
    different I/O methods.  Note that you shouldn't change these functions,
    but rather write replacement functions and then change them at run
    time with png_set_write_fn(...) or png_set_read_fn(...), etc */

 #define PNG_INTERNAL
 #include "png.h"

 /* Write the data to whatever output you are using.  The default routine
    writes to a file pointer.  Note that this routine sometimes gets called
    with very small lengths, so you should implement some kind of simple
    buffering if you are using unbuffered writes.  This should never be asked
    to write more then 64K on a 16 bit machine.  The cast to png_size_t is
    there to quiet warnings of certain compilers. */

 void
 png_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
 {
    if (png_ptr->write_data_fn)
       (*(png_ptr->write_data_fn))(png_ptr, data, length);
    else
       png_error(png_ptr, "Call to NULL write function");
 }

 /* This is the function which does the actual writing of data.  If you are
    not writing to a standard C stream, you should create a replacement
    write_data function and use it at run time with png_set_write_fn(), rather
    than changing the library. */
 #ifndef USE_FAR_KEYWORD
 void
 png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
 {
    png_uint_32 check;

    check = fwrite(data, 1, (png_size_t)length, png_ptr->fp);
    if (check != length)
    {
       png_error(png_ptr, "Write Error");
    }
 }
 #else
 /* this is the model-independent version. Since the standard I/O library
    can't handle far buffers in the medium and small models, we have to copy
    the data.
 */

 #define NEAR_BUF_SIZE 1024
 #define MIN(a,b) (a <= b ? a : b)

 #ifdef _MSC_VER
 /* for FP_OFF */
 #include <dos.h>
 #endif

 void
 png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
 {
    png_uint_32 check;
    png_byte *n_data;

    /* Check if data really is near. If so, use usual code. */
 #ifdef _MSC_VER
    /* do it this way just to quiet warning */
    FP_OFF(n_data) = FP_OFF(data);
    if (FP_SEG(n_data) == FP_SEG(data))
 #else
    /* this works in MSC also but with lost segment warning */
    n_data = (png_byte *)data;
    if ((png_bytep)n_data == data)
 #endif
    {
       check = fwrite(n_data, 1, (png_size_t)length, png_ptr->fp);
    }
    else
    {
       png_byte buf[NEAR_BUF_SIZE];
       png_size_t written, remaining, err;
       check = 0;
       remaining = (png_size_t)length;
       do
       {
          written = MIN(NEAR_BUF_SIZE, remaining);
          png_memcpy(buf, data, written); /* copy far buffer to near buffer */
          err = fwrite(buf, 1, written, png_ptr->fp);
          if (err != written)
             break;
          else
             check += err;
          data += written;
          remaining -= written;
       }
       while (remaining != 0);
    }
    if (check != length)
    {
       png_error(png_ptr, "Write Error");
    }
 }

 #endif

 /* Read the data from whatever input you are using.  The default routine
    reads from a file pointer.  Note that this routine sometimes gets called
    with very small lengths, so you should implement some kind of simple
    buffering if you are using unbuffered reads.  This should never be asked
    to read more then 64K on a 16 bit machine.  The cast to png_size_t is
    there to quiet some compilers */
 void
 png_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
 {
 #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
    if (png_ptr->read_mode == PNG_READ_PUSH_MODE)
    {
       png_push_fill_buffer(png_ptr, data, length);
    }
    else
 #endif
    {
       if (png_ptr->read_data_fn)
          (*(png_ptr->read_data_fn))(png_ptr, data, length);
       else
          png_error(png_ptr, "Call to NULL read function");
    }
 }

 /* This is the function which does the actual reading of data.  If you are
    not reading from a standard C stream, you should create a replacement
    read_data function and use it at run time with png_set_read_fn(), rather
    than changing the library. */
 #ifndef USE_FAR_KEYWORD
 void
 png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
 {
    png_uint_32 check;

    check = fread(data, 1, (size_t)length, png_ptr->fp);
    if (check != length)
    {
       png_error(png_ptr, "Read Error");
    }
 }
 #else
 void
 png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
 {
    png_uint_32 check;
    png_byte *n_data;

    /* Check if data really is near. If so, use usual code. */
 #ifdef _MSC_VER
    /* do it this way just to quiet warning */
    FP_OFF(n_data) = FP_OFF(data);
    if (FP_SEG(n_data) == FP_SEG(data))
 #else
    /* this works in MSC also but with lost segment warning */
    n_data = (png_byte *)data;
    if ((png_bytep)n_data == data)
 #endif
    {
       check = fread(n_data, 1, (size_t)length, png_ptr->fp);
    }
    else
    {
       png_byte buf[NEAR_BUF_SIZE];
       png_size_t read, remaining, err;
       check = 0;
       remaining = (png_size_t)length;
       do
       {
          read = MIN(NEAR_BUF_SIZE, remaining);
          err = fread(buf, 1, read, png_ptr->fp);
          png_memcpy(data, buf, read); /* copy far buffer to near buffer */
          if(err != read)
             break;
          else
             check += err;
          data += read;
          remaining -= read;
       }
       while (remaining != 0);
    }
    if (check != length)
    {
       png_error(png_ptr, "read Error");
    }
 }
 #endif

 /* This function is called to output any data pending writing (normally
    to disk.  After png_flush is called, there should be no data pending
    writing in any buffers. */
 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
 void
 png_flush(png_structp png_ptr)
 {
    if (png_ptr->output_flush_fn)
       (*(png_ptr->output_flush_fn))(png_ptr);
 }

 void
 png_default_flush(png_structp png_ptr)
 {
    if (png_ptr->fp)
       fflush(png_ptr->fp);
 }
 #endif

 /* This function allows the application to supply new output functions for
    libpng if standard C streams aren't being used.

    This function takes as its arguments:
    png_ptr       - pointer to a png output data structure
    io_ptr        - pointer to user supplied structure containing info about
                    the output functions.  May be NULL.
    write_data_fn - pointer to a new output function which takes as its
                    arguments a pointer to a png_struct, a pointer to
                    data to be written, and a 32-bit unsigned int which is
                    the number of bytes to be written.  The new write
                    function should call png_error(png_ptr, "Error msg")
                    to exit and output any fatal error messages.
    flush_data_fn - pointer to a new flush function which takes as its
                    arguments a pointer to a png_struct.  After a call to
                    the flush function, there should be no data in any buffers
                    or pending transmission.  If the output method doesn't do
                    any buffering of ouput, a function prototype must still be
                    supplied although it doesn't have to do anything.  If
                    PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
                    time, output_flush_fn will be ignored, although it must be
                    supplied for compatibility. */
 void
 png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
    png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
 {
    png_ptr->io_ptr = io_ptr;

    if (write_data_fn)
       png_ptr->write_data_fn = write_data_fn;
    else
       png_ptr->write_data_fn = png_default_write_data;

 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
    if (output_flush_fn)
       png_ptr->output_flush_fn = output_flush_fn;
    else
       png_ptr->output_flush_fn = png_default_flush;
 #endif /* PNG_WRITE_FLUSH_SUPPORTED */

    /* It is an error to read while writing a png file */
    png_ptr->read_data_fn = NULL;
 }


 /* This function allows the application to supply a new input function
    for libpng if standard C streams aren't being used.

    This function takes as its arguments:
    png_ptr      - pointer to a png input data structure
    io_ptr       - pointer to user supplied structure containing info about
                   the input functions.  May be NULL.
    read_data_fn - pointer to a new input function which takes as it's
                   arguments a pointer to a png_struct, a pointer to
                   a location where input data can be stored, and a 32-bit
                   unsigned int which is the number of bytes to be read.
                   To exit and output any fatal error messages the new write
                   function should call png_error(png_ptr, "Error msg"). */
 void
 png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
    png_rw_ptr read_data_fn)
 {
    png_ptr->io_ptr = io_ptr;

    if (read_data_fn)
       png_ptr->read_data_fn = read_data_fn;
    else
       png_ptr->read_data_fn = png_default_read_data;

    /* It is an error to write to a read device */
    png_ptr->write_data_fn = NULL;

 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
    png_ptr->output_flush_fn = NULL;
 #endif /* PNG_WRITE_FLUSH_SUPPORTED */
 }


 /* This function returns a pointer to the io_ptr associated with the user
    functions.  The application should free any memory associated with this
    pointer before png_write_destroy and png_read_destroy are called. */
 png_voidp
 png_get_io_ptr(png_structp png_ptr)
 {
    return png_ptr->io_ptr;
 }

 /* Initialize the default input/output functions for the png file.  If you
    change the read, or write routines, you can call either png_set_read_fn()
    or png_set_write_fn() instead of png_init_io(). */
 void
 png_init_io(png_structp png_ptr, FILE *fp)
 {
    png_ptr->fp = fp;
    png_ptr->read_data_fn = png_default_read_data;
    png_ptr->write_data_fn = png_default_write_data;
 #ifdef PNG_WRITE_FLUSH_SUPPORTED
    png_ptr->output_flush_fn = png_default_flush;
 #endif
 }

	/* pngio.c - stub functions for i/o and memory allocation

	libpng 1.0 beta 2 - version 0.88
	For conditions of distribution and use, see copyright notice in png.h
	Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
	January 25, 1996

	This file provides a location for all input/output. Users which need
	special handling are expected to write functions which have the same
	arguments as these, and perform similar functions, but possibly have
	different I/O methods. Note that you shouldn't change these functions,
	but rather write replacement functions and then change them at run
	time with png_set_write_fn(...) or png_set_read_fn(...), etc */

	#define PNG_INTERNAL
	#include "png.h"

	/* Write the data to whatever output you are using. The default routine
	writes to a file pointer. Note that this routine sometimes gets called
	with very small lengths, so you should implement some kind of simple
	buffering if you are using unbuffered writes. This should never be asked
	to write more then 64K on a 16 bit machine. The cast to png_size_t is
	there to quiet warnings of certain compilers. */

	void
	png_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
	{
	if (png_ptr->write_data_fn)
	(*(png_ptr->write_data_fn))(png_ptr, data, length);
	else
	png_error(png_ptr, "Call to NULL write function");
	}

	/* This is the function which does the actual writing of data. If you are
	not writing to a standard C stream, you should create a replacement
	write_data function and use it at run time with png_set_write_fn(), rather
	than changing the library. */
	#ifndef USE_FAR_KEYWORD
	void
	png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
	{
	png_uint_32 check;

	check = fwrite(data, 1, (png_size_t)length, png_ptr->fp);
	if (check != length)
	{
	png_error(png_ptr, "Write Error");
	}
	}
	#else
	/* this is the model-independent version. Since the standard I/O library
	can't handle far buffers in the medium and small models, we have to copy
	the data.
	*/

	#define NEAR_BUF_SIZE 1024
	#define MIN(a,b) (a <= b ? a : b)

	#ifdef _MSC_VER
	/* for FP_OFF */
	#include <dos.h>
	#endif

	void
	png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
	{
	png_uint_32 check;
	png_byte *n_data;

	/* Check if data really is near. If so, use usual code. */
	#ifdef _MSC_VER
	/* do it this way just to quiet warning */
	FP_OFF(n_data) = FP_OFF(data);
	if (FP_SEG(n_data) == FP_SEG(data))
	#else
	/* this works in MSC also but with lost segment warning */
	n_data = (png_byte *)data;
	if ((png_bytep)n_data == data)
	#endif
	{
	check = fwrite(n_data, 1, (png_size_t)length, png_ptr->fp);
	}
	else
	{
	png_byte buf[NEAR_BUF_SIZE];
	png_size_t written, remaining, err;
	check = 0;
	remaining = (png_size_t)length;
	do
	{
	written = MIN(NEAR_BUF_SIZE, remaining);
	png_memcpy(buf, data, written); /* copy far buffer to near buffer */
	err = fwrite(buf, 1, written, png_ptr->fp);
	if (err != written)
	break;
	else
	check += err;
	data += written;
	remaining -= written;
	}
	while (remaining != 0);
	}
	if (check != length)
	{
	png_error(png_ptr, "Write Error");
	}
	}

	#endif

	/* Read the data from whatever input you are using. The default routine
	reads from a file pointer. Note that this routine sometimes gets called
	with very small lengths, so you should implement some kind of simple
	buffering if you are using unbuffered reads. This should never be asked
	to read more then 64K on a 16 bit machine. The cast to png_size_t is
	there to quiet some compilers */
	void
	png_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
	{
	#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
	if (png_ptr->read_mode == PNG_READ_PUSH_MODE)
	{
	png_push_fill_buffer(png_ptr, data, length);
	}
	else
	#endif
	{
	if (png_ptr->read_data_fn)
	(*(png_ptr->read_data_fn))(png_ptr, data, length);
	else
	png_error(png_ptr, "Call to NULL read function");
	}
	}

	/* This is the function which does the actual reading of data. If you are
	not reading from a standard C stream, you should create a replacement
	read_data function and use it at run time with png_set_read_fn(), rather
	than changing the library. */
	#ifndef USE_FAR_KEYWORD
	void
	png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
	{
	png_uint_32 check;

	check = fread(data, 1, (size_t)length, png_ptr->fp);
	if (check != length)
	{
	png_error(png_ptr, "Read Error");
	}
	}
	#else
	void
	png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
	{
	png_uint_32 check;
	png_byte *n_data;

	/* Check if data really is near. If so, use usual code. */
	#ifdef _MSC_VER
	/* do it this way just to quiet warning */
	FP_OFF(n_data) = FP_OFF(data);
	if (FP_SEG(n_data) == FP_SEG(data))
	#else
	/* this works in MSC also but with lost segment warning */
	n_data = (png_byte *)data;
	if ((png_bytep)n_data == data)
	#endif
	{
	check = fread(n_data, 1, (size_t)length, png_ptr->fp);
	}
	else
	{
	png_byte buf[NEAR_BUF_SIZE];
	png_size_t read, remaining, err;
	check = 0;
	remaining = (png_size_t)length;
	do
	{
	read = MIN(NEAR_BUF_SIZE, remaining);
	err = fread(buf, 1, read, png_ptr->fp);
	png_memcpy(data, buf, read); /* copy far buffer to near buffer */
	if(err != read)
	break;
	else
	check += err;
	data += read;
	remaining -= read;
	}
	while (remaining != 0);
	}
	if (check != length)
	{
	png_error(png_ptr, "read Error");
	}
	}
	#endif

	/* This function is called to output any data pending writing (normally
	to disk. After png_flush is called, there should be no data pending
	writing in any buffers. */
	#if defined(PNG_WRITE_FLUSH_SUPPORTED)
	void
	png_flush(png_structp png_ptr)
	{
	if (png_ptr->output_flush_fn)
	(*(png_ptr->output_flush_fn))(png_ptr);
	}

	void
	png_default_flush(png_structp png_ptr)
	{
	if (png_ptr->fp)
	fflush(png_ptr->fp);
	}
	#endif

	/* This function allows the application to supply new output functions for
	libpng if standard C streams aren't being used.

	This function takes as its arguments:
	png_ptr - pointer to a png output data structure
	io_ptr - pointer to user supplied structure containing info about
	the output functions. May be NULL.
	write_data_fn - pointer to a new output function which takes as its
	arguments a pointer to a png_struct, a pointer to
	data to be written, and a 32-bit unsigned int which is
	the number of bytes to be written. The new write
	function should call png_error(png_ptr, "Error msg")
	to exit and output any fatal error messages.
	flush_data_fn - pointer to a new flush function which takes as its
	arguments a pointer to a png_struct. After a call to
	the flush function, there should be no data in any buffers
	or pending transmission. If the output method doesn't do
	any buffering of ouput, a function prototype must still be
	supplied although it doesn't have to do anything. If
	PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile
	time, output_flush_fn will be ignored, although it must be
	supplied for compatibility. */
	void
	png_set_write_fn(png_structp png_ptr, png_voidp io_ptr,
	png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn)
	{
	png_ptr->io_ptr = io_ptr;

	if (write_data_fn)
	png_ptr->write_data_fn = write_data_fn;
	else
	png_ptr->write_data_fn = png_default_write_data;

	#if defined(PNG_WRITE_FLUSH_SUPPORTED)
	if (output_flush_fn)
	png_ptr->output_flush_fn = output_flush_fn;
	else
	png_ptr->output_flush_fn = png_default_flush;
	#endif /* PNG_WRITE_FLUSH_SUPPORTED */

	/* It is an error to read while writing a png file */
	png_ptr->read_data_fn = NULL;
	}


	/* This function allows the application to supply a new input function
	for libpng if standard C streams aren't being used.

	This function takes as its arguments:
	png_ptr - pointer to a png input data structure
	io_ptr - pointer to user supplied structure containing info about
	the input functions. May be NULL.
	read_data_fn - pointer to a new input function which takes as it's
	arguments a pointer to a png_struct, a pointer to
	a location where input data can be stored, and a 32-bit
	unsigned int which is the number of bytes to be read.
	To exit and output any fatal error messages the new write
	function should call png_error(png_ptr, "Error msg"). */
	void
	png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
	png_rw_ptr read_data_fn)
	{
	png_ptr->io_ptr = io_ptr;

	if (read_data_fn)
	png_ptr->read_data_fn = read_data_fn;
	else
	png_ptr->read_data_fn = png_default_read_data;

	/* It is an error to write to a read device */
	png_ptr->write_data_fn = NULL;

	#if defined(PNG_WRITE_FLUSH_SUPPORTED)
	png_ptr->output_flush_fn = NULL;
	#endif /* PNG_WRITE_FLUSH_SUPPORTED */
	}


	/* This function returns a pointer to the io_ptr associated with the user
	functions. The application should free any memory associated with this
	pointer before png_write_destroy and png_read_destroy are called. */
	png_voidp
	png_get_io_ptr(png_structp png_ptr)
	{
	return png_ptr->io_ptr;
	}

	/* Initialize the default input/output functions for the png file. If you
	change the read, or write routines, you can call either png_set_read_fn()
	or png_set_write_fn() instead of png_init_io(). */
	void
	png_init_io(png_structp png_ptr, FILE *fp)
	{
	png_ptr->fp = fp;
	png_ptr->read_data_fn = png_default_read_data;
	png_ptr->write_data_fn = png_default_write_data;
	#ifdef PNG_WRITE_FLUSH_SUPPORTED
	png_ptr->output_flush_fn = png_default_flush;
	#endif
	}