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libpng/pngio.c

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/* pngstub.c - stub functions for i/o and memory allocation
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libpng 1.0 beta 2 - version 0.85
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For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc.
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December 19, 1995
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This file provides a location for all input/output. Users which need
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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 */
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#define PNG_INTERNAL
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#include "png.h"
/* Write the data to whatever output you are using. The default
routine writes to a file pointer. If you need to write to something
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else, this is a good example of how to do it. 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 for insurance. */
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");
}
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#ifndef USE_FAR_KEYWORD
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void
png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
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{
png_uint_32 check;
check = fwrite(data, 1, (png_size_t)length, png_ptr->fp);
if (check != length)
{
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png_error(png_ptr, "Write Error");
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}
}
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#else
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/* 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
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the data.
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*/
#define NEAR_BUF_SIZE 1024
#define MIN(a,b) (a <= b ? a : b)
#ifdef _MSC_VER
/* for FP_OFF */
#include <dos.h>
#endif
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void
png_default_write_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
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{
png_uint_32 check;
png_byte *n_data;
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/* Check if data really is near. If so, use usual code. */
#ifdef _MSC_VER
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/* do it this way just to quiet warning */
FP_OFF(n_data) = FP_OFF(data);
if (FP_SEG(n_data) == FP_SEG(data))
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#else
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/* this works in MSC also but with lost segment warning */
n_data = (png_byte *)data;
if ((png_bytep)n_data == data)
#endif
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{
check = fwrite(n_data, 1, (png_size_t)length, png_ptr->fp);
}
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else
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{
png_byte buf[NEAR_BUF_SIZE];
png_size_t written, remaining, err;
check = 0;
remaining = (png_size_t)length;
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do
{
written = MIN(NEAR_BUF_SIZE, remaining);
png_memcpy(buf, data, written); /* copy far buffer to near buffer */
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err = fwrite(buf, 1, written, png_ptr->fp);
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if (err != written)
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break;
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else
check += err;
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data += written;
remaining -= written;
}
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while (remaining != 0);
}
if (check != length)
{
png_error(png_ptr, "Write Error");
}
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}
#endif
/* Read the data from whatever input you are using. The default
routine reads from a file pointer. If you need to read from something
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else, this is the place to do it. We suggest saving the old code
for future use. 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 for insurance, but if you are having problems
with it, you can take it out. Just be sure to cast length to whatever
fread needs in that spot if you don't have a function prototype for
it. */
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");
}
}
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#ifndef USE_FAR_KEYWORD
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void
png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
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{
png_uint_32 check;
check = fread(data, 1, (size_t)length, png_ptr->fp);
if (check != length)
{
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png_error(png_ptr, "Read Error");
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}
}
#else
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void
png_default_read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
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{
png_uint_32 check;
png_byte *n_data;
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/* Check if data really is near. If so, use usual code. */
#ifdef _MSC_VER
/* do it this way just to quiet warning */
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FP_OFF(n_data) = FP_OFF(data);
if (FP_SEG(n_data) == FP_SEG(data))
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#else
/* this works in MSC also but with lost segment warning */
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n_data = (png_byte *)data;
if ((PNG_BYTEP )n_data == data)
#endif
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{
check = fread(n_data, 1, (size_t)length, png_ptr->fp);
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}
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else
{
png_byte buf[NEAR_BUF_SIZE];
png_size_t read, remaining, err;
check = 0;
remaining = (png_size_t)length;
do
{
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read = MIN(NEAR_BUF_SIZE, remaining);
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err = fread(buf, 1, read, png_ptr->fp);
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png_memcpy(data, buf, read); /* copy far buffer to near buffer */
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if(err != read)
break;
else
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check += err;
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data += read;
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remaining -= read;
}
while (remaining != 0);
}
if (check != length)
{
png_error(png_ptr, "read Error");
}
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}
#endif
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#if defined(PNG_WRITE_FLUSH_SUPPORTED)
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void
png_flush(png_struct *png_ptr)
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{
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if (png_ptr->output_flush_fn)
(*(png_ptr->output_flush_fn))(png_ptr);
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}
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void
png_default_flush(png_struct *png_ptr)
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{
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if (png_ptr->fp)
fflush(png_ptr->fp);
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}
#endif
/* This function allows the application to supply new output functions for
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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_ptr->error_fn))("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, this parameter can be NULL. 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. */
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void
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png_set_write_fn(png_structp png_ptr, png_voidp io_ptr, png_rw_ptr write_data_fn,
png_flush_ptr output_flush_fn)
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{
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png_ptr->io_ptr = io_ptr;
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if (write_data_fn)
png_ptr->write_data_fn = write_data_fn;
else
png_ptr->write_data_fn = png_default_write_data;
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#if defined(PNG_WRITE_FLUSH_SUPPORTED)
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if (output_flush_fn == NULL)
png_ptr->output_flush_fn = png_default_flush;
else
png_ptr->output_flush_fn = output_flush_fn;
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#endif /* PNG_WRITE_FLUSH_SUPPORTED */
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/* It is an error to read while writing a png file */
png_ptr->read_data_fn = NULL;
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}
/* This function allows the application to supply a new input function
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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. */
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void
png_set_read_fn(png_struct *png_ptr, void *io_ptr, png_rw_ptr read_data_fn)
{
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png_ptr->io_ptr = io_ptr;
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if (read_data_fn)
png_ptr->read_data_fn = read_data_fn;
else
png_ptr->read_data_fn = png_default_read_data;
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/* It is an error to write to a read device */
png_ptr->write_data_fn = NULL;
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#if defined(PNG_WRITE_FLUSH_SUPPORTED)
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png_ptr->output_flush_fn = NULL;
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#endif /* PNG_WRITE_FLUSH_SUPPORTED */
}
/* This function returns a pointer to the io_ptr associated with the user
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functions. The application should free any memory associated with this
pointer before png_write_destroy and png_read_destroy are called. */
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void *
png_get_io_ptr(png_struct *png_ptr)
{
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return png_ptr->io_ptr;
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}
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/* Initialize the input/output for the png file. If you change
the read and write routines, you will probably need to change
this routine (or write your own). If you change the parameters
of this routine, remember to change png.h also. */
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void
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png_init_io(png_structp png_ptr, FILE *fp)
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{
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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
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}