0,0 → 1,176 |
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/* pngrio.c - functions for data input |
* |
* Last changed in libpng 1.5.0 [January 6, 2011] |
* Copyright (c) 1998-2011 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.) |
* |
* This code is released under the libpng license. |
* For conditions of distribution and use, see the disclaimer |
* and license in png.h |
* |
* This file provides a location for all input. Users who need |
* special handling are expected to write a function that has the same |
* arguments as this and performs a similar function, but that possibly |
* has a different input method. Note that you shouldn't change this |
* function, but rather write a replacement function and then make |
* libpng use it at run time with png_set_read_fn(...). |
*/ |
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#include "pngpriv.h" |
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#ifdef PNG_READ_SUPPORTED |
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/* 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. |
*/ |
void /* PRIVATE */ |
png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
{ |
png_debug1(4, "reading %d bytes", (int)length); |
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if (png_ptr->read_data_fn != NULL) |
(*(png_ptr->read_data_fn))(png_ptr, data, length); |
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else |
png_error(png_ptr, "Call to NULL read function"); |
} |
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#ifdef PNG_STDIO_SUPPORTED |
/* This is the function that 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 PNGCBAPI |
png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
{ |
png_size_t check; |
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if (png_ptr == NULL) |
return; |
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/* fread() returns 0 on error, so it is OK to store this in a png_size_t |
* instead of an int, which is what fread() actually returns. |
*/ |
check = fread(data, 1, length, (png_FILE_p)png_ptr->io_ptr); |
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if (check != length) |
png_error(png_ptr, "Read 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. |
*/ |
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#define NEAR_BUF_SIZE 1024 |
#define MIN(a,b) (a <= b ? a : b) |
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static void PNGCBAPI |
png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
{ |
png_size_t check; |
png_byte *n_data; |
png_FILE_p io_ptr; |
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if (png_ptr == NULL) |
return; |
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/* Check if data really is near. If so, use usual code. */ |
n_data = (png_byte *)CVT_PTR_NOCHECK(data); |
io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); |
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if ((png_bytep)n_data == data) |
{ |
check = fread(n_data, 1, length, io_ptr); |
} |
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else |
{ |
png_byte buf[NEAR_BUF_SIZE]; |
png_size_t read, remaining, err; |
check = 0; |
remaining = length; |
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do |
{ |
read = MIN(NEAR_BUF_SIZE, remaining); |
err = fread(buf, 1, read, io_ptr); |
png_memcpy(data, buf, read); /* copy far buffer to near buffer */ |
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if (err != read) |
break; |
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else |
check += err; |
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data += read; |
remaining -= read; |
} |
while (remaining != 0); |
} |
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if ((png_uint_32)check != (png_uint_32)length) |
png_error(png_ptr, "read Error"); |
} |
# endif |
#endif |
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/* 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 that takes as its |
* arguments a pointer to a png_struct, a pointer to |
* a location where input data can be stored, and a 32-bit |
* unsigned int that 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"). |
* May be NULL, in which case libpng's default function will |
* be used. |
*/ |
void PNGAPI |
png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, |
png_rw_ptr read_data_fn) |
{ |
if (png_ptr == NULL) |
return; |
|
png_ptr->io_ptr = io_ptr; |
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#ifdef PNG_STDIO_SUPPORTED |
if (read_data_fn != NULL) |
png_ptr->read_data_fn = read_data_fn; |
|
else |
png_ptr->read_data_fn = png_default_read_data; |
#else |
png_ptr->read_data_fn = read_data_fn; |
#endif |
|
/* It is an error to write to a read device */ |
if (png_ptr->write_data_fn != NULL) |
{ |
png_ptr->write_data_fn = NULL; |
png_warning(png_ptr, |
"Can't set both read_data_fn and write_data_fn in the" |
" same structure"); |
} |
|
#ifdef PNG_WRITE_FLUSH_SUPPORTED |
png_ptr->output_flush_fn = NULL; |
#endif |
} |
#endif /* PNG_READ_SUPPORTED */ |