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254 lines
7.5 KiB
254 lines
7.5 KiB
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/* pngwio.c - functions for data output |
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* |
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* Last changed in libpng 1.5.0 [January 6, 2011] |
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* Copyright (c) 1998-2011 Glenn Randers-Pehrson |
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* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) |
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* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) |
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* |
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* This code is released under the libpng license. |
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* For conditions of distribution and use, see the disclaimer |
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* and license in png.h |
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* |
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* This file provides a location for all output. Users who need |
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* special handling are expected to write functions that have the same |
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* arguments as these and perform similar functions, but that possibly |
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* use different output methods. Note that you shouldn't change these |
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* functions, but rather write replacement functions and then change |
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* them at run time with png_set_write_fn(...). |
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*/ |
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#include "pngpriv.h" |
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#ifdef PNG_WRITE_SUPPORTED |
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/* Write the data to whatever output you are using. The default routine |
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* writes to a file pointer. Note that this routine sometimes gets called |
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* with very small lengths, so you should implement some kind of simple |
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* buffering if you are using unbuffered writes. This should never be asked |
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* to write more than 64K on a 16 bit machine. |
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*/ |
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void /* PRIVATE */ |
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png_write_data(png_structp png_ptr, png_const_bytep data, png_size_t length) |
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{ |
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/* NOTE: write_data_fn must not change the buffer! */ |
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if (png_ptr->write_data_fn != NULL ) |
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(*(png_ptr->write_data_fn))(png_ptr, (png_bytep)data, length); |
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else |
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png_error(png_ptr, "Call to NULL write function"); |
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} |
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#ifdef PNG_STDIO_SUPPORTED |
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/* This is the function that does the actual writing of data. If you are |
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* not writing to a standard C stream, you should create a replacement |
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* write_data function and use it at run time with png_set_write_fn(), rather |
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* than changing the library. |
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*/ |
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#ifndef USE_FAR_KEYWORD |
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void PNGCBAPI |
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png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length) |
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{ |
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png_size_t check; |
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if (png_ptr == NULL) |
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return; |
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check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr)); |
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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 |
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* 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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*/ |
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#define NEAR_BUF_SIZE 1024 |
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#define MIN(a,b) (a <= b ? a : b) |
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void PNGCBAPI |
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png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length) |
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{ |
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png_uint_32 check; |
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png_byte *near_data; /* Needs to be "png_byte *" instead of "png_bytep" */ |
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png_FILE_p io_ptr; |
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if (png_ptr == NULL) |
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return; |
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/* Check if data really is near. If so, use usual code. */ |
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near_data = (png_byte *)CVT_PTR_NOCHECK(data); |
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io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); |
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if ((png_bytep)near_data == data) |
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{ |
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check = fwrite(near_data, 1, length, io_ptr); |
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} |
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else |
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{ |
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png_byte buf[NEAR_BUF_SIZE]; |
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png_size_t written, remaining, err; |
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check = 0; |
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remaining = length; |
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do |
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{ |
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written = MIN(NEAR_BUF_SIZE, remaining); |
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png_memcpy(buf, data, written); /* Copy far buffer to near buffer */ |
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err = fwrite(buf, 1, written, io_ptr); |
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if (err != written) |
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break; |
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else |
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check += err; |
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data += written; |
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remaining -= written; |
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} |
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while (remaining != 0); |
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} |
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if (check != length) |
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png_error(png_ptr, "Write Error"); |
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} |
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#endif |
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#endif |
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/* This function is called to output any data pending writing (normally |
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* to disk). After png_flush is called, there should be no data pending |
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* writing in any buffers. |
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*/ |
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#ifdef PNG_WRITE_FLUSH_SUPPORTED |
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void /* PRIVATE */ |
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png_flush(png_structp png_ptr) |
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{ |
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if (png_ptr->output_flush_fn != NULL) |
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(*(png_ptr->output_flush_fn))(png_ptr); |
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} |
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# ifdef PNG_STDIO_SUPPORTED |
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void PNGCBAPI |
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png_default_flush(png_structp png_ptr) |
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{ |
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png_FILE_p io_ptr; |
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if (png_ptr == NULL) |
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return; |
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io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr)); |
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fflush(io_ptr); |
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} |
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# endif |
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#endif |
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/* This function allows the application to supply new output functions for |
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* libpng if standard C streams aren't being used. |
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* |
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* This function takes as its arguments: |
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* png_ptr - pointer to a png output data structure |
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* io_ptr - pointer to user supplied structure containing info about |
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* the output functions. May be NULL. |
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* write_data_fn - pointer to a new output function that takes as its |
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* arguments a pointer to a png_struct, a pointer to |
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* data to be written, and a 32-bit unsigned int that is |
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* the number of bytes to be written. The new write |
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* function should call png_error(png_ptr, "Error msg") |
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* to exit and output any fatal error messages. May be |
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* NULL, in which case libpng's default function will |
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* be used. |
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* flush_data_fn - pointer to a new flush function that takes as its |
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* arguments a pointer to a png_struct. After a call to |
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* the flush function, there should be no data in any buffers |
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* or pending transmission. If the output method doesn't do |
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* any buffering of output, a function prototype must still be |
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* supplied although it doesn't have to do anything. If |
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* PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile |
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* time, output_flush_fn will be ignored, although it must be |
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* supplied for compatibility. May be NULL, in which case |
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* libpng's default function will be used, if |
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* PNG_WRITE_FLUSH_SUPPORTED is defined. This is not |
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* a good idea if io_ptr does not point to a standard |
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* *FILE structure. |
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*/ |
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void PNGAPI |
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png_set_write_fn(png_structp png_ptr, png_voidp io_ptr, |
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png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn) |
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{ |
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if (png_ptr == NULL) |
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return; |
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png_ptr->io_ptr = io_ptr; |
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#ifdef PNG_STDIO_SUPPORTED |
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if (write_data_fn != NULL) |
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png_ptr->write_data_fn = write_data_fn; |
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else |
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png_ptr->write_data_fn = png_default_write_data; |
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#else |
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png_ptr->write_data_fn = write_data_fn; |
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#endif |
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#ifdef PNG_WRITE_FLUSH_SUPPORTED |
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# ifdef PNG_STDIO_SUPPORTED |
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if (output_flush_fn != NULL) |
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png_ptr->output_flush_fn = output_flush_fn; |
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else |
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png_ptr->output_flush_fn = png_default_flush; |
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# else |
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png_ptr->output_flush_fn = output_flush_fn; |
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# endif |
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#endif /* PNG_WRITE_FLUSH_SUPPORTED */ |
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/* It is an error to read while writing a png file */ |
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if (png_ptr->read_data_fn != NULL) |
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{ |
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png_ptr->read_data_fn = NULL; |
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png_warning(png_ptr, |
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"Can't set both read_data_fn and write_data_fn in the" |
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" same structure"); |
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} |
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} |
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#ifdef USE_FAR_KEYWORD |
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# ifdef _MSC_VER |
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void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check) |
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{ |
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void *near_ptr; |
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void FAR *far_ptr; |
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FP_OFF(near_ptr) = FP_OFF(ptr); |
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far_ptr = (void FAR *)near_ptr; |
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if (check != 0) |
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if (FP_SEG(ptr) != FP_SEG(far_ptr)) |
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png_error(png_ptr, "segment lost in conversion"); |
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return(near_ptr); |
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} |
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# else |
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void *png_far_to_near(png_structp png_ptr, png_voidp ptr, int check) |
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{ |
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void *near_ptr; |
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void FAR *far_ptr; |
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near_ptr = (void FAR *)ptr; |
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far_ptr = (void FAR *)near_ptr; |
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if (check != 0) |
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if (far_ptr != ptr) |
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png_error(png_ptr, "segment lost in conversion"); |
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return(near_ptr); |
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} |
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# endif |
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#endif |
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#endif /* PNG_WRITE_SUPPORTED */
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