214 lines
6.8 KiB
C
214 lines
6.8 KiB
C
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/* pngwio.c - functions for data output
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*
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* libpng 1.0.2 - June 14, 1998
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* For conditions of distribution and use, see copyright notice in png.h
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* Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
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* Copyright (c) 1996, 1997 Andreas Dilger
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* Copyright (c) 1998, Glenn Randers-Pehrson
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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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#define PNG_INTERNAL
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#include "png.h"
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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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void
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png_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
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{
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if (png_ptr->write_data_fn != NULL )
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(*(png_ptr->write_data_fn))(png_ptr, 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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#if !defined(PNG_NO_STDIO)
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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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#ifndef USE_FAR_KEYWORD
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static void
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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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check = fwrite(data, 1, length, (FILE *)(png_ptr->io_ptr));
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if (check != length)
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{
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png_error(png_ptr, "Write Error");
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}
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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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static void
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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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FILE *io_ptr;
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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 = (FILE *)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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{
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png_error(png_ptr, "Write Error");
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}
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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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#if defined(PNG_WRITE_FLUSH_SUPPORTED)
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void
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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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#if !defined(PNG_NO_STDIO)
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static void
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png_default_flush(png_structp png_ptr)
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{
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FILE *io_ptr;
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io_ptr = (FILE *)CVT_PTR((png_ptr->io_ptr));
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if (io_ptr != NULL)
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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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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.
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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 ouput, 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. */
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void
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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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png_ptr->io_ptr = io_ptr;
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#if !defined(PNG_NO_STDIO)
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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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#if defined(PNG_WRITE_FLUSH_SUPPORTED)
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#if !defined(PNG_NO_STDIO)
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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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"Attempted to set both read_data_fn and write_data_fn in");
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png_warning(png_ptr,
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"the same structure. Resetting read_data_fn to NULL.");
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}
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}
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#if defined(USE_FAR_KEYWORD)
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#if defined(_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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