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168 lines
5.5 KiB
168 lines
5.5 KiB
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/* pngwio.c - functions for data output |
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* |
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* Copyright (c) 2018 Cosmin Truta |
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* Copyright (c) 1998-2002,2004,2006-2014,2016,2018 Glenn Randers-Pehrson |
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* Copyright (c) 1996-1997 Andreas Dilger |
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* 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_structrp png_ptr, png_const_bytep data, 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_constcast(png_bytep,data), |
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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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void PNGCBAPI |
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png_default_write_data(png_structp png_ptr, png_bytep data, size_t length) |
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{ |
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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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#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_structrp 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_voidcast(png_FILE_p, (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_structrp 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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#else |
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PNG_UNUSED(output_flush_fn) |
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#endif /* WRITE_FLUSH */ |
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#ifdef PNG_READ_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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#endif |
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} |
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#endif /* WRITE */
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