/* pngwio.c - functions for data output * * Copyright (c) 2018 Cosmin Truta * Copyright (c) 1998-2002,2004,2006-2014,2016,2018 Glenn Randers-Pehrson * Copyright (c) 1996-1997 Andreas Dilger * 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 output. Users who need * special handling are expected to write functions that have the same * arguments as these and perform similar functions, but that possibly * use different output 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(...). */ #include "pngpriv.h" #ifdef PNG_WRITE_SUPPORTED /* Write the data to whatever output you are using. The default routine * writes to 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 writes. This should never be asked * to write more than 64K on a 16-bit machine. */ void /* PRIVATE */ png_write_data(png_structrp png_ptr, png_const_bytep data, size_t length) { … } #ifdef PNG_STDIO_SUPPORTED /* This is the function that does the actual writing of data. If you are * not writing to a standard C stream, you should create a replacement * write_data function and use it at run time with png_set_write_fn(), rather * than changing the library. */ void PNGCBAPI png_default_write_data(png_structp png_ptr, png_bytep data, size_t length) { … } #endif /* This function is called to output any data pending writing (normally * to disk). After png_flush is called, there should be no data pending * writing in any buffers. */ #ifdef PNG_WRITE_FLUSH_SUPPORTED void /* PRIVATE */ png_flush(png_structrp png_ptr) { … } # ifdef PNG_STDIO_SUPPORTED void PNGCBAPI png_default_flush(png_structp png_ptr) { … } # endif #endif /* This function allows the application to supply new output functions for * 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 that takes as its * arguments a pointer to a png_struct, a pointer to * data to be written, and a 32-bit unsigned int that is * the number of bytes to be written. The new write * function should call png_error(png_ptr, "Error msg") * to exit and output any fatal error messages. May be * NULL, in which case libpng's default function will * be used. * flush_data_fn - pointer to a new flush function that 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 output, a function prototype must still be * supplied although it doesn't have to do anything. 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. May be NULL, in which case * libpng's default function will be used, if * PNG_WRITE_FLUSH_SUPPORTED is defined. This is not * a good idea if io_ptr does not point to a standard * *FILE structure. */ void PNGAPI png_set_write_fn(png_structrp png_ptr, png_voidp io_ptr, png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn) { … } #endif /* WRITE */
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