1 2 /* pngwio.c - functions for data output 3 * 4 * Last changed in libpng 1.6.24 [August 4, 2016] 5 * Copyright (c) 1998-2002,2004,2006-2014,2016 Glenn Randers-Pehrson 6 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) 7 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) 8 * 9 * This code is released under the libpng license. 10 * For conditions of distribution and use, see the disclaimer 11 * and license in png.h 12 * 13 * This file provides a location for all output. Users who need 14 * special handling are expected to write functions that have the same 15 * arguments as these and perform similar functions, but that possibly 16 * use different output methods. Note that you shouldn't change these 17 * functions, but rather write replacement functions and then change 18 * them at run time with png_set_write_fn(...). 19 */ 20 21 #include "pngpriv.h" 22 23 #ifdef PNG_WRITE_SUPPORTED 24 25 /* Write the data to whatever output you are using. The default routine 26 * writes to a file pointer. Note that this routine sometimes gets called 27 * with very small lengths, so you should implement some kind of simple 28 * buffering if you are using unbuffered writes. This should never be asked 29 * to write more than 64K on a 16-bit machine. 30 */ 31 32 void /* PRIVATE */ 33 png_write_data(png_structrp png_ptr, png_const_bytep data, png_size_t length) 34 { 35 /* NOTE: write_data_fn must not change the buffer! */ 36 if (png_ptr->write_data_fn != NULL ) 37 (*(png_ptr->write_data_fn))(png_ptr, png_constcast(png_bytep,data), 38 length); 39 40 else 41 png_error(png_ptr, "Call to NULL write function"); 42 } 43 44 #ifdef PNG_STDIO_SUPPORTED 45 /* This is the function that does the actual writing of data. If you are 46 * not writing to a standard C stream, you should create a replacement 47 * write_data function and use it at run time with png_set_write_fn(), rather 48 * than changing the library. 49 */ 50 void PNGCBAPI 51 png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length) 52 { 53 png_size_t check; 54 55 if (png_ptr == NULL) 56 return; 57 58 check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr)); 59 60 if (check != length) 61 png_error(png_ptr, "Write Error"); 62 } 63 #endif 64 65 /* This function is called to output any data pending writing (normally 66 * to disk). After png_flush is called, there should be no data pending 67 * writing in any buffers. 68 */ 69 #ifdef PNG_WRITE_FLUSH_SUPPORTED 70 void /* PRIVATE */ 71 png_flush(png_structrp png_ptr) 72 { 73 if (png_ptr->output_flush_fn != NULL) 74 (*(png_ptr->output_flush_fn))(png_ptr); 75 } 76 77 # ifdef PNG_STDIO_SUPPORTED 78 void PNGCBAPI 79 png_default_flush(png_structp png_ptr) 80 { 81 png_FILE_p io_ptr; 82 83 if (png_ptr == NULL) 84 return; 85 86 io_ptr = png_voidcast(png_FILE_p, (png_ptr->io_ptr)); 87 fflush(io_ptr); 88 } 89 # endif 90 #endif 91 92 /* This function allows the application to supply new output functions for 93 * libpng if standard C streams aren't being used. 94 * 95 * This function takes as its arguments: 96 * png_ptr - pointer to a png output data structure 97 * io_ptr - pointer to user supplied structure containing info about 98 * the output functions. May be NULL. 99 * write_data_fn - pointer to a new output function that takes as its 100 * arguments a pointer to a png_struct, a pointer to 101 * data to be written, and a 32-bit unsigned int that is 102 * the number of bytes to be written. The new write 103 * function should call png_error(png_ptr, "Error msg") 104 * to exit and output any fatal error messages. May be 105 * NULL, in which case libpng's default function will 106 * be used. 107 * flush_data_fn - pointer to a new flush function that takes as its 108 * arguments a pointer to a png_struct. After a call to 109 * the flush function, there should be no data in any buffers 110 * or pending transmission. If the output method doesn't do 111 * any buffering of output, a function prototype must still be 112 * supplied although it doesn't have to do anything. If 113 * PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile 114 * time, output_flush_fn will be ignored, although it must be 115 * supplied for compatibility. May be NULL, in which case 116 * libpng's default function will be used, if 117 * PNG_WRITE_FLUSH_SUPPORTED is defined. This is not 118 * a good idea if io_ptr does not point to a standard 119 * *FILE structure. 120 */ 121 void PNGAPI 122 png_set_write_fn(png_structrp png_ptr, png_voidp io_ptr, 123 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn) 124 { 125 if (png_ptr == NULL) 126 return; 127 128 png_ptr->io_ptr = io_ptr; 129 130 #ifdef PNG_STDIO_SUPPORTED 131 if (write_data_fn != NULL) 132 png_ptr->write_data_fn = write_data_fn; 133 134 else 135 png_ptr->write_data_fn = png_default_write_data; 136 #else 137 png_ptr->write_data_fn = write_data_fn; 138 #endif 139 140 #ifdef PNG_WRITE_FLUSH_SUPPORTED 141 # ifdef PNG_STDIO_SUPPORTED 142 143 if (output_flush_fn != NULL) 144 png_ptr->output_flush_fn = output_flush_fn; 145 146 else 147 png_ptr->output_flush_fn = png_default_flush; 148 149 # else 150 png_ptr->output_flush_fn = output_flush_fn; 151 # endif 152 #else 153 PNG_UNUSED(output_flush_fn) 154 #endif /* WRITE_FLUSH */ 155 156 #ifdef PNG_READ_SUPPORTED 157 /* It is an error to read while writing a png file */ 158 if (png_ptr->read_data_fn != NULL) 159 { 160 png_ptr->read_data_fn = NULL; 161 162 png_warning(png_ptr, 163 "Can't set both read_data_fn and write_data_fn in the" 164 " same structure"); 165 } 166 #endif 167 } 168 #endif /* WRITE */ 169
