1 2/* pngwio.c - functions for data output 3 * 4 * libpng 1.2.7 - September 12, 2004 5 * For conditions of distribution and use, see copyright notice in png.h 6 * Copyright (c) 1998-2004 Glenn Randers-Pehrson 7 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) 8 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) 9 * 10 * This file provides a location for all output. Users who need 11 * special handling are expected to write functions that have the same 12 * arguments as these and perform similar functions, but that possibly 13 * use different output methods. Note that you shouldn't change these 14 * functions, but rather write replacement functions and then change 15 * them at run time with png_set_write_fn(...). 16 */ 17 18#define PNG_INTERNAL 19#include "png.h" 20#ifdef PNG_WRITE_SUPPORTED 21 22/* Write the data to whatever output you are using. The default routine 23 writes to a file pointer. Note that this routine sometimes gets called 24 with very small lengths, so you should implement some kind of simple 25 buffering if you are using unbuffered writes. This should never be asked 26 to write more than 64K on a 16 bit machine. */ 27 28void /* PRIVATE */ 29png_write_data(png_structp png_ptr, png_bytep data, png_size_t length) 30{ 31 if (png_ptr->write_data_fn != NULL ) 32 (*(png_ptr->write_data_fn))(png_ptr, data, length); 33 else 34 png_error(png_ptr, "Call to NULL write function"); 35} 36 37#if !defined(PNG_NO_STDIO) 38/* This is the function that does the actual writing of data. If you are 39 not writing to a standard C stream, you should create a replacement 40 write_data function and use it at run time with png_set_write_fn(), rather 41 than changing the library. */ 42#ifndef USE_FAR_KEYWORD 43void PNGAPI 44png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length) 45{ 46 png_uint_32 check; 47 48#if defined(_WIN32_WCE) 49 if ( !WriteFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) 50 check = 0; 51#else 52 check = fwrite(data, 1, length, (png_FILE_p)(png_ptr->io_ptr)); 53#endif 54 if (check != length) 55 png_error(png_ptr, "Write Error"); 56} 57#else 58/* this is the model-independent version. Since the standard I/O library 59 can't handle far buffers in the medium and small models, we have to copy 60 the data. 61*/ 62 63#define NEAR_BUF_SIZE 1024 64#define MIN(a,b) (a <= b ? a : b) 65 66void PNGAPI 67png_default_write_data(png_structp png_ptr, png_bytep data, png_size_t length) 68{ 69 png_uint_32 check; 70 png_byte *near_data; /* Needs to be "png_byte *" instead of "png_bytep" */ 71 png_FILE_p io_ptr; 72 73 /* Check if data really is near. If so, use usual code. */ 74 near_data = (png_byte *)CVT_PTR_NOCHECK(data); 75 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); 76 if ((png_bytep)near_data == data) 77 { 78#if defined(_WIN32_WCE) 79 if ( !WriteFile(io_ptr, near_data, length, &check, NULL) ) 80 check = 0; 81#else 82 check = fwrite(near_data, 1, length, io_ptr); 83#endif 84 } 85 else 86 { 87 png_byte buf[NEAR_BUF_SIZE]; 88 png_size_t written, remaining, err; 89 check = 0; 90 remaining = length; 91 do 92 { 93 written = MIN(NEAR_BUF_SIZE, remaining); 94 png_memcpy(buf, data, written); /* copy far buffer to near buffer */ 95#if defined(_WIN32_WCE) 96 if ( !WriteFile(io_ptr, buf, written, &err, NULL) ) 97 err = 0; 98#else 99 err = fwrite(buf, 1, written, io_ptr); 100#endif 101 if (err != written) 102 break; 103 else 104 check += err; 105 data += written; 106 remaining -= written; 107 } 108 while (remaining != 0); 109 } 110 if (check != length) 111 png_error(png_ptr, "Write Error"); 112} 113 114#endif 115#endif 116 117/* This function is called to output any data pending writing (normally 118 to disk). After png_flush is called, there should be no data pending 119 writing in any buffers. */ 120#if defined(PNG_WRITE_FLUSH_SUPPORTED) 121void /* PRIVATE */ 122png_flush(png_structp png_ptr) 123{ 124 if (png_ptr->output_flush_fn != NULL) 125 (*(png_ptr->output_flush_fn))(png_ptr); 126} 127 128#if !defined(PNG_NO_STDIO) 129void PNGAPI 130png_default_flush(png_structp png_ptr) 131{ 132#if !defined(_WIN32_WCE) 133 png_FILE_p io_ptr; 134 io_ptr = (png_FILE_p)CVT_PTR((png_ptr->io_ptr)); 135 if (io_ptr != NULL) 136 fflush(io_ptr); 137#endif 138} 139#endif 140#endif 141 142/* This function allows the application to supply new output functions for 143 libpng if standard C streams aren't being used. 144 145 This function takes as its arguments: 146 png_ptr - pointer to a png output data structure 147 io_ptr - pointer to user supplied structure containing info about 148 the output functions. May be NULL. 149 write_data_fn - pointer to a new output function that takes as its 150 arguments a pointer to a png_struct, a pointer to 151 data to be written, and a 32-bit unsigned int that is 152 the number of bytes to be written. The new write 153 function should call png_error(png_ptr, "Error msg") 154 to exit and output any fatal error messages. 155 flush_data_fn - pointer to a new flush function that takes as its 156 arguments a pointer to a png_struct. After a call to 157 the flush function, there should be no data in any buffers 158 or pending transmission. If the output method doesn't do 159 any buffering of ouput, a function prototype must still be 160 supplied although it doesn't have to do anything. If 161 PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile 162 time, output_flush_fn will be ignored, although it must be 163 supplied for compatibility. */ 164void PNGAPI 165png_set_write_fn(png_structp png_ptr, png_voidp io_ptr, 166 png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn) 167{ 168 png_ptr->io_ptr = io_ptr; 169 170#if !defined(PNG_NO_STDIO) 171 if (write_data_fn != NULL) 172 png_ptr->write_data_fn = write_data_fn; 173 else 174 png_ptr->write_data_fn = png_default_write_data; 175#else 176 png_ptr->write_data_fn = write_data_fn; 177#endif 178 179#if defined(PNG_WRITE_FLUSH_SUPPORTED) 180#if !defined(PNG_NO_STDIO) 181 if (output_flush_fn != NULL) 182 png_ptr->output_flush_fn = output_flush_fn; 183 else 184 png_ptr->output_flush_fn = png_default_flush; 185#else 186 png_ptr->output_flush_fn = output_flush_fn; 187#endif 188#endif /* PNG_WRITE_FLUSH_SUPPORTED */ 189 190 /* It is an error to read while writing a png file */ 191 if (png_ptr->read_data_fn != NULL) 192 { 193 png_ptr->read_data_fn = NULL; 194 png_warning(png_ptr, 195 "Attempted to set both read_data_fn and write_data_fn in"); 196 png_warning(png_ptr, 197 "the same structure. Resetting read_data_fn to NULL."); 198 } 199} 200 201#if defined(USE_FAR_KEYWORD) 202#if defined(_MSC_VER) 203void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check) 204{ 205 void *near_ptr; 206 void FAR *far_ptr; 207 FP_OFF(near_ptr) = FP_OFF(ptr); 208 far_ptr = (void FAR *)near_ptr; 209 if(check != 0) 210 if(FP_SEG(ptr) != FP_SEG(far_ptr)) 211 png_error(png_ptr,"segment lost in conversion"); 212 return(near_ptr); 213} 214# else 215void *png_far_to_near(png_structp png_ptr,png_voidp ptr, int check) 216{ 217 void *near_ptr; 218 void FAR *far_ptr; 219 near_ptr = (void FAR *)ptr; 220 far_ptr = (void FAR *)near_ptr; 221 if(check != 0) 222 if(far_ptr != ptr) 223 png_error(png_ptr,"segment lost in conversion"); 224 return(near_ptr); 225} 226# endif 227# endif 228#endif /* PNG_WRITE_SUPPORTED */ 229