1 2 /* pngrio.c - functions for data input 3 * 4 * Last changed in libpng 1.2.43 [February 25, 2010] 5 * Copyright (c) 1998-2010 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 input. Users who need 14 * special handling are expected to write a function that has the same 15 * arguments as this and performs a similar function, but that possibly 16 * has a different input method. Note that you shouldn't change this 17 * function, but rather write a replacement function and then make 18 * libpng use it at run time with png_set_read_fn(...). 19 */ 20 21 #define PNG_INTERNAL 22 #define PNG_NO_PEDANTIC_WARNINGS 23 #include "png.h" 24 #ifdef PNG_READ_SUPPORTED 25 26 /* Read the data from whatever input you are using. The default routine 27 * reads from a file pointer. Note that this routine sometimes gets called 28 * with very small lengths, so you should implement some kind of simple 29 * buffering if you are using unbuffered reads. This should never be asked 30 * to read more then 64K on a 16 bit machine. 31 */ 32 void /* PRIVATE */ 33 png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 34 { 35 png_debug1(4, "reading %d bytes", (int)length); 36 37 if (png_ptr->read_data_fn != NULL) 38 (*(png_ptr->read_data_fn))(png_ptr, data, length); 39 else 40 png_error(png_ptr, "Call to NULL read function"); 41 42 #ifdef PNG_INDEX_SUPPORTED 43 png_ptr->total_data_read += length; 44 #endif 45 } 46 47 #ifdef PNG_INDEX_SUPPORTED 48 void /* PRIVATE */ 49 png_seek_data(png_structp png_ptr, png_uint_32 offset) 50 { 51 if (png_ptr->seek_data_fn != NULL) 52 (*(png_ptr->seek_data_fn))(png_ptr, offset); 53 else 54 png_error(png_ptr, "Call to NULL seek function"); 55 } 56 #endif 57 58 #ifdef PNG_STDIO_SUPPORTED 59 /* This is the function that does the actual reading of data. If you are 60 * not reading from a standard C stream, you should create a replacement 61 * read_data function and use it at run time with png_set_read_fn(), rather 62 * than changing the library. 63 */ 64 #ifndef USE_FAR_KEYWORD 65 void PNGAPI 66 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 67 { 68 png_size_t check; 69 70 if (png_ptr == NULL) 71 return; 72 /* fread() returns 0 on error, so it is OK to store this in a png_size_t 73 * instead of an int, which is what fread() actually returns. 74 */ 75 #ifdef _WIN32_WCE 76 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) 77 check = 0; 78 #else 79 check = (png_size_t)fread(data, (png_size_t)1, length, 80 (png_FILE_p)png_ptr->io_ptr); 81 #endif 82 83 if (check != length) 84 png_error(png_ptr, "Read Error"); 85 } 86 #else 87 /* This is the model-independent version. Since the standard I/O library 88 can't handle far buffers in the medium and small models, we have to copy 89 the data. 90 */ 91 92 #define NEAR_BUF_SIZE 1024 93 #define MIN(a,b) (a <= b ? a : b) 94 95 static void PNGAPI 96 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 97 { 98 int check; 99 png_byte *n_data; 100 png_FILE_p io_ptr; 101 102 if (png_ptr == NULL) 103 return; 104 /* Check if data really is near. If so, use usual code. */ 105 n_data = (png_byte *)CVT_PTR_NOCHECK(data); 106 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); 107 if ((png_bytep)n_data == data) 108 { 109 #ifdef _WIN32_WCE 110 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, 111 NULL) ) 112 check = 0; 113 #else 114 check = fread(n_data, 1, length, io_ptr); 115 #endif 116 } 117 else 118 { 119 png_byte buf[NEAR_BUF_SIZE]; 120 png_size_t read, remaining, err; 121 check = 0; 122 remaining = length; 123 do 124 { 125 read = MIN(NEAR_BUF_SIZE, remaining); 126 #ifdef _WIN32_WCE 127 if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) ) 128 err = 0; 129 #else 130 err = fread(buf, (png_size_t)1, read, io_ptr); 131 #endif 132 png_memcpy(data, buf, read); /* copy far buffer to near buffer */ 133 if (err != read) 134 break; 135 else 136 check += err; 137 data += read; 138 remaining -= read; 139 } 140 while (remaining != 0); 141 } 142 if ((png_uint_32)check != (png_uint_32)length) 143 png_error(png_ptr, "read Error"); 144 } 145 #endif 146 #endif 147 148 /* This function allows the application to supply a new input function 149 * for libpng if standard C streams aren't being used. 150 * 151 * This function takes as its arguments: 152 * png_ptr - pointer to a png input data structure 153 * io_ptr - pointer to user supplied structure containing info about 154 * the input functions. May be NULL. 155 * read_data_fn - pointer to a new input function that takes as its 156 * arguments a pointer to a png_struct, a pointer to 157 * a location where input data can be stored, and a 32-bit 158 * unsigned int that is the number of bytes to be read. 159 * To exit and output any fatal error messages the new write 160 * function should call png_error(png_ptr, "Error msg"). 161 * May be NULL, in which case libpng's default function will 162 * be used. 163 */ 164 void PNGAPI 165 png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, 166 png_rw_ptr read_data_fn) 167 { 168 if (png_ptr == NULL) 169 return; 170 png_ptr->io_ptr = io_ptr; 171 172 #ifdef PNG_STDIO_SUPPORTED 173 if (read_data_fn != NULL) 174 png_ptr->read_data_fn = read_data_fn; 175 else 176 png_ptr->read_data_fn = png_default_read_data; 177 #else 178 png_ptr->read_data_fn = read_data_fn; 179 #endif 180 181 /* It is an error to write to a read device */ 182 if (png_ptr->write_data_fn != NULL) 183 { 184 png_ptr->write_data_fn = NULL; 185 png_warning(png_ptr, 186 "It's an error to set both read_data_fn and write_data_fn in the "); 187 png_warning(png_ptr, 188 "same structure. Resetting write_data_fn to NULL."); 189 } 190 191 #ifdef PNG_WRITE_FLUSH_SUPPORTED 192 png_ptr->output_flush_fn = NULL; 193 #endif 194 } 195 196 #ifdef PNG_INDEX_SUPPORTED 197 void PNGAPI 198 png_set_seek_fn(png_structp png_ptr, png_seek_ptr seek_data_fn) 199 { 200 if (png_ptr == NULL) 201 return; 202 png_ptr->seek_data_fn = seek_data_fn; 203 } 204 #endif 205 #endif /* PNG_READ_SUPPORTED */ 206
