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 43 #ifdef PNG_STDIO_SUPPORTED 44 /* This is the function that does the actual reading of data. If you are 45 * not reading from a standard C stream, you should create a replacement 46 * read_data function and use it at run time with png_set_read_fn(), rather 47 * than changing the library. 48 */ 49 #ifndef USE_FAR_KEYWORD 50 void PNGAPI 51 png_default_read_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 /* fread() returns 0 on error, so it is OK to store this in a png_size_t 58 * instead of an int, which is what fread() actually returns. 59 */ 60 #ifdef _WIN32_WCE 61 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) 62 check = 0; 63 #else 64 check = (png_size_t)fread(data, (png_size_t)1, length, 65 (png_FILE_p)png_ptr->io_ptr); 66 #endif 67 68 if (check != length) 69 png_error(png_ptr, "Read Error"); 70 } 71 #else 72 /* This is the model-independent version. Since the standard I/O library 73 can't handle far buffers in the medium and small models, we have to copy 74 the data. 75 */ 76 77 #define NEAR_BUF_SIZE 1024 78 #define MIN(a,b) (a <= b ? a : b) 79 80 static void PNGAPI 81 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 82 { 83 int check; 84 png_byte *n_data; 85 png_FILE_p io_ptr; 86 87 if (png_ptr == NULL) 88 return; 89 /* Check if data really is near. If so, use usual code. */ 90 n_data = (png_byte *)CVT_PTR_NOCHECK(data); 91 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); 92 if ((png_bytep)n_data == data) 93 { 94 #ifdef _WIN32_WCE 95 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, 96 NULL) ) 97 check = 0; 98 #else 99 check = fread(n_data, 1, length, io_ptr); 100 #endif 101 } 102 else 103 { 104 png_byte buf[NEAR_BUF_SIZE]; 105 png_size_t read, remaining, err; 106 check = 0; 107 remaining = length; 108 do 109 { 110 read = MIN(NEAR_BUF_SIZE, remaining); 111 #ifdef _WIN32_WCE 112 if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) ) 113 err = 0; 114 #else 115 err = fread(buf, (png_size_t)1, read, io_ptr); 116 #endif 117 png_memcpy(data, buf, read); /* copy far buffer to near buffer */ 118 if (err != read) 119 break; 120 else 121 check += err; 122 data += read; 123 remaining -= read; 124 } 125 while (remaining != 0); 126 } 127 if ((png_uint_32)check != (png_uint_32)length) 128 png_error(png_ptr, "read Error"); 129 } 130 #endif 131 #endif 132 133 /* This function allows the application to supply a new input function 134 * for libpng if standard C streams aren't being used. 135 * 136 * This function takes as its arguments: 137 * png_ptr - pointer to a png input data structure 138 * io_ptr - pointer to user supplied structure containing info about 139 * the input functions. May be NULL. 140 * read_data_fn - pointer to a new input function that takes as its 141 * arguments a pointer to a png_struct, a pointer to 142 * a location where input data can be stored, and a 32-bit 143 * unsigned int that is the number of bytes to be read. 144 * To exit and output any fatal error messages the new write 145 * function should call png_error(png_ptr, "Error msg"). 146 * May be NULL, in which case libpng's default function will 147 * be used. 148 */ 149 void PNGAPI 150 png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, 151 png_rw_ptr read_data_fn) 152 { 153 if (png_ptr == NULL) 154 return; 155 png_ptr->io_ptr = io_ptr; 156 157 #ifdef PNG_STDIO_SUPPORTED 158 if (read_data_fn != NULL) 159 png_ptr->read_data_fn = read_data_fn; 160 else 161 png_ptr->read_data_fn = png_default_read_data; 162 #else 163 png_ptr->read_data_fn = read_data_fn; 164 #endif 165 166 /* It is an error to write to a read device */ 167 if (png_ptr->write_data_fn != NULL) 168 { 169 png_ptr->write_data_fn = NULL; 170 png_warning(png_ptr, 171 "It's an error to set both read_data_fn and write_data_fn in the "); 172 png_warning(png_ptr, 173 "same structure. Resetting write_data_fn to NULL."); 174 } 175 176 #ifdef PNG_WRITE_FLUSH_SUPPORTED 177 png_ptr->output_flush_fn = NULL; 178 #endif 179 } 180 #endif /* PNG_READ_SUPPORTED */ 181
