/src/FreeImage/Source/LibPNG/pngrio.c
C | 176 lines | 92 code | 27 blank | 57 comment | 22 complexity | aaf0f5e7dcaa28b559e588a231083051 MD5 | raw file
1 2/* pngrio.c - functions for data input 3 * 4 * Last changed in libpng 1.5.0 [January 6, 2011] 5 * Copyright (c) 1998-2011 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#include "pngpriv.h" 22 23#ifdef PNG_READ_SUPPORTED 24 25/* Read the data from whatever input you are using. The default routine 26 * reads from 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 reads. This should never be asked 29 * to read more then 64K on a 16 bit machine. 30 */ 31void /* PRIVATE */ 32png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 33{ 34 png_debug1(4, "reading %d bytes", (int)length); 35 36 if (png_ptr->read_data_fn != NULL) 37 (*(png_ptr->read_data_fn))(png_ptr, data, length); 38 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 50void PNGCBAPI 51png_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 58 /* fread() returns 0 on error, so it is OK to store this in a png_size_t 59 * instead of an int, which is what fread() actually returns. 60 */ 61 check = fread(data, 1, length, (png_FILE_p)png_ptr->io_ptr); 62 63 if (check != length) 64 png_error(png_ptr, "Read Error"); 65} 66# else 67/* This is the model-independent version. Since the standard I/O library 68 can't handle far buffers in the medium and small models, we have to copy 69 the data. 70*/ 71 72#define NEAR_BUF_SIZE 1024 73#define MIN(a,b) (a <= b ? a : b) 74 75static void PNGCBAPI 76png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 77{ 78 png_size_t check; 79 png_byte *n_data; 80 png_FILE_p io_ptr; 81 82 if (png_ptr == NULL) 83 return; 84 85 /* Check if data really is near. If so, use usual code. */ 86 n_data = (png_byte *)CVT_PTR_NOCHECK(data); 87 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); 88 89 if ((png_bytep)n_data == data) 90 { 91 check = fread(n_data, 1, length, io_ptr); 92 } 93 94 else 95 { 96 png_byte buf[NEAR_BUF_SIZE]; 97 png_size_t read, remaining, err; 98 check = 0; 99 remaining = length; 100 101 do 102 { 103 read = MIN(NEAR_BUF_SIZE, remaining); 104 err = fread(buf, 1, read, io_ptr); 105 png_memcpy(data, buf, read); /* copy far buffer to near buffer */ 106 107 if (err != read) 108 break; 109 110 else 111 check += err; 112 113 data += read; 114 remaining -= read; 115 } 116 while (remaining != 0); 117 } 118 119 if ((png_uint_32)check != (png_uint_32)length) 120 png_error(png_ptr, "read Error"); 121} 122# endif 123#endif 124 125/* This function allows the application to supply a new input function 126 * for libpng if standard C streams aren't being used. 127 * 128 * This function takes as its arguments: 129 * 130 * png_ptr - pointer to a png input data structure 131 * 132 * io_ptr - pointer to user supplied structure containing info about 133 * the input functions. May be NULL. 134 * 135 * read_data_fn - pointer to a new input function that takes as its 136 * arguments a pointer to a png_struct, a pointer to 137 * a location where input data can be stored, and a 32-bit 138 * unsigned int that is the number of bytes to be read. 139 * To exit and output any fatal error messages the new write 140 * function should call png_error(png_ptr, "Error msg"). 141 * May be NULL, in which case libpng's default function will 142 * be used. 143 */ 144void PNGAPI 145png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, 146 png_rw_ptr read_data_fn) 147{ 148 if (png_ptr == NULL) 149 return; 150 151 png_ptr->io_ptr = io_ptr; 152 153#ifdef PNG_STDIO_SUPPORTED 154 if (read_data_fn != NULL) 155 png_ptr->read_data_fn = read_data_fn; 156 157 else 158 png_ptr->read_data_fn = png_default_read_data; 159#else 160 png_ptr->read_data_fn = read_data_fn; 161#endif 162 163 /* It is an error to write to a read device */ 164 if (png_ptr->write_data_fn != NULL) 165 { 166 png_ptr->write_data_fn = NULL; 167 png_warning(png_ptr, 168 "Can't set both read_data_fn and write_data_fn in the" 169 " same structure"); 170 } 171 172#ifdef PNG_WRITE_FLUSH_SUPPORTED 173 png_ptr->output_flush_fn = NULL; 174#endif 175} 176#endif /* PNG_READ_SUPPORTED */