1 2/* pngrio.c - functions for data input 3 * 4 * Last changed in libpng 1.6.9 [February 6, 2014] 5 * Copyright (c) 1998-2014 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_structrp 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#ifdef PNG_INDEX_SUPPORTED 42 png_ptr->total_data_read += length; 43#endif 44} 45 46#ifdef PNG_INDEX_SUPPORTED 47void /* PRIVATE */ 48png_seek_data(png_structp png_ptr, png_uint_32 offset) 49{ 50 if (png_ptr->seek_data_fn != NULL) 51 (*(png_ptr->seek_data_fn))(png_ptr, offset); 52 else 53 png_error(png_ptr, "Call to NULL seek function"); 54} 55#endif 56 57#ifdef PNG_STDIO_SUPPORTED 58/* This is the function that does the actual reading of data. If you are 59 * not reading from a standard C stream, you should create a replacement 60 * read_data function and use it at run time with png_set_read_fn(), rather 61 * than changing the library. 62 */ 63void PNGCBAPI 64png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 65{ 66 png_size_t check; 67 68 if (png_ptr == NULL) 69 return; 70 71 /* fread() returns 0 on error, so it is OK to store this in a png_size_t 72 * instead of an int, which is what fread() actually returns. 73 */ 74 check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr)); 75 76 if (check != length) 77 png_error(png_ptr, "Read Error"); 78} 79#endif 80 81/* This function allows the application to supply a new input function 82 * for libpng if standard C streams aren't being used. 83 * 84 * This function takes as its arguments: 85 * 86 * png_ptr - pointer to a png input data structure 87 * 88 * io_ptr - pointer to user supplied structure containing info about 89 * the input functions. May be NULL. 90 * 91 * read_data_fn - pointer to a new input function that takes as its 92 * arguments a pointer to a png_struct, a pointer to 93 * a location where input data can be stored, and a 32-bit 94 * unsigned int that is the number of bytes to be read. 95 * To exit and output any fatal error messages the new write 96 * function should call png_error(png_ptr, "Error msg"). 97 * May be NULL, in which case libpng's default function will 98 * be used. 99 */ 100void PNGAPI 101png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr, 102 png_rw_ptr read_data_fn) 103{ 104 if (png_ptr == NULL) 105 return; 106 107 png_ptr->io_ptr = io_ptr; 108 109#ifdef PNG_STDIO_SUPPORTED 110 if (read_data_fn != NULL) 111 png_ptr->read_data_fn = read_data_fn; 112 113 else 114 png_ptr->read_data_fn = png_default_read_data; 115#else 116 png_ptr->read_data_fn = read_data_fn; 117#endif 118 119#ifdef PNG_WRITE_SUPPORTED 120 /* It is an error to write to a read device */ 121 if (png_ptr->write_data_fn != NULL) 122 { 123 png_ptr->write_data_fn = NULL; 124 png_warning(png_ptr, 125 "Can't set both read_data_fn and write_data_fn in the" 126 " same structure"); 127 } 128#endif 129 130#ifdef PNG_WRITE_FLUSH_SUPPORTED 131 png_ptr->output_flush_fn = NULL; 132#endif 133} 134 135#ifdef PNG_INDEX_SUPPORTED 136void PNGAPI 137png_set_seek_fn(png_structp png_ptr, png_seek_ptr seek_data_fn) 138{ 139 if (png_ptr == NULL) 140 return; 141 png_ptr->seek_data_fn = seek_data_fn; 142} 143#endif 144 145#endif /* PNG_READ_SUPPORTED */ 146