1/* PDFlib GmbH cvsid: $Id: pngrio.c 14574 2005-10-29 16:27:43Z bonefish $ */ 2 3/* pngrio.c - functions for data input 4 * 5 * libpng 1.2.5 - October 3, 2002 6 * For conditions of distribution and use, see copyright notice in png.h 7 * Copyright (c) 1998-2002 Glenn Randers-Pehrson 8 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger) 9 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.) 10 * 11 * This file provides a location for all input. Users who need 12 * special handling are expected to write a function that has the same 13 * arguments as this and performs a similar function, but that possibly 14 * has a different input method. Note that you shouldn't change this 15 * function, but rather write a replacement function and then make 16 * libpng use it at run time with png_set_read_fn(...). 17 */ 18 19#define PNG_INTERNAL 20#include "png.h" 21 22/* Read the data from whatever input you are using. The default routine 23 reads from 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 reads. This should never be asked 26 to read more then 64K on a 16 bit machine. */ 27void /* PRIVATE */ 28png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 29{ 30 png_debug1(4,"reading %d bytes\n", (int)length); 31 if (png_ptr->read_data_fn != NULL) 32 (*(png_ptr->read_data_fn))(png_ptr, data, length); 33 else 34 png_error(png_ptr, "Call to NULL read function"); 35} 36 37#if !defined(PNG_NO_STDIO) 38/* This is the function that does the actual reading of data. If you are 39 not reading from a standard C stream, you should create a replacement 40 read_data function and use it at run time with png_set_read_fn(), rather 41 than changing the library. */ 42#ifndef USE_FAR_KEYWORD 43void PNGAPI 44png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 45{ 46 png_size_t check; 47 48 /* fread() returns 0 on error, so it is OK to store this in a png_size_t 49 * instead of an int, which is what fread() actually returns. 50 */ 51/* PDFlib GmbH: 52#if defined(_WIN32_WCE) 53 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) 54 check = 0; 55#else 56*/ 57 check = (png_size_t)fread(data, (png_size_t)1, length, 58 (png_FILE_p)png_ptr->io_ptr); 59/* #endif PDFlib GmbH: */ 60 61 if (check != length) 62 png_error(png_ptr, "Read Error"); 63} 64#else 65/* this is the model-independent version. Since the standard I/O library 66 can't handle far buffers in the medium and small models, we have to copy 67 the data. 68*/ 69 70#define NEAR_BUF_SIZE 1024 71#define MIN(a,b) (a <= b ? a : b) 72 73static void /* PRIVATE */ 74png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) 75{ 76 int check; 77 png_byte *n_data; 78 png_FILE_p io_ptr; 79 80 /* Check if data really is near. If so, use usual code. */ 81 n_data = (png_byte *)CVT_PTR_NOCHECK(data); 82 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr); 83 if ((png_bytep)n_data == data) 84 { 85/* PDFlib GmbH: 86#if defined(_WIN32_WCE) 87 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) ) 88 check = 0; 89#else 90*/ 91 check = fread(n_data, 1, length, io_ptr); 92/* #endif PDFlib GmbH: */ 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 do 101 { 102 read = MIN(NEAR_BUF_SIZE, remaining); 103/* PDFlib GmbH: 104#if defined(_WIN32_WCE) 105 if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) ) 106 err = 0; 107#else 108*/ 109 err = fread(buf, (png_size_t)1, read, io_ptr); 110/* #endif PDFlib GmbH: */ 111 png_memcpy(data, buf, read); /* copy far buffer to near buffer */ 112 if(err != read) 113 break; 114 else 115 check += err; 116 data += read; 117 remaining -= read; 118 } 119 while (remaining != 0); 120 } 121 if ((png_uint_32)check != (png_uint_32)length) 122 png_error(png_ptr, "read Error"); 123} 124#endif 125#endif 126 127/* This function allows the application to supply a new input function 128 for libpng if standard C streams aren't being used. 129 130 This function takes as its arguments: 131 png_ptr - pointer to a png input data structure 132 io_ptr - pointer to user supplied structure containing info about 133 the input functions. May be NULL. 134 read_data_fn - pointer to a new input function that takes as its 135 arguments a pointer to a png_struct, a pointer to 136 a location where input data can be stored, and a 32-bit 137 unsigned int that is the number of bytes to be read. 138 To exit and output any fatal error messages the new write 139 function should call png_error(png_ptr, "Error msg"). */ 140void PNGAPI 141png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, 142 png_rw_ptr read_data_fn) 143{ 144 png_ptr->io_ptr = io_ptr; 145 146#if !defined(PNG_NO_STDIO) 147 if (read_data_fn != NULL) 148 png_ptr->read_data_fn = read_data_fn; 149 else 150 png_ptr->read_data_fn = png_default_read_data; 151#else 152 png_ptr->read_data_fn = read_data_fn; 153#endif 154 155 /* It is an error to write to a read device */ 156 if (png_ptr->write_data_fn != NULL) 157 { 158 png_ptr->write_data_fn = NULL; 159 png_warning(png_ptr, 160 "It's an error to set both read_data_fn and write_data_fn in the "); 161 png_warning(png_ptr, 162 "same structure. Resetting write_data_fn to NULL."); 163 } 164 165#if defined(PNG_WRITE_FLUSH_SUPPORTED) 166 png_ptr->output_flush_fn = NULL; 167#endif 168} 169