| 1 | |
| 2 | /* pngrio.c - functions for data input |
| 3 | * |
| 4 | * libpng 1.0.3 - January 14, 1999 |
| 5 | * For conditions of distribution and use, see copyright notice in png.h |
| 6 | * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc. |
| 7 | * Copyright (c) 1996, 1997 Andreas Dilger |
| 8 | * Copyright (c) 1998, 1999 Glenn Randers-Pehrson |
| 9 | * |
| 10 | * This file provides a location for all input. Users who need |
| 11 | * special handling are expected to write a function that has the same |
| 12 | * arguments as this and performs a similar function, but that possibly |
| 13 | * has a different input method. Note that you shouldn't change this |
| 14 | * function, but rather write a replacement function and then make |
| 15 | * libpng use it at run time with png_set_read_fn(...). |
| 16 | */ |
| 17 | |
| 18 | #define PNG_INTERNAL |
| 19 | #include "png.h" |
| 20 | |
| 21 | /* Read the data from whatever input you are using. The default routine |
| 22 | reads from a file pointer. Note that this routine sometimes gets called |
| 23 | with very small lengths, so you should implement some kind of simple |
| 24 | buffering if you are using unbuffered reads. This should never be asked |
| 25 | to read more then 64K on a 16 bit machine. */ |
| 26 | void |
| 27 | png_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
| 28 | { |
| 29 | png_debug1(4,"reading %d bytes\n", length); |
| 30 | if (png_ptr->read_data_fn != NULL) |
| 31 | (*(png_ptr->read_data_fn))(png_ptr, data, length); |
| 32 | else |
| 33 | png_error(png_ptr, "Call to NULL read function"); |
| 34 | } |
| 35 | |
| 36 | #if !defined(PNG_NO_STDIO) |
| 37 | /* This is the function that does the actual reading of data. If you are |
| 38 | not reading from a standard C stream, you should create a replacement |
| 39 | read_data function and use it at run time with png_set_read_fn(), rather |
| 40 | than changing the library. */ |
| 41 | #ifndef USE_FAR_KEYWORD |
| 42 | #ifdef __VISAGECPP__ |
| 43 | static void _Optlink |
| 44 | png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
| 45 | #else |
| 46 | static void |
| 47 | png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
| 48 | #endif |
| 49 | { |
| 50 | png_size_t check; |
| 51 | |
| 52 | /* fread() returns 0 on error, so it is OK to store this in a png_size_t |
| 53 | * instead of an int, which is what fread() actually returns. |
| 54 | */ |
| 55 | check = (png_size_t)fread(data, (png_size_t)1, length, |
| 56 | (FILE *)png_ptr->io_ptr); |
| 57 | |
| 58 | if (check != length) |
| 59 | { |
| 60 | png_error(png_ptr, "Read Error"); |
| 61 | } |
| 62 | } |
| 63 | #else |
| 64 | /* this is the model-independent version. Since the standard I/O library |
| 65 | can't handle far buffers in the medium and small models, we have to copy |
| 66 | the data. |
| 67 | */ |
| 68 | |
| 69 | #define NEAR_BUF_SIZE 1024 |
| 70 | #define MIN(a,b) (a <= b ? a : b) |
| 71 | |
| 72 | static void |
| 73 | png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length) |
| 74 | { |
| 75 | int check; |
| 76 | png_byte *n_data; |
| 77 | FILE *io_ptr; |
| 78 | |
| 79 | /* Check if data really is near. If so, use usual code. */ |
| 80 | n_data = (png_byte *)CVT_PTR_NOCHECK(data); |
| 81 | io_ptr = (FILE *)CVT_PTR(png_ptr->io_ptr); |
| 82 | if ((png_bytep)n_data == data) |
| 83 | { |
| 84 | check = fread(n_data, 1, length, io_ptr); |
| 85 | } |
| 86 | else |
| 87 | { |
| 88 | png_byte buf[NEAR_BUF_SIZE]; |
| 89 | png_size_t read, remaining, err; |
| 90 | check = 0; |
| 91 | remaining = length; |
| 92 | do |
| 93 | { |
| 94 | read = MIN(NEAR_BUF_SIZE, remaining); |
| 95 | err = fread(buf, (png_size_t)1, read, io_ptr); |
| 96 | png_memcpy(data, buf, read); /* copy far buffer to near buffer */ |
| 97 | if(err != read) |
| 98 | break; |
| 99 | else |
| 100 | check += err; |
| 101 | data += read; |
| 102 | remaining -= read; |
| 103 | } |
| 104 | while (remaining != 0); |
| 105 | } |
| 106 | if ((png_uint_32)check != (png_uint_32)length) |
| 107 | { |
| 108 | png_error(png_ptr, "read Error"); |
| 109 | } |
| 110 | } |
| 111 | #endif |
| 112 | #endif |
| 113 | |
| 114 | /* This function allows the application to supply a new input function |
| 115 | for libpng if standard C streams aren't being used. |
| 116 | |
| 117 | This function takes as its arguments: |
| 118 | png_ptr - pointer to a png input data structure |
| 119 | io_ptr - pointer to user supplied structure containing info about |
| 120 | the input functions. May be NULL. |
| 121 | read_data_fn - pointer to a new input function that takes as its |
| 122 | arguments a pointer to a png_struct, a pointer to |
| 123 | a location where input data can be stored, and a 32-bit |
| 124 | unsigned int that is the number of bytes to be read. |
| 125 | To exit and output any fatal error messages the new write |
| 126 | function should call png_error(png_ptr, "Error msg"). */ |
| 127 | void |
| 128 | png_set_read_fn(png_structp png_ptr, png_voidp io_ptr, |
| 129 | png_rw_ptr read_data_fn) |
| 130 | { |
| 131 | png_ptr->io_ptr = io_ptr; |
| 132 | |
| 133 | #if !defined(PNG_NO_STDIO) |
| 134 | if (read_data_fn != NULL) |
| 135 | png_ptr->read_data_fn = read_data_fn; |
| 136 | else |
| 137 | png_ptr->read_data_fn = png_default_read_data; |
| 138 | #else |
| 139 | png_ptr->read_data_fn = read_data_fn; |
| 140 | #endif |
| 141 | |
| 142 | /* It is an error to write to a read device */ |
| 143 | if (png_ptr->write_data_fn != NULL) |
| 144 | { |
| 145 | png_ptr->write_data_fn = NULL; |
| 146 | png_warning(png_ptr, |
| 147 | "It's an error to set both read_data_fn and write_data_fn in the "); |
| 148 | png_warning(png_ptr, |
| 149 | "same structure. Resetting write_data_fn to NULL."); |
| 150 | } |
| 151 | |
| 152 | #if defined(PNG_WRITE_FLUSH_SUPPORTED) |
| 153 | png_ptr->output_flush_fn = NULL; |
| 154 | #endif /* PNG_WRITE_FLUSH_SUPPORTED */ |
| 155 | } |
| 156 | |