2 /* pngrio.c - functions for data input
4 * libpng 1.2.5 - October 3, 2002
5 * For conditions of distribution and use, see copyright notice in png.h
6 * Copyright (c) 1998-2002 Glenn Randers-Pehrson
7 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
8 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
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(...).
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. */
27 png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
29 png_debug1(4,"reading %d bytes\n", (int)length);
30 if (png_ptr->read_data_fn != NULL)
31 (*(png_ptr->read_data_fn))(png_ptr, data, length);
33 png_error(png_ptr, "Call to NULL read function");
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
43 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
47 /* fread() returns 0 on error, so it is OK to store this in a png_size_t
48 * instead of an int, which is what fread() actually returns.
50 #if defined(_WIN32_WCE)
51 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
54 check = (png_size_t)fread(data, (png_size_t)1, length,
55 (png_FILE_p)png_ptr->io_ptr);
59 png_error(png_ptr, "Read Error");
62 /* this is the model-independent version. Since the standard I/O library
63 can't handle far buffers in the medium and small models, we have to copy
67 #define NEAR_BUF_SIZE 1024
68 #define MIN(a,b) (a <= b ? a : b)
70 static void /* PRIVATE */
71 png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
77 /* Check if data really is near. If so, use usual code. */
78 n_data = (png_byte *)CVT_PTR_NOCHECK(data);
79 io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
80 if ((png_bytep)n_data == data)
82 #if defined(_WIN32_WCE)
83 if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
86 check = fread(n_data, 1, length, io_ptr);
91 png_byte buf[NEAR_BUF_SIZE];
92 png_size_t read, remaining, err;
97 read = MIN(NEAR_BUF_SIZE, remaining);
98 #if defined(_WIN32_WCE)
99 if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) )
102 err = fread(buf, (png_size_t)1, read, io_ptr);
104 png_memcpy(data, buf, read); /* copy far buffer to near buffer */
112 while (remaining != 0);
114 if ((png_uint_32)check != (png_uint_32)length)
115 png_error(png_ptr, "read Error");
120 /* This function allows the application to supply a new input function
121 for libpng if standard C streams aren't being used.
123 This function takes as its arguments:
124 png_ptr - pointer to a png input data structure
125 io_ptr - pointer to user supplied structure containing info about
126 the input functions. May be NULL.
127 read_data_fn - pointer to a new input function that takes as its
128 arguments a pointer to a png_struct, a pointer to
129 a location where input data can be stored, and a 32-bit
130 unsigned int that is the number of bytes to be read.
131 To exit and output any fatal error messages the new write
132 function should call png_error(png_ptr, "Error msg"). */
134 png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
135 png_rw_ptr read_data_fn)
137 png_ptr->io_ptr = io_ptr;
139 #if !defined(PNG_NO_STDIO)
140 if (read_data_fn != NULL)
141 png_ptr->read_data_fn = read_data_fn;
143 png_ptr->read_data_fn = png_default_read_data;
145 png_ptr->read_data_fn = read_data_fn;
148 /* It is an error to write to a read device */
149 if (png_ptr->write_data_fn != NULL)
151 png_ptr->write_data_fn = NULL;
153 "It's an error to set both read_data_fn and write_data_fn in the ");
155 "same structure. Resetting write_data_fn to NULL.");
158 #if defined(PNG_WRITE_FLUSH_SUPPORTED)
159 png_ptr->output_flush_fn = NULL;