pngrio.c 6.5 KB
Newer Older
D
duke 已提交
1 2 3 4 5
/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
6
 * published by the Free Software Foundation.  Oracle designates this
D
duke 已提交
7
 * particular file as subject to the "Classpath" exception as provided
8
 * by Oracle in the LICENSE file that accompanied this code.
D
duke 已提交
9 10 11 12 13 14 15 16 17 18 19
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
20 21 22
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
D
duke 已提交
23 24 25 26 27 28 29 30 31
 */

/* pngrio.c - functions for data input
 *
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file and, per its terms, should not be removed:
 *
A
azvegint 已提交
32 33
 * Last changed in libpng 1.5.0 [January 6, 2011]
 * Copyright (c) 1998-2011 Glenn Randers-Pehrson
D
duke 已提交
34 35 36
 * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
 * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
 *
B
bae 已提交
37 38 39 40
 * This code is released under the libpng license.
 * For conditions of distribution and use, see the disclaimer
 * and license in png.h
 *
D
duke 已提交
41 42 43 44 45 46 47 48
 * This file provides a location for all input.  Users who need
 * special handling are expected to write a function that has the same
 * arguments as this and performs a similar function, but that possibly
 * has a different input method.  Note that you shouldn't change this
 * function, but rather write a replacement function and then make
 * libpng use it at run time with png_set_read_fn(...).
 */

B
bae 已提交
49
#include "pngpriv.h"
D
duke 已提交
50

B
bae 已提交
51
#ifdef PNG_READ_SUPPORTED
D
duke 已提交
52 53

/* Read the data from whatever input you are using.  The default routine
B
bae 已提交
54 55 56 57 58
 * reads from a file pointer.  Note that this routine sometimes gets called
 * with very small lengths, so you should implement some kind of simple
 * buffering if you are using unbuffered reads.  This should never be asked
 * to read more then 64K on a 16 bit machine.
 */
D
duke 已提交
59
void /* PRIVATE */
A
azvegint 已提交
60
png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
D
duke 已提交
61
{
B
bae 已提交
62 63
   png_debug1(4, "reading %d bytes", (int)length);

D
duke 已提交
64 65
   if (png_ptr->read_data_fn != NULL)
      (*(png_ptr->read_data_fn))(png_ptr, data, length);
B
bae 已提交
66

D
duke 已提交
67 68 69 70
   else
      png_error(png_ptr, "Call to NULL read function");
}

B
bae 已提交
71
#ifdef PNG_STDIO_SUPPORTED
D
duke 已提交
72
/* This is the function that does the actual reading of data.  If you are
B
bae 已提交
73 74 75 76
 * not reading from a standard C stream, you should create a replacement
 * read_data function and use it at run time with png_set_read_fn(), rather
 * than changing the library.
 */
A
azvegint 已提交
77
#  ifndef USE_FAR_KEYWORD
B
bae 已提交
78
void PNGCBAPI
D
duke 已提交
79 80 81 82
png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
{
   png_size_t check;

B
bae 已提交
83 84 85
   if (png_ptr == NULL)
      return;

D
duke 已提交
86 87 88
   /* fread() returns 0 on error, so it is OK to store this in a png_size_t
    * instead of an int, which is what fread() actually returns.
    */
A
azvegint 已提交
89
   check = fread(data, 1, length, (png_FILE_p)png_ptr->io_ptr);
D
duke 已提交
90 91 92 93

   if (check != length)
      png_error(png_ptr, "Read Error");
}
A
azvegint 已提交
94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150
#  else
/* This is the model-independent version. Since the standard I/O library
   can't handle far buffers in the medium and small models, we have to copy
   the data.
*/

#define NEAR_BUF_SIZE 1024
#define MIN(a,b) (a <= b ? a : b)

static void PNGCBAPI
png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
{
   png_size_t check;
   png_byte *n_data;
   png_FILE_p io_ptr;

   if (png_ptr == NULL)
      return;

   /* Check if data really is near. If so, use usual code. */
   n_data = (png_byte *)CVT_PTR_NOCHECK(data);
   io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);

   if ((png_bytep)n_data == data)
   {
      check = fread(n_data, 1, length, io_ptr);
   }

   else
   {
      png_byte buf[NEAR_BUF_SIZE];
      png_size_t read, remaining, err;
      check = 0;
      remaining = length;

      do
      {
         read = MIN(NEAR_BUF_SIZE, remaining);
         err = fread(buf, 1, read, io_ptr);
         png_memcpy(data, buf, read); /* copy far buffer to near buffer */

         if (err != read)
            break;

         else
            check += err;

         data += read;
         remaining -= read;
      }
      while (remaining != 0);
   }

   if ((png_uint_32)check != (png_uint_32)length)
      png_error(png_ptr, "read Error");
}
#  endif
D
duke 已提交
151 152 153
#endif

/* This function allows the application to supply a new input function
B
bae 已提交
154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171
 * for libpng if standard C streams aren't being used.
 *
 * This function takes as its arguments:
 *
 * png_ptr      - pointer to a png input data structure
 *
 * io_ptr       - pointer to user supplied structure containing info about
 *                the input functions.  May be NULL.
 *
 * read_data_fn - pointer to a new input function that takes as its
 *                arguments a pointer to a png_struct, a pointer to
 *                a location where input data can be stored, and a 32-bit
 *                unsigned int that is the number of bytes to be read.
 *                To exit and output any fatal error messages the new write
 *                function should call png_error(png_ptr, "Error msg").
 *                May be NULL, in which case libpng's default function will
 *                be used.
 */
D
duke 已提交
172
void PNGAPI
A
azvegint 已提交
173
png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
D
duke 已提交
174 175
   png_rw_ptr read_data_fn)
{
B
bae 已提交
176 177 178
   if (png_ptr == NULL)
      return;

D
duke 已提交
179 180
   png_ptr->io_ptr = io_ptr;

B
bae 已提交
181
#ifdef PNG_STDIO_SUPPORTED
D
duke 已提交
182 183
   if (read_data_fn != NULL)
      png_ptr->read_data_fn = read_data_fn;
B
bae 已提交
184

D
duke 已提交
185 186 187 188 189 190 191 192 193 194 195
   else
      png_ptr->read_data_fn = png_default_read_data;
#else
   png_ptr->read_data_fn = read_data_fn;
#endif

   /* It is an error to write to a read device */
   if (png_ptr->write_data_fn != NULL)
   {
      png_ptr->write_data_fn = NULL;
      png_warning(png_ptr,
B
bae 已提交
196 197
          "Can't set both read_data_fn and write_data_fn in the"
          " same structure");
D
duke 已提交
198 199
   }

B
bae 已提交
200
#ifdef PNG_WRITE_FLUSH_SUPPORTED
D
duke 已提交
201 202 203
   png_ptr->output_flush_fn = NULL;
#endif
}
A
azvegint 已提交
204
#endif /* PNG_READ_SUPPORTED */