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/thirdparty/libpng/pngrio.c

http://crashrpt.googlecode.com/
C | 161 lines | 102 code | 13 blank | 46 comment | 19 complexity | 9a624d3ad1efeb2c08ae11448c35a485 MD5 | raw file
  1
  2/* pngrio.c - functions for data input
  3 *
  4 * libpng 1.2.7 - September 12, 2004
  5 * For conditions of distribution and use, see copyright notice in png.h
  6 * Copyright (c) 1998-2004 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.)
  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. */
 26void /* PRIVATE */
 27png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
 28{
 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);
 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
 42void PNGAPI
 43png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
 44{
 45   png_size_t check;
 46
 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.
 49    */
 50#if defined(_WIN32_WCE)
 51   if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
 52      check = 0;
 53#else
 54   check = (png_size_t)fread(data, (png_size_t)1, length,
 55      (png_FILE_p)png_ptr->io_ptr);
 56#endif
 57
 58   if (check != length)
 59      png_error(png_ptr, "Read Error");
 60}
 61#else
 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
 64   the data.
 65*/
 66
 67#define NEAR_BUF_SIZE 1024
 68#define MIN(a,b) (a <= b ? a : b)
 69
 70static void /* PRIVATE */
 71png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
 72{
 73   int check;
 74   png_byte *n_data;
 75   png_FILE_p io_ptr;
 76
 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)
 81   {
 82#if defined(_WIN32_WCE)
 83      if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
 84         check = 0;
 85#else
 86      check = fread(n_data, 1, length, io_ptr);
 87#endif
 88   }
 89   else
 90   {
 91      png_byte buf[NEAR_BUF_SIZE];
 92      png_size_t read, remaining, err;
 93      check = 0;
 94      remaining = length;
 95      do
 96      {
 97         read = MIN(NEAR_BUF_SIZE, remaining);
 98#if defined(_WIN32_WCE)
 99         if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) )
100            err = 0;
101#else
102         err = fread(buf, (png_size_t)1, read, io_ptr);
103#endif
104         png_memcpy(data, buf, read); /* copy far buffer to near buffer */
105         if(err != read)
106            break;
107         else
108            check += err;
109         data += read;
110         remaining -= read;
111      }
112      while (remaining != 0);
113   }
114   if ((png_uint_32)check != (png_uint_32)length)
115      png_error(png_ptr, "read Error");
116}
117#endif
118#endif
119
120/* This function allows the application to supply a new input function
121   for libpng if standard C streams aren't being used.
122
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"). */
133void PNGAPI
134png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
135   png_rw_ptr read_data_fn)
136{
137   png_ptr->io_ptr = io_ptr;
138
139#if !defined(PNG_NO_STDIO)
140   if (read_data_fn != NULL)
141      png_ptr->read_data_fn = read_data_fn;
142   else
143      png_ptr->read_data_fn = png_default_read_data;
144#else
145   png_ptr->read_data_fn = read_data_fn;
146#endif
147
148   /* It is an error to write to a read device */
149   if (png_ptr->write_data_fn != NULL)
150   {
151      png_ptr->write_data_fn = NULL;
152      png_warning(png_ptr,
153         "It's an error to set both read_data_fn and write_data_fn in the ");
154      png_warning(png_ptr,
155         "same structure.  Resetting write_data_fn to NULL.");
156   }
157
158#if defined(PNG_WRITE_FLUSH_SUPPORTED)
159   png_ptr->output_flush_fn = NULL;
160#endif
161}