Subversion Repositories Kolibri OS

Rev

Blame | Last modification | View Log | Download | RSS feed

  1.  
  2. /* pngrio.c - functions for data input
  3.  *
  4.  * Last changed in libpng 1.5.0 [January 6, 2011]
  5.  * Copyright (c) 1998-2011 Glenn Randers-Pehrson
  6.  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  7.  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
  8.  *
  9.  * This code is released under the libpng license.
  10.  * For conditions of distribution and use, see the disclaimer
  11.  * and license in png.h
  12.  *
  13.  * This file provides a location for all input.  Users who need
  14.  * special handling are expected to write a function that has the same
  15.  * arguments as this and performs a similar function, but that possibly
  16.  * has a different input method.  Note that you shouldn't change this
  17.  * function, but rather write a replacement function and then make
  18.  * libpng use it at run time with png_set_read_fn(...).
  19.  */
  20.  
  21. #include "pngpriv.h"
  22.  
  23. #ifdef PNG_READ_SUPPORTED
  24.  
  25. /* Read the data from whatever input you are using.  The default routine
  26.  * reads from a file pointer.  Note that this routine sometimes gets called
  27.  * with very small lengths, so you should implement some kind of simple
  28.  * buffering if you are using unbuffered reads.  This should never be asked
  29.  * to read more then 64K on a 16 bit machine.
  30.  */
  31. void /* PRIVATE */
  32. png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
  33. {
  34.    png_debug1(4, "reading %d bytes", (int)length);
  35.  
  36.    if (png_ptr->read_data_fn != NULL)
  37.       (*(png_ptr->read_data_fn))(png_ptr, data, length);
  38.  
  39.    else
  40.       png_error(png_ptr, "Call to NULL read function");
  41. }
  42.  
  43. #ifdef PNG_STDIO_SUPPORTED
  44. /* This is the function that does the actual reading of data.  If you are
  45.  * not reading from a standard C stream, you should create a replacement
  46.  * read_data function and use it at run time with png_set_read_fn(), rather
  47.  * than changing the library.
  48.  */
  49. #  ifndef USE_FAR_KEYWORD
  50. void PNGCBAPI
  51. png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
  52. {
  53.    png_size_t check;
  54.  
  55.    if (png_ptr == NULL)
  56.       return;
  57.  
  58.    /* fread() returns 0 on error, so it is OK to store this in a png_size_t
  59.     * instead of an int, which is what fread() actually returns.
  60.     */
  61.    check = fread(data, 1, length, (png_FILE_p)png_ptr->io_ptr);
  62.  
  63.    if (check != length)
  64.       png_error(png_ptr, "Read Error");
  65. }
  66. #  else
  67. /* This is the model-independent version. Since the standard I/O library
  68.    can't handle far buffers in the medium and small models, we have to copy
  69.    the data.
  70. */
  71.  
  72. #define NEAR_BUF_SIZE 1024
  73. #define MIN(a,b) (a <= b ? a : b)
  74.  
  75. static void PNGCBAPI
  76. png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
  77. {
  78.    png_size_t check;
  79.    png_byte *n_data;
  80.    png_FILE_p io_ptr;
  81.  
  82.    if (png_ptr == NULL)
  83.       return;
  84.  
  85.    /* Check if data really is near. If so, use usual code. */
  86.    n_data = (png_byte *)CVT_PTR_NOCHECK(data);
  87.    io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
  88.  
  89.    if ((png_bytep)n_data == data)
  90.    {
  91.       check = fread(n_data, 1, length, io_ptr);
  92.    }
  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.  
  101.       do
  102.       {
  103.          read = MIN(NEAR_BUF_SIZE, remaining);
  104.          err = fread(buf, 1, read, io_ptr);
  105.          png_memcpy(data, buf, read); /* copy far buffer to near buffer */
  106.  
  107.          if (err != read)
  108.             break;
  109.  
  110.          else
  111.             check += err;
  112.  
  113.          data += read;
  114.          remaining -= read;
  115.       }
  116.       while (remaining != 0);
  117.    }
  118.  
  119.    if ((png_uint_32)check != (png_uint_32)length)
  120.       png_error(png_ptr, "read Error");
  121. }
  122. #  endif
  123. #endif
  124.  
  125. /* This function allows the application to supply a new input function
  126.  * for libpng if standard C streams aren't being used.
  127.  *
  128.  * This function takes as its arguments:
  129.  *
  130.  * png_ptr      - pointer to a png input data structure
  131.  *
  132.  * io_ptr       - pointer to user supplied structure containing info about
  133.  *                the input functions.  May be NULL.
  134.  *
  135.  * read_data_fn - pointer to a new input function that takes as its
  136.  *                arguments a pointer to a png_struct, a pointer to
  137.  *                a location where input data can be stored, and a 32-bit
  138.  *                unsigned int that is the number of bytes to be read.
  139.  *                To exit and output any fatal error messages the new write
  140.  *                function should call png_error(png_ptr, "Error msg").
  141.  *                May be NULL, in which case libpng's default function will
  142.  *                be used.
  143.  */
  144. void PNGAPI
  145. png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
  146.    png_rw_ptr read_data_fn)
  147. {
  148.    if (png_ptr == NULL)
  149.       return;
  150.  
  151.    png_ptr->io_ptr = io_ptr;
  152.  
  153. #ifdef PNG_STDIO_SUPPORTED
  154.    if (read_data_fn != NULL)
  155.       png_ptr->read_data_fn = read_data_fn;
  156.  
  157.    else
  158.       png_ptr->read_data_fn = png_default_read_data;
  159. #else
  160.    png_ptr->read_data_fn = read_data_fn;
  161. #endif
  162.  
  163.    /* It is an error to write to a read device */
  164.    if (png_ptr->write_data_fn != NULL)
  165.    {
  166.       png_ptr->write_data_fn = NULL;
  167.       png_warning(png_ptr,
  168.           "Can't set both read_data_fn and write_data_fn in the"
  169.           " same structure");
  170.    }
  171.  
  172. #ifdef PNG_WRITE_FLUSH_SUPPORTED
  173.    png_ptr->output_flush_fn = NULL;
  174. #endif
  175. }
  176. #endif /* PNG_READ_SUPPORTED */
  177.