Line data    Source code

       1             : 
       2             : /* pngrio.c - functions for data input
       3             :  *
       4             :  * Last changed in libpng 1.6.24 [August 4, 2016]
       5             :  * Copyright (c) 1998-2002,2004,2006-2016 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 than 64K on a 16-bit machine.
      30             :  */
      31             : void /* PRIVATE */
      32         702 : png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length)
      33             : {
      34             :    png_debug1(4, "reading %d bytes", (int)length);
      35             : 
      36         702 :    if (png_ptr->read_data_fn != NULL)
      37         702 :       (*(png_ptr->read_data_fn))(png_ptr, data, length);
      38             : 
      39             :    else
      40           0 :       png_error(png_ptr, "Call to NULL read function");
      41         702 : }
      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             : void PNGCBAPI
      50           0 : png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
      51             : {
      52             :    png_size_t check;
      53             : 
      54           0 :    if (png_ptr == NULL)
      55           0 :       return;
      56             : 
      57             :    /* fread() returns 0 on error, so it is OK to store this in a png_size_t
      58             :     * instead of an int, which is what fread() actually returns.
      59             :     */
      60           0 :    check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr));
      61             : 
      62           0 :    if (check != length)
      63           0 :       png_error(png_ptr, "Read Error");
      64             : }
      65             : #endif
      66             : 
      67             : /* This function allows the application to supply a new input function
      68             :  * for libpng if standard C streams aren't being used.
      69             :  *
      70             :  * This function takes as its arguments:
      71             :  *
      72             :  * png_ptr      - pointer to a png input data structure
      73             :  *
      74             :  * io_ptr       - pointer to user supplied structure containing info about
      75             :  *                the input functions.  May be NULL.
      76             :  *
      77             :  * read_data_fn - pointer to a new input function that takes as its
      78             :  *                arguments a pointer to a png_struct, a pointer to
      79             :  *                a location where input data can be stored, and a 32-bit
      80             :  *                unsigned int that is the number of bytes to be read.
      81             :  *                To exit and output any fatal error messages the new write
      82             :  *                function should call png_error(png_ptr, "Error msg").
      83             :  *                May be NULL, in which case libpng's default function will
      84             :  *                be used.
      85             :  */
      86             : void PNGAPI
      87          62 : png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
      88             :     png_rw_ptr read_data_fn)
      89             : {
      90          62 :    if (png_ptr == NULL)
      91           0 :       return;
      92             : 
      93          62 :    png_ptr->io_ptr = io_ptr;
      94             : 
      95             : #ifdef PNG_STDIO_SUPPORTED
      96          62 :    if (read_data_fn != NULL)
      97          31 :       png_ptr->read_data_fn = read_data_fn;
      98             : 
      99             :    else
     100          31 :       png_ptr->read_data_fn = png_default_read_data;
     101             : #else
     102             :    png_ptr->read_data_fn = read_data_fn;
     103             : #endif
     104             : 
     105             : #ifdef PNG_WRITE_SUPPORTED
     106             :    /* It is an error to write to a read device */
     107          62 :    if (png_ptr->write_data_fn != NULL)
     108             :    {
     109           0 :       png_ptr->write_data_fn = NULL;
     110           0 :       png_warning(png_ptr,
     111             :           "Can't set both read_data_fn and write_data_fn in the"
     112             :           " same structure");
     113             :    }
     114             : #endif
     115             : 
     116             : #ifdef PNG_WRITE_FLUSH_SUPPORTED
     117          62 :    png_ptr->output_flush_fn = NULL;
     118             : #endif
     119             : }
     120             : #endif /* READ */