michael@0: 
michael@0: /* pngrio.c - functions for data input
michael@0:  *
michael@0:  * Last changed in libpng 1.6.9 [February 6, 2014]
michael@0:  * Copyright (c) 1998-2014 Glenn Randers-Pehrson
michael@0:  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
michael@0:  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
michael@0:  *
michael@0:  * This code is released under the libpng license.
michael@0:  * For conditions of distribution and use, see the disclaimer
michael@0:  * and license in png.h
michael@0:  *
michael@0:  * This file provides a location for all input.  Users who need
michael@0:  * special handling are expected to write a function that has the same
michael@0:  * arguments as this and performs a similar function, but that possibly
michael@0:  * has a different input method.  Note that you shouldn't change this
michael@0:  * function, but rather write a replacement function and then make
michael@0:  * libpng use it at run time with png_set_read_fn(...).
michael@0:  */
michael@0: 
michael@0: #include "pngpriv.h"
michael@0: 
michael@0: #ifdef PNG_READ_SUPPORTED
michael@0: 
michael@0: /* Read the data from whatever input you are using.  The default routine
michael@0:  * reads from a file pointer.  Note that this routine sometimes gets called
michael@0:  * with very small lengths, so you should implement some kind of simple
michael@0:  * buffering if you are using unbuffered reads.  This should never be asked
michael@0:  * to read more then 64K on a 16 bit machine.
michael@0:  */
michael@0: void /* PRIVATE */
michael@0: png_read_data(png_structrp png_ptr, png_bytep data, png_size_t length)
michael@0: {
michael@0:    png_debug1(4, "reading %d bytes", (int)length);
michael@0: 
michael@0:    if (png_ptr->read_data_fn != NULL)
michael@0:       (*(png_ptr->read_data_fn))(png_ptr, data, length);
michael@0: 
michael@0:    else
michael@0:       png_error(png_ptr, "Call to NULL read function");
michael@0: }
michael@0: 
michael@0: #ifdef PNG_STDIO_SUPPORTED
michael@0: /* This is the function that does the actual reading of data.  If you are
michael@0:  * not reading from a standard C stream, you should create a replacement
michael@0:  * read_data function and use it at run time with png_set_read_fn(), rather
michael@0:  * than changing the library.
michael@0:  */
michael@0: void PNGCBAPI
michael@0: png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
michael@0: {
michael@0:    png_size_t check;
michael@0: 
michael@0:    if (png_ptr == NULL)
michael@0:       return;
michael@0: 
michael@0:    /* fread() returns 0 on error, so it is OK to store this in a png_size_t
michael@0:     * instead of an int, which is what fread() actually returns.
michael@0:     */
michael@0:    check = fread(data, 1, length, png_voidcast(png_FILE_p, png_ptr->io_ptr));
michael@0: 
michael@0:    if (check != length)
michael@0:       png_error(png_ptr, "Read Error");
michael@0: }
michael@0: #endif
michael@0: 
michael@0: /* This function allows the application to supply a new input function
michael@0:  * for libpng if standard C streams aren't being used.
michael@0:  *
michael@0:  * This function takes as its arguments:
michael@0:  *
michael@0:  * png_ptr      - pointer to a png input data structure
michael@0:  *
michael@0:  * io_ptr       - pointer to user supplied structure containing info about
michael@0:  *                the input functions.  May be NULL.
michael@0:  *
michael@0:  * read_data_fn - pointer to a new input function that takes as its
michael@0:  *                arguments a pointer to a png_struct, a pointer to
michael@0:  *                a location where input data can be stored, and a 32-bit
michael@0:  *                unsigned int that is the number of bytes to be read.
michael@0:  *                To exit and output any fatal error messages the new write
michael@0:  *                function should call png_error(png_ptr, "Error msg").
michael@0:  *                May be NULL, in which case libpng's default function will
michael@0:  *                be used.
michael@0:  */
michael@0: void PNGAPI
michael@0: png_set_read_fn(png_structrp png_ptr, png_voidp io_ptr,
michael@0:    png_rw_ptr read_data_fn)
michael@0: {
michael@0:    if (png_ptr == NULL)
michael@0:       return;
michael@0: 
michael@0:    png_ptr->io_ptr = io_ptr;
michael@0: 
michael@0: #ifdef PNG_STDIO_SUPPORTED
michael@0:    if (read_data_fn != NULL)
michael@0:       png_ptr->read_data_fn = read_data_fn;
michael@0: 
michael@0:    else
michael@0:       png_ptr->read_data_fn = png_default_read_data;
michael@0: #else
michael@0:    png_ptr->read_data_fn = read_data_fn;
michael@0: #endif
michael@0: 
michael@0: #ifdef PNG_WRITE_SUPPORTED
michael@0:    /* It is an error to write to a read device */
michael@0:    if (png_ptr->write_data_fn != NULL)
michael@0:    {
michael@0:       png_ptr->write_data_fn = NULL;
michael@0:       png_warning(png_ptr,
michael@0:           "Can't set both read_data_fn and write_data_fn in the"
michael@0:           " same structure");
michael@0:    }
michael@0: #endif
michael@0: 
michael@0: #ifdef PNG_WRITE_FLUSH_SUPPORTED
michael@0:    png_ptr->output_flush_fn = NULL;
michael@0: #endif
michael@0: }
michael@0: #endif /* PNG_READ_SUPPORTED */