nuclear@14: 
nuclear@14: /* pngrio.c - functions for data input
nuclear@14:  *
nuclear@14:  * Last changed in libpng 1.2.30 [August 15, 2008]
nuclear@14:  * For conditions of distribution and use, see copyright notice in png.h
nuclear@14:  * Copyright (c) 1998-2008 Glenn Randers-Pehrson
nuclear@14:  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
nuclear@14:  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
nuclear@14:  *
nuclear@14:  * This file provides a location for all input.  Users who need
nuclear@14:  * special handling are expected to write a function that has the same
nuclear@14:  * arguments as this and performs a similar function, but that possibly
nuclear@14:  * has a different input method.  Note that you shouldn't change this
nuclear@14:  * function, but rather write a replacement function and then make
nuclear@14:  * libpng use it at run time with png_set_read_fn(...).
nuclear@14:  */
nuclear@14: 
nuclear@14: #define PNG_INTERNAL
nuclear@14: #include "png.h"
nuclear@14: #if defined(PNG_READ_SUPPORTED)
nuclear@14: 
nuclear@14: /* Read the data from whatever input you are using.  The default routine
nuclear@14:    reads from a file pointer.  Note that this routine sometimes gets called
nuclear@14:    with very small lengths, so you should implement some kind of simple
nuclear@14:    buffering if you are using unbuffered reads.  This should never be asked
nuclear@14:    to read more then 64K on a 16 bit machine. */
nuclear@14: void /* PRIVATE */
nuclear@14: png_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
nuclear@14: {
nuclear@14:    png_debug1(4, "reading %d bytes\n", (int)length);
nuclear@14:    if (png_ptr->read_data_fn != NULL)
nuclear@14:       (*(png_ptr->read_data_fn))(png_ptr, data, length);
nuclear@14:    else
nuclear@14:       png_error(png_ptr, "Call to NULL read function");
nuclear@14: }
nuclear@14: 
nuclear@14: #if !defined(PNG_NO_STDIO)
nuclear@14: /* This is the function that does the actual reading of data.  If you are
nuclear@14:    not reading from a standard C stream, you should create a replacement
nuclear@14:    read_data function and use it at run time with png_set_read_fn(), rather
nuclear@14:    than changing the library. */
nuclear@14: #ifndef USE_FAR_KEYWORD
nuclear@14: void PNGAPI
nuclear@14: png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
nuclear@14: {
nuclear@14:    png_size_t check;
nuclear@14: 
nuclear@14:    if (png_ptr == NULL) return;
nuclear@14:    /* fread() returns 0 on error, so it is OK to store this in a png_size_t
nuclear@14:     * instead of an int, which is what fread() actually returns.
nuclear@14:     */
nuclear@14: #if defined(_WIN32_WCE)
nuclear@14:    if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
nuclear@14:       check = 0;
nuclear@14: #else
nuclear@14:    check = (png_size_t)fread(data, (png_size_t)1, length,
nuclear@14:       (png_FILE_p)png_ptr->io_ptr);
nuclear@14: #endif
nuclear@14: 
nuclear@14:    if (check != length)
nuclear@14:       png_error(png_ptr, "Read Error");
nuclear@14: }
nuclear@14: #else
nuclear@14: /* this is the model-independent version. Since the standard I/O library
nuclear@14:    can't handle far buffers in the medium and small models, we have to copy
nuclear@14:    the data.
nuclear@14: */
nuclear@14: 
nuclear@14: #define NEAR_BUF_SIZE 1024
nuclear@14: #define MIN(a,b) (a <= b ? a : b)
nuclear@14: 
nuclear@14: static void PNGAPI
nuclear@14: png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
nuclear@14: {
nuclear@14:    int check;
nuclear@14:    png_byte *n_data;
nuclear@14:    png_FILE_p io_ptr;
nuclear@14: 
nuclear@14:    if (png_ptr == NULL) return;
nuclear@14:    /* Check if data really is near. If so, use usual code. */
nuclear@14:    n_data = (png_byte *)CVT_PTR_NOCHECK(data);
nuclear@14:    io_ptr = (png_FILE_p)CVT_PTR(png_ptr->io_ptr);
nuclear@14:    if ((png_bytep)n_data == data)
nuclear@14:    {
nuclear@14: #if defined(_WIN32_WCE)
nuclear@14:       if ( !ReadFile((HANDLE)(png_ptr->io_ptr), data, length, &check, NULL) )
nuclear@14:          check = 0;
nuclear@14: #else
nuclear@14:       check = fread(n_data, 1, length, io_ptr);
nuclear@14: #endif
nuclear@14:    }
nuclear@14:    else
nuclear@14:    {
nuclear@14:       png_byte buf[NEAR_BUF_SIZE];
nuclear@14:       png_size_t read, remaining, err;
nuclear@14:       check = 0;
nuclear@14:       remaining = length;
nuclear@14:       do
nuclear@14:       {
nuclear@14:          read = MIN(NEAR_BUF_SIZE, remaining);
nuclear@14: #if defined(_WIN32_WCE)
nuclear@14:          if ( !ReadFile((HANDLE)(io_ptr), buf, read, &err, NULL) )
nuclear@14:             err = 0;
nuclear@14: #else
nuclear@14:          err = fread(buf, (png_size_t)1, read, io_ptr);
nuclear@14: #endif
nuclear@14:          png_memcpy(data, buf, read); /* copy far buffer to near buffer */
nuclear@14:          if (err != read)
nuclear@14:             break;
nuclear@14:          else
nuclear@14:             check += err;
nuclear@14:          data += read;
nuclear@14:          remaining -= read;
nuclear@14:       }
nuclear@14:       while (remaining != 0);
nuclear@14:    }
nuclear@14:    if ((png_uint_32)check != (png_uint_32)length)
nuclear@14:       png_error(png_ptr, "read Error");
nuclear@14: }
nuclear@14: #endif
nuclear@14: #endif
nuclear@14: 
nuclear@14: /* This function allows the application to supply a new input function
nuclear@14:    for libpng if standard C streams aren't being used.
nuclear@14: 
nuclear@14:    This function takes as its arguments:
nuclear@14:    png_ptr      - pointer to a png input data structure
nuclear@14:    io_ptr       - pointer to user supplied structure containing info about
nuclear@14:                   the input functions.  May be NULL.
nuclear@14:    read_data_fn - pointer to a new input function that takes as its
nuclear@14:                   arguments a pointer to a png_struct, a pointer to
nuclear@14:                   a location where input data can be stored, and a 32-bit
nuclear@14:                   unsigned int that is the number of bytes to be read.
nuclear@14:                   To exit and output any fatal error messages the new write
nuclear@14:                   function should call png_error(png_ptr, "Error msg"). */
nuclear@14: void PNGAPI
nuclear@14: png_set_read_fn(png_structp png_ptr, png_voidp io_ptr,
nuclear@14:    png_rw_ptr read_data_fn)
nuclear@14: {
nuclear@14:    if (png_ptr == NULL) return;
nuclear@14:    png_ptr->io_ptr = io_ptr;
nuclear@14: 
nuclear@14: #if !defined(PNG_NO_STDIO)
nuclear@14:    if (read_data_fn != NULL)
nuclear@14:       png_ptr->read_data_fn = read_data_fn;
nuclear@14:    else
nuclear@14:       png_ptr->read_data_fn = png_default_read_data;
nuclear@14: #else
nuclear@14:    png_ptr->read_data_fn = read_data_fn;
nuclear@14: #endif
nuclear@14: 
nuclear@14:    /* It is an error to write to a read device */
nuclear@14:    if (png_ptr->write_data_fn != NULL)
nuclear@14:    {
nuclear@14:       png_ptr->write_data_fn = NULL;
nuclear@14:       png_warning(png_ptr,
nuclear@14:          "It's an error to set both read_data_fn and write_data_fn in the ");
nuclear@14:       png_warning(png_ptr,
nuclear@14:          "same structure.  Resetting write_data_fn to NULL.");
nuclear@14:    }
nuclear@14: 
nuclear@14: #if defined(PNG_WRITE_FLUSH_SUPPORTED)
nuclear@14:    png_ptr->output_flush_fn = NULL;
nuclear@14: #endif
nuclear@14: }
nuclear@14: #endif /* PNG_READ_SUPPORTED */