/*
 * jdatasrc.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * Modified 2009-2011 by Guido Vollbeding.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains decompression data source routines for the case of
 * reading JPEG data from memory or from a file (or any stdio stream).
 * While these routines are sufficient for most applications,
 * some will want to use a different source manager.
 * IMPORTANT: we assume that fread() will correctly transcribe an array of
 * JOCTETs from 8-bit-wide elements on external storage.  If char is wider
 * than 8 bits on your machine, you may need to do some tweaking.
 */

#include "third_party/libjpeg/jpeg.h"

#include <jpeglib.h>
#include <jerror.h>

// jpeg_mem_src is only available since jpeg v8
// Following code are copied from libjpeg v8d jdatasrc.c.
#if JPEG_LIB_VERSION < 80

static void init_mem_source(j_decompress_ptr cinfo)
{
	/* no work necessary here */
	(void)cinfo;
}

static boolean fill_mem_input_buffer(j_decompress_ptr cinfo)
{
	static const JOCTET mybuffer[4] = {
		(JOCTET) 0xFF, (JOCTET) JPEG_EOI, 0, 0
	};

	/* The whole JPEG data is expected to reside in the supplied memory
	 * buffer, so any request for more data beyond the given buffer size
	 * is treated as an error.
	 */
	WARNMS(cinfo, JWRN_JPEG_EOF);

	/* Insert a fake EOI marker */

	cinfo->src->next_input_byte = mybuffer;
	cinfo->src->bytes_in_buffer = 2;

	return TRUE;
}

static void skip_input_data(j_decompress_ptr cinfo, long num_bytes)
{
	struct jpeg_source_mgr *src = cinfo->src;

	/* Just a dumb implementation for now.  Could use fseek() except
	 * it doesn't work on pipes.  Not clear that being smart is worth
	 * any trouble anyway --- large skips are infrequent.
	 */
	if (num_bytes > 0) {
		while (num_bytes > (long)src->bytes_in_buffer) {
			num_bytes -= (long)src->bytes_in_buffer;
			(void)(*src->fill_input_buffer) (cinfo);
			/* note we assume that fill_input_buffer will never return FALSE,
			 * so suspension need not be handled.
			 */
		}
		src->next_input_byte += (size_t) num_bytes;
		src->bytes_in_buffer -= (size_t) num_bytes;
	}
}

static void term_source(j_decompress_ptr cinfo)
{
	/* no work necessary here */
	(void)cinfo;
}

void jpeg_mem_src(j_decompress_ptr cinfo,
		  unsigned char *inbuffer, unsigned long insize)
{
	struct jpeg_source_mgr *src;

	if (inbuffer == NULL || insize == 0)	/* Treat empty input as fatal error */
		ERREXIT(cinfo, JERR_INPUT_EMPTY);

	/* The source object is made permanent so that a series of JPEG images
	 * can be read from the same buffer by calling jpeg_mem_src only before
	 * the first one.
	 */
	if (cinfo->src == NULL) {	/* first time for this JPEG object? */
		cinfo->src = (struct jpeg_source_mgr *)
		    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo,
						JPOOL_PERMANENT,
						sizeof(struct jpeg_source_mgr));
	}

	src = cinfo->src;
	src->init_source = init_mem_source;
	src->fill_input_buffer = fill_mem_input_buffer;
	src->skip_input_data = skip_input_data;
	src->resync_to_restart = jpeg_resync_to_restart;	/* use default method */
	src->term_source = term_source;
	src->bytes_in_buffer = (size_t) insize;
	src->next_input_byte = (JOCTET *) inbuffer;
}
#endif