/*
 * jdatasrc.c
 *
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * 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 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.
 */

/* this is not a core library module, so it doesn't define JPEG_INTERNALS */
#include "jinclude.h"
#include "jpeglib.h"
#include "jerror.h"


#ifndef JPEG_MKLUDGE
#define JPEG_MKLUDGE

char *mbuf = NULL;
int msize = 0;
int mptr = 0;

#endif



/* Expanded data source object for stdio input */

typedef struct {
  struct jpeg_source_mgr pub;   /* public fields */

  FILE * infile;        /* source stream */
  JOCTET * buffer;      /* start of buffer */
  jboolean start_of_file;   /* have we gotten any data yet? */
} my_source_mgr;

typedef my_source_mgr * my_src_ptr;

#define INPUT_BUF_SIZE  4096    /* choose an efficiently fread'able size */


/*
 * Initialize source --- called by jpeg_read_header
 * before any data is actually read.
 */

METHODDEF(void)
init_source (j_decompress_ptr cinfo)
{
  my_src_ptr src = (my_src_ptr) cinfo->src;

  /* We reset the empty-input-file flag for each image,
   * but we don't clear the input buffer.
   * This is correct behavior for reading a series of images from one source.
   */
  src->start_of_file = TRUE;
}


/*
 * Fill the input buffer --- called whenever buffer is emptied.
 *
 * In typical applications, this should read fresh data into the buffer
 * (ignoring the current state of next_input_byte & bytes_in_buffer),
 * reset the pointer & count to the start of the buffer, and return TRUE
 * indicating that the buffer has been reloaded.  It is not necessary to
 * fill the buffer entirely, only to obtain at least one more byte.
 *
 * There is no such thing as an EOF return.  If the end of the file has been
 * reached, the routine has a choice of ERREXIT() or inserting fake data into
 * the buffer.  In most cases, generating a warning message and inserting a
 * fake EOI marker is the best course of action --- this will allow the
 * decompressor to output however much of the image is there.  However,
 * the resulting error message is misleading if the real problem is an empty
 * input file, so we handle that case specially.
 *
 * In applications that need to be able to suspend compression due to input
 * not being available yet, a FALSE return indicates that no more data can be
 * obtained right now, but more may be forthcoming later.  In this situation,
 * the decompressor will return to its caller (with an indication of the
 * number of scanlines it has read, if any).  The application should resume
 * decompression after it has loaded more data into the input buffer.  Note
 * that there are substantial restrictions on the use of suspension --- see
 * the documentation.
 *
 * When suspending, the decompressor will back up to a convenient restart point
 * (typically the start of the current MCU). next_input_byte & bytes_in_buffer
 * indicate where the restart point will be if the current call returns FALSE.
 * Data beyond this point must be rescanned after resumption, so move it to
 * the front of the buffer rather than discarding it.
 */

METHODDEF(jboolean)
fill_input_buffer (j_decompress_ptr cinfo)
{
  my_src_ptr src = (my_src_ptr) cinfo->src;
  size_t nbytes;

	unsigned int rsize;
//  char num[16];

	rsize = INPUT_BUF_SIZE;
	if ( mptr + rsize > (unsigned int)msize )
	{
		rsize = msize - mptr;
	}

//  nbytes = JFREAD(src->infile, src->buffer, INPUT_BUF_SIZE);

/*
	printf( "Doing memcopy.. mbuf: " );
	itoa( (unsigned int) mbuf, (char *) num, 10 );
	printf( "%s mptr: ", num );
	itoa( mptr, (char *) num, 10 );
	printf( "%s msize: ", num );
	itoa( msize, (char *) num, 10 );
	printf( "%s rsize: ", num );
	itoa( rsize, (char *) num, 10 );
	printf( "%s\n", num );
*/

	memcpy( src->buffer, mbuf + mptr, rsize );
	mptr += rsize;
	if ( mptr > msize )
	{
		mptr = msize;
	}
	nbytes = rsize;


  if (nbytes <= 0) {
	if (src->start_of_file) /* Treat empty input file as fatal error */
	  ERREXIT(cinfo, JERR_INPUT_EMPTY);
	WARNMS(cinfo, JWRN_JPEG_EOF);
	/* Insert a fake EOI marker */
	src->buffer[0] = (JOCTET) 0xFF;
	src->buffer[1] = (JOCTET) JPEG_EOI;
	nbytes = 2;
  }

  src->pub.next_input_byte = src->buffer;
  src->pub.bytes_in_buffer = nbytes;
  src->start_of_file = FALSE;

  return TRUE;
}


/*
 * Skip data --- used to skip over a potentially large amount of
 * uninteresting data (such as an APPn marker).
 *
 * Writers of suspendable-input applications must note that skip_input_data
 * is not granted the right to give a suspension return.  If the skip extends
 * beyond the data currently in the buffer, the buffer can be marked empty so
 * that the next read will cause a fill_input_buffer call that can suspend.
 * Arranging for additional bytes to be discarded before reloading the input
 * buffer is the application writer's problem.
 */

METHODDEF(void)
skip_input_data (j_decompress_ptr cinfo, long num_bytes)
{
  my_src_ptr src = (my_src_ptr) 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->pub.bytes_in_buffer) {
	  num_bytes -= (long) src->pub.bytes_in_buffer;
	  (void) fill_input_buffer(cinfo);
	  /* note we assume that fill_input_buffer will never return FALSE,
	   * so suspension need not be handled.
	   */
	}
	src->pub.next_input_byte += (size_t) num_bytes;
	src->pub.bytes_in_buffer -= (size_t) num_bytes;
  }
}


/*
 * An additional method that can be provided by data source modules is the
 * resync_to_restart method for error recovery in the presence of RST markers.
 * For the moment, this source module just uses the default resync method
 * provided by the JPEG library.  That method assumes that no backtracking
 * is possible.
 */


/*
 * Terminate source --- called by jpeg_finish_decompress
 * after all data has been read.  Often a no-op.
 *
 * NB: *not* called by jpeg_abort or jpeg_destroy; surrounding
 * application must deal with any cleanup that should happen even
 * for error exit.
 */

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


/*
 * Prepare for input from a stdio stream.
 * The caller must have already opened the stream, and is responsible
 * for closing it after finishing decompression.
 */

GLOBAL(void)
//jpeg_stdio_src ( j_decompress_ptr cinfo, FILE * infile)
jpeg_stdio_src ( j_decompress_ptr cinfo, char *inbuf, int insize )
{
  my_src_ptr src;

	mbuf = inbuf;
	msize = insize;
	mptr = 0;

  /* The source object and input buffer are made permanent so that a series
   * of JPEG images can be read from the same file by calling jpeg_stdio_src
   * only before the first one.  (If we discarded the buffer at the end of
   * one image, we'd likely lose the start of the next one.)
   * This makes it unsafe to use this manager and a different source
   * manager serially with the same JPEG object.  Caveat programmer.
   */
  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(my_source_mgr));
	src = (my_src_ptr) cinfo->src;
	src->buffer = (JOCTET *)
	  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
				  INPUT_BUF_SIZE * SIZEOF(JOCTET));
  }

  src = (my_src_ptr) cinfo->src;
  src->pub.init_source = init_source;
  src->pub.fill_input_buffer = fill_input_buffer;
  src->pub.skip_input_data = skip_input_data;
  src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */
  src->pub.term_source = term_source;
//  src->infile = infile;
  src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */
  src->pub.next_input_byte = NULL; /* until buffer loaded */
}