//$T JDATADST.C GC! 1.081 01/25/01 08:49:34 




//  * jdatadst.c Copyright (C) 1994, 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 compression data destination
//  * routines for the case of emitting JPEG data to a file (or any stdio stream).
//  * While these routines are sufficient for most applications, some will want to
//  * use a different destination manager. IMPORTANT: we assume that fwrite() will
//  * correctly transcribe an array of JOCTETs into 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 "INTERFCE.h"
#include "JPEGLIB.h"
#include "JERROR.h"

//  -----------------------------------------------------------------------------------------------------------------------
//     Expanded data destination object for stdio output
//  -----------------------------------------------------------------------------------------------------------------------
typedef struct
{
	struct jpeg_destination_mgr pub;		// public fields 
	FILE						*outfile;	// target stream 
	JOCTET						*buffer;	// start of buffer 
} my_destination_mgr;

typedef my_destination_mgr	*my_dest_ptr;

#define OUTPUT_BUF_SIZE 4096				// choose an efficiently fwrite'able size 

//  =======================================================================================================================
//     Initialize destination --- called by jpeg_start_compress before any data is actually written.
//  =======================================================================================================================
METHODDEF void init_destination(j_compress_ptr cinfo)
{
	my_dest_ptr dest;

	dest = (my_dest_ptr) cinfo->dest;

	// Allocate the output buffer --- it will be released when done with image 
	dest->buffer = (JOCTET *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, OUTPUT_BUF_SIZE * SIZEOF(JOCTET));
	dest->pub.next_output_byte = dest->buffer;
	dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;
}

//  =======================================================================================================================
//     Empty the output buffer --- called whenever buffer fills up. In typical applications, this should write the entire
//     output buffer (ignoring the current state of next_output_byte & free_in_buffer), reset the pointer & count to the
//     start of the buffer, and return TRUE indicating that the buffer has been dumped. In applications that need to be
//     able to suspend compression due to output overrun, a FALSE return indicates that the buffer cannot be emptied now.
//     In this situation, the compressor will return to its caller (possibly with an indication that it has not accepted
//     all the supplied scanlines). The application should resume compression after it has made more room in the output
//     buffer. Note that there are substantial restrictions on the use of suspension --- see the documentation. When
//     suspending, the compressor will back up to a convenient restart point (typically the start of the current MCU).
//     next_output_byte & free_in_buffer indicate where the restart point will be if the current call returns FALSE. Data
//     beyond this point will be regenerated after resumption, so do not write it out when emptying the buffer externally.
//  =======================================================================================================================
METHODDEF boolean empty_output_buffer(j_compress_ptr cinfo)
{
	my_dest_ptr pst_Dest;
	char		*pc_Buffer;

	pst_Dest = (my_dest_ptr) cinfo->dest;
	pc_Buffer = ((char *) pst_Dest->outfile) + lJPEG_INPOUT_FILE_LENGHT;
	JFWRITE(pc_Buffer, pst_Dest->buffer, OUTPUT_BUF_SIZE);
	lJPEG_INPOUT_FILE_LENGHT += OUTPUT_BUF_SIZE;

	pst_Dest->pub.next_output_byte = pst_Dest->buffer;
	pst_Dest->pub.free_in_buffer = OUTPUT_BUF_SIZE;

	return TRUE;
}

//  =======================================================================================================================
//     Terminate destination --- called by jpeg_finish_compress after all data has been written. Usually needs to flush
//     buffer. 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_destination(j_compress_ptr cinfo)
{
	my_dest_ptr pst_Dest;
	char		*pc_Buffer;
	size_t		datacount;

	pst_Dest = (my_dest_ptr) cinfo->dest;
	datacount = OUTPUT_BUF_SIZE - pst_Dest->pub.free_in_buffer;

	// Write any data remaining in the buffer 
	if(datacount > 0)
	{
		pc_Buffer = ((char *) pst_Dest->outfile) + lJPEG_INPOUT_FILE_LENGHT;
		JFWRITE(pc_Buffer, pst_Dest->buffer, OUTPUT_BUF_SIZE);
		lJPEG_INPOUT_FILE_LENGHT += datacount;
	}
}

//  =======================================================================================================================
//     Prepare for output to a stdio stream. The caller must have already opened the stream, and is responsible for
//     closing it after finishing compression.
//  =======================================================================================================================
GLOBAL void jpeg_stdio_dest(j_compress_ptr cinfo, FILE *outfile)
{
	my_dest_ptr dest;

// 	 * The destination object is made permanent so that multiple JPEG images can be
// 	 * written to the same file without re-executing jpeg_stdio_dest. This makes it
// 	 * dangerous to use this manager and a different destination manager serially with
// 	 * the same JPEG object, because their private object sizes may be different.
// 	 * Caveat programmer.
	if(cinfo->dest == NULL) // first time for this JPEG object? 
	{
		cinfo->dest = (struct jpeg_destination_mgr *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, SIZEOF(my_destination_mgr));
	}

	dest = (my_dest_ptr) cinfo->dest;
	dest->pub.init_destination = init_destination;
	dest->pub.empty_output_buffer = empty_output_buffer;
	dest->pub.term_destination = term_destination;
	dest->outfile = outfile;
}