/* 31/01/01 Libtiny compression/decompression library v1.0 source file
		Huffman compression routine
		Huffman code: (C) David Bourgin */

/* includes */
#include	<libps.h>
#include	"stdio.h"

#include	"tiny.h"

/* extern */
/* huffman variables */
extern	u_char bit_counter_to_write;
extern	u_int val_to_write;

extern	u_char	*srce_p;	
extern	u_char	*start_p;
extern	u_char	*end_p;
extern	u_char	*dest_p;

extern 	int	buflen;
extern	int	bytecount;
extern	int	errval;
	
/* Compress data using huffman encoding,
		*source_p - pointer to  data to compress,
		sourcelen - number of bytes to compress,
		destination_p - pointer to buffer to store compressed data
	 Return values
	 	>0							compressed data size in bytes, including header,
	 	 0(T_LEN_ERROR)	sourcelen is zero,
	 	-2(T_MEM_ERROR)	out of memory, workspace couldn't be allocated,
		-3(T_BUF_ERROR) destination buffer too small, returned if the source data cannot 
		                be compressed, 
	The destination buffer length should be 0.1% plus 32 bytes larger than the source data length*/
int huf_compress(u_char *source_p, u_int sourcelen, u_char *destination_p)
{
	S_HDR *hdr_p = (S_HDR *)destination_p;
	int	status = T_LEN_ERROR;

	if(sourcelen)
	{
		hdr_p->id = ID_HUFF;
		hdr_p->orig_size = sourcelen;
	
		destination_p += sizeof(S_HDR);				/* start of compression data after header */
	
		/* set required variables in dcodhuff.c */
		start_p = srce_p	= source_p;					/* ptr to data to compress */
		end_p		= (srce_p + sourcelen) -1;		/* ptr at end of data */
		dest_p	=	destination_p;								/* ptr to compression buffer */
	
		errval = bytecount = 0;
		bit_counter_to_write = val_to_write = 0;
		
		buflen = sourcelen + (int) (sourcelen * 0.001) + 24;		/* used to watch for a buffer overrun */

		status = huffmanencoding();
	
		if(status >= 0)
		{
			hdr_p->comp_size = status;  /* compression successful, place compressed data length in header */
			status += sizeof(S_HDR);		/* add header to compression data length */
		}
		/* else error value returned */
	}
	
	return status;
}