From 5db94eda78fefe77ff30d93a0b99041e17332c4a Mon Sep 17 00:00:00 2001
From: Vince Weaver <vincent.weaver@maine.edu>
Date: Mon, 5 Feb 2018 14:40:07 -0500
Subject: [PATCH] mockingboard: add lzss compression tool

should probably be in a separate directory
---
 mockingboard/lzss_compress.c | 384 +++++++++++++++++++++++++++++++++++
 1 file changed, 384 insertions(+)
 create mode 100644 mockingboard/lzss_compress.c

diff --git a/mockingboard/lzss_compress.c b/mockingboard/lzss_compress.c
new file mode 100644
index 00000000..1848e7d5
--- /dev/null
+++ b/mockingboard/lzss_compress.c
@@ -0,0 +1,384 @@
+/**************************************************************
+	LZSS.C -- A Data Compression Program
+	(tab = 4 spaces)
+***************************************************************
+	4/6/1989 Haruhiko Okumura
+	Use, distribute, and modify this program freely.
+	Please send me your improved versions.
+		PC-VAN		SCIENCE
+		NIFTY-Serve	PAF01022
+		CompuServe	74050,1022
+**************************************************************
+         WARNING: order of match_position and match_lenght changed!
+         see lines 178 to 182
+         Mofication by <stephan.walter@gmx.ch>
+
+         Also modified to have N,F,etc, etc to be parameters, not
+         hard-coded  -- vmw
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+
+/* output types */
+#define NORMAL_ASM 0
+
+#define num_trees 256
+
+	/* initialize trees */
+static void newInitTree(int ring_buffer_size,int binary_search_index,
+		 int *rson, int *dad) {
+
+	int  i;
+
+	/* For i = 0 to N - 1, rson[i] and lson[i] will be the right and
+	   left children of node i.  These nodes need not be initialized.
+	   Also, dad[i] is the parent of node i.  These are initialized to
+	   NIL (= N), which stands for 'not used.'
+	   For i = 0 to 255, rson[N + i + 1] is the root of the tree
+	   for strings that begin with character i.  These are initialized
+	   to NIL.  Note there are 256 trees. */
+
+	for (i=ring_buffer_size+1; i<=ring_buffer_size+num_trees; i++) {
+		rson[i] = binary_search_index;
+	}
+	for (i=0; i<ring_buffer_size; i++) {
+		dad[i] = binary_search_index;
+	}
+}
+
+static void newInsertNode(
+		int r, int ring_buffer_size, int binary_search_index,
+		int match_length_limit,
+		unsigned char *text_buf, int *rson,int *lson, int *dad,
+		int *match_length, int *match_position) {
+	/* Inserts string of length F, text_buf[r..r+F-1], into one of the
+	   trees (text_buf[r]'th tree) and returns the longest-match position
+	   and length via the global variables match_position and match_length.
+	   If match_length = F, then removes the old node in favor of the new
+	   one, because the old one will be deleted sooner.
+	   Note r plays double role, as tree node and position in buffer. */
+
+	int  i, p, cmp;
+	unsigned char  *key;
+
+	cmp = 1;
+	key = text_buf+r;
+	p = ring_buffer_size + 1 + key[0];
+	rson[r] = lson[r] = binary_search_index;
+	*match_length = 0;
+
+	for( ; ; ) {
+
+		if (cmp >= 0) {
+			if (rson[p] != binary_search_index) p = rson[p];
+			else {
+				rson[p] = r;
+				dad[r] = p;
+				return;
+			}
+		}
+		else {
+			if (lson[p] != binary_search_index) p = lson[p];
+			else {
+				lson[p] = r;
+				dad[r] = p;
+				return;
+			}
+		}
+
+		for(i = 1; i < match_length_limit; i++)
+			if ((cmp = key[i] - text_buf[p + i]) != 0)  break;
+		if (i > *match_length) {
+			*match_position = p;
+			if ((*match_length = i) >= match_length_limit)  break;
+		}
+	}
+
+	dad[r] = dad[p];
+	lson[r] = lson[p];
+	rson[r] = rson[p];
+	dad[lson[p]] = r;
+	dad[rson[p]] = r;
+
+	if (rson[dad[p]] == p) rson[dad[p]] = r;
+	else                   lson[dad[p]] = r;
+	dad[p] = binary_search_index;  /* remove p */
+
+}
+
+	/* deletes node p from tree */
+static void newDeleteNode(int p, int binary_search_index,
+		   int *dad, int *rson, int *lson) {
+
+	int  q;
+
+	if (dad[p] == binary_search_index) return;  /* not in tree */
+	if (rson[p] == binary_search_index) q = lson[p];
+	else if (lson[p] == binary_search_index) q = rson[p];
+	else {
+		q = lson[p];
+		if (rson[q] != binary_search_index) {
+			do {  q = rson[q];  } while (rson[q] != binary_search_index);
+			rson[dad[q]] = lson[q];
+			dad[lson[q]] = dad[q];
+			lson[q] = lson[p];
+			dad[lson[p]] = q;
+		}
+		rson[q] = rson[p];  dad[rson[p]] = q;
+	}
+	dad[q] = dad[p];
+	if (rson[dad[p]] == p) rson[dad[p]] = q;
+	else lson[dad[p]] = q;
+	dad[p] = binary_search_index;
+}
+
+static int lzss_encode_better(
+		FILE *infile,
+		unsigned char frequent_char,
+		int ring_buffer_size, int position_length_threshold,
+		int output_type) {
+
+//	unsigned char frequent_char='#';
+//	int ring_buffer_size=1024;  /* N */
+	int match_length_limit;  //=64;  /* F */
+	/*int position_length_threshold=2;  THRESHOLD */
+	int binary_search_index=ring_buffer_size;  /* NIL */
+	int position_bits; //=10;
+//	int length_bits=16-position_bits;
+
+	unsigned long int codesize = 0;	/* code size counter */
+
+	int  i, c, len, r, s, last_match_length, code_buf_ptr;
+
+	unsigned char  code_buf[8*2+1], mask;
+
+	unsigned char *text_buf;
+
+	int match_position, match_length;  /* of longest match.  These are
+			                 set by the InsertNode() procedure. */
+	int *lson, *rson, *dad;  /* left & right children &
+			                        parents -- These constitute
+					        binary search trees. */
+
+	/* determine stuff from ring_buffer_size */
+	/* fake log2 algorithm */
+
+	i=1;
+	while (((ring_buffer_size-1)>>i) >=1) {
+		i++;
+	};
+
+	position_bits=i;
+	match_length_limit=1<<(16-position_bits);
+//	printf("%i, %i %i %i '%c'\n",ring_buffer_size,position_bits,match_length_limit
+//		,position_length_threshold,frequent_char);
+
+                                   /* ring buffer of size N, with extra F-1
+				      bytes to facilitate string comparison */
+	text_buf=calloc(ring_buffer_size+match_length_limit-1,sizeof(unsigned char));
+	lson=calloc(ring_buffer_size+1,sizeof(int));
+	rson=calloc(ring_buffer_size+num_trees+1,sizeof(int));
+	dad=calloc(ring_buffer_size+1,sizeof(int));
+
+	/* initialize trees */
+	newInitTree(ring_buffer_size,binary_search_index,rson,dad);
+
+
+
+	/* code_buf[1..16] saves eight units of code, and
+	   code_buf[0] works as eight flags, "1" representing
+	   that the unit is an unencoded letter (1 byte),
+	   "0" a position-and-length pair (2 bytes).
+	   Thus, eight units require at most 16 bytes of code. */
+
+	code_buf[0] = 0;
+
+	code_buf_ptr = mask = 1;
+	s = 0;
+	r = ring_buffer_size - match_length_limit;
+
+	if (frequent_char<32) {
+		printf(".equ FREQUENT_CHAR,%d\n",frequent_char);
+	}
+	else {
+		printf(".equ FREQUENT_CHAR,'%c'\n",frequent_char);
+	}
+	printf(".equ N,%i\n",ring_buffer_size);
+	printf(".equ F,%i\n",match_length_limit);
+	printf(".equ THRESHOLD,%i\n",position_length_threshold);
+	printf(".equ P_BITS,%i\n",position_bits);
+	printf(".equ POSITION_MASK,%i\n",(0xff>>(8-(position_bits-8))));
+
+	printf("logo:\n");
+
+	/* Clear the buffer with any character that will appear often. */
+	for(i=0; i<(ring_buffer_size-match_length_limit); i++) {
+		text_buf[i]=frequent_char;
+	}
+
+//	printf("%i to %i = %i\n",0,ring_buffer_size-match_length_limit,frequent_char);
+
+//	printf("%i to %i = ",r,r+match_length_limit);
+	for(len=0; len<match_length_limit && (c=getc(infile))!=EOF; len++) {
+		/* Read F bytes into the last F bytes of the buffer */
+		text_buf[r+len]=c;
+//		printf("%i ",text_buf[r+len]);
+	}
+//	printf("\n");
+	if (len== 0) return 0;  /* trying to compress empty file */
+
+	for(i = 1; i <= match_length_limit; i++) {
+		newInsertNode(r-i,ring_buffer_size,binary_search_index,
+			match_length_limit,text_buf,rson,lson,dad,
+			&match_length,&match_position);
+	}
+
+	/* Insert the F strings,
+		each of which begins with one or more 'space' characters.  Note
+		the order in which these strings are inserted.  This way,
+		degenerate trees will be less likely to occur. */
+	newInsertNode(r,ring_buffer_size,binary_search_index,
+			match_length_limit,text_buf,rson,lson,dad,
+			&match_length,&match_position);
+	/* Finally, insert the whole string just read.  The
+		global variables match_length and match_position are set. */
+	do {
+		/* match_length may be spuriously long near the end of text. */
+		if (match_length > len) match_length = len;
+
+		if (match_length <= position_length_threshold) {
+			match_length=1;  /* Not long enough match.  Send one byte. */
+			code_buf[0] |= mask;  /* 'send one byte' flag */
+			code_buf[code_buf_ptr++] = text_buf[r];  /* Send uncoded. */
+//			printf("single: %i @ %i\n",text_buf[r],r);
+		} else {
+//			printf("pos : %i\tlen : %i\n",match_position,match_length);
+
+			code_buf[code_buf_ptr++] = (unsigned char) match_position;
+
+			code_buf[code_buf_ptr++] = (unsigned char)
+				( ((match_position>>8) & (0xff >> (8-(position_bits-8)))) |
+				((match_length-(position_length_threshold+1))<<(position_bits-8)) );
+
+//			code_buf[code_buf_ptr++] = (unsigned char)
+//					(((match_position >> 8) & 7) |
+//					(match_length - (position_length_threshold+1))<<3);
+		}
+		if ((mask <<= 1) == 0) {  /* Shift mask left one bit. */
+			printf("\t.byte\t");
+			for(i=0; i<code_buf_ptr; i++) { /* Send at most 8 units of */
+				printf("$%02X%c",code_buf[i],(i==code_buf_ptr-1)?'\n':',');
+			}
+			codesize += code_buf_ptr;
+			code_buf[0] = 0;  code_buf_ptr = mask = 1;
+		}
+
+		last_match_length = match_length;
+		for (i = 0; i < last_match_length && (c = getc(infile)) != EOF; i++) {
+			/* Delete old strings and */
+			newDeleteNode(s,binary_search_index,dad,rson,lson);
+			/* read new bytes */
+			text_buf[s] = c;
+
+			/* If the position is near the end of buffer,
+				extend the buffer to make string comparison easier. */
+			if (s < match_length_limit - 1) {
+				text_buf[s + ring_buffer_size] = c;
+			}
+
+			s = (s + 1) & (ring_buffer_size - 1);
+			r = (r + 1) & (ring_buffer_size - 1);
+			/* Since this is a ring buffer, increment the position
+			modulo N. */
+			newInsertNode(r,ring_buffer_size,binary_search_index,
+				match_length_limit,text_buf,rson,lson,dad,
+				&match_length,&match_position);
+			/* Register the string in text_buf[r..r+F-1] */
+		}
+
+		/* After the end of text, */
+		while (i++ < last_match_length) {
+
+			/* no need to read, but */
+			newDeleteNode(s,binary_search_index,dad,rson,lson);
+
+			s = (s + 1) & (ring_buffer_size - 1);
+			r = (r + 1) & (ring_buffer_size - 1);
+			if (--len) {
+				newInsertNode(r,ring_buffer_size,binary_search_index,
+					match_length_limit,text_buf,rson,lson,dad,
+					&match_length,&match_position);
+			}
+			/* buffer may not be empty. */
+		}
+		/* until length of string to be processed is zero */
+	} while (len > 0);
+
+
+	/* Send remaining code. */
+	if (code_buf_ptr > 1) {
+
+
+		printf("\t.byte\t");
+
+		for(i=0; i<code_buf_ptr; i++) {
+			printf("$%02x",code_buf[i]);
+
+			if (i==code_buf_ptr-1) {
+				printf("\n");
+			} else {
+				printf(",");
+			}
+		}
+		codesize += code_buf_ptr;
+	}
+
+	printf("logo_end:\n");
+
+	free(text_buf);
+	free(lson);
+	free(rson);
+	free(dad);
+	return codesize;
+}
+
+int main(int argc, char **argv) {
+
+	FILE *input;
+	int ch,byte_count=0,orig_byte_count=0;
+
+	/* Check command line arguments */
+	if (argc<2) {
+		printf("\nUsage:\n\t%s file_to_compress\n\n",argv[0]);
+		return 3;
+	}
+
+	/* Open input file */
+	input=fopen(argv[1],"r");
+	if (input==NULL) {
+		printf("Could not open \"%s\"\n",argv[1]);
+		return 2;
+	}
+
+	byte_count=lzss_encode_better(input,'\0',1024,2,NORMAL_ASM);
+
+	rewind(input);
+
+	/* calculate size of original */
+	/* Why aren't we using stat()? */
+	while((ch=fgetc(input))!=EOF) {
+		orig_byte_count++;
+	}
+
+	fclose(input);
+
+	printf("; Size of original version: %i\n",orig_byte_count);
+	printf("; Size of compressed version: %i\n",byte_count);
+
+	return 0;
+
+}