+++ /dev/null
-/*
- * JFFS2 -- Journalling Flash File System, Version 2.
- *
- * Copyright (C) 2004 Patrik Kluba,
- * University of Szeged, Hungary
- *
- * For licensing information, see the file 'LICENCE' in the
- * jffs2 directory.
- *
- * $Id: compr_lzari.c,v 1.3 2004/06/23 16:34:39 havasi Exp $
- *
- */
-
-/*
- Lempel-Ziv-Arithmetic coding compression module for jffs2
- Based on the LZARI source included in LDS (lossless datacompression sources)
-*/
-
-/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 4; tab-width: 4 -*- */
-
-/*
-Original copyright follows:
-
-**************************************************************
- LZARI.C -- A Data Compression Program
- (tab = 4 spaces)
-**************************************************************
- 4/7/1989 Haruhiko Okumura
- Use, distribute, and modify this program freely.
- Please send me your improved versions.
- PC-VAN SCIENCE
- NIFTY-Serve PAF01022
- CompuServe 74050,1022
-**************************************************************
-
-LZARI.C (c)1989 by Haruyasu Yoshizaki, Haruhiko Okumura, and Kenji Rikitake.
-All rights reserved. Permission granted for non-commercial use.
-
-*/
-
-/*
-
- 2004-02-18 pajko <pajko(AT)halom(DOT)u-szeged(DOT)hu>
- Removed unused variables and fixed no return value
-
- 2004-02-16 pajko <pajko(AT)halom(DOT)u-szeged(DOT)hu>
- Initial release
-
-*/
-
-
-#include <config.h>
-#include <linux/stddef.h>
-#include <jffs2/jffs2.h>
-
-
-#define N 4096 /* size of ring buffer */
-#define F 60 /* upper limit for match_length */
-#define THRESHOLD 2 /* encode string into position and length
- if match_length is greater than this */
-#define NIL N /* index for root of binary search trees */
-
-static unsigned char
- text_buf[N + F - 1]; /* ring buffer of size N,
- with extra F-1 bytes to facilitate string comparison */
-
-/********** Arithmetic Compression **********/
-
-/* If you are not familiar with arithmetic compression, you should read
- I. E. Witten, R. M. Neal, and J. G. Cleary,
- Communications of the ACM, Vol. 30, pp. 520-540 (1987),
- from which much have been borrowed. */
-
-#define M 15
-
-/* Q1 (= 2 to the M) must be sufficiently large, but not so
- large as the unsigned long 4 * Q1 * (Q1 - 1) overflows. */
-
-#define Q1 (1UL << M)
-#define Q2 (2 * Q1)
-#define Q3 (3 * Q1)
-#define Q4 (4 * Q1)
-#define MAX_CUM (Q1 - 1)
-
-#define N_CHAR (256 - THRESHOLD + F)
- /* character code = 0, 1, ..., N_CHAR - 1 */
-
-static unsigned long char_to_sym[N_CHAR], sym_to_char[N_CHAR + 1];
-static unsigned long
- sym_freq[N_CHAR + 1], /* frequency for symbols */
- sym_cum[N_CHAR + 1], /* cumulative freq for symbols */
- position_cum[N + 1]; /* cumulative freq for positions */
-
-static void StartModel(void) /* Initialize model */
-{
- unsigned long ch, sym, i;
-
- sym_cum[N_CHAR] = 0;
- for (sym = N_CHAR; sym >= 1; sym--) {
- ch = sym - 1;
- char_to_sym[ch] = sym; sym_to_char[sym] = ch;
- sym_freq[sym] = 1;
- sym_cum[sym - 1] = sym_cum[sym] + sym_freq[sym];
- }
- sym_freq[0] = 0; /* sentinel (!= sym_freq[1]) */
- position_cum[N] = 0;
- for (i = N; i >= 1; i--)
- position_cum[i - 1] = position_cum[i] + 10000 / (i + 200);
- /* empirical distribution function (quite tentative) */
- /* Please devise a better mechanism! */
-}
-
-static void UpdateModel(unsigned long sym)
-{
- unsigned long c, ch_i, ch_sym;
- unsigned long i;
- if (sym_cum[0] >= MAX_CUM) {
- c = 0;
- for (i = N_CHAR; i > 0; i--) {
- sym_cum[i] = c;
- c += (sym_freq[i] = (sym_freq[i] + 1) >> 1);
- }
- sym_cum[0] = c;
- }
- for (i = sym; sym_freq[i] == sym_freq[i - 1]; i--) ;
- if (i < sym) {
- ch_i = sym_to_char[i]; ch_sym = sym_to_char[sym];
- sym_to_char[i] = ch_sym; sym_to_char[sym] = ch_i;
- char_to_sym[ch_i] = sym; char_to_sym[ch_sym] = i;
- }
- sym_freq[i]++;
- while (--i > 0) sym_cum[i]++;
- sym_cum[0]++;
-}
-
-static unsigned long BinarySearchSym(unsigned long x)
- /* 1 if x >= sym_cum[1],
- N_CHAR if sym_cum[N_CHAR] > x,
- i such that sym_cum[i - 1] > x >= sym_cum[i] otherwise */
-{
- unsigned long i, j, k;
-
- i = 1; j = N_CHAR;
- while (i < j) {
- k = (i + j) / 2;
- if (sym_cum[k] > x) i = k + 1; else j = k;
- }
- return i;
-}
-
-unsigned long BinarySearchPos(unsigned long x)
- /* 0 if x >= position_cum[1],
- N - 1 if position_cum[N] > x,
- i such that position_cum[i] > x >= position_cum[i + 1] otherwise */
-{
- unsigned long i, j, k;
-
- i = 1; j = N;
- while (i < j) {
- k = (i + j) / 2;
- if (position_cum[k] > x) i = k + 1; else j = k;
- }
- return i - 1;
-}
-
-static int Decode(unsigned char *srcbuf, unsigned char *dstbuf, unsigned long srclen,
- unsigned long dstlen) /* Just the reverse of Encode(). */
-{
- unsigned long i, r, j, k, c, range, sym;
- unsigned char *ip, *op;
- unsigned char *srcend = srcbuf + srclen;
- unsigned char *dstend = dstbuf + dstlen;
- unsigned char buffer = 0;
- unsigned char mask = 0;
- unsigned long low = 0;
- unsigned long high = Q4;
- unsigned long value = 0;
-
- ip = srcbuf;
- op = dstbuf;
- for (i = 0; i < M + 2; i++) {
- value *= 2;
- if ((mask >>= 1) == 0) {
- buffer = (ip >= srcend) ? 0 : *(ip++);
- mask = 128;
- }
- value += ((buffer & mask) != 0);
- }
-
- StartModel();
- for (i = 0; i < N - F; i++) text_buf[i] = ' ';
- r = N - F;
-
- while (op < dstend) {
- range = high - low;
- sym = BinarySearchSym((unsigned long)
- (((value - low + 1) * sym_cum[0] - 1) / range));
- high = low + (range * sym_cum[sym - 1]) / sym_cum[0];
- low += (range * sym_cum[sym ]) / sym_cum[0];
- for ( ; ; ) {
- if (low >= Q2) {
- value -= Q2; low -= Q2; high -= Q2;
- } else if (low >= Q1 && high <= Q3) {
- value -= Q1; low -= Q1; high -= Q1;
- } else if (high > Q2) break;
- low += low; high += high;
- value *= 2;
- if ((mask >>= 1) == 0) {
- buffer = (ip >= srcend) ? 0 : *(ip++);
- mask = 128;
- }
- value += ((buffer & mask) != 0);
- }
- c = sym_to_char[sym];
- UpdateModel(sym);
- if (c < 256) {
- if (op >= dstend) return -1;
- *(op++) = c;
- text_buf[r++] = c;
- r &= (N - 1);
- } else {
- j = c - 255 + THRESHOLD;
- range = high - low;
- i = BinarySearchPos((unsigned long)
- (((value - low + 1) * position_cum[0] - 1) / range));
- high = low + (range * position_cum[i ]) / position_cum[0];
- low += (range * position_cum[i + 1]) / position_cum[0];
- for ( ; ; ) {
- if (low >= Q2) {
- value -= Q2; low -= Q2; high -= Q2;
- } else if (low >= Q1 && high <= Q3) {
- value -= Q1; low -= Q1; high -= Q1;
- } else if (high > Q2) break;
- low += low; high += high;
- value *= 2;
- if ((mask >>= 1) == 0) {
- buffer = (ip >= srcend) ? 0 : *(ip++);
- mask = 128;
- }
- value += ((buffer & mask) != 0);
- }
- i = (r - i - 1) & (N - 1);
- for (k = 0; k < j; k++) {
- c = text_buf[(i + k) & (N - 1)];
- if (op >= dstend) return -1;
- *(op++) = c;
- text_buf[r++] = c;
- r &= (N - 1);
- }
- }
- }
- return 0;
-}
-
-int lzari_decompress(unsigned char *data_in, unsigned char *cpage_out,
- u32 srclen, u32 destlen)
-{
- return Decode(data_in, cpage_out, srclen, destlen);
-}
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