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/*
* 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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