/* * 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> #if defined(CONFIG_CMD_JFFS2) && defined(CONFIG_JFFS2_LZO_LZARI) #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); } #endif