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Diffstat (limited to 'fs/jffs2/compr_lzari.c')
| -rw-r--r-- | fs/jffs2/compr_lzari.c | 262 |
1 files changed, 262 insertions, 0 deletions
diff --git a/fs/jffs2/compr_lzari.c b/fs/jffs2/compr_lzari.c new file mode 100644 index 000000000..a6a708bcd --- /dev/null +++ b/fs/jffs2/compr_lzari.c @@ -0,0 +1,262 @@ +/* + * 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 ((CONFIG_COMMANDS & CFG_CMD_JFFS2) && defined(CONFIG_JFFS2_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 /* ((CONFIG_COMMANDS & CFG_CMD_JFFS2) && defined(CONFIG_JFFS2_LZARI)) */ |