456 lines
8.7 KiB
C
456 lines
8.7 KiB
C
/*
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* JFFS2 -- Journalling Flash File System, Version 2.
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*
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* Copyright © 2001-2007 Red Hat, Inc.
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* Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
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*
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* Created by Arjan van de Ven <arjanv@redhat.com>
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*
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* For licensing information, see the file 'LICENCE' in this directory.
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*
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*/
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/jffs2.h>
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#include <linux/errno.h>
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#include "compr.h"
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#define RUBIN_REG_SIZE 16
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#define UPPER_BIT_RUBIN (((long) 1)<<(RUBIN_REG_SIZE-1))
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#define LOWER_BITS_RUBIN ((((long) 1)<<(RUBIN_REG_SIZE-1))-1)
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#define BIT_DIVIDER_MIPS 1043
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static int bits_mips[8] = { 277, 249, 290, 267, 229, 341, 212, 241};
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struct pushpull {
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unsigned char *buf;
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unsigned int buflen;
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unsigned int ofs;
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unsigned int reserve;
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};
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struct rubin_state {
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unsigned long p;
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unsigned long q;
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unsigned long rec_q;
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long bit_number;
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struct pushpull pp;
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int bit_divider;
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int bits[8];
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};
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static inline void init_pushpull(struct pushpull *pp, char *buf,
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unsigned buflen, unsigned ofs,
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unsigned reserve)
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{
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pp->buf = buf;
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pp->buflen = buflen;
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pp->ofs = ofs;
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pp->reserve = reserve;
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}
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static inline int pushbit(struct pushpull *pp, int bit, int use_reserved)
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{
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if (pp->ofs >= pp->buflen - (use_reserved?0:pp->reserve))
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return -ENOSPC;
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if (bit)
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pp->buf[pp->ofs >> 3] |= (1<<(7-(pp->ofs & 7)));
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else
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pp->buf[pp->ofs >> 3] &= ~(1<<(7-(pp->ofs & 7)));
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pp->ofs++;
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return 0;
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}
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static inline int pushedbits(struct pushpull *pp)
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{
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return pp->ofs;
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}
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static inline int pullbit(struct pushpull *pp)
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{
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int bit;
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bit = (pp->buf[pp->ofs >> 3] >> (7-(pp->ofs & 7))) & 1;
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pp->ofs++;
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return bit;
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}
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static inline int pulledbits(struct pushpull *pp)
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{
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return pp->ofs;
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}
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static void init_rubin(struct rubin_state *rs, int div, int *bits)
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{
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int c;
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rs->q = 0;
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rs->p = (long) (2 * UPPER_BIT_RUBIN);
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rs->bit_number = (long) 0;
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rs->bit_divider = div;
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for (c=0; c<8; c++)
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rs->bits[c] = bits[c];
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}
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static int encode(struct rubin_state *rs, long A, long B, int symbol)
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{
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long i0, i1;
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int ret;
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while ((rs->q >= UPPER_BIT_RUBIN) ||
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((rs->p + rs->q) <= UPPER_BIT_RUBIN)) {
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rs->bit_number++;
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ret = pushbit(&rs->pp, (rs->q & UPPER_BIT_RUBIN) ? 1 : 0, 0);
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if (ret)
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return ret;
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rs->q &= LOWER_BITS_RUBIN;
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rs->q <<= 1;
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rs->p <<= 1;
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}
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i0 = A * rs->p / (A + B);
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if (i0 <= 0)
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i0 = 1;
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if (i0 >= rs->p)
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i0 = rs->p - 1;
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i1 = rs->p - i0;
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if (symbol == 0)
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rs->p = i0;
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else {
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rs->p = i1;
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rs->q += i0;
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}
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return 0;
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}
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static void end_rubin(struct rubin_state *rs)
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{
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int i;
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for (i = 0; i < RUBIN_REG_SIZE; i++) {
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pushbit(&rs->pp, (UPPER_BIT_RUBIN & rs->q) ? 1 : 0, 1);
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rs->q &= LOWER_BITS_RUBIN;
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rs->q <<= 1;
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}
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}
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static void init_decode(struct rubin_state *rs, int div, int *bits)
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{
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init_rubin(rs, div, bits);
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/* behalve lower */
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rs->rec_q = 0;
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for (rs->bit_number = 0; rs->bit_number++ < RUBIN_REG_SIZE;
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rs->rec_q = rs->rec_q * 2 + (long) (pullbit(&rs->pp)))
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;
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}
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static void __do_decode(struct rubin_state *rs, unsigned long p,
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unsigned long q)
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{
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register unsigned long lower_bits_rubin = LOWER_BITS_RUBIN;
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unsigned long rec_q;
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int c, bits = 0;
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/*
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* First, work out how many bits we need from the input stream.
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* Note that we have already done the initial check on this
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* loop prior to calling this function.
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*/
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do {
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bits++;
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q &= lower_bits_rubin;
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q <<= 1;
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p <<= 1;
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} while ((q >= UPPER_BIT_RUBIN) || ((p + q) <= UPPER_BIT_RUBIN));
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rs->p = p;
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rs->q = q;
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rs->bit_number += bits;
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/*
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* Now get the bits. We really want this to be "get n bits".
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*/
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rec_q = rs->rec_q;
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do {
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c = pullbit(&rs->pp);
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rec_q &= lower_bits_rubin;
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rec_q <<= 1;
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rec_q += c;
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} while (--bits);
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rs->rec_q = rec_q;
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}
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static int decode(struct rubin_state *rs, long A, long B)
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{
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unsigned long p = rs->p, q = rs->q;
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long i0, threshold;
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int symbol;
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if (q >= UPPER_BIT_RUBIN || ((p + q) <= UPPER_BIT_RUBIN))
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__do_decode(rs, p, q);
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i0 = A * rs->p / (A + B);
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if (i0 <= 0)
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i0 = 1;
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if (i0 >= rs->p)
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i0 = rs->p - 1;
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threshold = rs->q + i0;
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symbol = rs->rec_q >= threshold;
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if (rs->rec_q >= threshold) {
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rs->q += i0;
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i0 = rs->p - i0;
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}
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rs->p = i0;
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return symbol;
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}
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static int out_byte(struct rubin_state *rs, unsigned char byte)
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{
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int i, ret;
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struct rubin_state rs_copy;
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rs_copy = *rs;
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for (i=0; i<8; i++) {
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ret = encode(rs, rs->bit_divider-rs->bits[i],
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rs->bits[i], byte & 1);
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if (ret) {
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/* Failed. Restore old state */
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*rs = rs_copy;
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return ret;
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}
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byte >>= 1 ;
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}
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return 0;
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}
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static int in_byte(struct rubin_state *rs)
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{
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int i, result = 0, bit_divider = rs->bit_divider;
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for (i = 0; i < 8; i++)
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result |= decode(rs, bit_divider - rs->bits[i],
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rs->bits[i]) << i;
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return result;
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}
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static int rubin_do_compress(int bit_divider, int *bits, unsigned char *data_in,
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unsigned char *cpage_out, uint32_t *sourcelen,
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uint32_t *dstlen)
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{
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int outpos = 0;
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int pos=0;
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struct rubin_state rs;
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init_pushpull(&rs.pp, cpage_out, *dstlen * 8, 0, 32);
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init_rubin(&rs, bit_divider, bits);
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while (pos < (*sourcelen) && !out_byte(&rs, data_in[pos]))
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pos++;
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end_rubin(&rs);
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if (outpos > pos) {
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/* We failed */
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return -1;
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}
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/* Tell the caller how much we managed to compress,
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* and how much space it took */
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outpos = (pushedbits(&rs.pp)+7)/8;
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if (outpos >= pos)
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return -1; /* We didn't actually compress */
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*sourcelen = pos;
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*dstlen = outpos;
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return 0;
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}
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#if 0
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/* _compress returns the compressed size, -1 if bigger */
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int jffs2_rubinmips_compress(unsigned char *data_in, unsigned char *cpage_out,
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uint32_t *sourcelen, uint32_t *dstlen)
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{
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return rubin_do_compress(BIT_DIVIDER_MIPS, bits_mips, data_in,
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cpage_out, sourcelen, dstlen);
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}
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#endif
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static int jffs2_dynrubin_compress(unsigned char *data_in,
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unsigned char *cpage_out,
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uint32_t *sourcelen, uint32_t *dstlen)
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{
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int bits[8];
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unsigned char histo[256];
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int i;
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int ret;
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uint32_t mysrclen, mydstlen;
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mysrclen = *sourcelen;
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mydstlen = *dstlen - 8;
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if (*dstlen <= 12)
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return -1;
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memset(histo, 0, 256);
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for (i=0; i<mysrclen; i++)
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histo[data_in[i]]++;
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memset(bits, 0, sizeof(int)*8);
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for (i=0; i<256; i++) {
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if (i&128)
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bits[7] += histo[i];
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if (i&64)
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bits[6] += histo[i];
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if (i&32)
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bits[5] += histo[i];
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if (i&16)
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bits[4] += histo[i];
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if (i&8)
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bits[3] += histo[i];
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if (i&4)
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bits[2] += histo[i];
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if (i&2)
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bits[1] += histo[i];
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if (i&1)
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bits[0] += histo[i];
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}
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for (i=0; i<8; i++) {
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bits[i] = (bits[i] * 256) / mysrclen;
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if (!bits[i]) bits[i] = 1;
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if (bits[i] > 255) bits[i] = 255;
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cpage_out[i] = bits[i];
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}
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ret = rubin_do_compress(256, bits, data_in, cpage_out+8, &mysrclen,
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&mydstlen);
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if (ret)
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return ret;
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/* Add back the 8 bytes we took for the probabilities */
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mydstlen += 8;
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if (mysrclen <= mydstlen) {
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/* We compressed */
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return -1;
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}
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*sourcelen = mysrclen;
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*dstlen = mydstlen;
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return 0;
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}
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static void rubin_do_decompress(int bit_divider, int *bits,
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unsigned char *cdata_in,
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unsigned char *page_out, uint32_t srclen,
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uint32_t destlen)
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{
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int outpos = 0;
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struct rubin_state rs;
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init_pushpull(&rs.pp, cdata_in, srclen, 0, 0);
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init_decode(&rs, bit_divider, bits);
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while (outpos < destlen)
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page_out[outpos++] = in_byte(&rs);
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}
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static int jffs2_rubinmips_decompress(unsigned char *data_in,
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unsigned char *cpage_out,
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uint32_t sourcelen, uint32_t dstlen)
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{
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rubin_do_decompress(BIT_DIVIDER_MIPS, bits_mips, data_in,
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cpage_out, sourcelen, dstlen);
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return 0;
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}
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static int jffs2_dynrubin_decompress(unsigned char *data_in,
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unsigned char *cpage_out,
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uint32_t sourcelen, uint32_t dstlen)
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{
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int bits[8];
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int c;
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for (c=0; c<8; c++)
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bits[c] = data_in[c];
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rubin_do_decompress(256, bits, data_in+8, cpage_out, sourcelen-8,
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dstlen);
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return 0;
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}
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static struct jffs2_compressor jffs2_rubinmips_comp = {
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.priority = JFFS2_RUBINMIPS_PRIORITY,
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.name = "rubinmips",
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.compr = JFFS2_COMPR_DYNRUBIN,
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.compress = NULL, /*&jffs2_rubinmips_compress,*/
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.decompress = &jffs2_rubinmips_decompress,
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#ifdef JFFS2_RUBINMIPS_DISABLED
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.disabled = 1,
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#else
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.disabled = 0,
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#endif
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};
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int jffs2_rubinmips_init(void)
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{
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return jffs2_register_compressor(&jffs2_rubinmips_comp);
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}
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void jffs2_rubinmips_exit(void)
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{
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jffs2_unregister_compressor(&jffs2_rubinmips_comp);
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}
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static struct jffs2_compressor jffs2_dynrubin_comp = {
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.priority = JFFS2_DYNRUBIN_PRIORITY,
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.name = "dynrubin",
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.compr = JFFS2_COMPR_RUBINMIPS,
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.compress = jffs2_dynrubin_compress,
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.decompress = &jffs2_dynrubin_decompress,
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#ifdef JFFS2_DYNRUBIN_DISABLED
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.disabled = 1,
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#else
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.disabled = 0,
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#endif
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};
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int jffs2_dynrubin_init(void)
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{
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return jffs2_register_compressor(&jffs2_dynrubin_comp);
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}
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void jffs2_dynrubin_exit(void)
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{
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jffs2_unregister_compressor(&jffs2_dynrubin_comp);
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}
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