linux-stable/fs/jffs2/compr_rubin.c

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