diff options
Diffstat (limited to 'fs/jffs2/compr_rubin.c')
| -rw-r--r-- | fs/jffs2/compr_rubin.c | 270 |
1 files changed, 270 insertions, 0 deletions
diff --git a/fs/jffs2/compr_rubin.c b/fs/jffs2/compr_rubin.c new file mode 100644 index 0000000000..3e4faa739a --- /dev/null +++ b/fs/jffs2/compr_rubin.c @@ -0,0 +1,270 @@ +/* + * 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 "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 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 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 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, + .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, + .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); +} |