linux/lib/lzo/lzo1x_compress.c
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   1/*
   2 *  LZO1X Compressor from MiniLZO
   3 *
   4 *  Copyright (C) 1996-2005 Markus F.X.J. Oberhumer <markus@oberhumer.com>
   5 *
   6 *  The full LZO package can be found at:
   7 *  http://www.oberhumer.com/opensource/lzo/
   8 *
   9 *  Changed for kernel use by:
  10 *  Nitin Gupta <nitingupta910@gmail.com>
  11 *  Richard Purdie <rpurdie@openedhand.com>
  12 */
  13
  14#include <linux/module.h>
  15#include <linux/kernel.h>
  16#include <linux/lzo.h>
  17#include <asm/unaligned.h>
  18#include "lzodefs.h"
  19
  20static noinline size_t
  21_lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
  22                unsigned char *out, size_t *out_len, void *wrkmem)
  23{
  24        const unsigned char * const in_end = in + in_len;
  25        const unsigned char * const ip_end = in + in_len - M2_MAX_LEN - 5;
  26        const unsigned char ** const dict = wrkmem;
  27        const unsigned char *ip = in, *ii = ip;
  28        const unsigned char *end, *m, *m_pos;
  29        size_t m_off, m_len, dindex;
  30        unsigned char *op = out;
  31
  32        ip += 4;
  33
  34        for (;;) {
  35                dindex = ((size_t)(0x21 * DX3(ip, 5, 5, 6)) >> 5) & D_MASK;
  36                m_pos = dict[dindex];
  37
  38                if (m_pos < in)
  39                        goto literal;
  40
  41                if (ip == m_pos || ((size_t)(ip - m_pos) > M4_MAX_OFFSET))
  42                        goto literal;
  43
  44                m_off = ip - m_pos;
  45                if (m_off <= M2_MAX_OFFSET || m_pos[3] == ip[3])
  46                        goto try_match;
  47
  48                dindex = (dindex & (D_MASK & 0x7ff)) ^ (D_HIGH | 0x1f);
  49                m_pos = dict[dindex];
  50
  51                if (m_pos < in)
  52                        goto literal;
  53
  54                if (ip == m_pos || ((size_t)(ip - m_pos) > M4_MAX_OFFSET))
  55                        goto literal;
  56
  57                m_off = ip - m_pos;
  58                if (m_off <= M2_MAX_OFFSET || m_pos[3] == ip[3])
  59                        goto try_match;
  60
  61                goto literal;
  62
  63try_match:
  64                if (get_unaligned((const unsigned short *)m_pos)
  65                                == get_unaligned((const unsigned short *)ip)) {
  66                        if (likely(m_pos[2] == ip[2]))
  67                                        goto match;
  68                }
  69
  70literal:
  71                dict[dindex] = ip;
  72                ++ip;
  73                if (unlikely(ip >= ip_end))
  74                        break;
  75                continue;
  76
  77match:
  78                dict[dindex] = ip;
  79                if (ip != ii) {
  80                        size_t t = ip - ii;
  81
  82                        if (t <= 3) {
  83                                op[-2] |= t;
  84                        } else if (t <= 18) {
  85                                *op++ = (t - 3);
  86                        } else {
  87                                size_t tt = t - 18;
  88
  89                                *op++ = 0;
  90                                while (tt > 255) {
  91                                        tt -= 255;
  92                                        *op++ = 0;
  93                                }
  94                                *op++ = tt;
  95                        }
  96                        do {
  97                                *op++ = *ii++;
  98                        } while (--t > 0);
  99                }
 100
 101                ip += 3;
 102                if (m_pos[3] != *ip++ || m_pos[4] != *ip++
 103                                || m_pos[5] != *ip++ || m_pos[6] != *ip++
 104                                || m_pos[7] != *ip++ || m_pos[8] != *ip++) {
 105                        --ip;
 106                        m_len = ip - ii;
 107
 108                        if (m_off <= M2_MAX_OFFSET) {
 109                                m_off -= 1;
 110                                *op++ = (((m_len - 1) << 5)
 111                                                | ((m_off & 7) << 2));
 112                                *op++ = (m_off >> 3);
 113                        } else if (m_off <= M3_MAX_OFFSET) {
 114                                m_off -= 1;
 115                                *op++ = (M3_MARKER | (m_len - 2));
 116                                goto m3_m4_offset;
 117                        } else {
 118                                m_off -= 0x4000;
 119
 120                                *op++ = (M4_MARKER | ((m_off & 0x4000) >> 11)
 121                                                | (m_len - 2));
 122                                goto m3_m4_offset;
 123                        }
 124                } else {
 125                        end = in_end;
 126                        m = m_pos + M2_MAX_LEN + 1;
 127
 128                        while (ip < end && *m == *ip) {
 129                                m++;
 130                                ip++;
 131                        }
 132                        m_len = ip - ii;
 133
 134                        if (m_off <= M3_MAX_OFFSET) {
 135                                m_off -= 1;
 136                                if (m_len <= 33) {
 137                                        *op++ = (M3_MARKER | (m_len - 2));
 138                                } else {
 139                                        m_len -= 33;
 140                                        *op++ = M3_MARKER | 0;
 141                                        goto m3_m4_len;
 142                                }
 143                        } else {
 144                                m_off -= 0x4000;
 145                                if (m_len <= M4_MAX_LEN) {
 146                                        *op++ = (M4_MARKER
 147                                                | ((m_off & 0x4000) >> 11)
 148                                                | (m_len - 2));
 149                                } else {
 150                                        m_len -= M4_MAX_LEN;
 151                                        *op++ = (M4_MARKER
 152                                                | ((m_off & 0x4000) >> 11));
 153m3_m4_len:
 154                                        while (m_len > 255) {
 155                                                m_len -= 255;
 156                                                *op++ = 0;
 157                                        }
 158
 159                                        *op++ = (m_len);
 160                                }
 161                        }
 162m3_m4_offset:
 163                        *op++ = ((m_off & 63) << 2);
 164                        *op++ = (m_off >> 6);
 165                }
 166
 167                ii = ip;
 168                if (unlikely(ip >= ip_end))
 169                        break;
 170        }
 171
 172        *out_len = op - out;
 173        return in_end - ii;
 174}
 175
 176int lzo1x_1_compress(const unsigned char *in, size_t in_len, unsigned char *out,
 177                        size_t *out_len, void *wrkmem)
 178{
 179        const unsigned char *ii;
 180        unsigned char *op = out;
 181        size_t t;
 182
 183        if (unlikely(in_len <= M2_MAX_LEN + 5)) {
 184                t = in_len;
 185        } else {
 186                t = _lzo1x_1_do_compress(in, in_len, op, out_len, wrkmem);
 187                op += *out_len;
 188        }
 189
 190        if (t > 0) {
 191                ii = in + in_len - t;
 192
 193                if (op == out && t <= 238) {
 194                        *op++ = (17 + t);
 195                } else if (t <= 3) {
 196                        op[-2] |= t;
 197                } else if (t <= 18) {
 198                        *op++ = (t - 3);
 199                } else {
 200                        size_t tt = t - 18;
 201
 202                        *op++ = 0;
 203                        while (tt > 255) {
 204                                tt -= 255;
 205                                *op++ = 0;
 206                        }
 207
 208                        *op++ = tt;
 209                }
 210                do {
 211                        *op++ = *ii++;
 212                } while (--t > 0);
 213        }
 214
 215        *op++ = M4_MARKER | 1;
 216        *op++ = 0;
 217        *op++ = 0;
 218
 219        *out_len = op - out;
 220        return LZO_E_OK;
 221}
 222EXPORT_SYMBOL_GPL(lzo1x_1_compress);
 223
 224MODULE_LICENSE("GPL");
 225MODULE_DESCRIPTION("LZO1X-1 Compressor");
 226
 227
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