root/lib/lzo/lzo1x_compress.c

DEFINITIONS

1. _lzo1x_1_do_compress
2. lzo1x_1_compress

/*
 *  LZO1X Compressor from MiniLZO
 *
 *  Copyright (C) 1996-2005 Markus F.X.J. Oberhumer <markus@oberhumer.com>
 *
 *  The full LZO package can be found at:
 *  http://www.oberhumer.com/opensource/lzo/
 *
 *  Changed for kernel use by:
 *  Nitin Gupta <nitingupta910@gmail.com>
 *  Richard Purdie <rpurdie@openedhand.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/lzo.h>
#include <asm/unaligned.h>
#include "lzodefs.h"

static noinline size_t
_lzo1x_1_do_compress(const unsigned char *in, size_t in_len,
                unsigned char *out, size_t *out_len, void *wrkmem)
{
        const unsigned char * const in_end = in + in_len;
        const unsigned char * const ip_end = in + in_len - M2_MAX_LEN - 5;
        const unsigned char ** const dict = wrkmem;
        const unsigned char *ip = in, *ii = ip;
        const unsigned char *end, *m, *m_pos;
        size_t m_off, m_len, dindex;
        unsigned char *op = out;

        ip += 4;

        for (;;) {
                dindex = ((size_t)(0x21 * DX3(ip, 5, 5, 6)) >> 5) & D_MASK;
                m_pos = dict[dindex];

                if (m_pos < in)
                        goto literal;

                if (ip == m_pos || ((size_t)(ip - m_pos) > M4_MAX_OFFSET))
                        goto literal;

                m_off = ip - m_pos;
                if (m_off <= M2_MAX_OFFSET || m_pos[3] == ip[3])
                        goto try_match;

                dindex = (dindex & (D_MASK & 0x7ff)) ^ (D_HIGH | 0x1f);
                m_pos = dict[dindex];

                if (m_pos < in)
                        goto literal;

                if (ip == m_pos || ((size_t)(ip - m_pos) > M4_MAX_OFFSET))
                        goto literal;

                m_off = ip - m_pos;
                if (m_off <= M2_MAX_OFFSET || m_pos[3] == ip[3])
                        goto try_match;

                goto literal;

try_match:
                if (get_unaligned((const unsigned short *)m_pos)
                                == get_unaligned((const unsigned short *)ip)) {
                        if (likely(m_pos[2] == ip[2]))
                                        goto match;
                }

literal:
                dict[dindex] = ip;
                ++ip;
                if (unlikely(ip >= ip_end))
                        break;
                continue;

match:
                dict[dindex] = ip;
                if (ip != ii) {
                        size_t t = ip - ii;

                        if (t <= 3) {
                                op[-2] |= t;
                        } else if (t <= 18) {
                                *op++ = (t - 3);
                        } else {
                                size_t tt = t - 18;

                                *op++ = 0;
                                while (tt > 255) {
                                        tt -= 255;
                                        *op++ = 0;
                                }
                                *op++ = tt;
                        }
                        do {
                                *op++ = *ii++;
                        } while (--t > 0);
                }

                ip += 3;
                if (m_pos[3] != *ip++ || m_pos[4] != *ip++
                                || m_pos[5] != *ip++ || m_pos[6] != *ip++
                                || m_pos[7] != *ip++ || m_pos[8] != *ip++) {
                        --ip;
                        m_len = ip - ii;

                        if (m_off <= M2_MAX_OFFSET) {
                                m_off -= 1;
                                *op++ = (((m_len - 1) << 5)
                                                | ((m_off & 7) << 2));
                                *op++ = (m_off >> 3);
                        } else if (m_off <= M3_MAX_OFFSET) {
                                m_off -= 1;
                                *op++ = (M3_MARKER | (m_len - 2));
                                goto m3_m4_offset;
                        } else {
                                m_off -= 0x4000;

                                *op++ = (M4_MARKER | ((m_off & 0x4000) >> 11)
                                                | (m_len - 2));
                                goto m3_m4_offset;
                        }
                } else {
                        end = in_end;
                        m = m_pos + M2_MAX_LEN + 1;

                        while (ip < end && *m == *ip) {
                                m++;
                                ip++;
                        }
                        m_len = ip - ii;

                        if (m_off <= M3_MAX_OFFSET) {
                                m_off -= 1;
                                if (m_len <= 33) {
                                        *op++ = (M3_MARKER | (m_len - 2));
                                } else {
                                        m_len -= 33;
                                        *op++ = M3_MARKER | 0;
                                        goto m3_m4_len;
                                }
                        } else {
                                m_off -= 0x4000;
                                if (m_len <= M4_MAX_LEN) {
                                        *op++ = (M4_MARKER
                                                | ((m_off & 0x4000) >> 11)
                                                | (m_len - 2));
                                } else {
                                        m_len -= M4_MAX_LEN;
                                        *op++ = (M4_MARKER
                                                | ((m_off & 0x4000) >> 11));
m3_m4_len:
                                        while (m_len > 255) {
                                                m_len -= 255;
                                                *op++ = 0;
                                        }

                                        *op++ = (m_len);
                                }
                        }
m3_m4_offset:
                        *op++ = ((m_off & 63) << 2);
                        *op++ = (m_off >> 6);
                }

                ii = ip;
                if (unlikely(ip >= ip_end))
                        break;
        }

        *out_len = op - out;
        return in_end - ii;
}

int lzo1x_1_compress(const unsigned char *in, size_t in_len, unsigned char *out,
                        size_t *out_len, void *wrkmem)
{
        const unsigned char *ii;
        unsigned char *op = out;
        size_t t;

        if (unlikely(in_len <= M2_MAX_LEN + 5)) {
                t = in_len;
        } else {
                t = _lzo1x_1_do_compress(in, in_len, op, out_len, wrkmem);
                op += *out_len;
        }

        if (t > 0) {
                ii = in + in_len - t;

                if (op == out && t <= 238) {
                        *op++ = (17 + t);
                } else if (t <= 3) {
                        op[-2] |= t;
                } else if (t <= 18) {
                        *op++ = (t - 3);
                } else {
                        size_t tt = t - 18;

                        *op++ = 0;
                        while (tt > 255) {
                                tt -= 255;
                                *op++ = 0;
                        }

                        *op++ = tt;
                }
                do {
                        *op++ = *ii++;
                } while (--t > 0);
        }

        *op++ = M4_MARKER | 1;
        *op++ = 0;
        *op++ = 0;

        *out_len = op - out;
        return LZO_E_OK;
}
EXPORT_SYMBOL_GPL(lzo1x_1_compress);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("LZO1X-1 Compressor");