lzo1x_compress.c

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

#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");