lzo1x_decompress.c

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/*
 *  LZO1X Decompressor 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]>
 */

#ifndef STATIC
#include <linux/module.h>
#include <linux/kernel.h>
#endif

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

#define HAVE_IP(x, ip_end, ip) ((size_t)(ip_end - ip) < (x))
#define HAVE_OP(x, op_end, op) ((size_t)(op_end - op) < (x))
#define HAVE_LB(m_pos, out, op) (m_pos < out || m_pos >= op)

#define COPY4(dst, src) \
        put_unaligned(get_unaligned((const u32 *)(src)), (u32 *)(dst))

int lzo1x_decompress_safe(const unsigned char *in, size_t in_len,
            unsigned char *out, size_t *out_len)
{
    const unsigned char * const ip_end = in + in_len;
    unsigned char * const op_end = out + *out_len;
    const unsigned char *ip = in, *m_pos;
    unsigned char *op = out;
    size_t t;

    *out_len = 0;

    if (*ip > 17) {
        t = *ip++ - 17;
        if (t < 4)
            goto match_next;
        if (HAVE_OP(t, op_end, op))
            goto output_overrun;
        if (HAVE_IP(t + 1, ip_end, ip))
            goto input_overrun;
        do {
            *op++ = *ip++;
        } while (--t > 0);
        goto first_literal_run;
    }

    while ((ip < ip_end)) {
        t = *ip++;
        if (t >= 16)
            goto match;
        if (t == 0) {
            if (HAVE_IP(1, ip_end, ip))
                goto input_overrun;
            while (*ip == 0) {
                t += 255;
                ip++;
                if (HAVE_IP(1, ip_end, ip))
                    goto input_overrun;
            }
            t += 15 + *ip++;
        }
        if (HAVE_OP(t + 3, op_end, op))
            goto output_overrun;
        if (HAVE_IP(t + 4, ip_end, ip))
            goto input_overrun;

        COPY4(op, ip);
        op += 4;
        ip += 4;
        if (--t > 0) {
            if (t >= 4) {
                do {
                    COPY4(op, ip);
                    op += 4;
                    ip += 4;
                    t -= 4;
                } while (t >= 4);
                if (t > 0) {
                    do {
                        *op++ = *ip++;
                    } while (--t > 0);
                }
            } else {
                do {
                    *op++ = *ip++;
                } while (--t > 0);
            }
        }

first_literal_run:
        t = *ip++;
        if (t >= 16)
            goto match;
        m_pos = op - (1 + M2_MAX_OFFSET);
        m_pos -= t >> 2;
        m_pos -= *ip++ << 2;

        if (HAVE_LB(m_pos, out, op))
            goto lookbehind_overrun;

        if (HAVE_OP(3, op_end, op))
            goto output_overrun;
        *op++ = *m_pos++;
        *op++ = *m_pos++;
        *op++ = *m_pos;

        goto match_done;

        do {
match:
            if (t >= 64) {
                m_pos = op - 1;
                m_pos -= (t >> 2) & 7;
                m_pos -= *ip++ << 3;
                t = (t >> 5) - 1;
                if (HAVE_LB(m_pos, out, op))
                    goto lookbehind_overrun;
                if (HAVE_OP(t + 3 - 1, op_end, op))
                    goto output_overrun;
                goto copy_match;
            } else if (t >= 32) {
                t &= 31;
                if (t == 0) {
                    if (HAVE_IP(1, ip_end, ip))
                        goto input_overrun;
                    while (*ip == 0) {
                        t += 255;
                        ip++;
                        if (HAVE_IP(1, ip_end, ip))
                            goto input_overrun;
                    }
                    t += 31 + *ip++;
                }
                m_pos = op - 1;
                m_pos -= get_unaligned_le16(ip) >> 2;
                ip += 2;
            } else if (t >= 16) {
                m_pos = op;
                m_pos -= (t & 8) << 11;

                t &= 7;
                if (t == 0) {
                    if (HAVE_IP(1, ip_end, ip))
                        goto input_overrun;
                    while (*ip == 0) {
                        t += 255;
                        ip++;
                        if (HAVE_IP(1, ip_end, ip))
                            goto input_overrun;
                    }
                    t += 7 + *ip++;
                }
                m_pos -= get_unaligned_le16(ip) >> 2;
                ip += 2;
                if (m_pos == op)
                    goto eof_found;
                m_pos -= 0x4000;
            } else {
                m_pos = op - 1;
                m_pos -= t >> 2;
                m_pos -= *ip++ << 2;

                if (HAVE_LB(m_pos, out, op))
                    goto lookbehind_overrun;
                if (HAVE_OP(2, op_end, op))
                    goto output_overrun;

                *op++ = *m_pos++;
                *op++ = *m_pos;
                goto match_done;
            }

            if (HAVE_LB(m_pos, out, op))
                goto lookbehind_overrun;
            if (HAVE_OP(t + 3 - 1, op_end, op))
                goto output_overrun;

            if (t >= 2 * 4 - (3 - 1) && (op - m_pos) >= 4) {
                COPY4(op, m_pos);
                op += 4;
                m_pos += 4;
                t -= 4 - (3 - 1);
                do {
                    COPY4(op, m_pos);
                    op += 4;
                    m_pos += 4;
                    t -= 4;
                } while (t >= 4);
                if (t > 0)
                    do {
                        *op++ = *m_pos++;
                    } while (--t > 0);
            } else {
copy_match:
                *op++ = *m_pos++;
                *op++ = *m_pos++;
                do {
                    *op++ = *m_pos++;
                } while (--t > 0);
            }
match_done:
            t = ip[-2] & 3;
            if (t == 0)
                break;
match_next:
            if (HAVE_OP(t, op_end, op))
                goto output_overrun;
            if (HAVE_IP(t + 1, ip_end, ip))
                goto input_overrun;

            *op++ = *ip++;
            if (t > 1) {
                *op++ = *ip++;
                if (t > 2)
                    *op++ = *ip++;
            }

            t = *ip++;
        } while (ip < ip_end);
    }

    *out_len = op - out;
    return LZO_E_EOF_NOT_FOUND;

eof_found:
    *out_len = op - out;
    return (ip == ip_end ? LZO_E_OK :
        (ip < ip_end ? LZO_E_INPUT_NOT_CONSUMED : LZO_E_INPUT_OVERRUN));
input_overrun:
    *out_len = op - out;
    return LZO_E_INPUT_OVERRUN;

output_overrun:
    *out_len = op - out;
    return LZO_E_OUTPUT_OVERRUN;

lookbehind_overrun:
    *out_len = op - out;
    return LZO_E_LOOKBEHIND_OVERRUN;
}
#ifndef STATIC
EXPORT_SYMBOL_GPL(lzo1x_decompress_safe);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("LZO1X Decompressor");

#endif