/*-
 * Copyright (c) 2003-2007 Tim Kientzle
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This code borrows heavily from "compress" source code, which is
 * protected by the following copyright.  (Clause 3 dropped by request
 * of the Regents.)
 */

/*-
 * Copyright (c) 1985, 1986, 1992, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Diomidis Spinellis and James A. Woods, derived from original
 * work by Spencer Thomas and Joseph Orost.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


#include "archive_platform.h"
__FBSDID("$FreeBSD: src/lib/libarchive/archive_read_support_compression_compress.c,v 1.11 2008/12/06 06:45:15 kientzle Exp $");

#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "archive.h"
#include "archive_private.h"
#include "archive_read_private.h"

/*
 * Because LZW decompression is pretty simple, I've just implemented
 * the whole decompressor here (cribbing from "compress" source code,
 * of course), rather than relying on an external library.  I have
 * made an effort to clarify and simplify the algorithm, so the
 * names and structure here don't exactly match those used by compress.
 */

struct private_data {
    /* Input variables. */
    const unsigned char *next_in;
    size_t           avail_in;
    int          bit_buffer;
    int          bits_avail;
    size_t           bytes_in_section;

    /* Output variables. */
    size_t           out_block_size;
    void            *out_block;

    /* Decompression status variables. */
    int          use_reset_code;
    int          end_of_stream; /* EOF status. */
    int          maxcode;   /* Largest code. */
    int          maxcode_bits;  /* Length of largest code. */
    int          section_end_code; /* When to increase bits. */
    int          bits;      /* Current code length. */
    int          oldcode;   /* Previous code. */
    int          finbyte;   /* Last byte of prev code. */

    /* Dictionary. */
    int          free_ent;       /* Next dictionary entry. */
    unsigned char        suffix[65536];
    uint16_t         prefix[65536];

    /*
     * Scratch area for expanding dictionary entries.  Note:
     * "worst" case here comes from compressing /dev/zero: the
     * last code in the dictionary will code a sequence of
     * 65536-256 zero bytes.  Thus, we need stack space to expand
     * a 65280-byte dictionary entry.  (Of course, 32640:1
     * compression could also be considered the "best" case. ;-)
     */
    unsigned char       *stackp;
    unsigned char        stack[65300];
};

static int  compress_bidder_bid(struct archive_read_filter_bidder *, struct archive_read_filter *);
static int  compress_bidder_init(struct archive_read_filter *);
static int  compress_bidder_free(struct archive_read_filter_bidder *);

static ssize_t  compress_filter_read(struct archive_read_filter *, const void **);
static int  compress_filter_close(struct archive_read_filter *);

static int  getbits(struct archive_read_filter *, int n);
static int  next_code(struct archive_read_filter *);

int
archive_read_support_compression_compress(struct archive *_a)
{
    struct archive_read *a = (struct archive_read *)_a;
    struct archive_read_filter_bidder *bidder = __archive_read_get_bidder(a);

    if (bidder == NULL)
        return (ARCHIVE_FATAL);

    bidder->data = NULL;
    bidder->bid = compress_bidder_bid;
    bidder->init = compress_bidder_init;
    bidder->options = NULL;
    bidder->free = compress_bidder_free;
    return (ARCHIVE_OK);
}

/*
 * Test whether we can handle this data.
 *
 * This logic returns zero if any part of the signature fails.  It
 * also tries to Do The Right Thing if a very short buffer prevents us
 * from verifying as much as we would like.
 */
static int
compress_bidder_bid(struct archive_read_filter_bidder *self,
    struct archive_read_filter *filter)
{
    const unsigned char *buffer;
    ssize_t avail;
    int bits_checked;

    (void)self; /* UNUSED */

    buffer = __archive_read_filter_ahead(filter, 2, &avail);

    if (buffer == NULL)
        return (0);

    bits_checked = 0;
    if (buffer[0] != 037)   /* Verify first ID byte. */
        return (0);
    bits_checked += 8;

    if (buffer[1] != 0235)  /* Verify second ID byte. */
        return (0);
    bits_checked += 8;

    /*
     * TODO: Verify more.
     */

    return (bits_checked);
}

/*
 * Setup the callbacks.
 */
static int
compress_bidder_init(struct archive_read_filter *self)
{
    struct private_data *state;
    static const size_t out_block_size = 64 * 1024;
    void *out_block;
    int code;

    self->code = ARCHIVE_COMPRESSION_COMPRESS;
    self->name = "compress (.Z)";

    state = (struct private_data *)calloc(sizeof(*state), 1);
    out_block = malloc(out_block_size);
    if (state == NULL || out_block == NULL) {
        free(out_block);
        free(state);
        archive_set_error(&self->archive->archive, ENOMEM,
            "Can't allocate data for %s decompression",
            self->name);
        return (ARCHIVE_FATAL);
    }

    self->data = state;
    state->out_block_size = out_block_size;
    state->out_block = out_block;
    self->read = compress_filter_read;
    self->skip = NULL; /* not supported */
    self->close = compress_filter_close;

    /* XXX MOVE THE FOLLOWING OUT OF INIT() XXX */

    code = getbits(self, 8); /* Skip first signature byte. */
    code = getbits(self, 8); /* Skip second signature byte. */

    code = getbits(self, 8);
    state->maxcode_bits = code & 0x1f;
    state->maxcode = (1 << state->maxcode_bits);
    state->use_reset_code = code & 0x80;

    /* Initialize decompressor. */
    state->free_ent = 256;
    state->stackp = state->stack;
    if (state->use_reset_code)
        state->free_ent++;
    state->bits = 9;
    state->section_end_code = (1<<state->bits) - 1;
    state->oldcode = -1;
    for (code = 255; code >= 0; code--) {
        state->prefix[code] = 0;
        state->suffix[code] = code;
    }
    next_code(self);

    return (ARCHIVE_OK);
}

/*
 * Return a block of data from the decompression buffer.  Decompress more
 * as necessary.
 */
static ssize_t
compress_filter_read(struct archive_read_filter *self, const void **pblock)
{
    struct private_data *state;
    unsigned char *p, *start, *end;
    int ret;

    state = (struct private_data *)self->data;
    if (state->end_of_stream) {
        *pblock = NULL;
        return (0);
    }
    p = start = (unsigned char *)state->out_block;
    end = start + state->out_block_size;

    while (p < end && !state->end_of_stream) {
        if (state->stackp > state->stack) {
            *p++ = *--state->stackp;
        } else {
            ret = next_code(self);
            if (ret == -1)
                state->end_of_stream = ret;
            else if (ret != ARCHIVE_OK)
                return (ret);
        }
    }

    *pblock = start;
    return (p - start);
}

/*
 * Clean up the reader.
 */
static int
compress_bidder_free(struct archive_read_filter_bidder *self)
{
    self->data = NULL;
    return (ARCHIVE_OK);
}

/*
 * Close and release the filter.
 */
static int
compress_filter_close(struct archive_read_filter *self)
{
    struct private_data *state = (struct private_data *)self->data;

    free(state->out_block);
    free(state);
    return (ARCHIVE_OK);
}

/*
 * Process the next code and fill the stack with the expansion
 * of the code.  Returns ARCHIVE_FATAL if there is a fatal I/O or
 * format error, ARCHIVE_EOF if we hit end of data, ARCHIVE_OK otherwise.
 */
static int
next_code(struct archive_read_filter *self)
{
    struct private_data *state = (struct private_data *)self->data;
    int code, newcode;

    static int debug_buff[1024];
    static unsigned debug_index;

    code = newcode = getbits(self, state->bits);
    if (code < 0)
        return (code);

    debug_buff[debug_index++] = code;
    if (debug_index >= sizeof(debug_buff)/sizeof(debug_buff[0]))
        debug_index = 0;

    /* If it's a reset code, reset the dictionary. */
    if ((code == 256) && state->use_reset_code) {
        /*
         * The original 'compress' implementation blocked its
         * I/O in a manner that resulted in junk bytes being
         * inserted after every reset.  The next section skips
         * this junk.  (Yes, the number of *bytes* to skip is
         * a function of the current *bit* length.)
         */
        int skip_bytes =  state->bits -
            (state->bytes_in_section % state->bits);
        skip_bytes %= state->bits;
        state->bits_avail = 0; /* Discard rest of this byte. */
        while (skip_bytes-- > 0) {
            code = getbits(self, 8);
            if (code < 0)
                return (code);
        }
        /* Now, actually do the reset. */
        state->bytes_in_section = 0;
        state->bits = 9;
        state->section_end_code = (1 << state->bits) - 1;
        state->free_ent = 257;
        state->oldcode = -1;
        return (next_code(self));
    }

    if (code > state->free_ent) {
        /* An invalid code is a fatal error. */
        archive_set_error(&(self->archive->archive), -1,
            "Invalid compressed data");
        return (ARCHIVE_FATAL);
    }

    /* Special case for KwKwK string. */
    if (code >= state->free_ent) {
        *state->stackp++ = state->finbyte;
        code = state->oldcode;
    }

    /* Generate output characters in reverse order. */
    while (code >= 256) {
        *state->stackp++ = state->suffix[code];
        code = state->prefix[code];
    }
    *state->stackp++ = state->finbyte = code;

    /* Generate the new entry. */
    code = state->free_ent;
    if (code < state->maxcode && state->oldcode >= 0) {
        state->prefix[code] = state->oldcode;
        state->suffix[code] = state->finbyte;
        ++state->free_ent;
    }
    if (state->free_ent > state->section_end_code) {
        state->bits++;
        state->bytes_in_section = 0;
        if (state->bits == state->maxcode_bits)
            state->section_end_code = state->maxcode;
        else
            state->section_end_code = (1 << state->bits) - 1;
    }

    /* Remember previous code. */
    state->oldcode = newcode;
    return (ARCHIVE_OK);
}

/*
 * Return next 'n' bits from stream.
 *
 * -1 indicates end of available data.
 */
static int
getbits(struct archive_read_filter *self, int n)
{
    struct private_data *state = (struct private_data *)self->data;
    int code;
    ssize_t ret;
    static const int mask[] = {
        0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f, 0xff,
        0x1ff, 0x3ff, 0x7ff, 0xfff, 0x1fff, 0x3fff, 0x7fff, 0xffff
    };

    while (state->bits_avail < n) {
        if (state->avail_in <= 0) {
            state->next_in
                = __archive_read_filter_ahead(self->upstream,
                1, &ret);
            if (ret == 0)
                return (-1);
            if (ret < 0 || state->next_in == NULL)
                return (ARCHIVE_FATAL);
            state->avail_in = ret;
            __archive_read_filter_consume(self->upstream, ret);
        }
        state->bit_buffer |= *state->next_in++ << state->bits_avail;
        state->avail_in--;
        state->bits_avail += 8;
        state->bytes_in_section++;
    }

    code = state->bit_buffer;
    state->bit_buffer >>= n;
    state->bits_avail -= n;

    return (code & mask[n]);
}
