The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       auto_decoder.c
/// \brief      Autodetect between .xz Stream and .lzma (LZMA_Alone) formats
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "stream_decoder.h"
#include "alone_decoder.h"


struct lzma_coder_s {
    /// Stream decoder or LZMA_Alone decoder
    lzma_next_coder next;

    uint64_t memlimit;
    uint32_t flags;

    enum {
        SEQ_INIT,
        SEQ_CODE,
        SEQ_FINISH,
    } sequence;
};


static lzma_ret
auto_decode(lzma_coder *coder, lzma_allocator *allocator,
        const uint8_t *restrict in, size_t *restrict in_pos,
        size_t in_size, uint8_t *restrict out,
        size_t *restrict out_pos, size_t out_size, lzma_action action)
{
    switch (coder->sequence) {
    case SEQ_INIT:
        if (*in_pos >= in_size)
            return LZMA_OK;

        // Update the sequence now, because we want to continue from
        // SEQ_CODE even if we return some LZMA_*_CHECK.
        coder->sequence = SEQ_CODE;

        // Detect the file format. For now this is simple, since if
        // it doesn't start with 0xFD (the first magic byte of the
        // new format), it has to be LZMA_Alone, or something that
        // we don't support at all.
        if (in[*in_pos] == 0xFD) {
            return_if_error(lzma_stream_decoder_init(
                    &coder->next, allocator,
                    coder->memlimit, coder->flags));
        } else {
            return_if_error(lzma_alone_decoder_init(&coder->next,
                    allocator, coder->memlimit, true));

            // If the application wants to know about missing
            // integrity check or about the check in general, we
            // need to handle it here, because LZMA_Alone decoder
            // doesn't accept any flags.
            if (coder->flags & LZMA_TELL_NO_CHECK)
                return LZMA_NO_CHECK;

            if (coder->flags & LZMA_TELL_ANY_CHECK)
                return LZMA_GET_CHECK;
        }

    // Fall through

    case SEQ_CODE: {
        const lzma_ret ret = coder->next.code(
                coder->next.coder, allocator,
                in, in_pos, in_size,
                out, out_pos, out_size, action);
        if (ret != LZMA_STREAM_END
                || (coder->flags & LZMA_CONCATENATED) == 0)
            return ret;

        coder->sequence = SEQ_FINISH;
    }

    // Fall through

    case SEQ_FINISH:
        // When LZMA_DECODE_CONCATENATED was used and we were decoding
        // LZMA_Alone file, we need to check check that there is no
        // trailing garbage and wait for LZMA_FINISH.
        if (*in_pos < in_size)
            return LZMA_DATA_ERROR;

        return action == LZMA_FINISH ? LZMA_STREAM_END : LZMA_OK;

    default:
        assert(0);
        return LZMA_PROG_ERROR;
    }
}


static void
auto_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
{
    lzma_next_end(&coder->next, allocator);
    lzma_free(coder, allocator);
    return;
}


static lzma_check
auto_decoder_get_check(const lzma_coder *coder)
{
    // It is LZMA_Alone if get_check is NULL.
    return coder->next.get_check == NULL ? LZMA_CHECK_NONE
            : coder->next.get_check(coder->next.coder);
}


static lzma_ret
auto_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
        uint64_t *old_memlimit, uint64_t new_memlimit)
{
    lzma_ret ret;

    if (coder->next.memconfig != NULL) {
        ret = coder->next.memconfig(coder->next.coder,
                memusage, old_memlimit, new_memlimit);
        assert(*old_memlimit == coder->memlimit);
    } else {
        // No coder is configured yet. Use the base value as
        // the current memory usage.
        *memusage = LZMA_MEMUSAGE_BASE;
        *old_memlimit = coder->memlimit;
        ret = LZMA_OK;
    }

    if (ret == LZMA_OK && new_memlimit != 0)
        coder->memlimit = new_memlimit;

    return ret;
}


static lzma_ret
auto_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
        uint64_t memlimit, uint32_t flags)
{
    lzma_next_coder_init(&auto_decoder_init, next, allocator);

    if (memlimit == 0)
        return LZMA_PROG_ERROR;

    if (flags & ~LZMA_SUPPORTED_FLAGS)
        return LZMA_OPTIONS_ERROR;

    if (next->coder == NULL) {
        next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
        if (next->coder == NULL)
            return LZMA_MEM_ERROR;

        next->code = &auto_decode;
        next->end = &auto_decoder_end;
        next->get_check = &auto_decoder_get_check;
        next->memconfig = &auto_decoder_memconfig;
        next->coder->next = LZMA_NEXT_CODER_INIT;
    }

    next->coder->memlimit = memlimit;
    next->coder->flags = flags;
    next->coder->sequence = SEQ_INIT;

    return LZMA_OK;
}


extern LZMA_API(lzma_ret)
lzma_auto_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)
{
    lzma_next_strm_init(auto_decoder_init, strm, memlimit, flags);

    strm->internal->supported_actions[LZMA_RUN] = true;
    strm->internal->supported_actions[LZMA_FINISH] = true;

    return LZMA_OK;
}