source: vbox/trunk/src/libs/liblzma-5.4.1/common/microlzma_decoder.c

///////////////////////////////////////////////////////////////////////////////
//
/// \file       microlzma_decoder.c
/// \brief      Decode MicroLZMA format
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "lzma_decoder.h"
#include "lz_decoder.h"


typedef struct {
        /// LZMA1 decoder
        lzma_next_coder lzma;

        /// Compressed size of the stream as given by the application.
        /// This must be exactly correct.
        ///
        /// This will be decremented when input is read.
        uint64_t comp_size;

        /// Uncompressed size of the stream as given by the application.
        /// This may be less than the actual uncompressed size if
        /// uncomp_size_is_exact is false.
        ///
        /// This will be decremented when output is produced.
        lzma_vli uncomp_size;

        /// LZMA dictionary size as given by the application
        uint32_t dict_size;

        /// If true, the exact uncompressed size is known. If false,
        /// uncomp_size may be smaller than the real uncompressed size;
        /// uncomp_size may never be bigger than the real uncompressed size.
        bool uncomp_size_is_exact;

        /// True once the first byte of the MicroLZMA stream
        /// has been processed.
        bool props_decoded;
} lzma_microlzma_coder;


static lzma_ret
microlzma_decode(void *coder_ptr, const 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)
{
        lzma_microlzma_coder *coder = coder_ptr;

        // Remember the in start position so that we can update comp_size.
        const size_t in_start = *in_pos;

        // Remember the out start position so that we can update uncomp_size.
        const size_t out_start = *out_pos;

        // Limit the amount of input so that the decoder won't read more than
        // comp_size. This is required when uncomp_size isn't exact because
        // in that case the LZMA decoder will try to decode more input even
        // when it has no output space (it can be looking for EOPM).
        if (in_size - *in_pos > coder->comp_size)
                in_size = *in_pos + (size_t)(coder->comp_size);

        // When the exact uncompressed size isn't known, we must limit
        // the available output space to prevent the LZMA decoder from
        // trying to decode too much.
        if (!coder->uncomp_size_is_exact
                        && out_size - *out_pos > coder->uncomp_size)
                out_size = *out_pos + (size_t)(coder->uncomp_size);

        if (!coder->props_decoded) {
                // There must be at least one byte of input to decode
                // the properties byte.
                if (*in_pos >= in_size)
                        return LZMA_OK;

                lzma_options_lzma options = {
                        .dict_size = coder->dict_size,
                        .preset_dict = NULL,
                        .preset_dict_size = 0,
                        .ext_flags = 0, // EOPM not allowed when size is known
                        .ext_size_low = UINT32_MAX, // Unknown size by default
                        .ext_size_high = UINT32_MAX,
                };

                if (coder->uncomp_size_is_exact)
                        lzma_set_ext_size(options, coder->uncomp_size);

                // The properties are stored as bitwise-negation
                // of the typical encoding.
                if (lzma_lzma_lclppb_decode(&options, ~in[*in_pos]))
                        return LZMA_OPTIONS_ERROR;

                ++*in_pos;

                // Initialize the decoder.
                lzma_filter_info filters[2] = {
                        {
                                .id = LZMA_FILTER_LZMA1EXT,
                                .init = &lzma_lzma_decoder_init,
                                .options = &options,
                        }, {
                                .init = NULL,
                        }
                };

                return_if_error(lzma_next_filter_init(&coder->lzma,
                                allocator, filters));

                // Pass one dummy 0x00 byte to the LZMA decoder since that
                // is what it expects the first byte to be.
                const uint8_t dummy_in = 0;
                size_t dummy_in_pos = 0;
                if (coder->lzma.code(coder->lzma.coder, allocator,
                                &dummy_in, &dummy_in_pos, 1,
                                out, out_pos, out_size, LZMA_RUN) != LZMA_OK)
                        return LZMA_PROG_ERROR;

                assert(dummy_in_pos == 1);
                coder->props_decoded = true;
        }

        // The rest is normal LZMA decoding.
        lzma_ret ret = coder->lzma.code(coder->lzma.coder, allocator,
                                in, in_pos, in_size,
                                out, out_pos, out_size, action);

        // Update the remaining compressed size.
        assert(coder->comp_size >= *in_pos - in_start);
        coder->comp_size -= *in_pos - in_start;

        if (coder->uncomp_size_is_exact) {
                // After successful decompression of the complete stream
                // the compressed size must match.
                if (ret == LZMA_STREAM_END && coder->comp_size != 0)
                        ret = LZMA_DATA_ERROR;
        } else {
                // Update the amount of output remaining.
                assert(coder->uncomp_size >= *out_pos - out_start);
                coder->uncomp_size -= *out_pos - out_start;

                // - We must not get LZMA_STREAM_END because the stream
                //   shouldn't have EOPM.
                // - We must use uncomp_size to determine when to
                //   return LZMA_STREAM_END.
                if (ret == LZMA_STREAM_END)
                        ret = LZMA_DATA_ERROR;
                else if (coder->uncomp_size == 0)
                        ret = LZMA_STREAM_END;
        }

        return ret;
}


static void
microlzma_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
        lzma_microlzma_coder *coder = coder_ptr;
        lzma_next_end(&coder->lzma, allocator);
        lzma_free(coder, allocator);
        return;
}


static lzma_ret
microlzma_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
                uint64_t comp_size,
                uint64_t uncomp_size, bool uncomp_size_is_exact,
                uint32_t dict_size)
{
        lzma_next_coder_init(&microlzma_decoder_init, next, allocator);

        lzma_microlzma_coder *coder = next->coder;

        if (coder == NULL) {
                coder = lzma_alloc(sizeof(lzma_microlzma_coder), allocator);
                if (coder == NULL)
                        return LZMA_MEM_ERROR;

                next->coder = coder;
                next->code = &microlzma_decode;
                next->end = &microlzma_decoder_end;

                coder->lzma = LZMA_NEXT_CODER_INIT;
        }

        // The public API is uint64_t but the internal LZ decoder API uses
        // lzma_vli.
        if (uncomp_size > LZMA_VLI_MAX)
                return LZMA_OPTIONS_ERROR;

        coder->comp_size = comp_size;
        coder->uncomp_size = uncomp_size;
        coder->uncomp_size_is_exact = uncomp_size_is_exact;
        coder->dict_size = dict_size;

        coder->props_decoded = false;

        return LZMA_OK;
}


extern LZMA_API(lzma_ret)
lzma_microlzma_decoder(lzma_stream *strm, uint64_t comp_size,
                uint64_t uncomp_size, lzma_bool uncomp_size_is_exact,
                uint32_t dict_size)
{
        lzma_next_strm_init(microlzma_decoder_init, strm, comp_size,
                        uncomp_size, uncomp_size_is_exact, dict_size);

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

        return LZMA_OK;
}