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

///////////////////////////////////////////////////////////////////////////////
//
/// \file       microlzma_encoder.c
/// \brief      Encode into 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_encoder.h"


typedef struct {
        /// LZMA1 encoder
        lzma_next_coder lzma;

        /// LZMA properties byte (lc/lp/pb)
        uint8_t props;
} lzma_microlzma_coder;


static lzma_ret
microlzma_encode(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 *out_pos so that we can overwrite the first byte with
        // the LZMA properties byte.
        const size_t out_start = *out_pos;

        // Remember *in_pos so that we can set it based on how many
        // uncompressed bytes were actually encoded.
        const size_t in_start = *in_pos;

        // Set the output size limit based on the available output space.
        // We know that the encoder supports set_out_limit() so
        // LZMA_OPTIONS_ERROR isn't possible. LZMA_BUF_ERROR is possible
        // but lzma_code() has an assertion to not allow it to be returned
        // from here and I don't want to change that for now, so
        // LZMA_BUF_ERROR becomes LZMA_PROG_ERROR.
        uint64_t uncomp_size;
        if (coder->lzma.set_out_limit(coder->lzma.coder,
                        &uncomp_size, out_size - *out_pos) != LZMA_OK)
                return LZMA_PROG_ERROR;

        // set_out_limit fails if this isn't true.
        assert(out_size - *out_pos >= 6);

        // Encode as much as possible.
        const lzma_ret ret = coder->lzma.code(coder->lzma.coder, allocator,
                        in, in_pos, in_size, out, out_pos, out_size, action);

        if (ret != LZMA_STREAM_END) {
                if (ret == LZMA_OK) {
                        assert(0);
                        return LZMA_PROG_ERROR;
                }

                return ret;
        }

        // The first output byte is bitwise-negation of the properties byte.
        // We know that there is space for this byte because set_out_limit
        // and the actual encoding succeeded.
        out[out_start] = (uint8_t)(~coder->props);

        // The LZMA encoder likely read more input than it was able to encode.
        // Set *in_pos based on uncomp_size.
        assert(uncomp_size <= in_size - in_start);
        *in_pos = in_start + (size_t)(uncomp_size);

        return ret;
}


static void
microlzma_encoder_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_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
                const lzma_options_lzma *options)
{
        lzma_next_coder_init(&microlzma_encoder_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_encode;
                next->end = &microlzma_encoder_end;

                coder->lzma = LZMA_NEXT_CODER_INIT;
        }

        // Encode the properties byte. Bitwise-negation of it will be the
        // first output byte.
        if (lzma_lzma_lclppb_encode(options, &coder->props))
                return LZMA_OPTIONS_ERROR;

        // Initialize the LZMA encoder.
        const lzma_filter_info filters[2] = {
                {
                        .id = LZMA_FILTER_LZMA1,
                        .init = &lzma_lzma_encoder_init,
                        .options = (void *)(options),
                }, {
                        .init = NULL,
                }
        };

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


extern LZMA_API(lzma_ret)
lzma_microlzma_encoder(lzma_stream *strm, const lzma_options_lzma *options)
{
        lzma_next_strm_init(microlzma_encoder_init, strm, options);

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

        return LZMA_OK;

}