root/src/liblzma/common/block_encoder.c

DEFINITIONS

1. block_encode
2. block_encoder_end
3. block_encoder_update
4. lzma_block_encoder_init
5. LZMA_API

///////////////////////////////////////////////////////////////////////////////
//
/// \file       block_encoder.c
/// \brief      Encodes .xz Blocks
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "block_encoder.h"
#include "filter_encoder.h"
#include "check.h"


struct lzma_coder_s {
        /// The filters in the chain; initialized with lzma_raw_decoder_init().
        lzma_next_coder next;

        /// Encoding options; we also write Unpadded Size, Compressed Size,
        /// and Uncompressed Size back to this structure when the encoding
        /// has been finished.
        lzma_block *block;

        enum {
                SEQ_CODE,
                SEQ_PADDING,
                SEQ_CHECK,
        } sequence;

        /// Compressed Size calculated while encoding
        lzma_vli compressed_size;

        /// Uncompressed Size calculated while encoding
        lzma_vli uncompressed_size;

        /// Position in the Check field
        size_t pos;

        /// Check of the uncompressed data
        lzma_check_state check;
};


static lzma_ret
block_encode(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)
{
        // Check that our amount of input stays in proper limits.
        if (LZMA_VLI_MAX - coder->uncompressed_size < in_size - *in_pos)
                return LZMA_DATA_ERROR;

        switch (coder->sequence) {
        case SEQ_CODE: {
                const size_t in_start = *in_pos;
                const size_t out_start = *out_pos;

                const lzma_ret ret = coder->next.code(coder->next.coder,
                                allocator, in, in_pos, in_size,
                                out, out_pos, out_size, action);

                const size_t in_used = *in_pos - in_start;
                const size_t out_used = *out_pos - out_start;

                if (COMPRESSED_SIZE_MAX - coder->compressed_size < out_used)
                        return LZMA_DATA_ERROR;

                coder->compressed_size += out_used;

                // No need to check for overflow because we have already
                // checked it at the beginning of this function.
                coder->uncompressed_size += in_used;

                lzma_check_update(&coder->check, coder->block->check,
                                in + in_start, in_used);

                if (ret != LZMA_STREAM_END || action == LZMA_SYNC_FLUSH)
                        return ret;

                assert(*in_pos == in_size);
                assert(action == LZMA_FINISH);

                // Copy the values into coder->block. The caller
                // may use this information to construct Index.
                coder->block->compressed_size = coder->compressed_size;
                coder->block->uncompressed_size = coder->uncompressed_size;

                coder->sequence = SEQ_PADDING;
        }

        // Fall through

        case SEQ_PADDING:
                // Pad Compressed Data to a multiple of four bytes. We can
                // use coder->compressed_size for this since we don't need
                // it for anything else anymore.
                while (coder->compressed_size & 3) {
                        if (*out_pos >= out_size)
                                return LZMA_OK;

                        out[*out_pos] = 0x00;
                        ++*out_pos;
                        ++coder->compressed_size;
                }

                if (coder->block->check == LZMA_CHECK_NONE)
                        return LZMA_STREAM_END;

                lzma_check_finish(&coder->check, coder->block->check);

                coder->sequence = SEQ_CHECK;

        // Fall through

        case SEQ_CHECK: {
                const size_t check_size = lzma_check_size(coder->block->check);
                lzma_bufcpy(coder->check.buffer.u8, &coder->pos, check_size,
                                out, out_pos, out_size);
                if (coder->pos < check_size)
                        return LZMA_OK;

                memcpy(coder->block->raw_check, coder->check.buffer.u8,
                                check_size);
                return LZMA_STREAM_END;
        }
        }

        return LZMA_PROG_ERROR;
}


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


static lzma_ret
block_encoder_update(lzma_coder *coder, lzma_allocator *allocator,
                const lzma_filter *filters lzma_attribute((__unused__)),
                const lzma_filter *reversed_filters)
{
        if (coder->sequence != SEQ_CODE)
                return LZMA_PROG_ERROR;

        return lzma_next_filter_update(
                        &coder->next, allocator, reversed_filters);
}


extern lzma_ret
lzma_block_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
                lzma_block *block)
{
        lzma_next_coder_init(&lzma_block_encoder_init, next, allocator);

        if (block == NULL)
                return LZMA_PROG_ERROR;

        // The contents of the structure may depend on the version so
        // check the version first.
        if (block->version != 0)
                return LZMA_OPTIONS_ERROR;

        // If the Check ID is not supported, we cannot calculate the check and
        // thus not create a proper Block.
        if ((unsigned int)(block->check) > LZMA_CHECK_ID_MAX)
                return LZMA_PROG_ERROR;

        if (!lzma_check_is_supported(block->check))
                return LZMA_UNSUPPORTED_CHECK;

        // Allocate and initialize *next->coder if needed.
        if (next->coder == NULL) {
                next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
                if (next->coder == NULL)
                        return LZMA_MEM_ERROR;

                next->code = &block_encode;
                next->end = &block_encoder_end;
                next->update = &block_encoder_update;
                next->coder->next = LZMA_NEXT_CODER_INIT;
        }

        // Basic initializations
        next->coder->sequence = SEQ_CODE;
        next->coder->block = block;
        next->coder->compressed_size = 0;
        next->coder->uncompressed_size = 0;
        next->coder->pos = 0;

        // Initialize the check
        lzma_check_init(&next->coder->check, block->check);

        // Initialize the requested filters.
        return lzma_raw_encoder_init(&next->coder->next, allocator,
                        block->filters);
}


extern LZMA_API(lzma_ret)
lzma_block_encoder(lzma_stream *strm, lzma_block *block)
{
        lzma_next_strm_init(lzma_block_encoder_init, strm, block);

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

        return LZMA_OK;
}