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

///////////////////////////////////////////////////////////////////////////////
//
/// \file       stream_buffer_encoder.c
/// \brief      Single-call .xz Stream encoder
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "common.h"
#include "index.h"


/// Maximum size of Index that has exactly one Record.
/// Index Indicator + Number of Records + Record + CRC32 rounded up to
/// the next multiple of four.
#define INDEX_BOUND ((1 + 1 + 2 * LZMA_VLI_BYTES_MAX + 4 + 3) & ~3)

/// Stream Header, Stream Footer, and Index
#define HEADERS_BOUND (2 * LZMA_STREAM_HEADER_SIZE + INDEX_BOUND)


extern LZMA_API(size_t)
lzma_stream_buffer_bound(size_t uncompressed_size)
{
        // Get the maximum possible size of a Block.
        const size_t block_bound = lzma_block_buffer_bound(uncompressed_size);
        if (block_bound == 0)
                return 0;

        // Catch the possible integer overflow and also prevent the size of
        // the Stream exceeding LZMA_VLI_MAX (theoretically possible on
        // 64-bit systems).
        if (my_min(SIZE_MAX, LZMA_VLI_MAX) - block_bound < HEADERS_BOUND)
                return 0;

        return block_bound + HEADERS_BOUND;
}


extern LZMA_API(lzma_ret)
lzma_stream_buffer_encode(lzma_filter *filters, lzma_check check,
                const lzma_allocator *allocator,
                const uint8_t *in, size_t in_size,
                uint8_t *out, size_t *out_pos_ptr, size_t out_size)
{
        // Sanity checks
        if (filters == NULL || (unsigned int)(check) > LZMA_CHECK_ID_MAX
                        || (in == NULL && in_size != 0) || out == NULL
                        || out_pos_ptr == NULL || *out_pos_ptr > out_size)
                return LZMA_PROG_ERROR;

        if (!lzma_check_is_supported(check))
                return LZMA_UNSUPPORTED_CHECK;

        // Note for the paranoids: Index encoder prevents the Stream from
        // getting too big and still being accepted with LZMA_OK, and Block
        // encoder catches if the input is too big. So we don't need to
        // separately check if the buffers are too big.

        // Use a local copy. We update *out_pos_ptr only if everything
        // succeeds.
        size_t out_pos = *out_pos_ptr;

        // Check that there's enough space for both Stream Header and
        // Stream Footer.
        if (out_size - out_pos <= 2 * LZMA_STREAM_HEADER_SIZE)
                return LZMA_BUF_ERROR;

        // Reserve space for Stream Footer so we don't need to check for
        // available space again before encoding Stream Footer.
        out_size -= LZMA_STREAM_HEADER_SIZE;

        // Encode the Stream Header.
        lzma_stream_flags stream_flags = {
                .version = 0,
                .check = check,
        };

        if (lzma_stream_header_encode(&stream_flags, out + out_pos)
                        != LZMA_OK)
                return LZMA_PROG_ERROR;

        out_pos += LZMA_STREAM_HEADER_SIZE;

        // Encode a Block but only if there is at least one byte of input.
        lzma_block block = {
                .version = 0,
                .check = check,
                .filters = filters,
        };

        if (in_size > 0)
                return_if_error(lzma_block_buffer_encode(&block, allocator,
                                in, in_size, out, &out_pos, out_size));

        // Index
        {
                // Create an Index. It will have one Record if there was
                // at least one byte of input to encode. Otherwise the
                // Index will be empty.
                lzma_index *i = lzma_index_init(allocator);
                if (i == NULL)
                        return LZMA_MEM_ERROR;

                lzma_ret ret = LZMA_OK;

                if (in_size > 0)
                        ret = lzma_index_append(i, allocator,
                                        lzma_block_unpadded_size(&block),
                                        block.uncompressed_size);

                // If adding the Record was successful, encode the Index
                // and get its size which will be stored into Stream Footer.
                if (ret == LZMA_OK) {
                        ret = lzma_index_buffer_encode(
                                        i, out, &out_pos, out_size);

                        stream_flags.backward_size = lzma_index_size(i);
                }

                lzma_index_end(i, allocator);

                if (ret != LZMA_OK)
                        return ret;
        }

        // Stream Footer. We have already reserved space for this.
        if (lzma_stream_footer_encode(&stream_flags, out + out_pos)
                        != LZMA_OK)
                return LZMA_PROG_ERROR;

        out_pos += LZMA_STREAM_HEADER_SIZE;

        // Everything went fine, make the new output position available
        // to the application.
        *out_pos_ptr = out_pos;
        return LZMA_OK;
}