root/debug/known_sizes.c

DEFINITIONS

1. main

///////////////////////////////////////////////////////////////////////////////
//
/// \file       known_sizes.c
/// \brief      Encodes .lzma Stream with sizes known in Block Header
///
/// The input file is encoded in RAM, and the known Compressed Size
/// and/or Uncompressed Size values are stored in the Block Header.
/// As of writing there's no such Stream encoder in liblzma.
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "sysdefs.h"
#include "lzma.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/unistd.h>
#include <stdio.h>


// Support file sizes up to 1 MiB. We use this for output space too, so files
// close to 1 MiB had better compress at least a little or we have a buffer
// overflow.
#define BUFFER_SIZE (1U << 20)


int
main(void)
{
        // Allocate the buffers.
        uint8_t *in = malloc(BUFFER_SIZE);
        uint8_t *out = malloc(BUFFER_SIZE);
        if (in == NULL || out == NULL)
                return 1;

        // Fill the input buffer.
        const size_t in_size = fread(in, 1, BUFFER_SIZE, stdin);

        // Filter setup
        lzma_options_lzma opt_lzma;
        if (lzma_lzma_preset(&opt_lzma, 1))
                return 1;

        lzma_filter filters[] = {
                {
                        .id = LZMA_FILTER_LZMA2,
                        .options = &opt_lzma
                },
                {
                        .id = LZMA_VLI_UNKNOWN
                }
        };

        lzma_block block = {
                .check = LZMA_CHECK_CRC32,
                .compressed_size = BUFFER_SIZE, // Worst case reserve
                .uncompressed_size = in_size,
                .filters = filters,
        };

        lzma_stream strm = LZMA_STREAM_INIT;
        if (lzma_block_encoder(&strm, &block) != LZMA_OK)
                return 1;

        // Reserve space for Stream Header and Block Header. We need to
        // calculate the size of the Block Header first.
        if (lzma_block_header_size(&block) != LZMA_OK)
                return 1;

        size_t out_size = LZMA_STREAM_HEADER_SIZE + block.header_size;

        strm.next_in = in;
        strm.avail_in = in_size;
        strm.next_out = out + out_size;
        strm.avail_out = BUFFER_SIZE - out_size;

        if (lzma_code(&strm, LZMA_FINISH) != LZMA_STREAM_END)
                return 1;

        out_size += strm.total_out;

        if (lzma_block_header_encode(&block, out + LZMA_STREAM_HEADER_SIZE)
                        != LZMA_OK)
                return 1;

        lzma_index *idx = lzma_index_init(NULL);
        if (idx == NULL)
                return 1;

        if (lzma_index_append(idx, NULL, block.header_size + strm.total_out,
                        strm.total_in) != LZMA_OK)
                return 1;

        if (lzma_index_encoder(&strm, idx) != LZMA_OK)
                return 1;

        if (lzma_code(&strm, LZMA_RUN) != LZMA_STREAM_END)
                return 1;

        out_size += strm.total_out;

        lzma_end(&strm);

        lzma_index_end(idx, NULL);

        // Encode the Stream Header and Stream Footer. backwards_size is
        // needed only for the Stream Footer.
        lzma_stream_flags sf = {
                .backward_size = strm.total_out,
                .check = block.check,
        };

        if (lzma_stream_header_encode(&sf, out) != LZMA_OK)
                return 1;

        if (lzma_stream_footer_encode(&sf, out + out_size) != LZMA_OK)
                return 1;

        out_size += LZMA_STREAM_HEADER_SIZE;

        // Write out the file.
        fwrite(out, 1, out_size, stdout);

        return 0;
}