Build: Comment that elf_aux_info(3) will be available on OpenBSD >= 7.6

[xz.git] / src / xz / coder.c

// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////
//
/// \file       coder.c
/// \brief      Compresses or uncompresses a file
//
//  Authors:    Lasse Collin
//              Jia Tan
//
///////////////////////////////////////////////////////////////////////////////

#include "private.h"
#include "tuklib_integer.h"


/// Return value type for coder_init().
enum coder_init_ret {
        CODER_INIT_NORMAL,
        CODER_INIT_PASSTHRU,
        CODER_INIT_ERROR,
};


enum operation_mode opt_mode = MODE_COMPRESS;
enum format_type opt_format = FORMAT_AUTO;
bool opt_auto_adjust = true;
bool opt_single_stream = false;
uint64_t opt_block_size = 0;
block_list_entry *opt_block_list = NULL;
uint64_t block_list_largest;
uint32_t block_list_chain_mask;

/// Stream used to communicate with liblzma
static lzma_stream strm = LZMA_STREAM_INIT;

/// Maximum number of filter chains. The first filter chain is the default,
/// and 9 other filter chains can be specified with --filtersX.
#define NUM_FILTER_CHAIN_MAX 10

/// The default filter chain is in chains[0]. It is used for encoding
/// in all supported formats and also for decdoing raw streams. The other
/// filter chains are set by --filtersX to support changing filters with
/// the --block-list option.
static lzma_filter chains[NUM_FILTER_CHAIN_MAX][LZMA_FILTERS_MAX + 1];

/// Bitmask indicating which filter chains are actually used when encoding
/// in the .xz format. This is needed since the filter chains specified using
/// --filtersX (or the default filter chain) might in reality be unneeded
/// if they are never used in --block-list. When --block-list isn't
/// specified, only the default filter chain is used, thus the initial
/// value of this variable is 1U << 0 (the number of the default chain is 0).
static uint32_t chains_used_mask = 1U << 0;

/// Input and output buffers
static io_buf in_buf;
static io_buf out_buf;

/// Number of filters in the default filter chain. Zero indicates that
/// we are using a preset.
static uint32_t filters_count = 0;

/// Number of the preset (0-9)
static uint32_t preset_number = LZMA_PRESET_DEFAULT;

/// True if the current default filter chain was set using the --filters
/// option. The filter chain is reset if a preset option (like -9) or an
/// old-style filter option (like --lzma2) is used after a --filters option.
static bool string_to_filter_used = false;

/// Integrity check type
static lzma_check check;

/// This becomes false if the --check=CHECK option is used.
static bool check_default = true;

/// Indicates if unconsumed input is allowed to remain after
/// decoding has successfully finished. This is set for each file
/// in coder_init().
static bool allow_trailing_input;

#ifdef MYTHREAD_ENABLED
static lzma_mt mt_options = {
        .flags = 0,
        .timeout = 300,
};
#endif


extern void
coder_set_check(lzma_check new_check)
{
        check = new_check;
        check_default = false;
        return;
}


static void
forget_filter_chain(void)
{
        // Setting a preset or using --filters makes us forget
        // the earlier custom filter chain (if any).
        if (filters_count > 0) {
                lzma_filters_free(chains[0], NULL);
                filters_count = 0;
        }

        string_to_filter_used = false;
        return;
}


extern void
coder_set_preset(uint32_t new_preset)
{
        preset_number &= ~LZMA_PRESET_LEVEL_MASK;
        preset_number |= new_preset;
        forget_filter_chain();
        return;
}


extern void
coder_set_extreme(void)
{
        preset_number |= LZMA_PRESET_EXTREME;
        forget_filter_chain();
        return;
}


extern void
coder_add_filter(lzma_vli id, void *options)
{
        if (filters_count == LZMA_FILTERS_MAX)
                message_fatal(_("Maximum number of filters is four"));

        if (string_to_filter_used)
                forget_filter_chain();

        chains[0][filters_count].id = id;
        chains[0][filters_count].options = options;

        // Terminate the filter chain with LZMA_VLI_UNKNOWN to simplify
        // implementation of forget_filter_chain().
        chains[0][++filters_count].id = LZMA_VLI_UNKNOWN;

        // Setting a custom filter chain makes us forget the preset options.
        // This makes a difference if one specifies e.g. "xz -9 --lzma2 -e"
        // where the custom filter chain resets the preset level back to
        // the default 6, making the example equivalent to "xz -6e".
        preset_number = LZMA_PRESET_DEFAULT;

        return;
}


static void
str_to_filters(const char *str, uint32_t index, uint32_t flags)
{
        int error_pos;
        const char *err = lzma_str_to_filters(str, &error_pos,
                        chains[index], flags, NULL);

        if (err != NULL) {
                char filter_num[2] = "";
                if (index > 0)
                        filter_num[0] = '0' + index;

                // FIXME? The message in err isn't translated.
                // Including the translations in the xz translations is
                // slightly ugly but possible. Creating a new domain for
                // liblzma might not be worth it especially since on some
                // OSes it adds extra dependencies to translation libraries.
                message(V_ERROR, _("Error in --filters%s=FILTERS option:"),
                                filter_num);
                message(V_ERROR, "%s", str);
                message(V_ERROR, "%*s^", error_pos, "");
                message_fatal("%s", err);
        }
}


extern void
coder_add_filters_from_str(const char *filter_str)
{
        // Forget presets and previously defined filter chain. See
        // coder_add_filter() above for why preset_number must be reset too.
        forget_filter_chain();
        preset_number = LZMA_PRESET_DEFAULT;

        string_to_filter_used = true;

        // Include LZMA_STR_ALL_FILTERS so this can be used with --format=raw.
        str_to_filters(filter_str, 0, LZMA_STR_ALL_FILTERS);

        // Set the filters_count to be the number of filters converted from
        // the string.
        for (filters_count = 0; chains[0][filters_count].id
                        != LZMA_VLI_UNKNOWN;
                        ++filters_count) ;

        assert(filters_count > 0);
        return;
}


extern void
coder_add_block_filters(const char *str, size_t slot)
{
        // Free old filters first, if they were previously allocated.
        if (chains_used_mask & (1U << slot))
                lzma_filters_free(chains[slot], NULL);

        str_to_filters(str, slot, 0);

        chains_used_mask |= 1U << slot;
}


tuklib_attr_noreturn
static void
memlimit_too_small(uint64_t memory_usage)
{
        message(V_ERROR, _("Memory usage limit is too low for the given "
                        "filter setup."));
        message_mem_needed(V_ERROR, memory_usage);
        tuklib_exit(E_ERROR, E_ERROR, false);
}


#ifdef HAVE_ENCODERS
/// \brief      Calculate the memory usage of each filter chain.
///
/// \param      chains_memusages    If non-NULL, the memusage of the encoder
///                                 or decoder for each chain is stored in
///                                 this array.
/// \param      mt                  If non-NULL, calculate memory usage of
///                                 multithreaded encoder.
/// \param      encode              Whether to calculate encoder or decoder
///                                 memory usage. This must be true if
///                                 mt != NULL.
///
/// \return     Return the highest memory usage of all of the filter chains.
static uint64_t
get_chains_memusage(uint64_t *chains_memusages, const lzma_mt *mt, bool encode)
{
        uint64_t max_memusage = 0;

#ifdef MYTHREAD_ENABLED
        // Copy multithreading options to a temporary struct since the
        // "filters" member needs to be changed.
        lzma_mt mt_local;
        if (mt != NULL)
                mt_local = *mt;
#else
        (void)mt;
#endif

        for (uint32_t i = 0; i < ARRAY_SIZE(chains); i++) {
                if (!(chains_used_mask & (1U << i)))
                        continue;

                uint64_t memusage = UINT64_MAX;
#ifdef MYTHREAD_ENABLED
                if (mt != NULL) {
                        assert(encode);
                        mt_local.filters = chains[i];
                        memusage = lzma_stream_encoder_mt_memusage(&mt_local);
                } else
#endif
                if (encode) {
                        memusage = lzma_raw_encoder_memusage(chains[i]);
                }
#ifdef HAVE_DECODERS
                else {
                        memusage = lzma_raw_decoder_memusage(chains[i]);
                }
#endif

                if (chains_memusages != NULL)
                        chains_memusages[i] = memusage;

                if (memusage > max_memusage)
                        max_memusage = memusage;
        }

        return max_memusage;
}
#endif


extern void
coder_set_compression_settings(void)
{
#ifdef HAVE_LZIP_DECODER
        // .lz compression isn't supported.
        assert(opt_format != FORMAT_LZIP);
#endif

        // The default check type is CRC64, but fallback to CRC32
        // if CRC64 isn't supported by the copy of liblzma we are
        // using. CRC32 is always supported.
        if (check_default) {
                check = LZMA_CHECK_CRC64;
                if (!lzma_check_is_supported(check))
                        check = LZMA_CHECK_CRC32;
        }

#ifdef HAVE_ENCODERS
        if (opt_block_list != NULL) {
                // args.c ensures these.
                assert(opt_mode == MODE_COMPRESS);
                assert(opt_format == FORMAT_XZ);

                // Find out if block_list_chain_mask has a bit set that
                // isn't set in chains_used_mask.
                const uint32_t missing_chains_mask
                                = (block_list_chain_mask ^ chains_used_mask)
                                & block_list_chain_mask;

                // If a filter chain was specified in --block-list but no
                // matching --filtersX option was used, exit with an error.
                if (missing_chains_mask != 0) {
                        // Get the number of the first missing filter chain
                        // and show it in the error message.
                        const unsigned first_missing
                                = (unsigned)ctz32(missing_chains_mask);

                        message_fatal(_("filter chain %u used by "
                                "--block-list but not specified "
                                "with --filters%u="),
                                first_missing, first_missing);
                }

                // Omit the unused filter chains from mask of used chains.
                //
                // (FIXME? When built with debugging, coder_free() will free()
                // the filter chains (except the default chain) which makes
                // Valgrind show fewer reachable allocations. But coder_free()
                // uses this mask to determine which chains to free. Thus it
                // won't free the ones that are cleared here from the mask.
                // In practice this doesn't matter.)
                chains_used_mask &= block_list_chain_mask;
        } else {
                // Reset filters used mask in case --block-list is not
                // used, but --filtersX is used.
                chains_used_mask = 1U << 0;
        }
#endif

        // Options for LZMA1 or LZMA2 in case we are using a preset.
        static lzma_options_lzma opt_lzma;

        // The first filter in the chains[] array is for the default
        // filter chain.
        lzma_filter *default_filters = chains[0];

        if (filters_count == 0 && chains_used_mask & 1) {
                // We are using a preset. This is not a good idea in raw mode
                // except when playing around with things. Different versions
                // of this software may use different options in presets, and
                // thus make uncompressing the raw data difficult.
                if (opt_format == FORMAT_RAW) {
                        // The message is shown only if warnings are allowed
                        // but the exit status isn't changed.
                        message(V_WARNING, _("Using a preset in raw mode "
                                        "is discouraged."));
                        message(V_WARNING, _("The exact options of the "
                                        "presets may vary between software "
                                        "versions."));
                }

                // Get the preset for LZMA1 or LZMA2.
                if (lzma_lzma_preset(&opt_lzma, preset_number))
                        message_bug();

                // Use LZMA2 except with --format=lzma we use LZMA1.
                default_filters[0].id = opt_format == FORMAT_LZMA
                                ? LZMA_FILTER_LZMA1 : LZMA_FILTER_LZMA2;
                default_filters[0].options = &opt_lzma;

                filters_count = 1;

                // Terminate the filter options array.
                default_filters[1].id = LZMA_VLI_UNKNOWN;
        }

        // If we are using the .lzma format, allow exactly one filter
        // which has to be LZMA1. There is no need to check if the default
        // filter chain is being used since it can only be disabled if
        // --block-list is used, which is incompatible with FORMAT_LZMA.
        if (opt_format == FORMAT_LZMA && (filters_count != 1
                        || default_filters[0].id != LZMA_FILTER_LZMA1))
                message_fatal(_("The .lzma format supports only "
                                "the LZMA1 filter"));

        // If we are using the .xz format, make sure that there is no LZMA1
        // filter to prevent LZMA_PROG_ERROR. With the chains from --filtersX
        // we have already ensured this by calling lzma_str_to_filters()
        // without setting the flags that would allow non-.xz filters.
        if (opt_format == FORMAT_XZ && chains_used_mask & 1)
                for (size_t i = 0; i < filters_count; ++i)
                        if (default_filters[i].id == LZMA_FILTER_LZMA1)
                                message_fatal(_("LZMA1 cannot be used "
                                                "with the .xz format"));

        if (chains_used_mask & 1) {
                // Print the selected default filter chain.
                message_filters_show(V_DEBUG, default_filters);
        }

        // The --flush-timeout option requires LZMA_SYNC_FLUSH support
        // from the filter chain. Currently the threaded encoder doesn't
        // support LZMA_SYNC_FLUSH so single-threaded mode must be used.
        if (opt_mode == MODE_COMPRESS && opt_flush_timeout != 0) {
                for (unsigned i = 0; i < ARRAY_SIZE(chains); ++i) {
                        if (!(chains_used_mask & (1U << i)))
                                continue;

                        const lzma_filter *fc = chains[i];
                        for (size_t j = 0; fc[j].id != LZMA_VLI_UNKNOWN; j++) {
                                switch (fc[j].id) {
                                case LZMA_FILTER_LZMA2:
                                case LZMA_FILTER_DELTA:
                                        break;

                                default:
                                        message_fatal(_("Filter chain %u is "
                                                        "incompatible with "
                                                        "--flush-timeout"),
                                                        i);
                                }
                        }
                }

                if (hardware_threads_is_mt()) {
                        message(V_WARNING, _("Switching to single-threaded "
                                        "mode due to --flush-timeout"));
                        hardware_threads_set(1);
                }
        }

        // Get memory limit and the memory usage of the used filter chains.
        // Note that if --format=raw was used, we can be decompressing
        // using the default filter chain.
        //
        // If multithreaded .xz compression is done, the memory limit
        // will be replaced.
        uint64_t memory_limit = hardware_memlimit_get(opt_mode);
        uint64_t memory_usage = UINT64_MAX;

#ifdef HAVE_ENCODERS
        // Memory usage for each encoder filter chain (default
        // or --filtersX). The encoder options may need to be
        // scaled down depending on the memory usage limit.
        uint64_t encoder_memusages[ARRAY_SIZE(chains)];
#endif

        if (opt_mode == MODE_COMPRESS) {
#ifdef HAVE_ENCODERS
#       ifdef MYTHREAD_ENABLED
                if (opt_format == FORMAT_XZ && hardware_threads_is_mt()) {
                        memory_limit = hardware_memlimit_mtenc_get();
                        mt_options.threads = hardware_threads_get();

                        uint64_t block_size = opt_block_size;

                        // If opt_block_size is not set, find the maximum
                        // recommended Block size based on the filter chains
                        if (block_size == 0) {
                                for (unsigned i = 0; i < ARRAY_SIZE(chains);
                                                i++) {
                                        if (!(chains_used_mask & (1U << i)))
                                                continue;

                                        uint64_t size = lzma_mt_block_size(
                                                        chains[i]);

                                        // If this returns an error, then one
                                        // of the filter chains in use is
                                        // invalid, so there is no point in
                                        // progressing further.
                                        if (size == UINT64_MAX)
                                                message_fatal(_("Unsupported "
                                                        "options in filter "
                                                        "chain %u"), i);

                                        if (size > block_size)
                                                block_size = size;
                                }

                                // If --block-list was used and our current
                                // Block size exceeds the largest size
                                // in --block-list, reduce the Block size of
                                // the multithreaded encoder. The extra size
                                // would only be a waste of RAM. With a
                                // smaller Block size we might even be able
                                // to use more threads in some cases.
                                if (block_list_largest > 0 && block_size
                                                > block_list_largest)
                                        block_size = block_list_largest;
                        }

                        mt_options.block_size = block_size;
                        mt_options.check = check;

                        memory_usage = get_chains_memusage(encoder_memusages,
                                                &mt_options, true);
                        if (memory_usage != UINT64_MAX)
                                message(V_DEBUG, _("Using up to %" PRIu32
                                                " threads."),
                                                mt_options.threads);
                } else
#       endif
                {
                        memory_usage = get_chains_memusage(encoder_memusages,
                                        NULL, true);
                }
#endif
        } else {
#ifdef HAVE_DECODERS
                memory_usage = lzma_raw_decoder_memusage(default_filters);
#endif
        }

        if (memory_usage == UINT64_MAX)
                message_fatal(_("Unsupported filter chain or filter options"));

        // Print memory usage info before possible dictionary
        // size auto-adjusting.
        //
        // NOTE: If only encoder support was built, we cannot show
        // what the decoder memory usage will be.
        message_mem_needed(V_DEBUG, memory_usage);

#if defined(HAVE_ENCODERS) && defined(HAVE_DECODERS)
        if (opt_mode == MODE_COMPRESS && message_verbosity_get() >= V_DEBUG) {
                const uint64_t decmem = get_chains_memusage(NULL, NULL, false);
                if (decmem != UINT64_MAX)
                        message(V_DEBUG, _("Decompression will need "
                                        "%s MiB of memory."), uint64_to_str(
                                                round_up_to_mib(decmem), 0));
        }
#endif

        if (memory_usage <= memory_limit)
                return;

        // With --format=raw settings are never adjusted to meet
        // the memory usage limit.
        if (opt_format == FORMAT_RAW)
                memlimit_too_small(memory_usage);

        assert(opt_mode == MODE_COMPRESS);

#ifdef HAVE_ENCODERS
#       ifdef MYTHREAD_ENABLED
        if (opt_format == FORMAT_XZ && hardware_threads_is_mt()) {
                // Try to reduce the number of threads before
                // adjusting the compression settings down.
                while (mt_options.threads > 1) {
                        // Reduce the number of threads by one and check
                        // the memory usage.
                        --mt_options.threads;
                        memory_usage = get_chains_memusage(encoder_memusages,
                                        &mt_options, true);
                        if (memory_usage == UINT64_MAX)
                                message_bug();

                        if (memory_usage <= memory_limit) {
                                // The memory usage is now low enough.
                                //
                                // Since 5.6.1: This is only shown at
                                // V_DEBUG instead of V_WARNING because
                                // changing the number of threads doesn't
                                // affect the output. On some systems this
                                // message would be too common now that
                                // multithreaded compression is the default.
                                message(V_DEBUG, _("Reduced the number of "
                                        "threads from %s to %s to not exceed "
                                        "the memory usage limit of %s MiB"),
                                        uint64_to_str(
                                                hardware_threads_get(), 0),
                                        uint64_to_str(mt_options.threads, 1),
                                        uint64_to_str(round_up_to_mib(
                                                memory_limit), 2));
                                return;
                        }
                }

                // If the memory usage limit is only a soft limit (automatic
                // number of threads and no --memlimit-compress), the limit
                // is only used to reduce the number of threads and once at
                // just one thread, the limit is completely ignored. This
                // way -T0 won't use insane amount of memory but at the same
                // time the soft limit will never make xz fail and never make
                // xz change settings that would affect the compressed output.
                //
                // Since 5.6.1: Like above, this is now shown at V_DEBUG
                // instead of V_WARNING.
                if (hardware_memlimit_mtenc_is_default()) {
                        message(V_DEBUG, _("Reduced the number of threads "
                                "from %s to one. The automatic memory usage "
                                "limit of %s MiB is still being exceeded. "
                                "%s MiB of memory is required. "
                                "Continuing anyway."),
                                uint64_to_str(hardware_threads_get(), 0),
                                uint64_to_str(
                                        round_up_to_mib(memory_limit), 1),
                                uint64_to_str(
                                        round_up_to_mib(memory_usage), 2));
                        return;
                }

                // If --no-adjust was used, we cannot drop to single-threaded
                // mode since it produces different compressed output.
                //
                // NOTE: In xz 5.2.x, --no-adjust also prevented reducing
                // the number of threads. This changed in 5.3.3alpha.
                if (!opt_auto_adjust)
                        memlimit_too_small(memory_usage);

                // Switch to single-threaded mode. It uses
                // less memory than using one thread in
                // the multithreaded mode but the output
                // is also different.
                hardware_threads_set(1);
                memory_usage = get_chains_memusage(encoder_memusages,
                                NULL, true);
                message(V_WARNING, _("Switching to single-threaded mode "
                        "to not exceed the memory usage limit of %s MiB"),
                        uint64_to_str(round_up_to_mib(memory_limit), 0));
        }
#       endif

        if (memory_usage <= memory_limit)
                return;

        // Don't adjust LZMA2 or LZMA1 dictionary size if --no-adjust
        // was specified as that would change the compressed output.
        if (!opt_auto_adjust)
                memlimit_too_small(memory_usage);

        // Adjust each filter chain that is exceeding the memory usage limit.
        for (unsigned i = 0; i < ARRAY_SIZE(chains); i++) {
                // Skip unused chains.
                if (!(chains_used_mask & (1U << i)))
                        continue;

                // Skip chains that already meet the memory usage limit.
                if (encoder_memusages[i] <=  memory_limit)
                        continue;

                // Look for the last filter if it is LZMA2 or LZMA1, so we
                // can make it use less RAM. We cannot adjust other filters.
                unsigned j = 0;
                while (chains[i][j].id != LZMA_FILTER_LZMA2
                                && chains[i][j].id != LZMA_FILTER_LZMA1) {
                        // NOTE: This displays the too high limit of this
                        // particular filter chain. If multiple chains are
                        // specified and another one would need more then
                        // this message could be confusing. As long as LZMA2
                        // is the only memory hungry filter in .xz this
                        // doesn't matter at all in practice.
                        //
                        // FIXME? However, it's sort of odd still if we had
                        // switched from multithreaded mode to single-threaded
                        // mode because single-threaded produces different
                        // output. So the messages could perhaps be clearer.
                        // Another case of this is a few lines below.
                        if (chains[i][j].id == LZMA_VLI_UNKNOWN)
                                memlimit_too_small(encoder_memusages[i]);

                        ++j;
                }

                // Decrease the dictionary size until we meet the memory
                // usage limit. First round down to full mebibytes.
                lzma_options_lzma *opt = chains[i][j].options;
                const uint32_t orig_dict_size = opt->dict_size;
                opt->dict_size &= ~((UINT32_C(1) << 20) - 1);

                while (true) {
                        // If it is below 1 MiB, auto-adjusting failed.
                        //
                        // FIXME? See the FIXME a few lines above.
                        if (opt->dict_size < (UINT32_C(1) << 20))
                                memlimit_too_small(encoder_memusages[i]);

                        encoder_memusages[i]
                                = lzma_raw_encoder_memusage(chains[i]);
                        if (encoder_memusages[i] == UINT64_MAX)
                                message_bug();

                        // Accept it if it is low enough.
                        if (encoder_memusages[i] <= memory_limit)
                                break;

                        // Otherwise adjust it 1 MiB down and try again.
                        opt->dict_size -= UINT32_C(1) << 20;
                }

                // Tell the user that we decreased the dictionary size.
                // The message is slightly different between the default
                // filter chain (0) or and chains from --filtersX.
                const char lzma_num = chains[i][j].id == LZMA_FILTER_LZMA2
                                        ? '2' : '1';
                const char *from_size = uint64_to_str(orig_dict_size >> 20, 0);
                const char *to_size = uint64_to_str(opt->dict_size >> 20, 1);
                const char *limit_size = uint64_to_str(round_up_to_mib(
                                        memory_limit), 2);
                if (i == 0)
                        message(V_WARNING, _("Adjusted LZMA%c dictionary "
                                "size from %s MiB to %s MiB to not exceed the "
                                "memory usage limit of %s MiB"),
                                lzma_num, from_size, to_size, limit_size);
                else
                        message(V_WARNING, _("Adjusted LZMA%c dictionary size "
                                "for --filters%u from %s MiB to %s MiB to not "
                                "exceed the memory usage limit of %s MiB"),
                                lzma_num, i, from_size, to_size, limit_size);
        }
#endif

        return;
}


#ifdef HAVE_DECODERS
/// Return true if the data in in_buf seems to be in the .xz format.
static bool
is_format_xz(void)
{
        // Specify the magic as hex to be compatible with EBCDIC systems.
        static const uint8_t magic[6] = { 0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00 };
        return strm.avail_in >= sizeof(magic)
                        && memcmp(in_buf.u8, magic, sizeof(magic)) == 0;
}


/// Return true if the data in in_buf seems to be in the .lzma format.
static bool
is_format_lzma(void)
{
        // The .lzma header is 13 bytes.
        if (strm.avail_in < 13)
                return false;

        // Decode the LZMA1 properties.
        lzma_filter filter = { .id = LZMA_FILTER_LZMA1 };
        if (lzma_properties_decode(&filter, NULL, in_buf.u8, 5) != LZMA_OK)
                return false;

        // A hack to ditch tons of false positives: We allow only dictionary
        // sizes that are 2^n or 2^n + 2^(n-1) or UINT32_MAX. LZMA_Alone
        // created only files with 2^n, but accepts any dictionary size.
        // If someone complains, this will be reconsidered.
        lzma_options_lzma *opt = filter.options;
        const uint32_t dict_size = opt->dict_size;
        free(opt);

        if (dict_size != UINT32_MAX) {
                uint32_t d = dict_size - 1;
                d |= d >> 2;
                d |= d >> 3;
                d |= d >> 4;
                d |= d >> 8;
                d |= d >> 16;
                ++d;
                if (d != dict_size || dict_size == 0)
                        return false;
        }

        // Another hack to ditch false positives: Assume that if the
        // uncompressed size is known, it must be less than 256 GiB.
        // Again, if someone complains, this will be reconsidered.
        uint64_t uncompressed_size = 0;
        for (size_t i = 0; i < 8; ++i)
                uncompressed_size |= (uint64_t)(in_buf.u8[5 + i]) << (i * 8);

        if (uncompressed_size != UINT64_MAX
                        && uncompressed_size > (UINT64_C(1) << 38))
                return false;

        return true;
}


#ifdef HAVE_LZIP_DECODER
/// Return true if the data in in_buf seems to be in the .lz format.
static bool
is_format_lzip(void)
{
        static const uint8_t magic[4] = { 0x4C, 0x5A, 0x49, 0x50 };
        return strm.avail_in >= sizeof(magic)
                        && memcmp(in_buf.u8, magic, sizeof(magic)) == 0;
}
#endif
#endif


/// Detect the input file type (for now, this done only when decompressing),
/// and initialize an appropriate coder. Return value indicates if a normal
/// liblzma-based coder was initialized (CODER_INIT_NORMAL), if passthru
/// mode should be used (CODER_INIT_PASSTHRU), or if an error occurred
/// (CODER_INIT_ERROR).
static enum coder_init_ret
coder_init(file_pair *pair)
{
        lzma_ret ret = LZMA_PROG_ERROR;

        // In most cases if there is input left when coding finishes,
        // something has gone wrong. Exceptions are --single-stream
        // and decoding .lz files which can contain trailing non-.lz data.
        // These will be handled later in this function.
        allow_trailing_input = false;

        // Set the first filter chain. If the --block-list option is not
        // used then use the default filter chain (chains[0]).
        // Otherwise, use first filter chain from the block list.
        lzma_filter *active_filters = opt_block_list == NULL
                        ? chains[0]
                        : chains[opt_block_list[0].chain_num];

        if (opt_mode == MODE_COMPRESS) {
#ifdef HAVE_ENCODERS
                switch (opt_format) {
                case FORMAT_AUTO:
                        // args.c ensures this.
                        assert(0);
                        break;

                case FORMAT_XZ:
#       ifdef MYTHREAD_ENABLED
                        mt_options.filters = active_filters;
                        if (hardware_threads_is_mt())
                                ret = lzma_stream_encoder_mt(
                                                &strm, &mt_options);
                        else
#       endif
                                ret = lzma_stream_encoder(
                                                &strm, active_filters, check);
                        break;

                case FORMAT_LZMA:
                        ret = lzma_alone_encoder(&strm,
                                        active_filters[0].options);
                        break;

#       ifdef HAVE_LZIP_DECODER
                case FORMAT_LZIP:
                        // args.c should disallow this.
                        assert(0);
                        ret = LZMA_PROG_ERROR;
                        break;
#       endif

                case FORMAT_RAW:
                        ret = lzma_raw_encoder(&strm, active_filters);
                        break;
                }
#endif
        } else {
#ifdef HAVE_DECODERS
                uint32_t flags = 0;

                // It seems silly to warn about unsupported check if the
                // check won't be verified anyway due to --ignore-check.
                if (opt_ignore_check)
                        flags |= LZMA_IGNORE_CHECK;
                else
                        flags |= LZMA_TELL_UNSUPPORTED_CHECK;

                if (opt_single_stream)
                        allow_trailing_input = true;
                else
                        flags |= LZMA_CONCATENATED;

                // We abuse FORMAT_AUTO to indicate unknown file format,
                // for which we may consider passthru mode.
                enum format_type init_format = FORMAT_AUTO;

                switch (opt_format) {
                case FORMAT_AUTO:
                        // .lz is checked before .lzma since .lzma detection
                        // is more complicated (no magic bytes).
                        if (is_format_xz())
                                init_format = FORMAT_XZ;
#       ifdef HAVE_LZIP_DECODER
                        else if (is_format_lzip())
                                init_format = FORMAT_LZIP;
#       endif
                        else if (is_format_lzma())
                                init_format = FORMAT_LZMA;
                        break;

                case FORMAT_XZ:
                        if (is_format_xz())
                                init_format = FORMAT_XZ;
                        break;

                case FORMAT_LZMA:
                        if (is_format_lzma())
                                init_format = FORMAT_LZMA;
                        break;

#       ifdef HAVE_LZIP_DECODER
                case FORMAT_LZIP:
                        if (is_format_lzip())
                                init_format = FORMAT_LZIP;
                        break;
#       endif

                case FORMAT_RAW:
                        init_format = FORMAT_RAW;
                        break;
                }

                switch (init_format) {
                case FORMAT_AUTO:
                        // Unknown file format. If --decompress --stdout
                        // --force have been given, then we copy the input
                        // as is to stdout. Checking for MODE_DECOMPRESS
                        // is needed, because we don't want to do use
                        // passthru mode with --test.
                        if (opt_mode == MODE_DECOMPRESS
                                        && opt_stdout && opt_force) {
                                // These are needed for progress info.
                                strm.total_in = 0;
                                strm.total_out = 0;
                                return CODER_INIT_PASSTHRU;
                        }

                        ret = LZMA_FORMAT_ERROR;
                        break;

                case FORMAT_XZ:
#       ifdef MYTHREAD_ENABLED
                        mt_options.flags = flags;

                        mt_options.threads = hardware_threads_get();
                        mt_options.memlimit_stop
                                = hardware_memlimit_get(MODE_DECOMPRESS);

                        // If single-threaded mode was requested, set the
                        // memlimit for threading to zero. This forces the
                        // decoder to use single-threaded mode which matches
                        // the behavior of lzma_stream_decoder().
                        //
                        // Otherwise use the limit for threaded decompression
                        // which has a sane default (users are still free to
                        // make it insanely high though).
                        mt_options.memlimit_threading
                                        = mt_options.threads == 1
                                        ? 0 : hardware_memlimit_mtdec_get();

                        ret = lzma_stream_decoder_mt(&strm, &mt_options);
#       else
                        ret = lzma_stream_decoder(&strm,
                                        hardware_memlimit_get(
                                                MODE_DECOMPRESS), flags);
#       endif
                        break;

                case FORMAT_LZMA:
                        ret = lzma_alone_decoder(&strm,
                                        hardware_memlimit_get(
                                                MODE_DECOMPRESS));
                        break;

#       ifdef HAVE_LZIP_DECODER
                case FORMAT_LZIP:
                        allow_trailing_input = true;
                        ret = lzma_lzip_decoder(&strm,
                                        hardware_memlimit_get(
                                                MODE_DECOMPRESS), flags);
                        break;
#       endif

                case FORMAT_RAW:
                        // Memory usage has already been checked in
                        // coder_set_compression_settings().
                        ret = lzma_raw_decoder(&strm, active_filters);
                        break;
                }

                // Try to decode the headers. This will catch too low
                // memory usage limit in case it happens in the first
                // Block of the first Stream, which is where it very
                // probably will happen if it is going to happen.
                //
                // This will also catch unsupported check type which
                // we treat as a warning only. If there are empty
                // concatenated Streams with unsupported check type then
                // the message can be shown more than once here. The loop
                // is used in case there is first a warning about
                // unsupported check type and then the first Block
                // would exceed the memlimit.
                if (ret == LZMA_OK && init_format != FORMAT_RAW) {
                        strm.next_out = NULL;
                        strm.avail_out = 0;
                        while ((ret = lzma_code(&strm, LZMA_RUN))
                                        == LZMA_UNSUPPORTED_CHECK)
                                message_warning(_("%s: %s"), pair->src_name,
                                                message_strm(ret));

                        // With --single-stream lzma_code won't wait for
                        // LZMA_FINISH and thus it can return LZMA_STREAM_END
                        // if the file has no uncompressed data inside.
                        // So treat LZMA_STREAM_END as LZMA_OK here.
                        // When lzma_code() is called again in coder_normal()
                        // it will return LZMA_STREAM_END again.
                        if (ret == LZMA_STREAM_END)
                                ret = LZMA_OK;
                }
#endif
        }

        if (ret != LZMA_OK) {
                message_error(_("%s: %s"), pair->src_name, message_strm(ret));
                if (ret == LZMA_MEMLIMIT_ERROR)
                        message_mem_needed(V_ERROR, lzma_memusage(&strm));

                return CODER_INIT_ERROR;
        }

        return CODER_INIT_NORMAL;
}


#ifdef HAVE_ENCODERS
/// Resolve conflicts between opt_block_size and opt_block_list in single
/// threaded mode. We want to default to opt_block_list, except when it is
/// larger than opt_block_size. If this is the case for the current Block
/// at *list_pos, then we break into smaller Blocks. Otherwise advance
/// to the next Block in opt_block_list, and break apart if needed.
static void
split_block(uint64_t *block_remaining,
            uint64_t *next_block_remaining,
            size_t *list_pos)
{
        if (*next_block_remaining > 0) {
                // The Block at *list_pos has previously been split up.
                assert(!hardware_threads_is_mt());
                assert(opt_block_size > 0);
                assert(opt_block_list != NULL);

                if (*next_block_remaining > opt_block_size) {
                        // We have to split the current Block at *list_pos
                        // into another opt_block_size length Block.
                        *block_remaining = opt_block_size;
                } else {
                        // This is the last remaining split Block for the
                        // Block at *list_pos.
                        *block_remaining = *next_block_remaining;
                }

                *next_block_remaining -= *block_remaining;

        } else {
                // The Block at *list_pos has been finished. Go to the next
                // entry in the list. If the end of the list has been
                // reached, reuse the size and filters of the last Block.
                if (opt_block_list[*list_pos + 1].size != 0) {
                        ++*list_pos;

                        // Update the filters if needed.
                        if (opt_block_list[*list_pos - 1].chain_num
                                != opt_block_list[*list_pos].chain_num) {
                                const unsigned chain_num
                                        = opt_block_list[*list_pos].chain_num;
                                const lzma_filter *next = chains[chain_num];
                                const lzma_ret ret = lzma_filters_update(
                                                &strm, next);

                                if (ret != LZMA_OK) {
                                        // This message is only possible if
                                        // the filter chain has unsupported
                                        // options since the filter chain is
                                        // validated using
                                        // lzma_raw_encoder_memusage() or
                                        // lzma_stream_encoder_mt_memusage().
                                        // Some options are not validated until
                                        // the encoders are initialized.
                                        message_fatal(
                                                _("Error changing to "
                                                "filter chain %u: %s"),
                                                chain_num,
                                                message_strm(ret));
                                }
                        }
                }

                *block_remaining = opt_block_list[*list_pos].size;

                // If in single-threaded mode, split up the Block if needed.
                // This is not needed in multi-threaded mode because liblzma
                // will do this due to how threaded encoding works.
                if (!hardware_threads_is_mt() && opt_block_size > 0
                                && *block_remaining > opt_block_size) {
                        *next_block_remaining
                                        = *block_remaining - opt_block_size;
                        *block_remaining = opt_block_size;
                }
        }
}
#endif


static bool
coder_write_output(file_pair *pair)
{
        if (opt_mode != MODE_TEST) {
                if (io_write(pair, &out_buf, IO_BUFFER_SIZE - strm.avail_out))
                        return true;
        }

        strm.next_out = out_buf.u8;
        strm.avail_out = IO_BUFFER_SIZE;
        return false;
}


/// Compress or decompress using liblzma.
static bool
coder_normal(file_pair *pair)
{
        // Encoder needs to know when we have given all the input to it.
        // The decoders need to know it too when we are using
        // LZMA_CONCATENATED. We need to check for src_eof here, because
        // the first input chunk has been already read if decompressing,
        // and that may have been the only chunk we will read.
        lzma_action action = pair->src_eof ? LZMA_FINISH : LZMA_RUN;

        lzma_ret ret;

        // Assume that something goes wrong.
        bool success = false;

#ifdef HAVE_ENCODERS
        // block_remaining indicates how many input bytes to encode before
        // finishing the current .xz Block. The Block size is set with
        // --block-size=SIZE and --block-list. They have an effect only when
        // compressing to the .xz format. If block_remaining == UINT64_MAX,
        // only a single block is created.
        uint64_t block_remaining = UINT64_MAX;

        // next_block_remaining for when we are in single-threaded mode and
        // the Block in --block-list is larger than the --block-size=SIZE.
        uint64_t next_block_remaining = 0;

        // Position in opt_block_list. Unused if --block-list wasn't used.
        size_t list_pos = 0;

        // Handle --block-size for single-threaded mode and the first step
        // of --block-list.
        if (opt_mode == MODE_COMPRESS && opt_format == FORMAT_XZ) {
                // --block-size doesn't do anything here in threaded mode,
                // because the threaded encoder will take care of splitting
                // to fixed-sized Blocks.
                if (!hardware_threads_is_mt() && opt_block_size > 0)
                        block_remaining = opt_block_size;

                // If --block-list was used, start with the first size.
                //
                // For threaded case, --block-size specifies how big Blocks
                // the encoder needs to be prepared to create at maximum
                // and --block-list will simultaneously cause new Blocks
                // to be started at specified intervals. To keep things
                // logical, the same is done in single-threaded mode. The
                // output is still not identical because in single-threaded
                // mode the size info isn't written into Block Headers.
                if (opt_block_list != NULL) {
                        if (block_remaining < opt_block_list[list_pos].size) {
                                assert(!hardware_threads_is_mt());
                                next_block_remaining =
                                                opt_block_list[list_pos].size
                                                - block_remaining;
                        } else {
                                block_remaining =
                                                opt_block_list[list_pos].size;
                        }
                }
        }
#endif

        strm.next_out = out_buf.u8;
        strm.avail_out = IO_BUFFER_SIZE;

        while (!user_abort) {
                // Fill the input buffer if it is empty and we aren't
                // flushing or finishing.
                if (strm.avail_in == 0 && action == LZMA_RUN) {
                        strm.next_in = in_buf.u8;
#ifdef HAVE_ENCODERS
                        const size_t read_size = my_min(block_remaining,
                                        IO_BUFFER_SIZE);
#else
                        const size_t read_size = IO_BUFFER_SIZE;
#endif
                        strm.avail_in = io_read(pair, &in_buf, read_size);

                        if (strm.avail_in == SIZE_MAX)
                                break;

                        if (pair->src_eof) {
                                action = LZMA_FINISH;
                        }
#ifdef HAVE_ENCODERS
                        else if (block_remaining != UINT64_MAX) {
                                // Start a new Block after every
                                // opt_block_size bytes of input.
                                block_remaining -= strm.avail_in;
                                if (block_remaining == 0)
                                        action = LZMA_FULL_BARRIER;
                        }

                        if (action == LZMA_RUN && pair->flush_needed)
                                action = LZMA_SYNC_FLUSH;
#endif
                }

                // Let liblzma do the actual work.
                ret = lzma_code(&strm, action);

                // Write out if the output buffer became full.
                if (strm.avail_out == 0) {
                        if (coder_write_output(pair))
                                break;
                }

#ifdef HAVE_ENCODERS
                if (ret == LZMA_STREAM_END && (action == LZMA_SYNC_FLUSH
                                || action == LZMA_FULL_BARRIER)) {
                        if (action == LZMA_SYNC_FLUSH) {
                                // Flushing completed. Write the pending data
                                // out immediately so that the reading side
                                // can decompress everything compressed so far.
                                if (coder_write_output(pair))
                                        break;

                                // Mark that we haven't seen any new input
                                // since the previous flush.
                                pair->src_has_seen_input = false;
                                pair->flush_needed = false;
                        } else {
                                // Start a new Block after LZMA_FULL_BARRIER.
                                if (opt_block_list == NULL) {
                                        assert(!hardware_threads_is_mt());
                                        assert(opt_block_size > 0);
                                        block_remaining = opt_block_size;
                                } else {
                                        split_block(&block_remaining,
                                                        &next_block_remaining,
                                                        &list_pos);
                                }
                        }

                        // Start a new Block after LZMA_FULL_FLUSH or continue
                        // the same block after LZMA_SYNC_FLUSH.
                        action = LZMA_RUN;
                } else
#endif
                if (ret != LZMA_OK) {
                        // Determine if the return value indicates that we
                        // won't continue coding. LZMA_NO_CHECK would be
                        // here too if LZMA_TELL_ANY_CHECK was used.
                        const bool stop = ret != LZMA_UNSUPPORTED_CHECK;

                        if (stop) {
                                // Write the remaining bytes even if something
                                // went wrong, because that way the user gets
                                // as much data as possible, which can be good
                                // when trying to get at least some useful
                                // data out of damaged files.
                                if (coder_write_output(pair))
                                        break;
                        }

                        if (ret == LZMA_STREAM_END) {
                                if (allow_trailing_input) {
                                        io_fix_src_pos(pair, strm.avail_in);
                                        success = true;
                                        break;
                                }

                                // Check that there is no trailing garbage.
                                // This is needed for LZMA_Alone and raw
                                // streams. This is *not* done with .lz files
                                // as that format specifically requires
                                // allowing trailing garbage.
                                if (strm.avail_in == 0 && !pair->src_eof) {
                                        // Try reading one more byte.
                                        // Hopefully we don't get any more
                                        // input, and thus pair->src_eof
                                        // becomes true.
                                        strm.avail_in = io_read(
                                                        pair, &in_buf, 1);
                                        if (strm.avail_in == SIZE_MAX)
                                                break;

                                        assert(strm.avail_in == 0
                                                        || strm.avail_in == 1);
                                }

                                if (strm.avail_in == 0) {
                                        assert(pair->src_eof);
                                        success = true;
                                        break;
                                }

                                // We hadn't reached the end of the file.
                                ret = LZMA_DATA_ERROR;
                                assert(stop);
                        }

                        // If we get here and stop is true, something went
                        // wrong and we print an error. Otherwise it's just
                        // a warning and coding can continue.
                        if (stop) {
                                message_error(_("%s: %s"), pair->src_name,
                                                message_strm(ret));
                        } else {
                                message_warning(_("%s: %s"), pair->src_name,
                                                message_strm(ret));

                                // When compressing, all possible errors set
                                // stop to true.
                                assert(opt_mode != MODE_COMPRESS);
                        }

                        if (ret == LZMA_MEMLIMIT_ERROR) {
                                // Display how much memory it would have
                                // actually needed.
                                message_mem_needed(V_ERROR,
                                                lzma_memusage(&strm));
                        }

                        if (stop)
                                break;
                }

                // Show progress information under certain conditions.
                message_progress_update();
        }

        return success;
}


/// Copy from input file to output file without processing the data in any
/// way. This is used only when trying to decompress unrecognized files
/// with --decompress --stdout --force, so the output is always stdout.
static bool
coder_passthru(file_pair *pair)
{
        while (strm.avail_in != 0) {
                if (user_abort)
                        return false;

                if (io_write(pair, &in_buf, strm.avail_in))
                        return false;

                strm.total_in += strm.avail_in;
                strm.total_out = strm.total_in;
                message_progress_update();

                strm.avail_in = io_read(pair, &in_buf, IO_BUFFER_SIZE);
                if (strm.avail_in == SIZE_MAX)
                        return false;
        }

        return true;
}


extern void
coder_run(const char *filename)
{
        // Set and possibly print the filename for the progress message.
        message_filename(filename);

        // Try to open the input file.
        file_pair *pair = io_open_src(filename);
        if (pair == NULL)
                return;

        // Assume that something goes wrong.
        bool success = false;

        if (opt_mode == MODE_COMPRESS) {
                strm.next_in = NULL;
                strm.avail_in = 0;
        } else {
                // Read the first chunk of input data. This is needed
                // to detect the input file type.
                strm.next_in = in_buf.u8;
                strm.avail_in = io_read(pair, &in_buf, IO_BUFFER_SIZE);
        }

        if (strm.avail_in != SIZE_MAX) {
                // Initialize the coder. This will detect the file format
                // and, in decompression or testing mode, check the memory
                // usage of the first Block too. This way we don't try to
                // open the destination file if we see that coding wouldn't
                // work at all anyway. This also avoids deleting the old
                // "target" file if --force was used.
                const enum coder_init_ret init_ret = coder_init(pair);

                if (init_ret != CODER_INIT_ERROR && !user_abort) {
                        // Don't open the destination file when --test
                        // is used.
                        if (opt_mode == MODE_TEST || !io_open_dest(pair)) {
                                // Remember the current time. It is needed
                                // for progress indicator.
                                mytime_set_start_time();

                                // Initialize the progress indicator.
                                //
                                // NOTE: When reading from stdin, fstat()
                                // isn't called on it and thus src_st.st_size
                                // is zero. If stdin pointed to a regular
                                // file, it would still be possible to know
                                // the file size but then we would also need
                                // to take into account the current reading
                                // position since with stdin it isn't
                                // necessarily at the beginning of the file.
                                const bool is_passthru = init_ret
                                                == CODER_INIT_PASSTHRU;
                                const uint64_t in_size
                                        = pair->src_st.st_size <= 0
                                        ? 0 : (uint64_t)(pair->src_st.st_size);
                                message_progress_start(&strm,
                                                is_passthru, in_size);

                                // Do the actual coding or passthru.
                                if (is_passthru)
                                        success = coder_passthru(pair);
                                else
                                        success = coder_normal(pair);

                                message_progress_end(success);
                        }
                }
        }

        // Close the file pair. It needs to know if coding was successful to
        // know if the source or target file should be unlinked.
        io_close(pair, success);

        return;
}


#ifndef NDEBUG
extern void
coder_free(void)
{
        // Free starting from the second filter chain since the default
        // filter chain may have its options set from a static variable
        // in coder_set_compression_settings(). Since this is only run in
        // debug mode and will be freed when the process ends anyway, we
        // don't worry about freeing it.
        for (uint32_t i = 1; i < ARRAY_SIZE(chains); i++) {
                if (chains_used_mask & (1U << i))
                        lzma_filters_free(chains[i], NULL);
        }

        lzma_end(&strm);
        return;
}
#endif