liblzma: Refactor lzma_mf_is_supported() to use a switch-statement.

[xz.git] / src / liblzma / lz / lz_encoder.c

///////////////////////////////////////////////////////////////////////////////
//
/// \file       lz_encoder.c
/// \brief      LZ in window
///
//  Authors:    Igor Pavlov
//              Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "lz_encoder.h"
#include "lz_encoder_hash.h"

// See lz_encoder_hash.h. This is a bit hackish but avoids making
// endianness a conditional in makefiles.
#if defined(WORDS_BIGENDIAN) && !defined(HAVE_SMALL)
#       include "lz_encoder_hash_table.h"
#endif

#include "memcmplen.h"


typedef struct {
        /// LZ-based encoder e.g. LZMA
        lzma_lz_encoder lz;

        /// History buffer and match finder
        lzma_mf mf;

        /// Next coder in the chain
        lzma_next_coder next;
} lzma_coder;


/// \brief      Moves the data in the input window to free space for new data
///
/// mf->buffer is a sliding input window, which keeps mf->keep_size_before
/// bytes of input history available all the time. Now and then we need to
/// "slide" the buffer to make space for the new data to the end of the
/// buffer. At the same time, data older than keep_size_before is dropped.
///
static void
move_window(lzma_mf *mf)
{
        // Align the move to a multiple of 16 bytes. Some LZ-based encoders
        // like LZMA use the lowest bits of mf->read_pos to know the
        // alignment of the uncompressed data. We also get better speed
        // for memmove() with aligned buffers.
        assert(mf->read_pos > mf->keep_size_before);
        const uint32_t move_offset
                = (mf->read_pos - mf->keep_size_before) & ~UINT32_C(15);

        assert(mf->write_pos > move_offset);
        const size_t move_size = mf->write_pos - move_offset;

        assert(move_offset + move_size <= mf->size);

        memmove(mf->buffer, mf->buffer + move_offset, move_size);

        mf->offset += move_offset;
        mf->read_pos -= move_offset;
        mf->read_limit -= move_offset;
        mf->write_pos -= move_offset;

        return;
}


/// \brief      Tries to fill the input window (mf->buffer)
///
/// If we are the last encoder in the chain, our input data is in in[].
/// Otherwise we call the next filter in the chain to process in[] and
/// write its output to mf->buffer.
///
/// This function must not be called once it has returned LZMA_STREAM_END.
///
static lzma_ret
fill_window(lzma_coder *coder, const lzma_allocator *allocator,
                const uint8_t *in, size_t *in_pos, size_t in_size,
                lzma_action action)
{
        assert(coder->mf.read_pos <= coder->mf.write_pos);

        // Move the sliding window if needed.
        if (coder->mf.read_pos >= coder->mf.size - coder->mf.keep_size_after)
                move_window(&coder->mf);

        // Maybe this is ugly, but lzma_mf uses uint32_t for most things
        // (which I find cleanest), but we need size_t here when filling
        // the history window.
        size_t write_pos = coder->mf.write_pos;
        lzma_ret ret;
        if (coder->next.code == NULL) {
                // Not using a filter, simply memcpy() as much as possible.
                lzma_bufcpy(in, in_pos, in_size, coder->mf.buffer,
                                &write_pos, coder->mf.size);

                ret = action != LZMA_RUN && *in_pos == in_size
                                ? LZMA_STREAM_END : LZMA_OK;

        } else {
                ret = coder->next.code(coder->next.coder, allocator,
                                in, in_pos, in_size,
                                coder->mf.buffer, &write_pos,
                                coder->mf.size, action);
        }

        coder->mf.write_pos = write_pos;

        // Silence Valgrind. lzma_memcmplen() can read extra bytes
        // and Valgrind will give warnings if those bytes are uninitialized
        // because Valgrind cannot see that the values of the uninitialized
        // bytes are eventually ignored.
        memzero(coder->mf.buffer + write_pos, LZMA_MEMCMPLEN_EXTRA);

        // If end of stream has been reached or flushing completed, we allow
        // the encoder to process all the input (that is, read_pos is allowed
        // to reach write_pos). Otherwise we keep keep_size_after bytes
        // available as prebuffer.
        if (ret == LZMA_STREAM_END) {
                assert(*in_pos == in_size);
                ret = LZMA_OK;
                coder->mf.action = action;
                coder->mf.read_limit = coder->mf.write_pos;

        } else if (coder->mf.write_pos > coder->mf.keep_size_after) {
                // This needs to be done conditionally, because if we got
                // only little new input, there may be too little input
                // to do any encoding yet.
                coder->mf.read_limit = coder->mf.write_pos
                                - coder->mf.keep_size_after;
        }

        // Restart the match finder after finished LZMA_SYNC_FLUSH.
        if (coder->mf.pending > 0
                        && coder->mf.read_pos < coder->mf.read_limit) {
                // Match finder may update coder->pending and expects it to
                // start from zero, so use a temporary variable.
                const uint32_t pending = coder->mf.pending;
                coder->mf.pending = 0;

                // Rewind read_pos so that the match finder can hash
                // the pending bytes.
                assert(coder->mf.read_pos >= pending);
                coder->mf.read_pos -= pending;

                // Call the skip function directly instead of using
                // mf_skip(), since we don't want to touch mf->read_ahead.
                coder->mf.skip(&coder->mf, pending);
        }

        return ret;
}


static lzma_ret
lz_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_coder *coder = coder_ptr;

        while (*out_pos < out_size
                        && (*in_pos < in_size || action != LZMA_RUN)) {
                // Read more data to coder->mf.buffer if needed.
                if (coder->mf.action == LZMA_RUN && coder->mf.read_pos
                                >= coder->mf.read_limit)
                        return_if_error(fill_window(coder, allocator,
                                        in, in_pos, in_size, action));

                // Encode
                const lzma_ret ret = coder->lz.code(coder->lz.coder,
                                &coder->mf, out, out_pos, out_size);
                if (ret != LZMA_OK) {
                        // Setting this to LZMA_RUN for cases when we are
                        // flushing. It doesn't matter when finishing or if
                        // an error occurred.
                        coder->mf.action = LZMA_RUN;
                        return ret;
                }
        }

        return LZMA_OK;
}


static bool
lz_encoder_prepare(lzma_mf *mf, const lzma_allocator *allocator,
                const lzma_lz_options *lz_options)
{
        // For now, the dictionary size is limited to 1.5 GiB. This may grow
        // in the future if needed, but it needs a little more work than just
        // changing this check.
        if (lz_options->dict_size < LZMA_DICT_SIZE_MIN
                        || lz_options->dict_size
                                > (UINT32_C(1) << 30) + (UINT32_C(1) << 29)
                        || lz_options->nice_len > lz_options->match_len_max)
                return true;

        mf->keep_size_before = lz_options->before_size + lz_options->dict_size;

        mf->keep_size_after = lz_options->after_size
                        + lz_options->match_len_max;

        // To avoid constant memmove()s, allocate some extra space. Since
        // memmove()s become more expensive when the size of the buffer
        // increases, we reserve more space when a large dictionary is
        // used to make the memmove() calls rarer.
        //
        // This works with dictionaries up to about 3 GiB. If bigger
        // dictionary is wanted, some extra work is needed:
        //   - Several variables in lzma_mf have to be changed from uint32_t
        //     to size_t.
        //   - Memory usage calculation needs something too, e.g. use uint64_t
        //     for mf->size.
        uint32_t reserve = lz_options->dict_size / 2;
        if (reserve > (UINT32_C(1) << 30))
                reserve /= 2;

        reserve += (lz_options->before_size + lz_options->match_len_max
                        + lz_options->after_size) / 2 + (UINT32_C(1) << 19);

        const uint32_t old_size = mf->size;
        mf->size = mf->keep_size_before + reserve + mf->keep_size_after;

        // Deallocate the old history buffer if it exists but has different
        // size than what is needed now.
        if (mf->buffer != NULL && old_size != mf->size) {
                lzma_free(mf->buffer, allocator);
                mf->buffer = NULL;
        }

        // Match finder options
        mf->match_len_max = lz_options->match_len_max;
        mf->nice_len = lz_options->nice_len;

        // cyclic_size has to stay smaller than 2 Gi. Note that this doesn't
        // mean limiting dictionary size to less than 2 GiB. With a match
        // finder that uses multibyte resolution (hashes start at e.g. every
        // fourth byte), cyclic_size would stay below 2 Gi even when
        // dictionary size is greater than 2 GiB.
        //
        // It would be possible to allow cyclic_size >= 2 Gi, but then we
        // would need to be careful to use 64-bit types in various places
        // (size_t could do since we would need bigger than 32-bit address
        // space anyway). It would also require either zeroing a multigigabyte
        // buffer at initialization (waste of time and RAM) or allow
        // normalization in lz_encoder_mf.c to access uninitialized
        // memory to keep the code simpler. The current way is simple and
        // still allows pretty big dictionaries, so I don't expect these
        // limits to change.
        mf->cyclic_size = lz_options->dict_size + 1;

        // Validate the match finder ID and setup the function pointers.
        switch (lz_options->match_finder) {
#ifdef HAVE_MF_HC3
        case LZMA_MF_HC3:
                mf->find = &lzma_mf_hc3_find;
                mf->skip = &lzma_mf_hc3_skip;
                break;
#endif
#ifdef HAVE_MF_HC4
        case LZMA_MF_HC4:
                mf->find = &lzma_mf_hc4_find;
                mf->skip = &lzma_mf_hc4_skip;
                break;
#endif
#ifdef HAVE_MF_BT2
        case LZMA_MF_BT2:
                mf->find = &lzma_mf_bt2_find;
                mf->skip = &lzma_mf_bt2_skip;
                break;
#endif
#ifdef HAVE_MF_BT3
        case LZMA_MF_BT3:
                mf->find = &lzma_mf_bt3_find;
                mf->skip = &lzma_mf_bt3_skip;
                break;
#endif
#ifdef HAVE_MF_BT4
        case LZMA_MF_BT4:
                mf->find = &lzma_mf_bt4_find;
                mf->skip = &lzma_mf_bt4_skip;
                break;
#endif

        default:
                return true;
        }

        // Calculate the sizes of mf->hash and mf->son and check that
        // nice_len is big enough for the selected match finder.
        const uint32_t hash_bytes = lz_options->match_finder & 0x0F;
        if (hash_bytes > mf->nice_len)
                return true;

        const bool is_bt = (lz_options->match_finder & 0x10) != 0;
        uint32_t hs;

        if (hash_bytes == 2) {
                hs = 0xFFFF;
        } else {
                // Round dictionary size up to the next 2^n - 1 so it can
                // be used as a hash mask.
                hs = lz_options->dict_size - 1;
                hs |= hs >> 1;
                hs |= hs >> 2;
                hs |= hs >> 4;
                hs |= hs >> 8;
                hs >>= 1;
                hs |= 0xFFFF;

                if (hs > (UINT32_C(1) << 24)) {
                        if (hash_bytes == 3)
                                hs = (UINT32_C(1) << 24) - 1;
                        else
                                hs >>= 1;
                }
        }

        mf->hash_mask = hs;

        ++hs;
        if (hash_bytes > 2)
                hs += HASH_2_SIZE;
        if (hash_bytes > 3)
                hs += HASH_3_SIZE;
/*
        No match finder uses this at the moment.
        if (mf->hash_bytes > 4)
                hs += HASH_4_SIZE;
*/

        const uint32_t old_hash_count = mf->hash_count;
        const uint32_t old_sons_count = mf->sons_count;
        mf->hash_count = hs;
        mf->sons_count = mf->cyclic_size;
        if (is_bt)
                mf->sons_count *= 2;

        // Deallocate the old hash array if it exists and has different size
        // than what is needed now.
        if (old_hash_count != mf->hash_count
                        || old_sons_count != mf->sons_count) {
                lzma_free(mf->hash, allocator);
                mf->hash = NULL;

                lzma_free(mf->son, allocator);
                mf->son = NULL;
        }

        // Maximum number of match finder cycles
        mf->depth = lz_options->depth;
        if (mf->depth == 0) {
                if (is_bt)
                        mf->depth = 16 + mf->nice_len / 2;
                else
                        mf->depth = 4 + mf->nice_len / 4;
        }

        return false;
}


static bool
lz_encoder_init(lzma_mf *mf, const lzma_allocator *allocator,
                const lzma_lz_options *lz_options)
{
        // Allocate the history buffer.
        if (mf->buffer == NULL) {
                // lzma_memcmplen() is used for the dictionary buffer
                // so we need to allocate a few extra bytes to prevent
                // it from reading past the end of the buffer.
                mf->buffer = lzma_alloc(mf->size + LZMA_MEMCMPLEN_EXTRA,
                                allocator);
                if (mf->buffer == NULL)
                        return true;

                // Keep Valgrind happy with lzma_memcmplen() and initialize
                // the extra bytes whose value may get read but which will
                // effectively get ignored.
                memzero(mf->buffer + mf->size, LZMA_MEMCMPLEN_EXTRA);
        }

        // Use cyclic_size as initial mf->offset. This allows
        // avoiding a few branches in the match finders. The downside is
        // that match finder needs to be normalized more often, which may
        // hurt performance with huge dictionaries.
        mf->offset = mf->cyclic_size;
        mf->read_pos = 0;
        mf->read_ahead = 0;
        mf->read_limit = 0;
        mf->write_pos = 0;
        mf->pending = 0;

#if UINT32_MAX >= SIZE_MAX / 4
        // Check for integer overflow. (Huge dictionaries are not
        // possible on 32-bit CPU.)
        if (mf->hash_count > SIZE_MAX / sizeof(uint32_t)
                        || mf->sons_count > SIZE_MAX / sizeof(uint32_t))
                return true;
#endif

        // Allocate and initialize the hash table. Since EMPTY_HASH_VALUE
        // is zero, we can use lzma_alloc_zero() or memzero() for mf->hash.
        //
        // We don't need to initialize mf->son, but not doing that may
        // make Valgrind complain in normalization (see normalize() in
        // lz_encoder_mf.c). Skipping the initialization is *very* good
        // when big dictionary is used but only small amount of data gets
        // actually compressed: most of the mf->son won't get actually
        // allocated by the kernel, so we avoid wasting RAM and improve
        // initialization speed a lot.
        if (mf->hash == NULL) {
                mf->hash = lzma_alloc_zero(mf->hash_count * sizeof(uint32_t),
                                allocator);
                mf->son = lzma_alloc(mf->sons_count * sizeof(uint32_t),
                                allocator);

                if (mf->hash == NULL || mf->son == NULL) {
                        lzma_free(mf->hash, allocator);
                        mf->hash = NULL;

                        lzma_free(mf->son, allocator);
                        mf->son = NULL;

                        return true;
                }
        } else {
/*
                for (uint32_t i = 0; i < mf->hash_count; ++i)
                        mf->hash[i] = EMPTY_HASH_VALUE;
*/
                memzero(mf->hash, mf->hash_count * sizeof(uint32_t));
        }

        mf->cyclic_pos = 0;

        // Handle preset dictionary.
        if (lz_options->preset_dict != NULL
                        && lz_options->preset_dict_size > 0) {
                // If the preset dictionary is bigger than the actual
                // dictionary, use only the tail.
                mf->write_pos = my_min(lz_options->preset_dict_size, mf->size);
                memcpy(mf->buffer, lz_options->preset_dict
                                + lz_options->preset_dict_size - mf->write_pos,
                                mf->write_pos);
                mf->action = LZMA_SYNC_FLUSH;
                mf->skip(mf, mf->write_pos);
        }

        mf->action = LZMA_RUN;

        return false;
}


extern uint64_t
lzma_lz_encoder_memusage(const lzma_lz_options *lz_options)
{
        // Old buffers must not exist when calling lz_encoder_prepare().
        lzma_mf mf = {
                .buffer = NULL,
                .hash = NULL,
                .son = NULL,
                .hash_count = 0,
                .sons_count = 0,
        };

        // Setup the size information into mf.
        if (lz_encoder_prepare(&mf, NULL, lz_options))
                return UINT64_MAX;

        // Calculate the memory usage.
        return ((uint64_t)(mf.hash_count) + mf.sons_count) * sizeof(uint32_t)
                        + mf.size + sizeof(lzma_coder);
}


static void
lz_encoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
        lzma_coder *coder = coder_ptr;

        lzma_next_end(&coder->next, allocator);

        lzma_free(coder->mf.son, allocator);
        lzma_free(coder->mf.hash, allocator);
        lzma_free(coder->mf.buffer, allocator);

        if (coder->lz.end != NULL)
                coder->lz.end(coder->lz.coder, allocator);
        else
                lzma_free(coder->lz.coder, allocator);

        lzma_free(coder, allocator);
        return;
}


static lzma_ret
lz_encoder_update(void *coder_ptr, const lzma_allocator *allocator,
                const lzma_filter *filters_null lzma_attribute((__unused__)),
                const lzma_filter *reversed_filters)
{
        lzma_coder *coder = coder_ptr;

        if (coder->lz.options_update == NULL)
                return LZMA_PROG_ERROR;

        return_if_error(coder->lz.options_update(
                        coder->lz.coder, reversed_filters));

        return lzma_next_filter_update(
                        &coder->next, allocator, reversed_filters + 1);
}


static lzma_ret
lz_encoder_set_out_limit(void *coder_ptr, uint64_t *uncomp_size,
                uint64_t out_limit)
{
        lzma_coder *coder = coder_ptr;

        // This is supported only if there are no other filters chained.
        if (coder->next.code == NULL && coder->lz.set_out_limit != NULL)
                return coder->lz.set_out_limit(
                                coder->lz.coder, uncomp_size, out_limit);

        return LZMA_OPTIONS_ERROR;
}


extern lzma_ret
lzma_lz_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
                const lzma_filter_info *filters,
                lzma_ret (*lz_init)(lzma_lz_encoder *lz,
                        const lzma_allocator *allocator, const void *options,
                        lzma_lz_options *lz_options))
{
#ifdef HAVE_SMALL
        // We need that the CRC32 table has been initialized.
        lzma_crc32_init();
#endif

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

                next->coder = coder;
                next->code = &lz_encode;
                next->end = &lz_encoder_end;
                next->update = &lz_encoder_update;
                next->set_out_limit = &lz_encoder_set_out_limit;

                coder->lz.coder = NULL;
                coder->lz.code = NULL;
                coder->lz.end = NULL;

                // mf.size is initialized to silence Valgrind
                // when used on optimized binaries (GCC may reorder
                // code in a way that Valgrind gets unhappy).
                coder->mf.buffer = NULL;
                coder->mf.size = 0;
                coder->mf.hash = NULL;
                coder->mf.son = NULL;
                coder->mf.hash_count = 0;
                coder->mf.sons_count = 0;

                coder->next = LZMA_NEXT_CODER_INIT;
        }

        // Initialize the LZ-based encoder.
        lzma_lz_options lz_options;
        return_if_error(lz_init(&coder->lz, allocator,
                        filters[0].options, &lz_options));

        // Setup the size information into coder->mf and deallocate
        // old buffers if they have wrong size.
        if (lz_encoder_prepare(&coder->mf, allocator, &lz_options))
                return LZMA_OPTIONS_ERROR;

        // Allocate new buffers if needed, and do the rest of
        // the initialization.
        if (lz_encoder_init(&coder->mf, allocator, &lz_options))
                return LZMA_MEM_ERROR;

        // Initialize the next filter in the chain, if any.
        return lzma_next_filter_init(&coder->next, allocator, filters + 1);
}


extern LZMA_API(lzma_bool)
lzma_mf_is_supported(lzma_match_finder mf)
{
        switch (mf) {
#ifdef HAVE_MF_HC3
        case LZMA_MF_HC3:
                return true;
#endif
#ifdef HAVE_MF_HC4
        case LZMA_MF_HC4:
                return true;
#endif
#ifdef HAVE_MF_BT2
        case LZMA_MF_BT2:
                return true;
#endif
#ifdef HAVE_MF_BT3
        case LZMA_MF_BT3:
                return true;
#endif
#ifdef HAVE_MF_BT4
        case LZMA_MF_BT4:
                return true;
#endif
        default:
                return false;
        }
}