Some fixes to LZ encoder.

src/liblzma/lz/lz_encoder.c

@@ -86,12 +86,16 @@ fill_window(lzma_coder *coder, lzma_allocator *allocator, const uint8_t *in,
 	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;
 	size_t in_used;
 	lzma_ret ret;
 	if (coder->next.code == NULL) {
 		// Not using a filter, simply memcpy() as much as possible.
 		in_used = lzma_bufcpy(in, in_pos, in_size, coder->mf.buffer,
-				&coder->mf.write_pos, coder->mf.size);
+				&write_pos, coder->mf.size);
 
 		ret = action != LZMA_RUN && *in_pos == in_size
 				? LZMA_STREAM_END : LZMA_OK;
@@ -100,11 +104,13 @@ fill_window(lzma_coder *coder, lzma_allocator *allocator, const uint8_t *in,
 		const size_t in_start = *in_pos;
 		ret = coder->next.code(coder->next.coder, allocator,
 				in, in_pos, in_size,
-				coder->mf.buffer, &coder->mf.write_pos,
+				coder->mf.buffer, &write_pos,
 				coder->mf.size, action);
 		in_used = *in_pos - in_start;
 	}
 
+	coder->mf.write_pos = write_pos;
+
 	// 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
@@ -181,9 +187,12 @@ static bool
 lz_encoder_prepare(lzma_mf *mf, 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->dictionary_size < LZMA_DICTIONARY_SIZE_MIN
 			|| lz_options->dictionary_size
-				> LZMA_DICTIONARY_SIZE_MAX
+				> (UINT32_C(1) << 30) + (UINT32_C(1) << 29)
 			|| lz_options->find_len_max
 				> lz_options->match_len_max)
 		return true;
@@ -198,6 +207,13 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
 	// 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->dictionary_size / 2;
 	if (reserve > (UINT32_C(1) << 30))
 		reserve /= 2;
@@ -208,8 +224,6 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
 	const uint32_t old_size = mf->size;
 	mf->size = mf->keep_size_before + reserve + mf->keep_size_after;
 
-	// FIXME Integer overflows
-
 	// 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) {
@@ -220,7 +234,23 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
 	// Match finder options
 	mf->match_len_max = lz_options->match_len_max;
 	mf->find_len_max = lz_options->find_len_max;
-	mf->cyclic_buffer_size = lz_options->dictionary_size + 1;
+
+	// cyclic_size has to stay smaller than 2 Gi. Note that this doesn't
+	// mean limitting 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->dictionary_size + 1;
 
 	// Validate the match finder ID and setup the function pointers.
 	switch (lz_options->match_finder) {
@@ -298,9 +328,15 @@ lz_encoder_prepare(lzma_mf *mf, lzma_allocator *allocator,
 		hs += HASH_4_SIZE;
 */
 
+	// If the above code calculating hs is modified, make sure that
+	// this assertion stays valid (UINT32_MAX / 5 is not strictly the
+	// exact limit). If it doesn't, you need to calculate that
+	// hash_size_sum + sons_count cannot overflow.
+	assert(hs < UINT32_MAX / 5);
+
 	const uint32_t old_count = mf->hash_size_sum + mf->sons_count;
 	mf->hash_size_sum = hs;
-	mf->sons_count = mf->cyclic_buffer_size;
+	mf->sons_count = mf->cyclic_size;
 	if (is_bt)
 		mf->sons_count *= 2;
 
@@ -335,11 +371,11 @@ lz_encoder_init(lzma_mf *mf, lzma_allocator *allocator)
 			return true;
 	}
 
-	// Use cyclic_buffer_size as initial mf->offset. This allows
+	// 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_buffer_size;
+	mf->offset = mf->cyclic_size;
 	mf->read_pos = 0;
 	mf->read_ahead = 0;
 	mf->read_limit = 0;
@@ -364,7 +400,7 @@ lz_encoder_init(lzma_mf *mf, lzma_allocator *allocator)
 	}
 
 	mf->son = mf->hash + mf->hash_size_sum;
-	mf->cyclic_buffer_pos = 0;
+	mf->cyclic_pos = 0;
 
 	// Initialize the hash table. Since EMPTY_HASH_VALUE is zero, we
 	// can use memset().

src/liblzma/lz/lz_encoder.h

@@ -53,18 +53,20 @@ struct lzma_mf_s {
 
 	/// Number of bytes that must be kept in buffer after read_pos.
 	/// That is, read_pos <= write_pos - keep_size_after as long as
-	/// stream_end_was_reached is false (once it is true, read_pos
-	/// is allowed to reach write_pos).
+	/// action is LZMA_RUN; when action != LZMA_RUN, read_pos is allowed
+	/// to reach write_pos so that the last bytes get encoded too.
 	uint32_t keep_size_after;
 
 	/// Match finders store locations of matches using 32-bit integers.
 	/// To avoid adjusting several megabytes of integers every time the
-	/// input window is moved with move_window(), we only adjust the
-	/// offset of the buffer. Thus, buffer[match_finder_pos - offset]
-	/// is the byte pointed by match_finder_pos.
+	/// input window is moved with move_window, we only adjust the
+	/// offset of the buffer. Thus, buffer[value_in_hash_table - offset]
+	/// is the byte pointed by value_in_hash_table.
 	uint32_t offset;
 
-	/// buffer[read_pos] is the current byte.
+	/// buffer[read_pos] is the next byte to run through the match
+	/// finder. This is incremented in the match finder once the byte
+	/// has been processed.
 	uint32_t read_pos;
 
 	/// Number of bytes that have been ran through the match finder, but
@@ -103,8 +105,8 @@ struct lzma_mf_s {
 
 	uint32_t *hash;
 	uint32_t *son;
-	uint32_t cyclic_buffer_pos;
-	uint32_t cyclic_buffer_size; // Must be dictionary_size + 1.
+	uint32_t cyclic_pos;
+	uint32_t cyclic_size; // Must be dictionary size + 1.
 	uint32_t hash_mask;
 
 	/// Maximum number of loops in the match finder

src/liblzma/lz/lz_encoder_mf.c

@@ -121,7 +121,7 @@ normalize(lzma_mf *mf)
 	// In future we may not want to touch the lowest bits, because there
 	// may be match finders that use larger resolution than one byte.
 	const uint32_t subvalue
-			= (MUST_NORMALIZE_POS - mf->cyclic_buffer_size);
+			= (MUST_NORMALIZE_POS - mf->cyclic_size);
 				// & (~(UINT32_C(1) << 10) - 1);
 
 	const uint32_t count = mf->hash_size_sum + mf->sons_count;
@@ -155,8 +155,8 @@ normalize(lzma_mf *mf)
 static void
 move_pos(lzma_mf *mf)
 {
-	if (++mf->cyclic_buffer_pos == mf->cyclic_buffer_size)
-		mf->cyclic_buffer_pos = 0;
+	if (++mf->cyclic_pos == mf->cyclic_size)
+		mf->cyclic_pos = 0;
 
 	++mf->read_pos;
 	assert(mf->read_pos <= mf->write_pos);
@@ -177,7 +177,7 @@ move_pos(lzma_mf *mf)
 /// function (with small amount of input, it may start using mf->pending
 /// again if flushing).
 ///
-/// Due to this rewinding, we don't touch cyclic_buffer_pos or test for
+/// Due to this rewinding, we don't touch cyclic_pos or test for
 /// normalization. It will be done when the match finder's skip function
 /// catches up after a flush.
 static void
@@ -227,8 +227,7 @@ move_pending(lzma_mf *mf)
 #define call_find(func, len_best) \
 do { \
 	matches_count = func(len_limit, pos, cur, cur_match, mf->loops, \
-				mf->son, mf->cyclic_buffer_pos, \
-				mf->cyclic_buffer_size, \
+				mf->son, mf->cyclic_pos, mf->cyclic_size, \
 				matches + matches_count, len_best) \
 			- matches; \
 	move_pos(mf); \
@@ -249,8 +248,8 @@ do { \
 /// \param      cur_match       Start position of the current match candidate
 /// \param      loops           Maximum length of the hash chain
 /// \param      son             lzma_mf.son (contains the hash chain)
-/// \param      cyclic_buffer_pos
-/// \param      cyclic_buffer_size
+/// \param      cyclic_pos
+/// \param      cyclic_size
 /// \param      matches         Array to hold the matches.
 /// \param      len_best        The length of the longest match found so far.
 static lzma_match *
@@ -261,22 +260,21 @@ hc_find_func(
 		uint32_t cur_match,
 		uint32_t loops,
 		uint32_t *const son,
-		const uint32_t cyclic_buffer_pos,
-		const uint32_t cyclic_buffer_size,
+		const uint32_t cyclic_pos,
+		const uint32_t cyclic_size,
 		lzma_match *matches,
 		uint32_t len_best)
 {
-	son[cyclic_buffer_pos] = cur_match;
+	son[cyclic_pos] = cur_match;
 
 	while (true) {
 		const uint32_t delta = pos - cur_match;
-		if (loops-- == 0 || delta >= cyclic_buffer_size)
+		if (loops-- == 0 || delta >= cyclic_size)
 			return matches;
 
 		const uint8_t *const pb = cur - delta;
-		cur_match = son[cyclic_buffer_pos - delta
-				+ (delta > cyclic_buffer_pos
-					? cyclic_buffer_size : 0)];
+		cur_match = son[cyclic_pos - delta
+				+ (delta > cyclic_pos ? cyclic_size : 0)];
 
 		if (pb[len_best] == cur[len_best] && pb[0] == cur[0]) {
 			uint32_t len = 0;
@@ -297,23 +295,6 @@ hc_find_func(
 	}
 }
 
-/*
-#define hc_header_find(len_min, ret_op) \
-	uint32_t len_limit = mf_avail(mf); \
-	if (mf->find_len_max <= len_limit) { \
-		len_limit = mf->find_len_max; \
-	} else if (len_limit < (len_min)) { \
-		move_pending(mf); \
-		ret_op; \
-	} \
-#define header_hc(len_min, ret_op) \
-do { \
-	if (mf_avail(mf) < (len_min)) { \
-		move_pending(mf); \
-		ret_op; \
-	} \
-} while (0)
-*/
 
 #define hc_find(len_best) \
 	call_find(hc_find_func, len_best)
@@ -321,7 +302,7 @@ do { \
 
 #define hc_skip() \
 do { \
-	mf->son[mf->cyclic_buffer_pos] = cur_match; \
+	mf->son[mf->cyclic_pos] = cur_match; \
 	move_pos(mf); \
 } while (0)
 
@@ -344,7 +325,7 @@ lzma_mf_hc3_find(lzma_mf *mf, lzma_match *matches)
 
 	uint32_t len_best = 2;
 
-	if (delta2 < mf->cyclic_buffer_size && *(cur - delta2) == *cur) {
+	if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
 		for ( ; len_best != len_limit; ++len_best)
 			if (*(cur + len_best - delta2) != cur[len_best])
 				break;
@@ -409,14 +390,14 @@ lzma_mf_hc4_find(lzma_mf *mf, lzma_match *matches)
 
 	uint32_t len_best = 1;
 
-	if (delta2 < mf->cyclic_buffer_size && *(cur - delta2) == *cur) {
+	if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
 		len_best = 2;
 		matches[0].len = 2;
 		matches[0].dist = delta2 - 1;
 		matches_count = 1;
 	}
 
-	if (delta2 != delta3 && delta3 < mf->cyclic_buffer_size
+	if (delta2 != delta3 && delta3 < mf->cyclic_size
 			&& *(cur - delta3) == *cur) {
 		len_best = 3;
 		matches[matches_count++].dist = delta3 - 1;
@@ -484,28 +465,28 @@ bt_find_func(
 		uint32_t cur_match,
 		uint32_t loops,
 		uint32_t *const son,
-		const uint32_t cyclic_buffer_pos,
-		const uint32_t cyclic_buffer_size,
+		const uint32_t cyclic_pos,
+		const uint32_t cyclic_size,
 		lzma_match *matches,
 		uint32_t len_best)
 {
-	uint32_t *ptr0 = son + (cyclic_buffer_pos << 1) + 1;
-	uint32_t *ptr1 = son + (cyclic_buffer_pos << 1);
+	uint32_t *ptr0 = son + (cyclic_pos << 1) + 1;
+	uint32_t *ptr1 = son + (cyclic_pos << 1);
 
 	uint32_t len0 = 0;
 	uint32_t len1 = 0;
 
 	while (true) {
 		const uint32_t delta = pos - cur_match;
-		if (loops-- == 0 || delta >= cyclic_buffer_size) {
+		if (loops-- == 0 || delta >= cyclic_size) {
 			*ptr0 = EMPTY_HASH_VALUE;
 			*ptr1 = EMPTY_HASH_VALUE;
 			return matches;
 		}
 
-		uint32_t *const pair = son + ((cyclic_buffer_pos - delta
-				+ (delta > cyclic_buffer_pos
-					? cyclic_buffer_size : 0)) << 1);
+		uint32_t *const pair = son + ((cyclic_pos - delta
+				+ (delta > cyclic_pos ? cyclic_size : 0))
+				<< 1);
 
 		const uint8_t *const pb = cur - delta;
 		uint32_t len = MIN(len0, len1);
@@ -552,26 +533,26 @@ bt_skip_func(
 		uint32_t cur_match,
 		uint32_t loops,
 		uint32_t *const son,
-		const uint32_t cyclic_buffer_pos,
-		const uint32_t cyclic_buffer_size)
+		const uint32_t cyclic_pos,
+		const uint32_t cyclic_size)
 {
-	uint32_t *ptr0 = son + (cyclic_buffer_pos << 1) + 1;
-	uint32_t *ptr1 = son + (cyclic_buffer_pos << 1);
+	uint32_t *ptr0 = son + (cyclic_pos << 1) + 1;
+	uint32_t *ptr1 = son + (cyclic_pos << 1);
 
 	uint32_t len0 = 0;
 	uint32_t len1 = 0;
 
 	while (true) {
 		const uint32_t delta = pos - cur_match;
-		if (loops-- == 0 || delta >= cyclic_buffer_size) {
+		if (loops-- == 0 || delta >= cyclic_size) {
 			*ptr0 = EMPTY_HASH_VALUE;
 			*ptr1 = EMPTY_HASH_VALUE;
 			return;
 		}
 
-		uint32_t *pair = son + ((cyclic_buffer_pos - delta
-				+ (delta > cyclic_buffer_pos
-					? cyclic_buffer_size : 0)) << 1);
+		uint32_t *pair = son + ((cyclic_pos - delta
+				+ (delta > cyclic_pos ? cyclic_size : 0))
+				<< 1);
 		const uint8_t *pb = cur - delta;
 		uint32_t len = MIN(len0, len1);
 
@@ -608,8 +589,8 @@ bt_skip_func(
 #define bt_skip() \
 do { \
 	bt_skip_func(len_limit, pos, cur, cur_match, mf->loops, \
-			mf->son, mf->cyclic_buffer_pos, \
-			mf->cyclic_buffer_size); \
+			mf->son, mf->cyclic_pos, \
+			mf->cyclic_size); \
 	move_pos(mf); \
 } while (0)
 
@@ -665,7 +646,7 @@ lzma_mf_bt3_find(lzma_mf *mf, lzma_match *matches)
 
 	uint32_t len_best = 2;
 
-	if (delta2 < mf->cyclic_buffer_size && *(cur - delta2) == *cur) {
+	if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
 		for ( ; len_best != len_limit; ++len_best)
 			if (*(cur + len_best - delta2) != cur[len_best])
 				break;
@@ -724,14 +705,14 @@ lzma_mf_bt4_find(lzma_mf *mf, lzma_match *matches)
 
 	uint32_t len_best = 1;
 
-	if (delta2 < mf->cyclic_buffer_size && *(cur - delta2) == *cur) {
+	if (delta2 < mf->cyclic_size && *(cur - delta2) == *cur) {
 		len_best = 2;
 		matches[0].len = 2;
 		matches[0].dist = delta2 - 1;
 		matches_count = 1;
 	}
 
-	if (delta2 != delta3 && delta3 < mf->cyclic_buffer_size
+	if (delta2 != delta3 && delta3 < mf->cyclic_size
 			&& *(cur - delta3) == *cur) {
 		len_best = 3;
 		matches[matches_count++].dist = delta3 - 1;