Fix a design error in liblzma API.

Originally the idea was that using LZMA_FULL_FLUSH
with Stream encoder would read the filter chain
from the same array that was used to intialize the
Stream encoder. Since most apps wouldn't use
LZMA_FULL_FLUSH, most apps wouldn't need to keep
the filter chain available after initializing the
Stream encoder. However, due to my mistake, it
actually required keeping the array always available.

Since setting the new filter chain via the array
used at initialization time is not a nice way to do
it for a couple of reasons, this commit ditches it
and introduces lzma_filters_update(). This new function
replaces also the "persistent" flag used by LZMA2
(and to-be-designed Subblock filter), which was also
an ugly thing to do.

Thanks to Alexey Tourbin for reminding me about the problem
that Stream encoder used to require keeping the filter
chain allocated.

2 files changed, 34 insertions, 26 deletions

diff --git a/src/liblzma/lzma/lzma2_encoder.c b/src/liblzma/lzma/lzma2_encoder.c
index 8db81368..aa3216cc 100644
--- a/src/liblzma/lzma/lzma2_encoder.c
+++ b/src/liblzma/lzma/lzma2_encoder.c
@@ -29,10 +29,6 @@ struct lzma_coder_s {
 	/// LZMA encoder
 	lzma_coder *lzma;
 
-	/// If this is not NULL, we will check new options from this
-	/// structure when starting a new chunk.
-	const lzma_options_lzma *opt_new;
-
 	/// LZMA options currently in use.
 	lzma_options_lzma opt_cur;
 
@@ -155,25 +151,6 @@ lzma2_encode(lzma_coder *restrict coder, lzma_mf *restrict mf,
 					? LZMA_OK : LZMA_STREAM_END;
 		}
 
-		// Look if there are new options. At least for now,
-		// only lc/lp/pb can be changed.
-		if (coder->opt_new != NULL
-				&& (coder->opt_cur.lc != coder->opt_new->lc
-				|| coder->opt_cur.lp != coder->opt_new->lp
-				|| coder->opt_cur.pb != coder->opt_new->pb)) {
-			// Options have been changed, copy them to opt_cur.
-			// These get validated as part of
-			// lzma_lzma_encoder_reset() below.
-			coder->opt_cur.lc = coder->opt_new->lc;
-			coder->opt_cur.lp = coder->opt_new->lp;
-			coder->opt_cur.pb = coder->opt_new->pb;
-
-			// We need to write the new options and reset
-			// the encoder state.
-			coder->need_properties = true;
-			coder->need_state_reset = true;
-		}
-
 		if (coder->need_state_reset)
 			return_if_error(lzma_lzma_encoder_reset(
 					coder->lzma, &coder->opt_cur));
@@ -294,6 +271,39 @@ lzma2_encoder_end(lzma_coder *coder, lzma_allocator *allocator)
 
 
 static lzma_ret
+lzma2_encoder_options_update(lzma_coder *coder, const lzma_filter *filter)
+{
+	// New options can be set only when there is no incomplete chunk.
+        // This is the case at the beginning of the raw stream and right
+        // after LZMA_SYNC_FLUSH.
+        if (filter->options == NULL || coder->sequence != SEQ_INIT)
+		return LZMA_PROG_ERROR;
+
+	// Look if there are new options. At least for now,
+	// only lc/lp/pb can be changed.
+	const lzma_options_lzma *opt = filter->options;
+	if (coder->opt_cur.lc != opt->lc || coder->opt_cur.lp != opt->lp
+			|| coder->opt_cur.pb != opt->pb) {
+		// Validate the options.
+		if (opt->lc > LZMA_LCLP_MAX || opt->lp > LZMA_LCLP_MAX
+				|| opt->lc + opt->lp > LZMA_LCLP_MAX
+				|| opt->pb > LZMA_PB_MAX)
+			return LZMA_OPTIONS_ERROR;
+
+		// The new options will be used when the encoder starts
+		// a new LZMA2 chunk.
+		coder->opt_cur.lc = opt->lc;
+		coder->opt_cur.lp = opt->lp;
+		coder->opt_cur.pb = opt->pb;
+		coder->need_properties = true;
+		coder->need_state_reset = true;
+	}
+
+	return LZMA_OK;
+}
+
+
+static lzma_ret
 lzma2_encoder_init(lzma_lz_encoder *lz, lzma_allocator *allocator,
 		const void *options, lzma_lz_options *lz_options)
 {
@@ -307,13 +317,12 @@ lzma2_encoder_init(lzma_lz_encoder *lz, lzma_allocator *allocator,
 
 		lz->code = &lzma2_encode;
 		lz->end = &lzma2_encoder_end;
+		lz->options_update = &lzma2_encoder_options_update;
 
 		lz->coder->lzma = NULL;
 	}
 
 	lz->coder->opt_cur = *(const lzma_options_lzma *)(options);
-	lz->coder->opt_new = lz->coder->opt_cur.persistent
-				? options : NULL;
 
 	lz->coder->sequence = SEQ_INIT;
 	lz->coder->need_properties = true;
diff --git a/src/liblzma/lzma/lzma_encoder_presets.c b/src/liblzma/lzma/lzma_encoder_presets.c
index 68900a9b..c4c9c146 100644
--- a/src/liblzma/lzma/lzma_encoder_presets.c
+++ b/src/liblzma/lzma/lzma_encoder_presets.c
@@ -33,7 +33,6 @@ lzma_lzma_preset(lzma_options_lzma *options, uint32_t preset)
 	options->lp = LZMA_LP_DEFAULT;
 	options->pb = LZMA_PB_DEFAULT;
 
-	options->persistent = false;
 	options->mode = level <= 2 ? LZMA_MODE_FAST : LZMA_MODE_NORMAL;
 
 	options->nice_len = level == 0 ? 8 : level <= 5 ? 32 : 64;