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.

4 files changed, 20 insertions, 7 deletions

diff --git a/src/liblzma/delta/delta_common.c b/src/liblzma/delta/delta_common.c
index 6d55ff65..930ad215 100644
--- a/src/liblzma/delta/delta_common.c
+++ b/src/liblzma/delta/delta_common.c
@@ -25,7 +25,7 @@ delta_coder_end(lzma_coder *coder, lzma_allocator *allocator)
 
 extern lzma_ret
 lzma_delta_coder_init(lzma_next_coder *next, lzma_allocator *allocator,
-		const lzma_filter_info *filters, lzma_code_function code)
+		const lzma_filter_info *filters)
 {
 	// Allocate memory for the decoder if needed.
 	if (next->coder == NULL) {
@@ -38,9 +38,6 @@ lzma_delta_coder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		next->coder->next = LZMA_NEXT_CODER_INIT;
 	}
 
-	// Coding function is different for encoder and decoder.
-	next->code = code;
-
 	// Validate the options.
 	if (lzma_delta_coder_memusage(filters[0].options) == UINT64_MAX)
 		return LZMA_OPTIONS_ERROR;
diff --git a/src/liblzma/delta/delta_decoder.c b/src/liblzma/delta/delta_decoder.c
index 2ddf163d..2cf60d5b 100644
--- a/src/liblzma/delta/delta_decoder.c
+++ b/src/liblzma/delta/delta_decoder.c
@@ -50,7 +50,8 @@ extern lzma_ret
 lzma_delta_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		const lzma_filter_info *filters)
 {
-	return lzma_delta_coder_init(next, allocator, filters, &delta_decode);
+	next->code = &delta_decode;
+	return lzma_delta_coder_init(next, allocator, filters);
 }
 
 
diff --git a/src/liblzma/delta/delta_encoder.c b/src/liblzma/delta/delta_encoder.c
index 0244673e..80d0d176 100644
--- a/src/liblzma/delta/delta_encoder.c
+++ b/src/liblzma/delta/delta_encoder.c
@@ -83,11 +83,26 @@ delta_encode(lzma_coder *coder, lzma_allocator *allocator,
 }
 
 
+static lzma_ret
+delta_encoder_update(lzma_coder *coder, lzma_allocator *allocator,
+		const lzma_filter *filters_null lzma_attribute((unused)),
+		const lzma_filter *reversed_filters)
+{
+	// Delta doesn't and will never support changing the options in
+	// the middle of encoding. If the app tries to change them, we
+	// simply ignore them.
+	return lzma_next_filter_update(
+			&coder->next, allocator, reversed_filters + 1);
+}
+
+
 extern lzma_ret
 lzma_delta_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 		const lzma_filter_info *filters)
 {
-	return lzma_delta_coder_init(next, allocator, filters, &delta_encode);
+	next->code = &delta_encode;
+	next->update = &delta_encoder_update;
+	return lzma_delta_coder_init(next, allocator, filters);
 }
 
 
diff --git a/src/liblzma/delta/delta_private.h b/src/liblzma/delta/delta_private.h
index 69be82e2..62b7fed8 100644
--- a/src/liblzma/delta/delta_private.h
+++ b/src/liblzma/delta/delta_private.h
@@ -32,6 +32,6 @@ struct lzma_coder_s {
 
 extern lzma_ret lzma_delta_coder_init(
 		lzma_next_coder *next, lzma_allocator *allocator,
-		const lzma_filter_info *filters, lzma_code_function code);
+		const lzma_filter_info *filters);
 
 #endif