liblzma: Add new API function lzma_filters_free().

This is small but convenient and should have been added
a long time ago.

4 files changed, 49 insertions, 0 deletions

diff --git a/src/liblzma/api/lzma/filter.h b/src/liblzma/api/lzma/filter.h
index 5ec9976d..41c5895e 100644
--- a/src/liblzma/api/lzma/filter.h
+++ b/src/liblzma/api/lzma/filter.h
@@ -125,6 +125,27 @@ extern LZMA_API(lzma_ret) lzma_filters_copy(
 
 
 /**
+ * \brief       Free the options in the array of lzma_filter structures
+ *
+ * This frees the filter chain options. The filters array itself is not freed.
+ *
+ * The filters array must have at most LZMA_FILTERS_MAX + 1 elements
+ * including the terminating element which must have .id = LZMA_VLI_UNKNOWN.
+ * For all elements before the terminating element:
+ *   - options will be freed using the given lzma_allocator or,
+ *     if allocator is NULL, using free().
+ *   - options will be set to NULL.
+ *   - id will be set to LZMA_VLI_UNKNOWN.
+ *
+ * If filters is NULL, this does nothing but remember that this never frees
+ * the filters array itself.
+ */
+extern LZMA_API(void) lzma_filters_free(
+		lzma_filter *filters, const lzma_allocator *allocator)
+		lzma_nothrow;
+
+
+/**
  * \brief       Calculate approximate memory requirements for raw encoder
  *
  * This function can be used to calculate the memory requirements for
diff --git a/src/liblzma/common/filter_common.c b/src/liblzma/common/filter_common.c
index 0113035b..a803b4c2 100644
--- a/src/liblzma/common/filter_common.c
+++ b/src/liblzma/common/filter_common.c
@@ -205,6 +205,32 @@ error:
 }
 
 
+extern LZMA_API(void)
+lzma_filters_free(lzma_filter *filters, const lzma_allocator *allocator)
+{
+	if (filters == NULL)
+		return;
+
+	for (size_t i = 0; filters[i].id != LZMA_VLI_UNKNOWN; ++i) {
+		if (i == LZMA_FILTERS_MAX) {
+			// The API says that LZMA_FILTERS_MAX + 1 is the
+			// maximum allowed size including the terminating
+			// element. Thus, we should never get here but in
+			// case there is a bug and we do anyway, don't go
+			// past the (probable) end of the array.
+			assert(0);
+			break;
+		}
+
+		lzma_free(filters[i].options, allocator);
+		filters[i].options = NULL;
+		filters[i].id = LZMA_VLI_UNKNOWN;
+	}
+
+	return;
+}
+
+
 static lzma_ret
 validate_chain(const lzma_filter *filters, size_t *count)
 {
diff --git a/src/liblzma/liblzma_generic.map b/src/liblzma/liblzma_generic.map
index 7b9cec7a..3e3c52d5 100644
--- a/src/liblzma/liblzma_generic.map
+++ b/src/liblzma/liblzma_generic.map
@@ -114,4 +114,5 @@ global:
 	lzma_file_info_decoder;
 	lzma_stream_decoder_mt;
 	lzma_lzip_decoder;
+	lzma_filters_free;
 } XZ_5.2;
diff --git a/src/liblzma/liblzma_linux.map b/src/liblzma/liblzma_linux.map
index 89719ddb..7f320d8f 100644
--- a/src/liblzma/liblzma_linux.map
+++ b/src/liblzma/liblzma_linux.map
@@ -129,4 +129,5 @@ global:
 	lzma_file_info_decoder;
 	lzma_stream_decoder_mt;
 	lzma_lzip_decoder;
+	lzma_filters_free;
 } XZ_5.2;