Add lzma_filters_copy().

This will be needed internally by liblzma once I fix
a design mistake in the encoder API. This function may
be useful to applications too so it's good to export it.

src/liblzma/api/lzma/filter.h

@@ -94,6 +94,37 @@ extern LZMA_API(lzma_bool) lzma_filter_decoder_is_supported(lzma_vli id)
 		lzma_nothrow lzma_attr_const;
 
 
+/**
+ * \brief       Copy the filters array
+ *
+ * Copy the Filter IDs and filter-specific options from src to dest.
+ * Up to LZMA_FILTERS_MAX filters are copied, plus the terminating
+ * .id == LZMA_VLI_UNKNOWN. Thus, dest should have at least
+ * LZMA_FILTERS_MAX + 1 elements space unless the caller knows that
+ * src is smaller than that.
+ *
+ * Unless the filter-specific options is NULL, the Filter ID has to be
+ * supported by liblzma, because liblzma needs to know the size of every
+ * filter-specific options structure. The filter-specific options are not
+ * validated. If options is NULL, any unsupported Filter IDs are copied
+ * without returning an error.
+ *
+ * Old filter-specific options in dest are not freed, so dest doesn't
+ * need to be initialized by the caller in any way.
+ *
+ * If an error occurs, memory possibly already allocated by this function
+ * is always freed.
+ *
+ * \return      - LZMA_OK
+ *              - LZMA_MEM_ERROR
+ *              - LZMA_OPTIONS_ERROR: Unsupported Filter ID and its options
+ *                is not NULL.
+ *              - LZMA_PROG_ERROR: src or dest is NULL.
+ */
+extern LZMA_API(lzma_ret) lzma_filters_dup(const lzma_filter *src,
+		lzma_filter *dest, lzma_allocator *allocator);
+
+
 /**
  * \brief       Calculate rough memory requirements for raw encoder
  *

src/liblzma/common/filter_common.c

@@ -17,6 +17,9 @@ static const struct {
 	/// Filter ID
 	lzma_vli id;
 
+	/// Size of the filter-specific options structure
+	size_t options_size;
+
 	/// True if it is OK to use this filter as non-last filter in
 	/// the chain.
 	bool non_last_ok;
@@ -34,6 +37,7 @@ static const struct {
 #if defined (HAVE_ENCODER_LZMA1) || defined(HAVE_DECODER_LZMA1)
 	{
 		.id = LZMA_FILTER_LZMA1,
+		.options_size = sizeof(lzma_options_lzma),
 		.non_last_ok = false,
 		.last_ok = true,
 		.changes_size = true,
@@ -42,6 +46,7 @@ static const struct {
 #ifdef HAVE_DECODER_LZMA2
 	{
 		.id = LZMA_FILTER_LZMA2,
+		.options_size = sizeof(lzma_options_lzma),
 		.non_last_ok = false,
 		.last_ok = true,
 		.changes_size = true,
@@ -50,6 +55,7 @@ static const struct {
 #if defined(HAVE_ENCODER_SUBBLOCK) || defined(HAVE_DECODER_SUBBLOCK)
 	{
 		.id = LZMA_FILTER_SUBBLOCK,
+		.options_size = sizeof(lzma_options_subblock),
 		.non_last_ok = true,
 		.last_ok = true,
 		.changes_size = true,
@@ -58,6 +64,7 @@ static const struct {
 #ifdef HAVE_DECODER_X86
 	{
 		.id = LZMA_FILTER_X86,
+		.options_size = sizeof(lzma_options_bcj),
 		.non_last_ok = true,
 		.last_ok = false,
 		.changes_size = false,
@@ -66,6 +73,7 @@ static const struct {
 #if defined(HAVE_ENCODER_POWERPC) || defined(HAVE_DECODER_POWERPC)
 	{
 		.id = LZMA_FILTER_POWERPC,
+		.options_size = sizeof(lzma_options_bcj),
 		.non_last_ok = true,
 		.last_ok = false,
 		.changes_size = false,
@@ -74,6 +82,7 @@ static const struct {
 #ifdef HAVE_DECODER_IA64
 	{
 		.id = LZMA_FILTER_IA64,
+		.options_size = sizeof(lzma_options_bcj),
 		.non_last_ok = true,
 		.last_ok = false,
 		.changes_size = false,
@@ -82,6 +91,7 @@ static const struct {
 #if defined(HAVE_ENCODER_ARM) || defined(HAVE_DECODER_ARM)
 	{
 		.id = LZMA_FILTER_ARM,
+		.options_size = sizeof(lzma_options_bcj),
 		.non_last_ok = true,
 		.last_ok = false,
 		.changes_size = false,
@@ -90,6 +100,7 @@ static const struct {
 #if defined(HAVE_ENCODER_ARMTHUMB) || defined(HAVE_DECODER_ARMTHUMB)
 	{
 		.id = LZMA_FILTER_ARMTHUMB,
+		.options_size = sizeof(lzma_options_bcj),
 		.non_last_ok = true,
 		.last_ok = false,
 		.changes_size = false,
@@ -98,6 +109,7 @@ static const struct {
 #if defined(HAVE_ENCODER_SPARC) || defined(HAVE_DECODER_SPARC)
 	{
 		.id = LZMA_FILTER_SPARC,
+		.options_size = sizeof(lzma_options_bcj),
 		.non_last_ok = true,
 		.last_ok = false,
 		.changes_size = false,
@@ -106,6 +118,7 @@ static const struct {
 #if defined(HAVE_ENCODER_DELTA) || defined(HAVE_DECODER_DELTA)
 	{
 		.id = LZMA_FILTER_DELTA,
+		.options_size = sizeof(lzma_options_delta),
 		.non_last_ok = true,
 		.last_ok = false,
 		.changes_size = false,
@@ -117,6 +130,75 @@ static const struct {
 };
 
 
+extern LZMA_API(lzma_ret)
+lzma_filters_dup(const lzma_filter *src, lzma_filter *dest,
+		lzma_allocator *allocator)
+{
+	if (src == NULL || dest == NULL)
+		return LZMA_PROG_ERROR;
+
+	lzma_ret ret;
+	size_t i;
+	for (i = 0; src[i].id != LZMA_VLI_UNKNOWN; ++i) {
+		// There must be a maximum of four filters plus
+		// the array terminator.
+		if (i == LZMA_FILTERS_MAX) {
+			ret = LZMA_OPTIONS_ERROR;
+			goto error;
+		}
+
+		dest[i].id = src[i].id;
+
+		if (src[i].options == NULL) {
+			dest[i].options = NULL;
+		} else {
+			// See if the filter is supported only when the
+			// options is not NULL. This might be convenient
+			// sometimes if the app is actually copying only
+			// a partial filter chain with a place holder ID.
+			//
+			// When options is not NULL, the Filter ID must be
+			// supported by us, because otherwise we don't know
+			// how big the options are.
+			size_t j;
+			for (j = 0; src[i].id != features[j].id; ++j) {
+				if (features[j].id == LZMA_VLI_UNKNOWN) {
+					ret = LZMA_OPTIONS_ERROR;
+					goto error;
+				}
+			}
+
+			// Allocate and copy the options.
+			dest[i].options = lzma_alloc(features[j].options_size,
+					allocator);
+			if (dest[i].options == NULL) {
+				ret = LZMA_MEM_ERROR;
+				goto error;
+			}
+
+			memcpy(dest[i].options, src[i].options,
+					features[j].options_size);
+		}
+	}
+
+	// Terminate the filter array.
+	assert(i <= LZMA_FILTERS_MAX + 1);
+	dest[i].id = LZMA_VLI_UNKNOWN;
+	dest[i].options = NULL;
+
+	return LZMA_OK;
+
+error:
+	// Free the options which we have already allocated.
+	while (i-- > 0) {
+		lzma_free(dest[i].options, allocator);
+		dest[i].options = NULL;
+	}
+
+	return ret;
+}
+
+
 static lzma_ret
 validate_chain(const lzma_filter *filters, size_t *count)
 {