liblzma: Add LZMA_FULL_BARRIER support to single-threaded encoder.

In the single-threaded encoder LZMA_FULL_BARRIER is simply
an alias for LZMA_FULL_FLUSH.

src/liblzma/api/lzma/base.h

@@ -240,12 +240,12 @@ typedef enum {
 /**
  * \brief       The `action' argument for lzma_code()
  *
- * After the first use of LZMA_SYNC_FLUSH, LZMA_FULL_FLUSH, or LZMA_FINISH,
+ * After the first use of LZMA_SYNC_FLUSH, LZMA_FULL_FLUSH, LZMA_FULL_BARRIER,
- * the same `action' must is used until lzma_code() returns LZMA_STREAM_END.
+ * or LZMA_FINISH, the same `action' must is used until lzma_code() returns
- * Also, the amount of input (that is, strm->avail_in) must not be modified
+ * LZMA_STREAM_END. Also, the amount of input (that is, strm->avail_in) must
- * by the application until lzma_code() returns LZMA_STREAM_END. Changing the
+ * not be modified by the application until lzma_code() returns
- * `action' or modifying the amount of input will make lzma_code() return
+ * LZMA_STREAM_END. Changing the `action' or modifying the amount of input
- * LZMA_PROG_ERROR.
+ * will make lzma_code() return LZMA_PROG_ERROR.
  */
 typedef enum {
 	LZMA_RUN = 0,
@@ -302,6 +302,29 @@ typedef enum {
 		 * no unfinished Block, no empty Block is created.
 		 */
 
+	LZMA_FULL_BARRIER = 4,
+		/**<
+		 * \brief       Finish encoding of the current Block
+		 *
+		 * This is like LZMA_FULL_FLUSH except that this doesn't
+		 * necessarily wait until all the input has been made
+		 * available via the output buffer. That is, lzma_code()
+		 * might return LZMA_STREAM_END as soon as all the input
+		 * has been consumed (avail_in == 0).
+		 *
+		 * LZMA_FULL_BARRIER is useful with a threaded encoder if
+		 * one wants to split the .xz Stream into Blocks at specific
+		 * offsets but doesn't care if the output isn't flushed
+		 * immediately. Using LZMA_FULL_BARRIER allows keeping
+		 * the threads busy while LZMA_FULL_FLUSH would make
+		 * lzma_code() wait until all the threads have finished
+		 * until more data could be passed to the encoder.
+		 *
+		 * With a lzma_stream initialized with the single-threaded
+		 * lzma_stream_encoder() or lzma_easy_encoder(),
+		 * LZMA_FULL_BARRIER is an alias for LZMA_FULL_FLUSH.
+		 */
+
 	LZMA_FINISH = 3
 		/**<
 		 * \brief       Finish the coding operation

src/liblzma/common/common.c

@@ -176,7 +176,7 @@ lzma_code(lzma_stream *strm, lzma_action action)
 			|| (strm->next_out == NULL && strm->avail_out != 0)
 			|| strm->internal == NULL
 			|| strm->internal->next.code == NULL
-			|| (unsigned int)(action) > LZMA_FINISH
+			|| (unsigned int)(action) > LZMA_ACTION_MAX
 			|| !strm->internal->supported_actions[action])
 		return LZMA_PROG_ERROR;
 
@@ -211,6 +211,10 @@ lzma_code(lzma_stream *strm, lzma_action action)
 		case LZMA_FINISH:
 			strm->internal->sequence = ISEQ_FINISH;
 			break;
+
+		case LZMA_FULL_BARRIER:
+			strm->internal->sequence = ISEQ_FULL_BARRIER;
+			break;
 		}
 
 		break;
@@ -238,6 +242,13 @@ lzma_code(lzma_stream *strm, lzma_action action)
 
 		break;
 
+	case ISEQ_FULL_BARRIER:
+		if (action != LZMA_FULL_BARRIER
+				|| strm->internal->avail_in != strm->avail_in)
+			return LZMA_PROG_ERROR;
+
+		break;
+
 	case ISEQ_END:
 		return LZMA_STREAM_END;
 
@@ -288,7 +299,9 @@ lzma_code(lzma_stream *strm, lzma_action action)
 
 	case LZMA_STREAM_END:
 		if (strm->internal->sequence == ISEQ_SYNC_FLUSH
-				|| strm->internal->sequence == ISEQ_FULL_FLUSH)
+				|| strm->internal->sequence == ISEQ_FULL_FLUSH
+				|| strm->internal->sequence
+					== ISEQ_FULL_BARRIER)
 			strm->internal->sequence = ISEQ_RUN;
 		else
 			strm->internal->sequence = ISEQ_END;

src/liblzma/common/common.h

@@ -78,6 +78,10 @@
 	| LZMA_CONCATENATED )
 
 
+/// Largest valid lzma_action value as unsigned integer.
+#define LZMA_ACTION_MAX ((unsigned int)(LZMA_FULL_BARRIER))
+
+
 /// Special return value (lzma_ret) to indicate that a timeout was reached
 /// and lzma_code() must not return LZMA_BUF_ERROR. This is converted to
 /// LZMA_OK in lzma_code(). This is not in the lzma_ret enumeration because
@@ -207,6 +211,7 @@ struct lzma_internal_s {
 		ISEQ_SYNC_FLUSH,
 		ISEQ_FULL_FLUSH,
 		ISEQ_FINISH,
+		ISEQ_FULL_BARRIER,
 		ISEQ_END,
 		ISEQ_ERROR,
 	} sequence;
@@ -217,7 +222,7 @@ struct lzma_internal_s {
 	size_t avail_in;
 
 	/// Indicates which lzma_action values are allowed by next.code.
-	bool supported_actions[4];
+	bool supported_actions[LZMA_ACTION_MAX + 1];
 
 	/// If true, lzma_code will return LZMA_BUF_ERROR if no progress was
 	/// made (no input consumed and no output produced by next.code).

src/liblzma/common/stream_encoder.c

@@ -146,11 +146,12 @@ stream_encode(lzma_coder *coder, const lzma_allocator *allocator,
 	}
 
 	case SEQ_BLOCK_ENCODE: {
-		static const lzma_action convert[4] = {
+		static const lzma_action convert[LZMA_ACTION_MAX + 1] = {
 			LZMA_RUN,
 			LZMA_SYNC_FLUSH,
 			LZMA_FINISH,
 			LZMA_FINISH,
+			LZMA_FINISH,
 		};
 
 		const lzma_ret ret = coder->block_encoder.code(
@@ -324,6 +325,7 @@ lzma_stream_encoder(lzma_stream *strm,
 	strm->internal->supported_actions[LZMA_RUN] = true;
 	strm->internal->supported_actions[LZMA_SYNC_FLUSH] = true;
 	strm->internal->supported_actions[LZMA_FULL_FLUSH] = true;
+	strm->internal->supported_actions[LZMA_FULL_BARRIER] = true;
 	strm->internal->supported_actions[LZMA_FINISH] = true;
 
 	return LZMA_OK;