xz: Add --block-size=SIZE.

This uses LZMA_FULL_FLUSH every SIZE bytes of input.

Man page wasn't updated yet.

src/xz/args.c

@@ -72,6 +72,7 @@ parse_real(args_info *args, int argc, char **argv)
 		OPT_NO_SPARSE,
 		OPT_FILES,
 		OPT_FILES0,
+		OPT_BLOCK_SIZE,
 		OPT_MEM_COMPRESS,
 		OPT_MEM_DECOMPRESS,
 		OPT_NO_ADJUST,
@@ -105,6 +106,7 @@ parse_real(args_info *args, int argc, char **argv)
 		// Basic compression settings
 		{ "format",       required_argument, NULL,  'F' },
 		{ "check",        required_argument, NULL,  'C' },
+		{ "block-size",   required_argument, NULL,  OPT_BLOCK_SIZE },
 		{ "memlimit-compress",   required_argument, NULL, OPT_MEM_COMPRESS },
 		{ "memlimit-decompress", required_argument, NULL, OPT_MEM_DECOMPRESS },
 		{ "memlimit",     required_argument, NULL,  'M' },
@@ -370,6 +372,11 @@ parse_real(args_info *args, int argc, char **argv)
 			break;
 		}
 
+		case OPT_BLOCK_SIZE:
+			opt_block_size = str_to_uint64("block-size", optarg,
+					0, LZMA_VLI_MAX);
+			break;
+
 		case OPT_SINGLE_STREAM:
 			opt_single_stream = true;
 			break;

src/xz/coder.c

@@ -25,6 +25,7 @@ enum operation_mode opt_mode = MODE_COMPRESS;
 enum format_type opt_format = FORMAT_AUTO;
 bool opt_auto_adjust = true;
 bool opt_single_stream = false;
+uint64_t opt_block_size = 0;
 
 
 /// Stream used to communicate with liblzma
@@ -461,8 +462,8 @@ coder_normal(file_pair *pair)
 	// Encoder needs to know when we have given all the input to it.
 	// The decoders need to know it too when we are using
 	// LZMA_CONCATENATED. We need to check for src_eof here, because
-	// the first input chunk has been already read, and that may
-	// have been the only chunk we will read.
+	// the first input chunk has been already read if decompressing,
+	// and that may have been the only chunk we will read.
 	lzma_action action = pair->src_eof ? LZMA_FINISH : LZMA_RUN;
 
 	lzma_ret ret;
@@ -470,6 +471,16 @@ coder_normal(file_pair *pair)
 	// Assume that something goes wrong.
 	bool success = false;
 
+	// block_remaining indicates how many input bytes to encode until
+	// finishing the current .xz Block. The Block size is set with
+	// --block-size=SIZE. It has an effect only when compressing
+	// to the .xz format. If block_remaining == UINT64_MAX, only
+	// a single block is created.
+	uint64_t block_remaining = UINT64_MAX;
+	if (opt_mode == MODE_COMPRESS && opt_format == FORMAT_XZ
+			&& opt_block_size > 0)
+		block_remaining = opt_block_size;
+
 	strm.next_out = out_buf.u8;
 	strm.avail_out = IO_BUFFER_SIZE;
 
@@ -478,14 +489,23 @@ coder_normal(file_pair *pair)
 		// end of file yet.
 		if (strm.avail_in == 0 && !pair->src_eof) {
 			strm.next_in = in_buf.u8;
-			strm.avail_in = io_read(
-					pair, &in_buf, IO_BUFFER_SIZE);
+			strm.avail_in = io_read(pair, &in_buf,
+					my_min(block_remaining,
+						IO_BUFFER_SIZE));
 
 			if (strm.avail_in == SIZE_MAX)
 				break;
 
-			if (pair->src_eof)
+			if (pair->src_eof) {
 				action = LZMA_FINISH;
+
+			} else if (block_remaining != UINT64_MAX) {
+				// Start a new Block after every
+				// opt_block_size bytes of input.
+				block_remaining -= strm.avail_in;
+				if (block_remaining == 0)
+					action = LZMA_FULL_FLUSH;
+			}
 		}
 
 		// Let liblzma do the actual work.
@@ -501,7 +521,12 @@ coder_normal(file_pair *pair)
 			strm.avail_out = IO_BUFFER_SIZE;
 		}
 
-		if (ret != LZMA_OK) {
+		if (ret == LZMA_STREAM_END && action == LZMA_FULL_FLUSH) {
+			// Start a new Block.
+			action = LZMA_RUN;
+			block_remaining = opt_block_size;
+
+		} else if (ret != LZMA_OK) {
 			// Determine if the return value indicates that we
 			// won't continue coding.
 			const bool stop = ret != LZMA_NO_CHECK
@@ -627,10 +652,15 @@ coder_run(const char *filename)
 	// Assume that something goes wrong.
 	bool success = false;
 
-	// Read the first chunk of input data. This is needed to detect
-	// the input file type (for now, only for decompression).
-	strm.next_in = in_buf.u8;
-	strm.avail_in = io_read(pair, &in_buf, IO_BUFFER_SIZE);
+	if (opt_mode == MODE_COMPRESS) {
+		strm.next_in = NULL;
+		strm.avail_in = 0;
+	} else {
+		// Read the first chunk of input data. This is needed
+		// to detect the input file type.
+		strm.next_in = in_buf.u8;
+		strm.avail_in = io_read(pair, &in_buf, IO_BUFFER_SIZE);
+	}
 
 	if (strm.avail_in != SIZE_MAX) {
 		// Initialize the coder. This will detect the file format

src/xz/coder.h

@@ -44,6 +44,9 @@ extern bool opt_auto_adjust;
 /// If true, stop after decoding the first stream.
 extern bool opt_single_stream;
 
+/// If non-zero, start a new .xz Block after every opt_block_size bytes
+/// of input. This has an effect only when compressing to the .xz format.
+extern uint64_t opt_block_size;
 
 /// Set the integrity check type used when compressing
 extern void coder_set_check(lzma_check check);

src/xz/message.c

@@ -1128,6 +1128,10 @@ message_help(bool long_help)
 "                      `auto' (default), `xz', `lzma', and `raw'\n"
 "  -C, --check=CHECK   integrity check type: `none' (use with caution),\n"
 "                      `crc32', `crc64' (default), or `sha256'"));
+		puts(_(
+"      --block-size=SIZE\n"
+"                      when compressing to the .xz format, start a new block\n"
+"                      after every SIZE bytes of input; 0=disabled (default)"));
 	}
 
 	puts(_(