Some xz command line tool improvements.

src/xz/args.c

@@ -53,7 +53,7 @@ parse_real(args_info *args, int argc, char **argv)
 		OPT_FILES0,
 	};
 
-	static const char short_opts[] = "cC:dfF:hHlLkM:p:qrS:tT:vVz123456789";
+	static const char short_opts[] = "cC:defF:hHlkM:qrS:tT:vVz0123456789";
 
 	static const struct option long_opts[] = {
 		// Operation mode
@@ -77,11 +77,11 @@ parse_real(args_info *args, int argc, char **argv)
 		// Basic compression settings
 		{ "format",         required_argument, NULL,  'F' },
 		{ "check",          required_argument, NULL,  'C' },
-		{ "preset",         required_argument, NULL,  'p' },
 		{ "memory",         required_argument, NULL,  'M' },
 		{ "threads",        required_argument, NULL,  'T' },
 
-		{ "fast",           no_argument,       NULL,  '1' },
+		{ "extreme",        no_argument,       NULL,  'e' },
+		{ "fast",           no_argument,       NULL,  '0' },
 		{ "best",           no_argument,       NULL,  '9' },
 
 		// Filters
@@ -114,20 +114,12 @@ parse_real(args_info *args, int argc, char **argv)
 	while ((c = getopt_long(argc, argv, short_opts, long_opts, NULL))
 			!= -1) {
 		switch (c) {
-		// gzip-like options
-
-		case '1': case '2': case '3': case '4':
+		// Compression preset (also for decompression if --format=raw)
+		case '0': case '1': case '2': case '3': case '4':
 		case '5': case '6': case '7': case '8': case '9':
 			coder_set_preset(c - '0');
 			break;
 
-		case 'p': {
-			const uint64_t preset = str_to_uint64(
-					"preset", optarg, 1, 9);
-			coder_set_preset(preset);
-			break;
-		}
-
 		// --memory
 		case 'M':
 			// On 32-bit systems, SIZE_MAX would make more sense
@@ -162,6 +154,11 @@ parse_real(args_info *args, int argc, char **argv)
 			opt_mode = MODE_DECOMPRESS;
 			break;
 
+		// --extreme
+		case 'e':
+			coder_set_extreme();
+			break;
+
 		// --force
 		case 'f':
 			opt_force = true;

src/xz/message.c

@@ -891,8 +891,8 @@ message_help(bool long_help)
 	}
 
 	puts(_(
-"  -p, --preset=NUM    compression preset: 1-2 fast compression, 3-6 good\n"
-"                      compression, 7-9 excellent compression; default is 7"));
+"  -0 .. -9            compression preset; 0-2 fast compression, 3-5 good\n"
+"                      compression, 6-9 excellent compression; default is 6"));
 
 	puts(_(
 "  -M, --memory=NUM    use roughly NUM bytes of memory at maximum; 0 indicates\n"

src/xz/options.c

@@ -315,7 +315,7 @@ options_lzma(const char *str)
 	};
 
 	static const option_map opts[] = {
-		{ "preset", NULL,   1, 9 },
+		{ "preset", NULL,   0, 9 },
 		{ "dict",   NULL,   LZMA_DICT_SIZE_MIN,
 				(UINT32_C(1) << 30) + (UINT32_C(1) << 29) },
 		{ "lc",     NULL,   LZMA_LCLP_MIN, LZMA_LCLP_MAX },

src/xz/process.c

@@ -34,14 +34,22 @@ static lzma_filter filters[LZMA_FILTERS_MAX + 1];
 /// Number of filters. Zero indicates that we are using a preset.
 static size_t filters_count = 0;
 
-/// Number of the preset (1-9)
-static size_t preset_number = 7;
+/// Number of the preset (0-9)
+static size_t preset_number = 6;
 
-/// Indicate if no preset has been given. In that case, we will auto-adjust
-/// the compression preset so that it doesn't use too much RAM.
-// FIXME
+/// True if we should auto-adjust the compression settings to use less memory
+/// if memory usage limit is too low for the original settings.
+static bool auto_adjust = true;
+
+/// Indicate if no preset has been explicitly given. In that case, if we need
+/// to auto-adjust for lower memory usage, we won't print a warning.
 static bool preset_default = true;
 
+/// If a preset is used (no custom filter chain) and preset_extreme is true,
+/// a significantly slower compression is used to achieve slightly better
+/// compression ratio.
+static bool preset_extreme = false;
+
 /// Integrity check type
 static lzma_check check = LZMA_CHECK_CRC64;
 
@@ -63,6 +71,14 @@ coder_set_preset(size_t new_preset)
 }
 
 
+extern void
+coder_set_extreme(void)
+{
+	preset_extreme = true;
+	return;
+}
+
+
 extern void
 coder_add_filter(lzma_vli id, void *options)
 {
@@ -77,6 +93,15 @@ coder_add_filter(lzma_vli id, void *options)
 }
 
 
+static void lzma_attribute((noreturn))
+memlimit_too_small(uint64_t memory_usage, uint64_t memory_limit)
+{
+	message_fatal(_("Memory usage limit (%" PRIu64 " MiB) is too small "
+			"for the given filter setup (%" PRIu64 " MiB)"),
+			memory_limit >> 20, memory_usage >> 20);
+}
+
+
 extern void
 coder_set_compression_settings(void)
 {
@@ -99,6 +124,9 @@ coder_set_compression_settings(void)
 		}
 
 		// Get the preset for LZMA1 or LZMA2.
+		if (preset_extreme)
+			preset_number |= LZMA_PRESET_EXTREME;
+
 		if (lzma_lzma_preset(&opt_lzma, preset_number))
 			message_bug();
 
@@ -107,6 +135,8 @@ coder_set_compression_settings(void)
 				? LZMA_FILTER_LZMA1 : LZMA_FILTER_LZMA2;
 		filters[0].options = &opt_lzma;
 		filters_count = 1;
+	} else {
+		preset_default = false;
 	}
 
 	// Terminate the filter options array.
@@ -139,30 +169,77 @@ coder_set_compression_settings(void)
 		message_fatal("Unsupported filter chain or filter options");
 
 	// Print memory usage info.
-	message(V_DEBUG, _("%" PRIu64 " MiB of memory is required per thread, "
-			"limit is %" PRIu64 " MiB"),
-			memory_usage / (1024 * 1024),
-			memory_limit / (1024 * 1024));
+	message(V_DEBUG, _("%'" PRIu64 " MiB (%'" PRIu64 " B) of memory is "
+			"required per thread, "
+			"limit is %'" PRIu64 " MiB (%'" PRIu64 " B)"),
+			memory_usage >> 20, memory_usage,
+			memory_limit >> 20, memory_limit);
 
-	if (preset_default) {
-		// When no preset was explicitly requested, we use the default
-		// preset only if the memory usage limit allows. Otherwise we
-		// select a lower preset automatically.
-		while (memory_usage > memory_limit) {
-			if (preset_number == 1)
-				message_fatal(_("Memory usage limit is too "
-						"small for any internal "
-						"filter preset"));
+	if (memory_usage > memory_limit) {
+		// If --no-auto-adjust was used or we didn't find LZMA1 or
+		// LZMA2 as the last filter, give an error immediatelly.
+		// --format=raw implies --no-auto-adjust.
+		if (!auto_adjust || opt_format == FORMAT_RAW)
+			memlimit_too_small(memory_usage, memory_limit);
 
-			if (lzma_lzma_preset(&opt_lzma, --preset_number))
-				message_bug();
+		assert(opt_mode == MODE_COMPRESS);
+
+		// Look for the last filter if it is LZMA2 or LZMA1, so
+		// we can make it use less RAM. With other filters we don't
+		// know what to do.
+		size_t i = 0;
+		while (filters[i].id != LZMA_FILTER_LZMA2
+				&& filters[i].id != LZMA_FILTER_LZMA1) {
+			if (filters[i].id == LZMA_VLI_UNKNOWN)
+				memlimit_too_small(memory_usage, memory_limit);
+
+			++i;
+		}
+
+		// Decrease the dictionary size until we meet the memory
+		// usage limit. First round down to full mebibytes.
+		lzma_options_lzma *opt = filters[i].options;
+		const uint32_t orig_dict_size = opt->dict_size;
+		opt->dict_size &= ~((UINT32_C(1) << 20) - 1);
+		while (true) {
+			// If it is below 1 MiB, auto-adjusting failed. We
+			// could be more sophisticated and scale it down even
+			// more, but let's see if many complain about this
+			// version.
+			//
+			// FIXME: Displays the scaled memory usage instead
+			// of the original.
+			if (opt->dict_size < (UINT32_C(1) << 20))
+				memlimit_too_small(memory_usage, memory_limit);
 
 			memory_usage = lzma_memusage_encoder(filters);
+			if (memory_usage == UINT64_MAX)
+				message_bug();
+
+			// Accept it if it is low enough.
+			if (memory_usage <= memory_limit)
+				break;
+
+			// Otherwise 1 MiB down and try again. I hope this
+			// isn't too slow method for cases where the original
+			// dict_size is very big.
+			opt->dict_size -= UINT32_C(1) << 20;
 		}
-	} else {
-		if (memory_usage > memory_limit)
-			message_fatal(_("Memory usage limit is too small "
-					"for the given filter setup"));
+
+		// Tell the user that we decreased the dictionary size.
+		// However, omit the message if no preset or custom chain
+		// was given. FIXME: Always warn?
+		if (!preset_default)
+			message(V_WARNING, "Adjusted LZMA%c dictionary size "
+					"from %'" PRIu32 " MiB to "
+					"%'" PRIu32 " MiB to not exceed "
+					"the memory usage limit of "
+					"%'" PRIu64 " MiB",
+					filters[i].id == LZMA_FILTER_LZMA2
+						? '2' : '1',
+					orig_dict_size >> 20,
+					opt->dict_size >> 20,
+					memory_limit >> 20);
 	}
 
 	// Limit the number of worker threads so that memory usage
@@ -224,8 +301,8 @@ coder_init(void)
 			break;
 
 		case FORMAT_RAW:
-			// Memory usage has already been checked in args.c.
-			// FIXME Comment
+			// Memory usage has already been checked in
+			// coder_set_compression_settings().
 			ret = lzma_raw_decoder(&strm, filters);
 			break;
 		}

src/xz/process.h

@@ -57,6 +57,9 @@ extern void coder_set_check(lzma_check check);
 /// Set preset number
 extern void coder_set_preset(size_t new_preset);
 
+/// Enable extreme mode
+extern void coder_set_extreme(void);
+
 /// Add a filter to the custom filter chain
 extern void coder_add_filter(lzma_vli id, void *options);