From 9134b5ba8b2035df89c4be65484cbadc702f1161 Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Date: Tue, 21 May 2019 00:26:55 +0200
Subject: Add options for zstd compressor

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
---
 lib/comp/zstd.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 61 insertions(+), 6 deletions(-)

diff --git a/lib/comp/zstd.c b/lib/comp/zstd.c
index 4cbef38..2868cbf 100644
--- a/lib/comp/zstd.c
+++ b/lib/comp/zstd.c
@@ -3,6 +3,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
+#include <ctype.h>
 
 #include <zstd.h>
 
@@ -13,19 +14,36 @@
 typedef struct {
 	compressor_t base;
 	ZSTD_CCtx *zctx;
+	int level;
 } zstd_compressor_t;
 
+typedef struct {
+	uint32_t level;
+} zstd_options_t;
+
 static int zstd_write_options(compressor_t *base, int fd)
 {
-	(void)base; (void)fd;
-	return 0;
+	zstd_compressor_t *zstd = (zstd_compressor_t *)base;
+	zstd_options_t opt;
+	(void)fd;
+
+	if (zstd->level == ZSTD_DEFAULT_COMPRESSION_LEVEL)
+		return 0;
+
+	opt.level = htole32(zstd->level);
+	return generic_write_options(fd, &opt, sizeof(opt));
 }
 
 static int zstd_read_options(compressor_t *base, int fd)
 {
-	(void)base; (void)fd;
-	fputs("zstd extra options are not yet implemented\n", stderr);
-	return -1;
+	zstd_options_t opt;
+	(void)base;
+
+	if (generic_read_options(fd, &opt, sizeof(opt)))
+		return -1;
+
+	opt.level = le32toh(opt.level);
+	return 0;
 }
 
 static ssize_t zstd_comp_block(compressor_t *base, const uint8_t *in,
@@ -35,7 +53,7 @@ static ssize_t zstd_comp_block(compressor_t *base, const uint8_t *in,
 	size_t ret;
 
 	ret = ZSTD_compressCCtx(zstd->zctx, out, outsize, in, size,
-				ZSTD_DEFAULT_COMPRESSION_LEVEL);
+				zstd->level);
 
 	if (ZSTD_isError(ret)) {
 		fputs("internal error in ZSTD compressor\n", stderr);
@@ -74,6 +92,7 @@ compressor_t *create_zstd_compressor(bool compress, size_t block_size,
 {
 	zstd_compressor_t *zstd = calloc(1, sizeof(*zstd));
 	compressor_t *base = (compressor_t *)zstd;
+	size_t i;
 	(void)block_size;
 
 	if (zstd == NULL) {
@@ -81,6 +100,27 @@ compressor_t *create_zstd_compressor(bool compress, size_t block_size,
 		return NULL;
 	}
 
+	zstd->level = ZSTD_DEFAULT_COMPRESSION_LEVEL;
+
+	if (options != NULL) {
+		if (strncmp(options, "level=", 6) == 0) {
+			options += 6;
+
+			for (i = 0; isdigit(options[i]); ++i)
+				;
+
+			if (i == 0 || options[i] != '\0' || i > 6)
+				goto fail_level;
+
+			zstd->level = atoi(options);
+
+			if (zstd->level < 1 || zstd->level > ZSTD_maxCLevel())
+				goto fail_level;
+		} else {
+			goto fail_opt;
+		}
+	}
+
 	zstd->zctx = ZSTD_createCCtx();
 	if (zstd->zctx == NULL) {
 		fputs("error creating zstd compression context\n", stderr);
@@ -93,8 +133,23 @@ compressor_t *create_zstd_compressor(bool compress, size_t block_size,
 	base->write_options = zstd_write_options;
 	base->read_options = zstd_read_options;
 	return base;
+fail_level:
+	fprintf(stderr, "zstd compression level must be a number in the range "
+		"1...%d\n", ZSTD_maxCLevel());
+	free(zstd);
+	return NULL;
+fail_opt:
+	fputs("Unsupported extra options for zstd compressor\n", stderr);
+	free(zstd);
+	return NULL;
 }
 
 void compressor_zstd_print_help(void)
 {
+	printf("Available options for zstd compressor:\n"
+	       "\n"
+	       "    level=<value>    Set compression level. Defaults to %d.\n"
+	       "                     Maximum is %d.\n"
+	       "\n",
+	       ZSTD_DEFAULT_COMPRESSION_LEVEL, ZSTD_maxCLevel());
 }
-- 
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