dedup

commit 6dea955869804c893de2c0cd1d2b0700d72fe8ea
parent 9f38b53149dd3486e39b02d571fa5dda7ba11f83
Author: sin <sin@2f30.org>
Date:   Thu, 25 Apr 2019 14:40:58 +0100

Add magic field at the start of the storage header

Diffstat:
M
bstorage.c
 | 
14
+++++++++++---

1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/bstorage.c b/bstorage.c
@@ -37,9 +37,11 @@
 #define CALGOSHIFT	16
 #define CALGOMASK	0x7
 
+#define BHDRMAGIC	"DEDUPDIDUPDIDUP"
+#define NBHDRMAGIC	sizeof(BHDRMAGIC)
 #define BDTYPE		0x100
 
-#define BHDRSIZE	(8 + 8)
+#define BHDRSIZE	(NBHDRMAGIC + 8 + 8)
 #define BDSIZE		(8 + 8 + 8 + (MDSIZE))
 
 extern int pack(unsigned char *dst, char *fmt, ...);
@@ -63,6 +65,7 @@ static struct bops bops = {
 
 /* Block header structure */
 struct bhdr {
+	char magic[NBHDRMAGIC];
 	uint64_t flags;
 	uint64_t nent;
 };
@@ -174,11 +177,14 @@ unpackbhdr(int fd, struct bhdr *bhdr)
 	if (xread(fd, buf, sizeof(buf)) != sizeof(buf))
 		return -1;	
 
-	n = unpack(buf, "qq",
+	n = unpack(buf, "'16qq",
+	           bhdr->magic,
 	           &bhdr->flags,
 	           &bhdr->nent);
 
 	assert(n == sizeof(buf));
+	if (memcmp(bhdr->magic, BHDRMAGIC, NBHDRMAGIC) != 0)
+		return -1;
 	return n;
 }
 
@@ -189,7 +195,8 @@ packbhdr(int fd, struct bhdr *bhdr)
 	unsigned char buf[BHDRSIZE];
 	int n;
 
-	n = pack(buf, "qq",
+	n = pack(buf, "'16qq",
+	         bhdr->magic,
 	         bhdr->flags,
 	         bhdr->nent);
 
@@ -318,6 +325,7 @@ bscreat(struct bctx *bctx, char *path, int mode, struct bparam *bpar)
 	sctx = bctx->sctx;
 	RB_INIT(&sctx->bdcache);
 	bhdr = &sctx->bhdr;
+	memcpy(bhdr->magic, BHDRMAGIC, NBHDRMAGIC);
 	bhdr->flags = (VMAJ << VMAJSHIFT) | VMIN;
 
 	/* Set compression algorithm */