Initial stab at Venti.

src/cmd/venti/verifyarena.c

@@ -0,0 +1,127 @@
+#include "stdinc.h"
+#include "dat.h"
+#include "fns.h"
+
+static int	verbose;
+
+void
+usage(void)
+{
+	fprint(2, "usage: verifyarena [-v]\n");
+	threadexitsall(0);
+}
+
+static void
+readblock(uchar *buf, int n)
+{
+	int nr, m;
+
+	for(nr = 0; nr < n; nr += m){
+		m = n - nr;
+		m = read(0, &buf[nr], m);
+		if(m <= 0)
+			sysfatal("can't read arena from standard input: %r");
+	}
+}
+
+static void
+verifyarena(void)
+{
+	Arena arena;
+	ArenaHead head;
+	ZBlock *b;
+	DigestState s;
+	u64int n, e;
+	u32int bs;
+	u8int score[VtScoreSize];
+
+	fprint(2, "verify arena from standard input\n");
+
+	memset(&arena, 0, sizeof arena);
+	memset(&s, 0, sizeof s);
+
+	/*
+	 * read the little bit, which will included the header
+	 */
+	bs = MaxIoSize;
+	b = alloczblock(bs, 0);
+	readblock(b->data, HeadSize);
+	sha1(b->data, HeadSize, nil, &s);
+	if(unpackarenahead(&head, b->data) < 0)
+		sysfatal("corrupted arena header: %r");
+	if(head.version != ArenaVersion)
+		fprint(2, "warning: unknown arena version %d\n", head.version);
+
+	/*
+	 * now we know how much to read
+	 * read everything but the last block, which is special
+	 */
+	e = head.size - head.blocksize;
+	for(n = HeadSize; n < e; n += bs){
+		if(n + bs > e)
+			bs = e - n;
+		readblock(b->data, bs);
+		sha1(b->data, bs, nil, &s);
+	}
+
+	/*
+	 * read the last block update the sum.
+	 * the sum is calculated assuming the slot for the sum is zero.
+	 */
+	bs = head.blocksize;
+	readblock(b->data, bs);
+	sha1(b->data, bs-VtScoreSize, nil, &s);
+	sha1(zeroscore, VtScoreSize, nil, &s);
+	sha1(nil, 0, score, &s);
+
+	/*
+	 * validity check on the trailer
+	 */
+	arena.blocksize = head.blocksize;
+	if(unpackarena(&arena, b->data) < 0)
+		sysfatal("corrupted arena trailer: %r");
+	scorecp(arena.score, &b->data[arena.blocksize - VtScoreSize]);
+
+	if(namecmp(arena.name, head.name) != 0)
+		sysfatal("arena header and trailer names clash: %s vs. %s\n", head.name, arena.name);
+	if(arena.version != head.version)
+		sysfatal("arena header and trailer versions clash: %d vs. %d\n", head.version, arena.version);
+	arena.size = head.size - 2 * head.blocksize;
+
+	/*
+	 * check for no checksum or the same
+	 */
+	if(scorecmp(score, arena.score) != 0){
+		if(scorecmp(zeroscore, arena.score) != 0)
+			fprint(2, "warning: mismatched checksums for arena=%s, found=%V calculated=%V",
+				arena.name, arena.score, score);
+		scorecp(arena.score, score);
+	}else
+		fprint(2, "matched score\n");
+
+	printarena(2, &arena);
+}
+
+void
+threadmain(int argc, char *argv[])
+{
+	fmtinstall('V', vtscorefmt);
+	statsinit();
+
+	ARGBEGIN{
+	case 'v':
+		verbose++;
+		break;
+	default:
+		usage();
+		break;
+	}ARGEND
+
+	readonly = 1;
+
+	if(argc != 0)
+		usage();
+
+	verifyarena();
+	threadexitsall(0);
+}