From a0d146edd7a7de6236a0d60baafeeb59f8452aae Mon Sep 17 00:00:00 2001
From: rsc <devnull@localhost>
Date: Tue, 12 Jul 2005 15:23:36 +0000
Subject: return of venti

---
 src/cmd/venti/srv/buildbuck.c | 132 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 src/cmd/venti/srv/buildbuck.c

(limited to 'src/cmd/venti/srv/buildbuck.c')

diff --git a/src/cmd/venti/srv/buildbuck.c b/src/cmd/venti/srv/buildbuck.c
new file mode 100644
index 00000000..240e77d7
--- /dev/null
+++ b/src/cmd/venti/srv/buildbuck.c
@@ -0,0 +1,132 @@
+#include "stdinc.h"
+#include "dat.h"
+#include "fns.h"
+
+/*
+ * An IEStream is a sorted list of index entries.
+ */
+struct IEStream
+{
+	Part	*part;
+	u64int	off;		/* read position within part */
+	u64int	n;		/* number of valid ientries left to read */
+	u32int	size;		/* allocated space in buffer */
+	u8int	*buf;
+	u8int	*pos;		/* current place in buffer */
+	u8int	*epos;		/* end of valid buffer contents */
+};
+
+IEStream*
+initiestream(Part *part, u64int off, u64int clumps, u32int size)
+{
+	IEStream *ies;
+
+//ZZZ out of memory?
+	ies = MKZ(IEStream);
+	ies->buf = MKN(u8int, size);
+	ies->epos = ies->buf;
+	ies->pos = ies->epos;
+	ies->off = off;
+	ies->n = clumps;
+	ies->size = size;
+	ies->part = part;
+	return ies;
+}
+
+void
+freeiestream(IEStream *ies)
+{
+	if(ies == nil)
+		return;
+	free(ies->buf);
+	free(ies);
+}
+
+/*
+ * Return the next IEntry (still packed) in the stream.
+ */
+static u8int*
+peekientry(IEStream *ies)
+{
+	u32int n, nn;
+
+	n = ies->epos - ies->pos;
+	if(n < IEntrySize){
+		memmove(ies->buf, ies->pos, n);
+		ies->epos = &ies->buf[n];
+		ies->pos = ies->buf;
+		nn = ies->size;
+		if(nn > ies->n * IEntrySize)
+			nn = ies->n * IEntrySize;
+		nn -= n;
+		if(nn == 0)
+			return nil;
+//fprint(2, "peek %d from %llud into %p\n", nn, ies->off, ies->epos);
+		if(readpart(ies->part, ies->off, ies->epos, nn) < 0){
+			seterr(EOk, "can't read sorted index entries: %r");
+			return nil;
+		}
+		ies->epos += nn;
+		ies->off += nn;
+	}
+	return ies->pos;
+}
+
+/*
+ * Compute the bucket number for the given IEntry.
+ * Knows that the score is the first thing in the packed
+ * representation.
+ */
+static u32int
+iebuck(Index *ix, u8int *b, IBucket *ib, IEStream *ies)
+{
+	USED(ies);
+	USED(ib);
+	return hashbits(b, 32) / ix->div;
+}
+
+/*
+ * Fill ib with the next bucket in the stream.
+ */
+u32int
+buildbucket(Index *ix, IEStream *ies, IBucket *ib, uint maxdata)
+{
+	IEntry ie1, ie2;
+	u8int *b;
+	u32int buck;
+
+	buck = TWID32;
+	ib->n = 0;
+	while(ies->n){
+		b = peekientry(ies);
+		if(b == nil)
+			return TWID32;
+//fprint(2, "b=%p ies->n=%lld ib.n=%d buck=%d score=%V\n", b, ies->n, ib->n, iebuck(ix, b, ib, ies), b);
+		if(ib->n == 0)
+			buck = iebuck(ix, b, ib, ies);
+		else{
+			if(buck != iebuck(ix, b, ib, ies))
+				break;
+			if(ientrycmp(&ib->data[(ib->n - 1)* IEntrySize], b) == 0){
+				/*
+				 * guess that the larger address is the correct one to use
+				 */
+				unpackientry(&ie1, &ib->data[(ib->n - 1)* IEntrySize]);
+				unpackientry(&ie2, b);
+				seterr(EOk, "duplicate index entry for score=%V type=%d", ie1.score, ie1.ia.type);
+				ib->n--;
+				if(ie1.ia.addr > ie2.ia.addr)
+					memmove(b, &ib->data[ib->n * IEntrySize], IEntrySize);
+			}
+		}
+		if((ib->n+1)*IEntrySize > maxdata){
+			seterr(EOk, "bucket overflow");
+			return TWID32;
+		}
+		memmove(&ib->data[ib->n * IEntrySize], b, IEntrySize);
+		ib->n++;
+		ies->n--;
+		ies->pos += IEntrySize;
+	}
+	return buck;
+}
-- 
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