20060303a

1 files changed, 109 insertions, 0 deletions

diff --git a/appl/lib/attrhash.b b/appl/lib/attrhash.b
new file mode 100644
index 00000000..b48e0477
--- /dev/null
+++ b/appl/lib/attrhash.b
@@ -0,0 +1,109 @@
+implement Attrhash, Attrindex;
+
+include "sys.m";
+	sys: Sys;
+
+include "bufio.m";
+	bufio: Bufio;
+
+include "attrdb.m";
+
+init(): string
+{
+	sys = load Sys Sys->PATH;
+	bufio = load Bufio Bufio->PATH;
+	if(bufio == nil)
+		return sys->sprint("can't load %s: %r", Bufio->PATH);
+	return nil;
+}
+
+attrindex(): Attrindex
+{
+	return load Attrindex "$self";
+}
+
+Index.open(dbf: Attrdb->Dbf, attr: string, fd: ref Sys->FD): ref Index
+{
+	(ok, d) := sys->fstat(fd);
+	if(ok < 0 || dbf.dir == nil || dbf.dir.mtime > d.mtime)
+		return nil;
+	length := int d.length;
+	if(length < NDBHLEN)
+		return nil;
+	buf := array[length] of byte;
+	if(sys->read(fd, buf, len buf) != len buf)
+		return nil;
+	mtime := get4(buf);
+	if(mtime != dbf.dir.mtime)
+		return nil;
+	size := get3(buf[4:]);
+	return ref Index(fd, attr, d.mtime, size, buf[8:]);
+}
+
+#Index.firstoff(ind: self ref Index, val: string): ref Attrdb->Dbptr
+#{
+#	o := hash(val, ind.size)*NDBPLEN;
+#	p := get3(tab[o:]);
+#	if(p == NDBNAP)
+#		return nil;
+#	if((p & NDBCHAIN) == 0)
+#		return ref Attrdb.Direct(p);
+#	p &= ~NDBCHAIN;
+#	return ref Attrdb.Hash(get3(tab[p:]), get3(tab[p+NDBPLEN:]));
+#}
+
+#Index.nextoff(ind: self ref Index, val: string, ptr: ref Attrdb->Dbptr): (int, ref Attrdb->Dbptr)
+#{
+#	pick p := ptr {
+#	Hash =>
+#		o := get3(tab[p.current:]);
+#		if((o & NDBCHAIN) == 0)
+#			return (o, ref Attrdb.Direct(p.next));
+#		o &= ~NDBCHAIN;
+#		o1 := get3(tab[o:]);
+#		o2 := get3(tab[o+NDBPLEN:]);
+#		
+
+#	o := hash(val, ind.size)*NDBPLEN;
+#	p := get3(tab[o:]);
+#	if(p == NDBNAP)
+#		return nil;
+#	for(; (p := get3(tab[o:])) != NDBNAP; o = p & ~NDBCHAIN)
+#		if((p & NDBCHAIN) == 0){
+#			put3(tab[o:], chain | NDBCHAIN);
+#			put3(tab[chain:], p);
+#			put3(tab[chain+NDBPLEN:], offset);
+#			return chain+2*NDBPLEN;
+#		}
+#	return nil;
+#}
+
+#
+# this must be the same hash function used by Plan 9's ndb
+#
+hash(s: string, hlen: int): int
+{
+	h := 0;
+	for(i := 0; i < len s; i++)
+		if(s[i] >= 16r80){
+			# could optimise by calculating utf ourselves
+			a := array of byte s;
+			for(i=0; i<len a; i++)
+				h = (h*13) + int a[i] - 'a';
+			break;
+		}else
+			h = (h*13) + s[i]-'a';
+	if(h < 0)
+		return int((big h & big 16rFFFFFFFF)%big hlen);
+	return h%hlen;
+}
+
+get3(a: array of byte): int
+{
+	return (int a[2]<<16) | (int a[1]<<8) | int a[0];
+}
+
+get4(a: array of byte): int
+{
+	return (int a[3]<<24) | (int a[2]<<16) | (int a[1]<<8) | int a[0];
+}