new venti library.

src/libventi/zero.c

@@ -0,0 +1,55 @@
+#include <u.h>
+#include <libc.h>
+#include <venti.h>
+
+void
+vtzeroextend(int type, uchar *buf, uint n, uint nn)
+{
+	uchar *p, *ep;
+
+	switch(type&7) {
+	case 0:
+		memset(buf+n, 0, nn-n);
+		break;
+	default:
+		p = buf + (n/VtScoreSize)*VtScoreSize;
+		ep = buf + (nn/VtScoreSize)*VtScoreSize;
+		while(p < ep) {
+			memmove(p, vtzeroscore, VtScoreSize);
+			p += VtScoreSize;
+		}
+		memset(p, 0, buf+nn-p);
+		break;
+	}
+}
+
+uint 
+vtzerotruncate(int type, uchar *buf, uint n)
+{
+	uchar *p;
+
+	if(type == VtRootType){
+		if(n < VtRootSize)
+			return n;
+		return VtRootSize;
+	}
+
+	switch(type&7){
+	case 0:
+		for(p = buf + n; p > buf; p--) {
+			if(p[-1] != 0)
+				break;
+		}
+		return p - buf;
+	default:
+		/* ignore slop at end of block */
+		p = buf + (n/VtScoreSize)*VtScoreSize;
+
+		while(p > buf) {
+			if(memcmp(p - VtScoreSize, vtzeroscore, VtScoreSize) != 0)
+				break;
+			p -= VtScoreSize;
+		}
+		return p - buf;
+	}
+}