1 files changed, 115 insertions, 0 deletions
diff --git a/src/cmd/venti/srv/fmtbloom.c b/src/cmd/venti/srv/fmtbloom.c
new file mode 100644
index 00000000..3c50d82f
--- /dev/null
+++ b/src/cmd/venti/srv/fmtbloom.c
@@ -0,0 +1,115 @@
+#include "stdinc.h"
+#include "dat.h"
+#include "fns.h"
+
+Bloom b;
+
+void
+usage(void)
+{
+	fprint(2, "usage: fmtbloom [-s size] [-n nblocks | -N nhash] file\n");
+	threadexitsall(0);
+}
+
+void
+threadmain(int argc, char *argv[])
+{
+	Part *part;
+	char *file;
+	vlong bits, size, size2;
+	int nhash;
+	vlong nblocks;
+	
+	ventifmtinstall();
+	statsinit();
+
+	size = 0;
+	nhash = nblocks = 0;
+	ARGBEGIN{
+	case 'n':
+		if(nhash || nblocks)
+			usage();
+		nblocks = unittoull(EARGF(usage()));
+		break;
+	case 'N':
+		if(nhash || nblocks)
+			usage();
+		nhash = unittoull(EARGF(usage()));
+		if(nhash > BloomMaxHash){
+			fprint(2, "maximum possible is -N %d", BloomMaxHash);
+			usage();
+		}
+		break;
+	case 's':
+		size = unittoull(ARGF());
+		if(size == ~0)
+			usage();
+		break;
+	default:
+		usage();
+		break;
+	}ARGEND
+
+	if(argc != 1)
+		usage();
+
+	file = argv[0];
+
+	part = initpart(file, ORDWR|ODIRECT);
+	if(part == nil)
+		sysfatal("can't open partition %s: %r", file);
+
+	if(size == 0)
+		size = part->size;
+	
+	if(size < 1024*1024)
+		sysfatal("bloom filter too small");
+
+	if(size > MaxBloomSize){
+		fprint(2, "warning: not using entire %,lld bytes; using only %,lld bytes\n",
+			size, MaxBloomSize);
+		size = MaxBloomSize;
+	}
+	if(size&(size-1)){
+		for(size2=1; size2<size; size2*=2)
+			;
+		size = size2/2;
+		fprint(2, "warning: size not a power of 2; only using %lldMB\n", size/1024/1024);
+	}
+
+	if(nblocks){
+		/*
+		 * no use for more than 32 bits per block
+		 * shoot for less than 64 bits per block
+		 */
+		size2 = size;
+		while(size2*8 >= nblocks*64)
+			size2 >>= 1;
+		if(size2 != size){
+			size = size2;
+			fprint(2, "warning: using only %lldMB - not enough blocks to warrant more\n",
+				size/1024/1024);
+		}
+
+		/*
+		 * optimal is to use ln 2 times as many hash functions as we have bits per blocks.  
+		 */
+		bits = (8*size)/nblocks;
+		nhash = bits*7/10;
+		if(nhash > BloomMaxHash)
+			nhash = BloomMaxHash;
+	}
+	if(!nhash)
+		nhash = BloomMaxHash;
+	if(bloominit(&b, size, nil) < 0)
+		sysfatal("bloominit: %r");
+	b.nhash = nhash;
+	bits = nhash*10/7;
+	nblocks = (8*size)/bits;
+	fprint(2, "fmtbloom: using %lldMB, %d hashes/score, best up to %,lld blocks\n", size, nhash, nblocks);
+	b.data = vtmallocz(size);
+	b.part = part;
+	if(writebloom(&b) < 0)
+		sysfatal("writing %s: %r", file);
+	threadexitsall(0);
+}