Index: src/OFHashes.h
==================================================================
--- src/OFHashes.h
+++ src/OFHashes.h
@@ -16,12 +16,14 @@
 @interface OFMD5Hash: OFObject
 {
 	uint32_t buf[4];
 	uint32_t bits[2];
 	uint8_t	 in[64];
+
+	BOOL	 calculated;
 }
 
 - init;
 - (void)updateWithBuffer: (const uint8_t*)buf
 		  ofSize: (size_t)size;
 - (uint8_t*)digest;
 @end

Index: src/OFHashes.m
==================================================================
--- src/OFHashes.m
+++ src/OFHashes.m
@@ -19,21 +19,25 @@
 #ifdef BIG_ENDIAN
 inline void
 bswap(uint8_t *buf, size_t len)
 {
 	uint32_t t;
-	do {
+	while (len--) {
 		t = (uint32_t)((uint32_t)buf[3] << 8 | buf[2]) << 16 |
 		    ((uint32_t)buf[1] << 8 | buf[0]);
 		*(uint32_t*)buf = t;
 		buf += 4;
-	} while(--len);
+	}
 }
 #else
 #define bswap(buf, len)
 #endif
 
+/*******
+ * MD5 *
+ *******/
+
 /* The four MD5 core functions - F1 is optimized somewhat */
 #define F1(x, y, z) (z ^ (x & (y ^ z)))
 #define F2(x, y, z) F1(z, x, y)
 #define F3(x, y, z) (x ^ y ^ z)
 #define F4(x, y, z) (y ^ (x | ~z))
@@ -135,19 +139,26 @@
 		buf[2] = 0x98BADCFE;
 		buf[3] = 0x10325476;
 
 		bits[0] = 0;
 		bits[1] = 0;
+
+		calculated = NO;
 	}
 
 	return self;
 }
 
 - (void)updateWithBuffer: (const uint8_t*)buffer
 		  ofSize: (size_t)size
 {
 	uint32_t t;
+
+	if (calculated)
+		return;
+	if (size == 0)
+		return;
 
 	/* Update bitcount */
 	t = bits[0];
 	if ((bits[0] = t + ((uint32_t)size << 3)) < t)
 		bits[1]++;		/* Carry from low to high */
@@ -187,10 +198,13 @@
 - (uint8_t*)digest
 {
 	uint8_t	*p;
 	size_t	count;
 
+	if (calculated)
+		return (uint8_t*)buf;
+
 	/* Compute number of bytes mod 64 */
 	count = (bits[0] >> 3) & 0x3F;
 
 	/*
 	 * Set the first char of padding to 0x80. This is safe since there is
@@ -221,9 +235,11 @@
 	((uint32_t*)in)[14] = bits[0];
 	((uint32_t*)in)[15] = bits[1];
 
 	md5_transform(buf, (uint32_t*)in);
 	bswap((uint8_t*)buf, 4);
+
+	calculated = YES;
 
 	return (uint8_t*)buf;
 }
 @end