ref: b44d75aa4e97e9264e585712a8ec5fa757b645ec
parent: b7f192eea34e0bd36abcd457333ab37eb221789f
author: Simon Tatham <anakin@pobox.com>
date: Sat Oct 22 12:38:15 EDT 2005
Noticed recently that bitcount16() isn't 16-bit clean due to signed shift right. It doesn't actually matter in the current code since the input word only ever uses the bottom 9 bits, but if I ever extended Mines to work in a triangular grid then all 16 bits might be required. Fix this now, while I'm cleaning things up, so that it won't bite me unexpectedly in future. [originally from svn r6415]
--- a/mines.c
+++ b/mines.c
@@ -275,14 +275,16 @@
/*
* Count the bits in a word. Only needs to cope with 16 bits.
*/
-static int bitcount16(int word)
+static int bitcount16(int inword)
{+ unsigned int word = inword;
+
word = ((word & 0xAAAA) >> 1) + (word & 0x5555);
word = ((word & 0xCCCC) >> 2) + (word & 0x3333);
word = ((word & 0xF0F0) >> 4) + (word & 0x0F0F);
word = ((word & 0xFF00) >> 8) + (word & 0x00FF);
- return word;
+ return (int)word;
}
/*