Changeset 1552

Timestamp:

Oct 22, 2011, 2:41:44 PM (8 years ago)

Author:

ksherdy

Message:

Added bit stream scan.

File:

• trunk/lib/bitblock128.hpp (modified) (2 diffs)

trunk/lib/bitblock128.hpp

@@ -32 +32 @@
 static IDISA_ALWAYS_INLINE uint32_t count_forward_zeroes(bitblock128_t v);
 static IDISA_ALWAYS_INLINE uint32_t count_backward_zeroes(bitblock128_t v);
-
+static IDISA_ALWAYS_INLINE uint32_t bitstream_scan(bitblock_128_t * v, uint32_t pos)
 
 IDISA_ALWAYS_INLINE void adc(bitblock128_t x, bitblock128_t y, bitblock128_t & carry, bitblock128_t & sum)
@@ -128 +128 @@
 }
 
+IDISA_ALWAYS_INLINE uint32_t bitstream_scan(bitblock_128_t * v, uint32_t pos) {
+  unsigned long * bitstream_ptr = (unsigned long *) (((intptr_t) v) + pos/8);
+  unsigned long bitstream_slice = ((*bitstream_ptr) >> (pos % 8));
+  if (bitstream_slice != 0) return pos + cfzl(bitstream_slice);
+  else {
+    do {
+      bitstream_ptr++;
+      bitstream_slice = *bitstream_ptr;
+    } while (bitstream_slice == 0);
+    uint32_t base_posn = 8*((intptr_t) bitstream_ptr - (intptr_t) v);
+    return base_posn + cfzl(bitstream_slice);
+  }
+}
+
+
 #endif /* BITBLOCK128_HPP_ */