#include <stdio.h>
+/* this is a ~30% win for CPUs with fast 64x64->64 multiplication, but a huge loss otherwise */
+#define PARALLEL_PARITY 1
+
#define DATA_BITS 26
#define PARITY_BITS 6
#define EXTRA_BIT_POSITION (PARITY_BITS - 1)
#endif
}
+/* courtesy of neon/nocturnal :-) */
+unsigned find_parity_32x2(unsigned a, unsigned b)
+{
+ unsigned long long x = (unsigned long long)a | (((unsigned long long)b)<<32);
+ x = x ^ (x >> 1);
+ x = (x ^ (x >> 2)) & 0x1111111111111111ULL;
+ x = x * 0x11111111;
+ return ((x>>28)&1) | ((x>>(32+28-1))&2);
+}
+
unsigned generate_parity(unsigned data)
{
+#if PARALLEL_PARITY
+ return find_parity_32x2(data & 0x03b4e996, data & 0x00007fff) |
+ (find_parity_32x2(data & 0x003f80ff, data & 0x01c78f0f) << 2) |
+ (find_parity_32x2(data & 0x02d9b333, data & 0x036ad555) << 4);
+#else
unsigned parity1 = find_parity_32(data & 0x036ad555);
unsigned parity2 = find_parity_32(data & 0x02d9b333);
unsigned parity3 = find_parity_32(data & 0x01c78f0f);
unsigned parity4 = find_parity_32(data & 0x003f80ff);
unsigned parity5 = find_parity_32(data & 0x00007fff);
unsigned parity6 = find_parity_32(data & 0x03b4e996);
-
+
return parity6 | (parity5 << 1) | (parity4 << 2) | (parity3 << 3) | (parity2 << 4) | (parity1 << 5);
+#endif
}
unsigned make_codeword(unsigned data)