bit-shift

I need to get the 30th bit of the lParam param passed with the WM_KEYDOWN message. This bit as written here allows me to know if the key was pressed before. Is this code right to get it? (lParam >> 30) & 1 I would just use lParam & 0x40000000 . If that's non-zero, then b30 was set (I consider that the thirty first bit of the thirty two, by the way). And there's more likelihood that it will be a {logical-and, compare} operation rather than {shift, logical-and, compare} . Mind you, there's a good chance that a decent compiler would generate the more efficient code anyway even if you used (lParam

I have two approaches to convert long to byte array. for (int i = 0; i < 7; i++) { data[pos + i] = (byte) (value >> (7- i - 1 << 3)); } and for (int i = 7; i >= 0; --i) { data[p + i] = (byte)(newl & 0xff); newl >>= 8; } which of the two operations is more efficient? I suggest you look at how the Java code does it. public final void writeLong(long v) throws IOException { writeBuffer[0] = (byte)(v >>> 56); writeBuffer[1] = (byte)(v >>> 48); writeBuffer[2] = (byte)(v >>> 40); writeBuffer[3] = (byte)(v >>> 32); writeBuffer[4] = (byte)(v >>> 24); writeBuffer[5] = (byte)(v >>> 16); writeBuffer[6] =

I need to shift a __m128i variable, (say v), by m bits, in such a way that bits move through all of the variable (So, the resulting variable represents v*2^m). What is the best way to do this?! Note that _mm_slli_epi64 shifts v0 and v1 seperately: r0 := v0 << count r1 := v1 << count so the last bits of v0 missed, but I want to move those bits to r1. Edit: I looking for a code, faster than this (m<64): r0 = v0 << m; r1 = v0 >> (64-m); r1 ^= v1 << m; r2 = v1 >> (64-m); For compile-time constant shift counts, you can get fairly good results. Otherwise not really. This is just an SSE