minor optimization (DSpeed 665)

2016-03-23 14:09:51 +01:00
parent 2512597576
commit 3c017867de
2 changed files with 15 additions and 4 deletions
@@ -285,6 +285,17 @@ MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, si
    return srcSize;
 }

+MEM_STATIC size_t BIT_getUpperBits(size_t bitD, U32 const start)
+{
+    return bitD >> start;
+}
+
+MEM_STATIC size_t BIT_getNBits(size_t bitD, U32 const nbBits, U32 const start)
+{
+    static const unsigned mask[] = { 0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF, 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF,  0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF };   /* up to 26 bits */
+    return (bitD >> start) & mask[nbBits];
+}
+
 MEM_STATIC size_t BIT_consumeFirstBits(size_t* bitDPtr, U32 const nbBits)
 {
    static const unsigned mask[] = { 0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF, 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF,  0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF };   /* up to 26 bits */