/js/lib/Socket.IO-node/support/expresso/deps/jscoverage/js/jslog2.cpp

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13 * License.
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15 * The Original Code is Mozilla Communicator client code, released
16 * March 31, 1998.
17 *
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38
39#include "jsstddef.h"
40#include "jsbit.h"
41#include "jsutil.h"
42
43/*
44** Compute the log of the least power of 2 greater than or equal to n
45*/
46JS_PUBLIC_API(JSIntn) JS_CeilingLog2(JSUint32 n)
47{
48    JSIntn log2;
49
50    JS_CEILING_LOG2(log2, n);
51    return log2;
52}
53
54/*
55** Compute the log of the greatest power of 2 less than or equal to n.
56** This really just finds the highest set bit in the word.
57*/
58JS_PUBLIC_API(JSIntn) JS_FloorLog2(JSUint32 n)
59{
60    JSIntn log2;
61
62    JS_FLOOR_LOG2(log2, n);
63    return log2;
64}
65
66/*
67 * js_FloorLog2wImpl has to be defined only for 64-bit non-GCC case.
68 */
69#if !defined(JS_HAS_BUILTIN_BITSCAN64) && JS_BYTES_PER_WORD == 8
70
71JSUword
72js_FloorLog2wImpl(JSUword n)
73{
74    JSUword log2, m;
75
76    JS_ASSERT(n != 0);
77
78    log2 = 0;
79    m = n >> 32;
80    if (m != 0) { n = m; log2 = 32; }
81    m = n >> 16;
82    if (m != 0) { n = m; log2 |= 16; }
83    m = n >> 8;
84    if (m != 0) { n = m; log2 |= 8; }
85    m = n >> 4;
86    if (m != 0) { n = m; log2 |= 4; }
87    m = n >> 2;
88    if (m != 0) { n = m; log2 |= 2; }
89    log2 |= (n >> 1);
90
91    return log2;
92}
93
94#endif