Trung Nguyen
bdcc293fa8
- Resize the `page_protections` array in `cut_area` and also shift the bits if necessary. - Set the correct protection array as well as the real page protections for the second area produced by `cut_area`. Change-Id: I62293480487e869420ebe5a3bc729cec2a14c687 Reviewed-on: https://review.haiku-os.org/c/haiku/+/6395 Reviewed-by: Jérôme Duval <[email protected]> Tested-by: Commit checker robot <[email protected]>
116 lines
2.7 KiB
C++
116 lines
2.7 KiB
C++
/*
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* Copyright 2013 Haiku, Inc. All rights reserved.
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* Distributed under the terms of the MIT License.
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*
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* Authors:
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* Paweł Dziepak, [email protected]
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*/
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#ifndef KERNEL_UTIL_BITUTIL_H
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#define KERNEL_UTIL_BITUTIL_H
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#include <string.h>
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#include <SupportDefs.h>
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// http://graphics.stanford.edu/~seander/bithacks.html
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static inline uint32
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next_power_of_2(uint32 v)
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{
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v--;
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v |= v >> 1;
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v |= v >> 2;
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v |= v >> 4;
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v |= v >> 8;
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v |= v >> 16;
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v++;
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return v;
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}
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// http://graphics.stanford.edu/~seander/bithacks.html
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static inline uint32
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count_set_bits(uint32 v)
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{
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v = v - ((v >> 1) & 0x55555555);
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v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
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return (((v + (v >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
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}
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static inline uint32
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log2(uint32 v)
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{
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static const int MultiplyDeBruijnBitPosition[32] = {
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0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30,
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8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31
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};
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v |= v >> 1;
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v |= v >> 2;
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v |= v >> 4;
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v |= v >> 8;
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v |= v >> 16;
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return MultiplyDeBruijnBitPosition[(uint32)(v * 0x07C4ACDDU) >> 27];
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}
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template<typename T>
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void
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bitmap_shift(T* bits, size_t bitCount, ssize_t shift)
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{
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if (shift == 0)
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return;
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const size_t bitsPerElement = sizeof(T) * 8;
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const size_t elementsCount = (bitCount + bitsPerElement - 1) / bitsPerElement;
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const size_t absoluteShift = (shift > 0) ? shift : -shift;
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const size_t nElements = absoluteShift / bitsPerElement;
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const size_t nBits = absoluteShift % bitsPerElement;
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if (nElements != 0) {
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if (shift > 0) {
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// "Left" shift.
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memmove(&bits[nElements], bits, sizeof(T) * (elementsCount - nElements));
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memset(bits, 0, sizeof(T) * nElements);
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} else if (shift < 0) {
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// "Right" shift.
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memmove(bits, &bits[nElements], sizeof(T) * (elementsCount - nElements));
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memset(&bits[elementsCount - nElements], 0, sizeof(T) * nElements);
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}
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}
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// If the shift was by a multiple of the element size, nothing more to do.
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if (nBits == 0)
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return;
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// One set of bits comes from the "current" element and are shifted in the
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// direction of the shift; the other set comes from the next-processed
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// element and are shifted in the opposite direction.
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if (shift > 0) {
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// "Left" shift.
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for (ssize_t i = elementsCount - 1; i >= 0; i--) {
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T low = 0;
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if (i != 0)
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low = bits[i - 1] >> (bitsPerElement - nBits);
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const T high = bits[i] << nBits;
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bits[i] = low | high;
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}
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} else if (shift < 0) {
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// "Right" shift.
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for (size_t i = 0; i < elementsCount; i++) {
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const T low = bits[i] >> nBits;
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T high = 0;
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if (i != (elementsCount - 1))
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high = bits[i + 1] << (bitsPerElement - nBits);
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bits[i] = low | high;
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}
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}
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}
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#endif // KERNEL_UTIL_BITUTIL_H
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