107 lines
3.5 KiB
C++
107 lines
3.5 KiB
C++
/**
|
|
******************************************************************************
|
|
* Xenia : Xbox 360 Emulator Research Project *
|
|
******************************************************************************
|
|
* Copyright 2019 Ben Vanik. All rights reserved. *
|
|
* Released under the BSD license - see LICENSE in the root for more details. *
|
|
******************************************************************************
|
|
*/
|
|
|
|
#ifndef XENIA_BASE_BIT_RANGE_H_
|
|
#define XENIA_BASE_BIT_RANGE_H_
|
|
|
|
#include <climits>
|
|
#include <cstddef>
|
|
#include <cstdint>
|
|
#include <cstring>
|
|
#include <utility>
|
|
|
|
#include "xenia/base/math.h"
|
|
|
|
namespace xe {
|
|
namespace bit_range {
|
|
|
|
// Provided length is in bits since the first. Returns <first, length> of the
|
|
// range in bits, with length == 0 if not found.
|
|
template <typename Block>
|
|
std::pair<size_t, size_t> NextUnsetRange(const Block* bits, size_t first,
|
|
size_t length) {
|
|
if (!length) {
|
|
return std::make_pair(size_t(first), size_t(0));
|
|
}
|
|
size_t last = first + length - 1;
|
|
const size_t block_bits = sizeof(Block) * CHAR_BIT;
|
|
size_t block_first = first / block_bits;
|
|
size_t block_last = last / block_bits;
|
|
size_t range_start = SIZE_MAX;
|
|
for (size_t i = block_first; i <= block_last; ++i) {
|
|
Block block = bits[i];
|
|
// Ignore bits in the block outside the specified range by considering them
|
|
// set.
|
|
if (i == block_first) {
|
|
block |= (Block(1) << (first & (block_bits - 1))) - 1;
|
|
}
|
|
if (i == block_last && (last & (block_bits - 1)) != block_bits - 1) {
|
|
block |= ~((Block(1) << ((last & (block_bits - 1)) + 1)) - 1);
|
|
}
|
|
while (true) {
|
|
uint32_t block_bit;
|
|
if (range_start == SIZE_MAX) {
|
|
// Check if need to open a new range.
|
|
if (!xe::bit_scan_forward(~block, &block_bit)) {
|
|
break;
|
|
}
|
|
range_start = i * block_bits + block_bit;
|
|
} else {
|
|
// Check if need to close the range.
|
|
// Ignore the set bits before the beginning of the range.
|
|
Block block_bits_set_from_start = block;
|
|
if (i == range_start / block_bits) {
|
|
block_bits_set_from_start &=
|
|
~((Block(1) << (range_start & (block_bits - 1))) - 1);
|
|
}
|
|
if (!xe::bit_scan_forward(block_bits_set_from_start, &block_bit)) {
|
|
break;
|
|
}
|
|
return std::make_pair(range_start,
|
|
(i * block_bits) + block_bit - range_start);
|
|
}
|
|
}
|
|
}
|
|
if (range_start != SIZE_MAX) {
|
|
return std::make_pair(range_start, last + size_t(1) - range_start);
|
|
}
|
|
return std::make_pair(first + length, size_t(0));
|
|
}
|
|
|
|
template <typename Block>
|
|
void SetRange(Block* bits, size_t first, size_t length) {
|
|
if (!length) {
|
|
return;
|
|
}
|
|
size_t last = first + length - 1;
|
|
const size_t block_bits = sizeof(Block) * CHAR_BIT;
|
|
size_t block_first = first / block_bits;
|
|
size_t block_last = last / block_bits;
|
|
Block set_first = ~((Block(1) << (first & (block_bits - 1))) - 1);
|
|
Block set_last = ~Block(0);
|
|
if ((last & (block_bits - 1)) != (block_bits - 1)) {
|
|
set_last &= (Block(1) << ((last & (block_bits - 1)) + 1)) - 1;
|
|
}
|
|
if (block_first == block_last) {
|
|
bits[block_first] |= set_first & set_last;
|
|
return;
|
|
}
|
|
bits[block_first] |= set_first;
|
|
if (block_first + 1 < block_last) {
|
|
std::memset(bits + block_first + 1, CHAR_MAX,
|
|
(block_last - (block_first + 1)) * sizeof(Block));
|
|
}
|
|
bits[block_last] |= set_last;
|
|
}
|
|
|
|
} // namespace bit_range
|
|
} // namespace xe
|
|
|
|
#endif // XENIA_BASE_BIT_RANGE_H_
|