thin-provisioning-tools/persistent-data/data-structures/bitset.h

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2013-03-14 18:43:18 +05:30
// Copyright (C) 2013 Red Hat, Inc. All rights reserved.
//
// This file is part of the thin-provisioning-tools source.
//
// thin-provisioning-tools is free software: you can redistribute it
// and/or modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation, either version 3 of
// the License, or (at your option) any later version.
//
// thin-provisioning-tools is distributed in the hope that it will be
// useful, but WITHOUT ANY WARRANTY; without even the implied warranty
// of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with thin-provisioning-tools. If not, see
// <http://www.gnu.org/licenses/>.
#ifndef BITSET_H
#define BITSET_H
#include "persistent-data/math_utils.h"
#include "persistent-data/data-structures/array.h"
//----------------------------------------------------------------
namespace persistent_data {
namespace bitset_detail {
struct bitset_traits {
typedef base::__le64 disk_type;
typedef uint64_t value_type;
typedef no_op_ref_counter<uint64_t> ref_counter;
static void unpack(disk_type const &disk, value_type &value) {
value = base::to_cpu<uint64_t>(disk);
}
static void pack(value_type const &value, disk_type &disk) {
disk = base::to_disk<base::__le64>(value);
}
};
}
class bitset {
public:
typedef boost::shared_ptr<bitset> ptr;
typedef typename persistent_data::transaction_manager::ptr tm_ptr;
bitset(tm_ptr tm)
: nr_bits_(0),
array_(tm, rc_) {
}
bitset(tm_ptr tm, block_address root, unsigned nr_bits)
: nr_bits_(nr_bits),
array_(tm, rc_, root, nr_bits) {
}
block_address get_root() const {
return array_.get_root();
}
void grow(unsigned new_nr_bits, bool default_value) {
pad_last_block(default_value);
resize_array(new_nr_bits, default_value);
nr_bits_ = new_nr_bits;
}
void destroy();
// May trigger a flush, so cannot be const
bool get(unsigned n) {
check_bounds(n);
return get_bit(array_.get(word(n)), bit(n));
}
void set(unsigned n, bool value) {
check_bounds(n);
unsigned w_index = word(n);
uint64_t w = array_.get(w_index);
if (value)
w = set_bit(w, bit(n));
else
w = clear_bit(w, bit(n));
array_.set(w_index, w);
}
void flush() {
}
private:
void pad_last_block(bool default_value) {
// Set defaults in the final word
if (bit(nr_bits_)) {
unsigned w_index = word(nr_bits_);
uint64_t w = array_.get(w_index);
for (unsigned b = bit(nr_bits_); b < 64; b++)
if (default_value)
w = set_bit(w, b);
else
w = clear_bit(w, b);
array_.set(w_index, w);
}
}
void resize_array(unsigned new_nr_bits, bool default_value) {
unsigned old_nr_words = words_needed(nr_bits_);
unsigned new_nr_words = words_needed(new_nr_bits);
if (new_nr_words < old_nr_words)
throw runtime_error("bitset grow actually asked to shrink");
if (new_nr_words > old_nr_words)
array_.grow(new_nr_words, default_value ? ~0 : 0);
}
unsigned words_needed(unsigned nr_bits) const {
return base::div_up<unsigned>(nr_bits, 64u);
}
unsigned word(unsigned bit) const {
return bit / 64;
}
uint64_t mask(unsigned bit) const {
return 1ull << bit;
}
bool get_bit(uint64_t w, unsigned bit) const {
return w & mask(bit);
}
uint64_t set_bit(uint64_t w, unsigned bit) const {
return w | mask(bit);
}
uint64_t clear_bit(uint64_t w, unsigned bit) const {
return w & (~mask(bit));
}
unsigned bit(unsigned bit) const {
return bit % 64;
}
// The last word may be only partially full, so we have to
// do our own bounds checking rather than relying on array
// to do it.
void check_bounds(unsigned n) const {
if (n >= nr_bits_) {
std::ostringstream str;
str << "bitset index out of bounds ("
<< n << " >= " << nr_bits_ << endl;
throw runtime_error(str.str());
}
}
unsigned nr_bits_;
no_op_ref_counter<uint64_t> rc_;
array<bitset_detail::bitset_traits> array_;
};
}
//----------------------------------------------------------------
#endif