transmission/libtransmission/bitfield.cc

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// This file Copyright © 2008-2022 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0), GPLv3 (SPDX: GPL-3.0),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <algorithm>
#include <vector>
#include "transmission.h"
#include "bitfield.h"
#include "tr-assert.h"
#include "utils.h" /* tr_new0() */
/****
*****
****/
namespace
{
constexpr size_t getBytesNeeded(size_t bit_count)
{
return (bit_count >> 3) + ((bit_count & 7) != 0 ? 1 : 0);
}
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void setAllTrue(uint8_t* array, size_t bit_count)
{
uint8_t constexpr Val = 0xFF;
size_t const n = getBytesNeeded(bit_count);
if (n > 0)
{
std::fill_n(array, n, Val);
array[n - 1] = Val << (n * 8 - bit_count);
}
}
constexpr int8_t const trueBitCount[256] = {
0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2,
3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3,
3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5,
6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4,
3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4,
5, 5, 6, 5, 6, 6, 7, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6,
6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
};
} // namespace
/****
*****
****/
size_t tr_bitfield::countFlags() const
{
size_t ret = 0;
for (auto ch : flags_)
{
ret += trueBitCount[ch];
}
return ret;
}
size_t tr_bitfield::countFlags(size_t begin, size_t end) const
{
size_t ret = 0;
size_t const first_byte = begin >> 3U;
size_t const last_byte = (end - 1) >> 3U;
if (bit_count_ == 0)
{
return 0;
}
if (first_byte >= std::size(flags_))
{
return 0;
}
TR_ASSERT(begin < end);
TR_ASSERT(!std::empty(flags_));
if (first_byte == last_byte)
{
uint8_t val = flags_[first_byte];
int i = begin - (first_byte * 8);
val <<= i;
val >>= i;
i = (last_byte + 1) * 8 - end;
val >>= i;
val <<= i;
ret += trueBitCount[val];
}
else
{
size_t const walk_end = std::min(std::size(flags_), last_byte);
/* first byte */
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size_t const first_shift = begin - (first_byte * 8);
uint8_t val = flags_[first_byte];
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val <<= first_shift;
val >>= first_shift;
ret += trueBitCount[val];
/* middle bytes */
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for (size_t i = first_byte + 1; i < walk_end; ++i)
{
ret += trueBitCount[flags_[i]];
}
/* last byte */
if (last_byte < std::size(flags_))
{
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size_t const last_shift = (last_byte + 1) * 8 - end;
val = flags_[last_byte];
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val >>= last_shift;
val <<= last_shift;
ret += trueBitCount[val];
}
}
TR_ASSERT(ret <= (begin - end));
return ret;
}
size_t tr_bitfield::count(size_t begin, size_t end) const
{
if (hasAll())
{
return end - begin;
}
if (hasNone())
{
return 0;
}
return countFlags(begin, end);
}
bool tr_bitfield::testFlag(size_t n) const
{
if (n >> 3U >= std::size(flags_))
{
return false;
}
bool ret = (flags_[n >> 3U] << (n & 7U) & 0x80) != 0;
return ret;
}
/***
****
***/
bool tr_bitfield::isValid() const
{
return std::empty(flags_) || true_count_ == countFlags();
}
std::vector<uint8_t> tr_bitfield::raw() const
{
auto const n = getBytesNeeded(bit_count_);
if (!std::empty(flags_))
{
return flags_;
}
auto raw = std::vector<uint8_t>(n);
if (hasAll())
{
setAllTrue(std::data(raw), std::size(raw));
}
return raw;
}
void tr_bitfield::ensureBitsAlloced(size_t n)
{
bool const has_all = hasAll();
size_t const bytes_needed = has_all ? getBytesNeeded(std::max(n, true_count_)) : getBytesNeeded(n);
if (std::size(flags_) < bytes_needed)
{
flags_.resize(bytes_needed);
if (has_all)
{
setAllTrue(std::data(flags_), true_count_);
}
}
}
bool tr_bitfield::ensureNthBitAlloced(size_t nth)
{
// count is zero-based, so we need to allocate nth+1 bits before setting the nth */
if (nth == SIZE_MAX)
{
return false;
}
ensureBitsAlloced(nth + 1);
return true;
}
void tr_bitfield::freeArray()
{
flags_ = std::vector<uint8_t>{};
}
void tr_bitfield::setTrueCount(size_t n)
{
TR_ASSERT(bit_count_ == 0 || n <= bit_count_);
true_count_ = n;
have_all_hint_ = n == bit_count_;
have_none_hint_ = n == 0;
if (hasAll() || hasNone())
{
freeArray();
}
TR_ASSERT(isValid());
}
void tr_bitfield::rebuildTrueCount()
{
setTrueCount(countFlags());
}
void tr_bitfield::incrementTrueCount(size_t inc)
{
TR_ASSERT(bit_count_ == 0 || inc <= bit_count_);
TR_ASSERT(bit_count_ == 0 || true_count_ <= bit_count_ - inc);
setTrueCount(true_count_ + inc);
}
void tr_bitfield::decrementTrueCount(size_t dec)
{
TR_ASSERT(bit_count_ == 0 || dec <= bit_count_);
TR_ASSERT(bit_count_ == 0 || true_count_ >= dec);
setTrueCount(true_count_ - dec);
}
/****
*****
****/
tr_bitfield::tr_bitfield(size_t bit_count)
: bit_count_{ bit_count }
{
TR_ASSERT(isValid());
}
void tr_bitfield::setHasNone()
{
freeArray();
true_count_ = 0;
have_all_hint_ = false;
have_none_hint_ = true;
TR_ASSERT(isValid());
}
void tr_bitfield::setHasAll()
{
freeArray();
true_count_ = bit_count_;
have_all_hint_ = true;
have_none_hint_ = false;
TR_ASSERT(isValid());
}
void tr_bitfield::setRaw(uint8_t const* raw, size_t byte_count)
{
flags_ = std::vector<uint8_t>(raw, raw + byte_count);
// ensure any excess bits at the end of the array are set to '0'.
if (byte_count == getBytesNeeded(bit_count_))
{
int const excess_bit_count = byte_count * 8 - bit_count_;
TR_ASSERT(excess_bit_count >= 0);
TR_ASSERT(excess_bit_count <= 7);
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if (excess_bit_count != 0)
{
flags_.back() &= 0xff << excess_bit_count;
}
}
rebuildTrueCount();
}
void tr_bitfield::setFromBools(bool const* flags, size_t n)
{
size_t trueCount = 0;
freeArray();
ensureBitsAlloced(n);
for (size_t i = 0; i < n; ++i)
{
if (flags[i])
{
++trueCount;
flags_[i >> 3U] |= (0x80 >> (i & 7U));
}
}
setTrueCount(trueCount);
}
void tr_bitfield::set(size_t nth, bool value)
{
if (test(nth) == value)
{
return;
}
if (!ensureNthBitAlloced(nth))
{
return;
}
if (value)
{
flags_[nth >> 3U] |= 0x80 >> (nth & 7U);
incrementTrueCount(1);
}
else
{
flags_[nth >> 3U] &= 0xff7f >> (nth & 7U);
decrementTrueCount(1);
}
}
/* Sets bit range [begin, end) to 1 */
void tr_bitfield::setSpan(size_t begin, size_t end, bool value)
{
// bounds check
end = std::min(end, bit_count_);
if (end == 0 || begin >= end)
{
return;
}
// did anything change?
size_t const old_count = count(begin, end);
size_t const new_count = value ? (end - begin) : 0;
if (old_count == new_count)
{
return;
}
--end;
if (!ensureNthBitAlloced(end))
{
return;
}
size_t walk = begin >> 3;
size_t const last_byte = end >> 3;
if (value)
{
unsigned char const first_mask = ~(0xff << (8 - (begin & 7)));
unsigned char const last_mask = 0xff << (7 - (end & 7));
if (walk == last_byte)
{
flags_[walk] |= first_mask & last_mask;
}
else
{
flags_[walk] |= first_mask;
flags_[last_byte] |= last_mask;
if (++walk < last_byte)
{
std::fill_n(std::begin(flags_) + walk, last_byte - walk, 0xff);
}
}
incrementTrueCount(new_count - old_count);
}
else
{
unsigned char const first_mask = 0xff << (8 - (begin & 7));
unsigned char const last_mask = ~(0xff << (7 - (end & 7)));
if (walk == last_byte)
{
flags_[walk] &= first_mask | last_mask;
}
else
{
flags_[walk] &= first_mask;
flags_[last_byte] &= last_mask;
if (++walk < last_byte)
{
std::fill_n(std::begin(flags_) + walk, last_byte - walk, 0);
}
}
decrementTrueCount(old_count);
}
}