namespace detail {
-template <class Encoder, class Instructions>
+template <class Encoder, class Instructions, class SizeType>
class UpperBitsReader {
typedef typename Encoder::SkipValueType SkipValueType;
public:
void reset() {
block_ = start_ != nullptr ? folly::loadUnaligned<block_t>(start_) : 0;
+ position_ = std::numeric_limits<SizeType>::max();
outer_ = 0;
- position_ = std::numeric_limits<size_t>::max();
value_ = 0;
}
- size_t position() const { return position_; }
- ValueType value() const { return value_; }
+ SizeType position() const {
+ return position_;
+ }
+ ValueType value() const {
+ return value_;
+ }
ValueType next() {
// Skip to the first non-zero block.
return setValue(inner);
}
- ValueType skip(size_t n) {
+ ValueType skip(SizeType n) {
DCHECK_GT(n, 0);
position_ += n; // n 1-bits will be read.
if (Encoder::forwardQuantum == 0 || n <= Encoder::forwardQuantum) {
reset();
} else {
- position_ = size_t(-1); // Avoid reading the head, skip() will reposition.
+ // Avoid reading the head, skip() will reposition.
+ position_ = std::numeric_limits<SizeType>::max();
}
return skip(n);
}
}
ValueType previousValue() const {
- DCHECK_NE(position(), -1);
+ DCHECK_NE(position(), std::numeric_limits<SizeType>::max());
DCHECK_GT(position(), 0);
- size_t outer = outer_;
+ auto outer = outer_;
auto inner = size_t(value_) - 8 * outer_ + position_;
block_t block = folly::loadUnaligned<block_t>(start_ + outer);
block &= (block_t(1) << inner) - 1;
while (UNLIKELY(block == 0)) {
DCHECK_GT(outer, 0);
- outer -= std::min(sizeof(block_t), outer);
+ outer -= std::min<OuterType>(sizeof(block_t), outer);
block = folly::loadUnaligned<block_t>(start_ + outer);
}
return static_cast<ValueType>(8 * outer + inner - (position_ - 1));
}
- void setDone(size_t endPos) {
+ void setDone(SizeType endPos) {
position_ = endPos;
}
return value_;
}
- void reposition(size_t dest) {
+ void reposition(SizeType dest) {
outer_ = dest / 8;
block_ = folly::loadUnaligned<block_t>(start_ + outer_);
block_ &= ~((block_t(1) << (dest % 8)) - 1);
}
- typedef uint64_t block_t;
+ using block_t = uint64_t;
+ // The size in bytes of the upper bits is limited by n + universe / 8,
+ // so a type that can hold either sizes or values is sufficient.
+ using OuterType = typename std::common_type<ValueType, SizeType>::type;
+
const unsigned char* const forwardPointers_;
const unsigned char* const skipPointers_;
const unsigned char* const start_;
block_t block_;
- size_t outer_; // Outer offset: number of consumed bytes in upper.
- size_t position_; // Index of current value (= #reads - 1).
+ SizeType position_; // Index of current value (= #reads - 1).
+ OuterType outer_; // Outer offset: number of consumed bytes in upper.
ValueType value_;
};
// If kUnchecked = true the caller must guarantee that all the
// operations return valid elements, i.e., they would never return
// false if checked.
-template <class Encoder,
- class Instructions = instructions::Default,
- bool kUnchecked = false>
+template <
+ class Encoder,
+ class Instructions = instructions::Default,
+ bool kUnchecked = false,
+ class SizeType = size_t>
class EliasFanoReader {
public:
typedef Encoder EncoderType;
typedef typename Encoder::ValueType ValueType;
explicit EliasFanoReader(const typename Encoder::CompressedList& list)
- : size_(list.size),
+ : upper_(list),
lower_(list.lower),
- upper_(list),
+ size_(list.size),
numLowerBits_(list.numLowerBits) {
DCHECK(Instructions::supported());
// To avoid extra branching during skipTo() while reading
return true;
}
- bool skip(size_t n) {
+ bool skip(SizeType n) {
CHECK_GT(n, 0);
if (kUnchecked || LIKELY(position() + n < size_)) {
if (LIKELY(n < kLinearScanThreshold)) {
- for (size_t i = 0; i < n; ++i) upper_.next();
+ for (SizeType i = 0; i < n; ++i)
+ upper_.next();
} else {
upper_.skip(n);
}
return true;
}
- bool jump(size_t n) {
+ bool jump(SizeType n) {
if (LIKELY(n < size_)) { // Also checks that n != -1.
value_ = readLowerPart(n) | (upper_.jump(n + 1) << numLowerBits_);
return true;
(upper_.previousValue() << numLowerBits_);
}
- size_t size() const { return size_; }
+ SizeType size() const {
+ return size_;
+ }
bool valid() const {
return position() < size(); // Also checks that position() != -1.
}
- size_t position() const { return upper_.position(); }
+ SizeType position() const {
+ return upper_.position();
+ }
ValueType value() const {
DCHECK(valid());
return value_;
}
private:
+ // Must hold kInvalidValue + 1 == 0.
constexpr static ValueType kInvalidValue =
- std::numeric_limits<ValueType>::max(); // Must hold kInvalidValue + 1 == 0.
+ std::numeric_limits<ValueType>::max();
bool setDone() {
value_ = kInvalidValue;
return false;
}
- ValueType readLowerPart(size_t i) const {
+ ValueType readLowerPart(SizeType i) const {
DCHECK_LT(i, size_);
const size_t pos = i * numLowerBits_;
const unsigned char* ptr = lower_ + (pos / 8);
constexpr static size_t kLinearScanThreshold = 8;
- size_t size_;
+ detail::UpperBitsReader<Encoder, Instructions, SizeType> upper_;
const uint8_t* lower_;
- detail::UpperBitsReader<Encoder, Instructions> upper_;
+ SizeType size_;
ValueType value_ = kInvalidValue;
ValueType lastValue_;
uint8_t numLowerBits_;
projects / folly.git / blobdiff