Commit c37507e4 authored by Philip Pronin's avatar Philip Pronin Committed by Facebook GitHub Bot

fix overflow in EF::UpperBitsReader::reposition

Reviewed By: ot

Differential Revision: D23802800

fbshipit-source-id: 993060123790058b44d13c0b38eb4a04a28462a2
parent f8e41896
......@@ -77,7 +77,7 @@ struct EliasFanoCompressedListBase {
// WARNING: EliasFanoCompressedList has no ownership of data. The 7 bytes
// following the last byte should be readable if kUpperFirst = false, 8 bytes
// otherwise.
folly::Range<Pointer> data;
Range<Pointer> data;
Pointer skipPointers = nullptr;
Pointer forwardPointers = nullptr;
......@@ -85,8 +85,8 @@ struct EliasFanoCompressedListBase {
Pointer upper = nullptr;
};
typedef EliasFanoCompressedListBase<const uint8_t*> EliasFanoCompressedList;
typedef EliasFanoCompressedListBase<uint8_t*> MutableEliasFanoCompressedList;
using EliasFanoCompressedList = EliasFanoCompressedListBase<const uint8_t*>;
using MutableEliasFanoCompressedList = EliasFanoCompressedListBase<uint8_t*>;
template <
class Value,
......@@ -97,14 +97,14 @@ template <
bool kUpperFirst = false>
struct EliasFanoEncoderV2 {
static_assert(
std::is_integral<Value>::value && std::is_unsigned<Value>::value,
std::is_integral_v<Value> && std::is_unsigned_v<Value>,
"Value should be unsigned integral");
typedef EliasFanoCompressedList CompressedList;
typedef MutableEliasFanoCompressedList MutableCompressedList;
using CompressedList = EliasFanoCompressedList;
using MutableCompressedList = MutableEliasFanoCompressedList;
typedef Value ValueType;
typedef SkipValue SkipValueType;
using ValueType = Value;
using SkipValueType = SkipValue;
struct Layout;
static constexpr size_t skipQuantum = kSkipQuantum;
......@@ -119,7 +119,7 @@ struct EliasFanoEncoderV2 {
// "floor(a) - floor(b) - 1 <= floor(a - b) <= floor(a) - floor(b)".
// Assuming "candidate = floor(log(upperBound)) - floor(log(upperBound))",
// then result is either "candidate - 1" or "candidate".
auto candidate = folly::findLastSet(upperBound) - folly::findLastSet(size);
auto candidate = findLastSet(upperBound) - findLastSet(size);
// NOTE: As size != 0, "candidate" is always < 64.
return (size > (upperBound >> candidate)) ? candidate - 1 : candidate;
}
......@@ -175,7 +175,7 @@ struct EliasFanoEncoderV2 {
fillSkipPointersUpTo(upperBits);
if /* constexpr */ (forwardQuantum != 0) {
if constexpr (forwardQuantum != 0) {
if ((size_ + 1) % forwardQuantum == 0) {
const auto k = size_ / forwardQuantum;
// Store the number of preceding 0-bits.
......@@ -200,7 +200,7 @@ struct EliasFanoEncoderV2 {
private:
void fillSkipPointersUpTo(ValueType fillBoundary) {
if /* constexpr */ (skipQuantum != 0) {
if constexpr (skipQuantum != 0) {
while ((skipPointersSize_ + 1) * skipQuantum <= fillBoundary) {
// Store the number of preceding 1-bits.
skipPointers_[skipPointersSize_++] = static_cast<SkipValueType>(size_);
......@@ -213,9 +213,9 @@ struct EliasFanoEncoderV2 {
DCHECK_LE(uint32_t(len), 56);
DCHECK_EQ(0, value & ~((uint64_t(1) << len) - 1));
unsigned char* const ptr = data + (pos / 8);
uint64_t ptrv = folly::loadUnaligned<uint64_t>(ptr);
uint64_t ptrv = loadUnaligned<uint64_t>(ptr);
ptrv |= value << (pos % 8);
folly::storeUnaligned<uint64_t>(ptr, ptrv);
storeUnaligned<uint64_t>(ptr, ptrv);
}
unsigned char* lower_ = nullptr;
......@@ -276,7 +276,7 @@ struct EliasFanoEncoderV2<
// *** Skip pointers.
// Store (1-indexed) position of every skipQuantum-th
// 0-bit in upper bits sequence.
if /* constexpr */ (skipQuantum != 0) {
if constexpr (skipQuantum != 0) {
// 8 * upper is used here instead of upperSizeBits, as that is
// more serialization-friendly way (upperSizeBits doesn't need
// to be known by this function, unlike upper).
......@@ -288,7 +288,7 @@ struct EliasFanoEncoderV2<
// *** Forward pointers.
// Store (1-indexed) position of every forwardQuantum-th
// 1-bit in upper bits sequence.
if /* constexpr */ (forwardQuantum != 0) {
if constexpr (forwardQuantum != 0) {
size_t numForwardPointers = size / forwardQuantum;
layout.forwardPointers = numForwardPointers * sizeof(SkipValueType);
}
......@@ -317,7 +317,7 @@ struct EliasFanoEncoderV2<
result.skipPointers = advance(skipPointers);
result.forwardPointers = advance(forwardPointers);
if /* constexpr */ (kUpperFirst) {
if constexpr (kUpperFirst) {
result.upper = advance(upper);
result.lower = advance(lower);
} else {
......@@ -338,7 +338,7 @@ struct EliasFanoEncoderV2<
if (size > 0) {
buf = static_cast<uint8_t*>(malloc(bytes() + 8));
}
folly::MutableByteRange bufRange(buf, bytes());
MutableByteRange bufRange(buf, bytes());
return openList(bufRange);
}
......@@ -357,10 +357,10 @@ namespace detail {
template <class Encoder, class Instructions, class SizeType>
class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
SkipPointers<Encoder::skipQuantum> {
typedef typename Encoder::SkipValueType SkipValueType;
using SkipValueType = typename Encoder::SkipValueType;
public:
typedef typename Encoder::ValueType ValueType;
using ValueType = typename Encoder::ValueType;
explicit UpperBitsReader(const typename Encoder::CompressedList& list)
: ForwardPointers<Encoder::forwardQuantum>(list.forwardPointers),
......@@ -380,6 +380,7 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
FOLLY_ALWAYS_INLINE SizeType position() const {
return position_;
}
FOLLY_ALWAYS_INLINE ValueType value() const {
return value_;
}
......@@ -388,7 +389,7 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
size_t inner;
block_t block;
getPreviousInfo(block, inner, outer_);
block_ = folly::loadUnaligned<block_t>(start_ + outer_);
block_ = loadUnaligned<block_t>(start_ + outer_);
block_ ^= block;
--position_;
return setValue(inner);
......@@ -398,7 +399,7 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
// Skip to the first non-zero block.
while (block_ == 0) {
outer_ += sizeof(block_t);
block_ = folly::loadUnaligned<block_t>(start_ + outer_);
block_ = loadUnaligned<block_t>(start_ + outer_);
}
++position_;
......@@ -416,7 +417,7 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
// Use forward pointer.
if (Encoder::forwardQuantum > 0 && UNLIKELY(n > Encoder::forwardQuantum)) {
const size_t steps = position_ / Encoder::forwardQuantum;
const size_t dest = folly::loadUnaligned<SkipValueType>(
const size_t dest = loadUnaligned<SkipValueType>(
this->forwardPointers_ + (steps - 1) * sizeof(SkipValueType));
reposition(dest + steps * Encoder::forwardQuantum);
......@@ -428,7 +429,7 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
while ((cnt = Instructions::popcount(block_)) < n) {
n -= cnt;
outer_ += sizeof(block_t);
block_ = folly::loadUnaligned<block_t>(start_ + outer_);
block_ = loadUnaligned<block_t>(start_ + outer_);
}
// Skip to the n-th one in the block.
......@@ -448,7 +449,7 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
if (Encoder::skipQuantum > 0 &&
UNLIKELY(v >= value_ + Encoder::skipQuantum)) {
const size_t steps = v / Encoder::skipQuantum;
const size_t dest = folly::loadUnaligned<SkipValueType>(
const size_t dest = loadUnaligned<SkipValueType>(
this->skipPointers_ + (steps - 1) * sizeof(SkipValueType));
reposition(dest + Encoder::skipQuantum * steps);
......@@ -470,7 +471,7 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
skip -= cnt;
position_ += kBitsPerBlock - cnt;
outer_ += sizeof(block_t);
block_ = folly::loadUnaligned<block_t>(start_ + outer_);
block_ = loadUnaligned<block_t>(start_ + outer_);
}
if (LIKELY(skip)) {
......@@ -495,7 +496,7 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
if (Encoder::skipQuantum > 0 && v >= value_ + Encoder::skipQuantum) {
auto outer = outer_;
const size_t steps = v / Encoder::skipQuantum;
const size_t dest = folly::loadUnaligned<SkipValueType>(
const size_t dest = loadUnaligned<SkipValueType>(
this->skipPointers_ + (steps - 1) * sizeof(SkipValueType));
position = dest - 1;
......@@ -539,35 +540,37 @@ class UpperBitsReader : ForwardPointers<Encoder::forwardQuantum>,
}
private:
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_t<ValueType, SizeType>;
FOLLY_ALWAYS_INLINE ValueType setValue(size_t inner) {
value_ = static_cast<ValueType>(8 * outer_ + inner - position_);
return value_;
}
FOLLY_ALWAYS_INLINE void reposition(SizeType dest) {
// NOTE: dest is a position in the bit vector, use size_t as SizeType may
// not be sufficient here.
FOLLY_ALWAYS_INLINE void reposition(size_t dest) {
outer_ = dest / 8;
block_ = folly::loadUnaligned<block_t>(start_ + outer_);
block_ = loadUnaligned<block_t>(start_ + outer_);
block_ &= ~((block_t(1) << (dest % 8)) - 1);
}
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;
FOLLY_ALWAYS_INLINE void
getPreviousInfo(block_t& block, size_t& inner, OuterType& outer) const {
DCHECK_NE(position(), std::numeric_limits<SizeType>::max());
DCHECK_GT(position(), 0);
outer = outer_;
block = folly::loadUnaligned<block_t>(start_ + outer);
block = loadUnaligned<block_t>(start_ + outer);
inner = size_t(value_) - 8 * outer_ + position_;
block &= (block_t(1) << inner) - 1;
while (UNLIKELY(block == 0)) {
DCHECK_GT(outer, 0);
outer -= std::min<OuterType>(sizeof(block_t), outer);
block = folly::loadUnaligned<block_t>(start_ + outer);
block = loadUnaligned<block_t>(start_ + outer);
}
inner = 8 * sizeof(block_t) - 1 - Instructions::clz(block);
}
......@@ -594,8 +597,8 @@ template <
class SizeType = typename Encoder::SkipValueType>
class EliasFanoReader {
public:
typedef Encoder EncoderType;
typedef typename Encoder::ValueType ValueType;
using EncoderType = Encoder;
using ValueType = typename Encoder::ValueType;
explicit EliasFanoReader(const typename Encoder::CompressedList& list)
: upper_(list),
......@@ -614,7 +617,7 @@ class EliasFanoReader {
ValueType lastUpperValue = ValueType(8 * list.upperSizeBytes - size_);
auto it = list.upper + list.upperSizeBytes - 1;
DCHECK_NE(*it, 0);
lastUpperValue -= 8 - folly::findLastSet(*it);
lastUpperValue -= 8 - findLastSet(*it);
lastValue_ = readLowerPart(size_ - 1) | (lastUpperValue << numLowerBits_);
}
......@@ -735,7 +738,8 @@ class EliasFanoReader {
return true;
}
// We might be in the middle of a run, iterate backwards to the beginning.
// We might be in the middle of a run of equal values, reposition by
// iterating backwards to its first element.
auto valueLower = Instructions::bzhi(value_, numLowerBits_);
while (!upper_.isAtBeginningOfRun() &&
readLowerPart(upper_.position() - 1) == valueLower) {
......@@ -776,6 +780,7 @@ class EliasFanoReader {
SizeType position() const {
return upper_.position();
}
ValueType value() const {
DCHECK(valid());
return value_;
......@@ -795,7 +800,7 @@ class EliasFanoReader {
DCHECK_LT(i, size_);
const size_t pos = i * numLowerBits_;
const unsigned char* ptr = lower_ + (pos / 8);
const uint64_t ptrv = folly::loadUnaligned<uint64_t>(ptr);
const uint64_t ptrv = loadUnaligned<uint64_t>(ptr);
// This removes the branch in the fallback implementation of
// bzhi. The condition is verified at encoding time.
assume(numLowerBits_ < sizeof(ValueType) * 8);
......
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