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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#pragma once
#include <cassert>
#include "rocksdb/comparator.h"
#include "table/internal_iterator.h"
namespace ROCKSDB_NAMESPACE {
// An internal iterator that wraps another one and ensures that any keys
// returned are strictly within a range [start, end). If the underlying
// iterator has already performed the bounds checking, it relies on that result;
// otherwise, it performs the necessary key comparisons itself. Both bounds
// are optional.
class ClippingIterator : public InternalIterator {
public:
ClippingIterator(InternalIterator* iter, const Slice* start, const Slice* end,
const CompareInterface* cmp)
: iter_(iter), start_(start), end_(end), cmp_(cmp), valid_(false) {
assert(iter_);
assert(cmp_);
assert(!start_ || !end_ || cmp_->Compare(*start_, *end_) <= 0);
UpdateAndEnforceBounds();
}
bool Valid() const override { return valid_; }
void SeekToFirst() override {
if (start_) {
iter_->Seek(*start_);
} else {
iter_->SeekToFirst();
}
UpdateAndEnforceUpperBound();
}
void SeekToLast() override {
if (end_) {
iter_->SeekForPrev(*end_);
// Upper bound is exclusive, so we need a key which is strictly smaller
if (iter_->Valid() && cmp_->Compare(iter_->key(), *end_) == 0) {
iter_->Prev();
}
} else {
iter_->SeekToLast();
}
UpdateAndEnforceLowerBound();
}
void Seek(const Slice& target) override {
if (start_ && cmp_->Compare(target, *start_) < 0) {
iter_->Seek(*start_);
UpdateAndEnforceUpperBound();
return;
}
if (end_ && cmp_->Compare(target, *end_) >= 0) {
valid_ = false;
return;
}
iter_->Seek(target);
UpdateAndEnforceUpperBound();
}
void SeekForPrev(const Slice& target) override {
if (start_ && cmp_->Compare(target, *start_) < 0) {
valid_ = false;
return;
}
if (end_ && cmp_->Compare(target, *end_) >= 0) {
iter_->SeekForPrev(*end_);
// Upper bound is exclusive, so we need a key which is strictly smaller
if (iter_->Valid() && cmp_->Compare(iter_->key(), *end_) == 0) {
iter_->Prev();
}
UpdateAndEnforceLowerBound();
return;
}
iter_->SeekForPrev(target);
UpdateAndEnforceLowerBound();
}
void Next() override {
assert(valid_);
iter_->Next();
UpdateAndEnforceUpperBound();
}
bool NextAndGetResult(IterateResult* result) override {
assert(valid_);
assert(result);
IterateResult res;
valid_ = iter_->NextAndGetResult(&res);
if (!valid_) {
return false;
}
if (end_) {
EnforceUpperBoundImpl(res.bound_check_result);
if (!valid_) {
return false;
}
}
res.bound_check_result = IterBoundCheck::kInbound;
*result = res;
return true;
}
void Prev() override {
assert(valid_);
iter_->Prev();
UpdateAndEnforceLowerBound();
}
Slice key() const override {
assert(valid_);
return iter_->key();
}
Slice user_key() const override {
assert(valid_);
return iter_->user_key();
}
Slice value() const override {
assert(valid_);
return iter_->value();
}
Status status() const override { return iter_->status(); }
bool PrepareValue() override {
assert(valid_);
if (iter_->PrepareValue()) {
return true;
}
assert(!iter_->Valid());
valid_ = false;
return false;
}
bool MayBeOutOfLowerBound() override {
assert(valid_);
return false;
}
IterBoundCheck UpperBoundCheckResult() override {
assert(valid_);
return IterBoundCheck::kInbound;
}
void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) override {
iter_->SetPinnedItersMgr(pinned_iters_mgr);
}
bool IsKeyPinned() const override {
assert(valid_);
return iter_->IsKeyPinned();
}
bool IsValuePinned() const override {
assert(valid_);
return iter_->IsValuePinned();
}
Status GetProperty(std::string prop_name, std::string* prop) override {
return iter_->GetProperty(prop_name, prop);
}
private:
void UpdateValid() {
assert(!iter_->Valid() || iter_->status().ok());
valid_ = iter_->Valid();
}
void EnforceUpperBoundImpl(IterBoundCheck bound_check_result) {
if (bound_check_result == IterBoundCheck::kInbound) {
return;
}
if (bound_check_result == IterBoundCheck::kOutOfBound) {
valid_ = false;
return;
}
assert(bound_check_result == IterBoundCheck::kUnknown);
if (cmp_->Compare(key(), *end_) >= 0) {
valid_ = false;
}
}
void EnforceUpperBound() {
if (!valid_) {
return;
}
if (!end_) {
return;
}
EnforceUpperBoundImpl(iter_->UpperBoundCheckResult());
}
void EnforceLowerBound() {
if (!valid_) {
return;
}
if (!start_) {
return;
}
if (!iter_->MayBeOutOfLowerBound()) {
return;
}
if (cmp_->Compare(key(), *start_) < 0) {
valid_ = false;
}
}
void AssertBounds() {
assert(!valid_ || !start_ || cmp_->Compare(key(), *start_) >= 0);
assert(!valid_ || !end_ || cmp_->Compare(key(), *end_) < 0);
}
void UpdateAndEnforceBounds() {
UpdateValid();
EnforceUpperBound();
EnforceLowerBound();
AssertBounds();
}
void UpdateAndEnforceUpperBound() {
UpdateValid();
EnforceUpperBound();
AssertBounds();
}
void UpdateAndEnforceLowerBound() {
UpdateValid();
EnforceLowerBound();
AssertBounds();
}
InternalIterator* iter_;
const Slice* start_;
const Slice* end_;
const CompareInterface* cmp_;
bool valid_;
};
} // namespace ROCKSDB_NAMESPACE
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