jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 1 | // Copyright (c) 2011 The LevelDB Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. See the AUTHORS file for names of contributors. |
| 4 | |
| 5 | #include "db/memtable.h" |
| 6 | #include "db/dbformat.h" |
jorlow@chromium.org | fbd97aa | 2011-03-30 18:35:40 +0000 | [diff] [blame] | 7 | #include "leveldb/comparator.h" |
| 8 | #include "leveldb/env.h" |
| 9 | #include "leveldb/iterator.h" |
jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 10 | #include "util/coding.h" |
| 11 | |
| 12 | namespace leveldb { |
| 13 | |
| 14 | static Slice GetLengthPrefixedSlice(const char* data) { |
| 15 | uint32_t len; |
| 16 | const char* p = data; |
| 17 | p = GetVarint32Ptr(p, p + 5, &len); // +5: we assume "p" is not corrupted |
| 18 | return Slice(p, len); |
| 19 | } |
| 20 | |
| 21 | MemTable::MemTable(const InternalKeyComparator& cmp) |
| 22 | : comparator_(cmp), |
| 23 | table_(comparator_, &arena_) { |
| 24 | } |
| 25 | |
| 26 | MemTable::~MemTable() { |
| 27 | } |
| 28 | |
| 29 | size_t MemTable::ApproximateMemoryUsage() { return arena_.MemoryUsage(); } |
| 30 | |
| 31 | int MemTable::KeyComparator::operator()(const char* aptr, const char* bptr) |
| 32 | const { |
| 33 | // Internal keys are encoded as length-prefixed strings. |
| 34 | Slice a = GetLengthPrefixedSlice(aptr); |
| 35 | Slice b = GetLengthPrefixedSlice(bptr); |
| 36 | return comparator.Compare(a, b); |
| 37 | } |
| 38 | |
| 39 | // Encode a suitable internal key target for "target" and return it. |
| 40 | // Uses *scratch as scratch space, and the returned pointer will point |
| 41 | // into this scratch space. |
| 42 | static const char* EncodeKey(std::string* scratch, const Slice& target) { |
| 43 | scratch->clear(); |
| 44 | PutVarint32(scratch, target.size()); |
| 45 | scratch->append(target.data(), target.size()); |
| 46 | return scratch->data(); |
| 47 | } |
| 48 | |
| 49 | class MemTableIterator: public Iterator { |
| 50 | public: |
| 51 | explicit MemTableIterator(MemTable::Table* table) { |
| 52 | iter_ = new MemTable::Table::Iterator(table); |
| 53 | } |
| 54 | virtual ~MemTableIterator() { delete iter_; } |
| 55 | |
| 56 | virtual bool Valid() const { return iter_->Valid(); } |
| 57 | virtual void Seek(const Slice& k) { iter_->Seek(EncodeKey(&tmp_, k)); } |
| 58 | virtual void SeekToFirst() { iter_->SeekToFirst(); } |
| 59 | virtual void SeekToLast() { iter_->SeekToLast(); } |
| 60 | virtual void Next() { iter_->Next(); } |
| 61 | virtual void Prev() { iter_->Prev(); } |
| 62 | virtual Slice key() const { return GetLengthPrefixedSlice(iter_->key()); } |
| 63 | virtual Slice value() const { |
| 64 | Slice key_slice = GetLengthPrefixedSlice(iter_->key()); |
| 65 | return GetLengthPrefixedSlice(key_slice.data() + key_slice.size()); |
| 66 | } |
| 67 | |
| 68 | virtual Status status() const { return Status::OK(); } |
| 69 | |
| 70 | private: |
| 71 | MemTable::Table::Iterator* iter_; |
| 72 | std::string tmp_; // For passing to EncodeKey |
| 73 | |
| 74 | // No copying allowed |
| 75 | MemTableIterator(const MemTableIterator&); |
| 76 | void operator=(const MemTableIterator&); |
| 77 | }; |
| 78 | |
| 79 | Iterator* MemTable::NewIterator() { |
| 80 | return new MemTableIterator(&table_); |
| 81 | } |
| 82 | |
| 83 | void MemTable::Add(SequenceNumber s, ValueType type, |
| 84 | const Slice& key, |
| 85 | const Slice& value) { |
| 86 | // Format of an entry is concatenation of: |
| 87 | // key_size : varint32 of internal_key.size() |
| 88 | // key bytes : char[internal_key.size()] |
| 89 | // value_size : varint32 of value.size() |
| 90 | // value bytes : char[value.size()] |
| 91 | size_t key_size = key.size(); |
| 92 | size_t val_size = value.size(); |
| 93 | size_t internal_key_size = key_size + 8; |
| 94 | const size_t encoded_len = |
| 95 | VarintLength(internal_key_size) + internal_key_size + |
| 96 | VarintLength(val_size) + val_size; |
| 97 | char* buf = arena_.Allocate(encoded_len); |
| 98 | char* p = EncodeVarint32(buf, internal_key_size); |
| 99 | memcpy(p, key.data(), key_size); |
| 100 | p += key_size; |
| 101 | EncodeFixed64(p, (s << 8) | type); |
| 102 | p += 8; |
| 103 | p = EncodeVarint32(p, val_size); |
| 104 | memcpy(p, value.data(), val_size); |
| 105 | assert((p + val_size) - buf == encoded_len); |
| 106 | table_.Insert(buf); |
| 107 | } |
| 108 | |
| 109 | } |