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), |
dgrogan@chromium.org | a5b4129 | 2011-05-21 02:17:43 +0000 | [diff] [blame] | 23 | refs_(0), |
jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 24 | table_(comparator_, &arena_) { |
| 25 | } |
| 26 | |
| 27 | MemTable::~MemTable() { |
dgrogan@chromium.org | a5b4129 | 2011-05-21 02:17:43 +0000 | [diff] [blame] | 28 | assert(refs_ == 0); |
jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 29 | } |
| 30 | |
| 31 | size_t MemTable::ApproximateMemoryUsage() { return arena_.MemoryUsage(); } |
| 32 | |
| 33 | int MemTable::KeyComparator::operator()(const char* aptr, const char* bptr) |
| 34 | const { |
| 35 | // Internal keys are encoded as length-prefixed strings. |
| 36 | Slice a = GetLengthPrefixedSlice(aptr); |
| 37 | Slice b = GetLengthPrefixedSlice(bptr); |
| 38 | return comparator.Compare(a, b); |
| 39 | } |
| 40 | |
| 41 | // Encode a suitable internal key target for "target" and return it. |
| 42 | // Uses *scratch as scratch space, and the returned pointer will point |
| 43 | // into this scratch space. |
| 44 | static const char* EncodeKey(std::string* scratch, const Slice& target) { |
| 45 | scratch->clear(); |
| 46 | PutVarint32(scratch, target.size()); |
| 47 | scratch->append(target.data(), target.size()); |
| 48 | return scratch->data(); |
| 49 | } |
| 50 | |
| 51 | class MemTableIterator: public Iterator { |
| 52 | public: |
dgrogan@chromium.org | c6ac22e | 2011-05-28 00:53:58 +0000 | [diff] [blame] | 53 | explicit MemTableIterator(MemTable::Table* table) : iter_(table) { } |
jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 54 | |
dgrogan@chromium.org | c6ac22e | 2011-05-28 00:53:58 +0000 | [diff] [blame] | 55 | virtual bool Valid() const { return iter_.Valid(); } |
| 56 | virtual void Seek(const Slice& k) { iter_.Seek(EncodeKey(&tmp_, k)); } |
| 57 | virtual void SeekToFirst() { iter_.SeekToFirst(); } |
| 58 | virtual void SeekToLast() { iter_.SeekToLast(); } |
| 59 | virtual void Next() { iter_.Next(); } |
| 60 | virtual void Prev() { iter_.Prev(); } |
| 61 | virtual Slice key() const { return GetLengthPrefixedSlice(iter_.key()); } |
jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 62 | virtual Slice value() const { |
dgrogan@chromium.org | c6ac22e | 2011-05-28 00:53:58 +0000 | [diff] [blame] | 63 | Slice key_slice = GetLengthPrefixedSlice(iter_.key()); |
jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 64 | return GetLengthPrefixedSlice(key_slice.data() + key_slice.size()); |
| 65 | } |
| 66 | |
| 67 | virtual Status status() const { return Status::OK(); } |
| 68 | |
| 69 | private: |
dgrogan@chromium.org | c6ac22e | 2011-05-28 00:53:58 +0000 | [diff] [blame] | 70 | MemTable::Table::Iterator iter_; |
jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 71 | std::string tmp_; // For passing to EncodeKey |
| 72 | |
| 73 | // No copying allowed |
| 74 | MemTableIterator(const MemTableIterator&); |
| 75 | void operator=(const MemTableIterator&); |
| 76 | }; |
| 77 | |
| 78 | Iterator* MemTable::NewIterator() { |
dgrogan@chromium.org | c6ac22e | 2011-05-28 00:53:58 +0000 | [diff] [blame] | 79 | return new MemTableIterator(&table_); |
jorlow@chromium.org | 179be58 | 2011-03-18 22:37:00 +0000 | [diff] [blame] | 80 | } |
| 81 | |
| 82 | void MemTable::Add(SequenceNumber s, ValueType type, |
| 83 | const Slice& key, |
| 84 | const Slice& value) { |
| 85 | // Format of an entry is concatenation of: |
| 86 | // key_size : varint32 of internal_key.size() |
| 87 | // key bytes : char[internal_key.size()] |
| 88 | // value_size : varint32 of value.size() |
| 89 | // value bytes : char[value.size()] |
| 90 | size_t key_size = key.size(); |
| 91 | size_t val_size = value.size(); |
| 92 | size_t internal_key_size = key_size + 8; |
| 93 | const size_t encoded_len = |
| 94 | VarintLength(internal_key_size) + internal_key_size + |
| 95 | VarintLength(val_size) + val_size; |
| 96 | char* buf = arena_.Allocate(encoded_len); |
| 97 | char* p = EncodeVarint32(buf, internal_key_size); |
| 98 | memcpy(p, key.data(), key_size); |
| 99 | p += key_size; |
| 100 | EncodeFixed64(p, (s << 8) | type); |
| 101 | p += 8; |
| 102 | p = EncodeVarint32(p, val_size); |
| 103 | memcpy(p, value.data(), val_size); |
| 104 | assert((p + val_size) - buf == encoded_len); |
| 105 | table_.Insert(buf); |
| 106 | } |
| 107 | |
gabor@google.com | 8cd4ab8 | 2011-06-22 02:36:45 +0000 | [diff] [blame] | 108 | bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) { |
| 109 | Slice memkey = key.memtable_key(); |
| 110 | Table::Iterator iter(&table_); |
| 111 | iter.Seek(memkey.data()); |
| 112 | if (iter.Valid()) { |
| 113 | // entry format is: |
| 114 | // klength varint32 |
| 115 | // userkey char[klength] |
| 116 | // tag uint64 |
| 117 | // vlength varint32 |
| 118 | // value char[vlength] |
| 119 | // Check that it belongs to same user key. We do not check the |
| 120 | // sequence number since the Seek() call above should have skipped |
| 121 | // all entries with overly large sequence numbers. |
| 122 | const char* entry = iter.key(); |
| 123 | uint32_t key_length; |
| 124 | const char* key_ptr = GetVarint32Ptr(entry, entry+5, &key_length); |
| 125 | if (comparator_.comparator.user_comparator()->Compare( |
| 126 | Slice(key_ptr, key_length - 8), |
| 127 | key.user_key()) == 0) { |
| 128 | // Correct user key |
| 129 | const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8); |
| 130 | switch (static_cast<ValueType>(tag & 0xff)) { |
| 131 | case kTypeValue: { |
| 132 | Slice v = GetLengthPrefixedSlice(key_ptr + key_length); |
| 133 | value->assign(v.data(), v.size()); |
| 134 | return true; |
| 135 | } |
| 136 | case kTypeDeletion: |
| 137 | *s = Status::NotFound(Slice()); |
| 138 | return true; |
| 139 | } |
| 140 | } |
| 141 | } |
| 142 | return false; |
| 143 | } |
| 144 | |
hans@chromium.org | 45b9940 | 2011-10-31 17:34:55 +0000 | [diff] [blame] | 145 | } // namespace leveldb |