1 //===--- OnDiskHashTable.h - On-Disk Hash Table Implementation --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 /// \brief Defines facilities for reading and writing on-disk hash tables.
13 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_SUPPORT_ONDISKHASHTABLE_H
15 #define LLVM_SUPPORT_ONDISKHASHTABLE_H
17 #include "llvm/Support/AlignOf.h"
18 #include "llvm/Support/Allocator.h"
19 #include "llvm/Support/DataTypes.h"
20 #include "llvm/Support/EndianStream.h"
21 #include "llvm/Support/Host.h"
22 #include "llvm/Support/MathExtras.h"
23 #include "llvm/Support/raw_ostream.h"
29 /// \brief Generates an on disk hash table.
31 /// This needs an \c Info that handles storing values into the hash table's
32 /// payload and computes the hash for a given key. This should provide the
33 /// following interface:
36 /// class ExampleInfo {
38 /// typedef ExampleKey key_type; // Must be copy constructible
39 /// typedef ExampleKey &key_type_ref;
40 /// typedef ExampleData data_type; // Must be copy constructible
41 /// typedef ExampleData &data_type_ref;
42 /// typedef uint32_t hash_value_type; // The type the hash function returns.
43 /// typedef uint32_t offset_type; // The type for offsets into the table.
45 /// /// Calculate the hash for Key
46 /// static hash_value_type ComputeHash(key_type_ref Key);
47 /// /// Return the lengths, in bytes, of the given Key/Data pair.
48 /// static std::pair<offset_type, offset_type>
49 /// EmitKeyDataLength(raw_ostream &Out, key_type_ref Key, data_type_ref Data);
50 /// /// Write Key to Out. KeyLen is the length from EmitKeyDataLength.
51 /// static void EmitKey(raw_ostream &Out, key_type_ref Key,
52 /// offset_type KeyLen);
53 /// /// Write Data to Out. DataLen is the length from EmitKeyDataLength.
54 /// static void EmitData(raw_ostream &Out, key_type_ref Key,
55 /// data_type_ref Data, offset_type DataLen);
58 template <typename Info> class OnDiskChainedHashTableGenerator {
59 /// \brief A single item in the hash table.
62 typename Info::key_type Key;
63 typename Info::data_type Data;
65 const typename Info::hash_value_type Hash;
67 Item(typename Info::key_type_ref Key, typename Info::data_type_ref Data,
69 : Key(Key), Data(Data), Next(nullptr), Hash(InfoObj.ComputeHash(Key)) {}
72 typedef typename Info::offset_type offset_type;
73 offset_type NumBuckets;
74 offset_type NumEntries;
75 llvm::SpecificBumpPtrAllocator<Item> BA;
77 /// \brief A linked list of values in a particular hash bucket.
87 /// \brief Insert an item into the appropriate hash bucket.
88 void insert(Bucket *Buckets, size_t Size, Item *E) {
89 Bucket &B = Buckets[E->Hash & (Size - 1)];
95 /// \brief Resize the hash table, moving the old entries into the new buckets.
96 void resize(size_t NewSize) {
97 Bucket *NewBuckets = (Bucket *)std::calloc(NewSize, sizeof(Bucket));
98 // Populate NewBuckets with the old entries.
99 for (size_t I = 0; I < NumBuckets; ++I)
100 for (Item *E = Buckets[I].Head; E;) {
103 insert(NewBuckets, NewSize, E);
108 NumBuckets = NewSize;
109 Buckets = NewBuckets;
113 /// \brief Insert an entry into the table.
114 void insert(typename Info::key_type_ref Key,
115 typename Info::data_type_ref Data) {
117 insert(Key, Data, InfoObj);
120 /// \brief Insert an entry into the table.
122 /// Uses the provided Info instead of a stack allocated one.
123 void insert(typename Info::key_type_ref Key,
124 typename Info::data_type_ref Data, Info &InfoObj) {
127 if (4 * NumEntries >= 3 * NumBuckets)
128 resize(NumBuckets * 2);
129 insert(Buckets, NumBuckets, new (BA.Allocate()) Item(Key, Data, InfoObj));
132 /// \brief Emit the table to Out, which must not be at offset 0.
133 offset_type Emit(raw_ostream &Out) {
135 return Emit(Out, InfoObj);
138 /// \brief Emit the table to Out, which must not be at offset 0.
140 /// Uses the provided Info instead of a stack allocated one.
141 offset_type Emit(raw_ostream &Out, Info &InfoObj) {
142 using namespace llvm::support;
143 endian::Writer<little> LE(Out);
145 // Emit the payload of the table.
146 for (offset_type I = 0; I < NumBuckets; ++I) {
147 Bucket &B = Buckets[I];
151 // Store the offset for the data of this bucket.
153 assert(B.Off && "Cannot write a bucket at offset 0. Please add padding.");
155 // Write out the number of items in the bucket.
156 LE.write<uint16_t>(B.Length);
157 assert(B.Length != 0 && "Bucket has a head but zero length?");
159 // Write out the entries in the bucket.
160 for (Item *I = B.Head; I; I = I->Next) {
161 LE.write<typename Info::hash_value_type>(I->Hash);
162 const std::pair<offset_type, offset_type> &Len =
163 InfoObj.EmitKeyDataLength(Out, I->Key, I->Data);
164 InfoObj.EmitKey(Out, I->Key, Len.first);
165 InfoObj.EmitData(Out, I->Key, I->Data, Len.second);
169 // Pad with zeros so that we can start the hashtable at an aligned address.
170 offset_type TableOff = Out.tell();
171 uint64_t N = llvm::OffsetToAlignment(TableOff, alignOf<offset_type>());
174 LE.write<uint8_t>(0);
176 // Emit the hashtable itself.
177 LE.write<offset_type>(NumBuckets);
178 LE.write<offset_type>(NumEntries);
179 for (offset_type I = 0; I < NumBuckets; ++I)
180 LE.write<offset_type>(Buckets[I].Off);
185 OnDiskChainedHashTableGenerator() {
188 // Note that we do not need to run the constructors of the individual
189 // Bucket objects since 'calloc' returns bytes that are all 0.
190 Buckets = (Bucket *)std::calloc(NumBuckets, sizeof(Bucket));
193 ~OnDiskChainedHashTableGenerator() { std::free(Buckets); }
196 /// \brief Provides lookup on an on disk hash table.
198 /// This needs an \c Info that handles reading values from the hash table's
199 /// payload and computes the hash for a given key. This should provide the
200 /// following interface:
203 /// class ExampleLookupInfo {
205 /// typedef ExampleData data_type;
206 /// typedef ExampleInternalKey internal_key_type; // The stored key type.
207 /// typedef ExampleKey external_key_type; // The type to pass to find().
208 /// typedef uint32_t hash_value_type; // The type the hash function returns.
209 /// typedef uint32_t offset_type; // The type for offsets into the table.
211 /// /// Compare two keys for equality.
212 /// static bool EqualKey(internal_key_type &Key1, internal_key_type &Key2);
213 /// /// Calculate the hash for the given key.
214 /// static hash_value_type ComputeHash(internal_key_type &IKey);
215 /// /// Translate from the semantic type of a key in the hash table to the
216 /// /// type that is actually stored and used for hashing and comparisons.
217 /// /// The internal and external types are often the same, in which case this
218 /// /// can simply return the passed in value.
219 /// static const internal_key_type &GetInternalKey(external_key_type &EKey);
220 /// /// Read the key and data length from Buffer, leaving it pointing at the
221 /// /// following byte.
222 /// static std::pair<offset_type, offset_type>
223 /// ReadKeyDataLength(const unsigned char *&Buffer);
224 /// /// Read the key from Buffer, given the KeyLen as reported from
225 /// /// ReadKeyDataLength.
226 /// const internal_key_type &ReadKey(const unsigned char *Buffer,
227 /// offset_type KeyLen);
228 /// /// Read the data for Key from Buffer, given the DataLen as reported from
229 /// /// ReadKeyDataLength.
230 /// data_type ReadData(StringRef Key, const unsigned char *Buffer,
231 /// offset_type DataLen);
234 template <typename Info> class OnDiskChainedHashTable {
235 const typename Info::offset_type NumBuckets;
236 const typename Info::offset_type NumEntries;
237 const unsigned char *const Buckets;
238 const unsigned char *const Base;
242 typedef typename Info::internal_key_type internal_key_type;
243 typedef typename Info::external_key_type external_key_type;
244 typedef typename Info::data_type data_type;
245 typedef typename Info::hash_value_type hash_value_type;
246 typedef typename Info::offset_type offset_type;
248 OnDiskChainedHashTable(offset_type NumBuckets, offset_type NumEntries,
249 const unsigned char *Buckets,
250 const unsigned char *Base,
251 const Info &InfoObj = Info())
252 : NumBuckets(NumBuckets), NumEntries(NumEntries), Buckets(Buckets),
253 Base(Base), InfoObj(InfoObj) {
254 assert((reinterpret_cast<uintptr_t>(Buckets) & 0x3) == 0 &&
255 "'buckets' must have a 4-byte alignment");
258 /// Read the number of buckets and the number of entries from a hash table
259 /// produced by OnDiskHashTableGenerator::Emit, and advance the Buckets
260 /// pointer past them.
261 static std::pair<offset_type, offset_type>
262 readNumBucketsAndEntries(const unsigned char *&Buckets) {
263 assert((reinterpret_cast<uintptr_t>(Buckets) & 0x3) == 0 &&
264 "buckets should be 4-byte aligned.");
265 using namespace llvm::support;
266 offset_type NumBuckets =
267 endian::readNext<offset_type, little, aligned>(Buckets);
268 offset_type NumEntries =
269 endian::readNext<offset_type, little, aligned>(Buckets);
270 return std::make_pair(NumBuckets, NumEntries);
273 offset_type getNumBuckets() const { return NumBuckets; }
274 offset_type getNumEntries() const { return NumEntries; }
275 const unsigned char *getBase() const { return Base; }
276 const unsigned char *getBuckets() const { return Buckets; }
278 bool isEmpty() const { return NumEntries == 0; }
281 internal_key_type Key;
282 const unsigned char *const Data;
283 const offset_type Len;
287 iterator() : Data(nullptr), Len(0) {}
288 iterator(const internal_key_type K, const unsigned char *D, offset_type L,
290 : Key(K), Data(D), Len(L), InfoObj(InfoObj) {}
292 data_type operator*() const { return InfoObj->ReadData(Key, Data, Len); }
293 bool operator==(const iterator &X) const { return X.Data == Data; }
294 bool operator!=(const iterator &X) const { return X.Data != Data; }
297 /// \brief Look up the stored data for a particular key.
298 iterator find(const external_key_type &EKey, Info *InfoPtr = nullptr) {
299 const internal_key_type &IKey = InfoObj.GetInternalKey(EKey);
300 hash_value_type KeyHash = InfoObj.ComputeHash(IKey);
301 return find_hashed(IKey, KeyHash, InfoPtr);
304 /// \brief Look up the stored data for a particular key with a known hash.
305 iterator find_hashed(const internal_key_type &IKey, hash_value_type KeyHash,
306 Info *InfoPtr = nullptr) {
307 using namespace llvm::support;
312 // Each bucket is just an offset into the hash table file.
313 offset_type Idx = KeyHash & (NumBuckets - 1);
314 const unsigned char *Bucket = Buckets + sizeof(offset_type) * Idx;
316 offset_type Offset = endian::readNext<offset_type, little, aligned>(Bucket);
318 return iterator(); // Empty bucket.
319 const unsigned char *Items = Base + Offset;
321 // 'Items' starts with a 16-bit unsigned integer representing the
322 // number of items in this bucket.
323 unsigned Len = endian::readNext<uint16_t, little, unaligned>(Items);
325 for (unsigned i = 0; i < Len; ++i) {
327 hash_value_type ItemHash =
328 endian::readNext<hash_value_type, little, unaligned>(Items);
330 // Determine the length of the key and the data.
331 const std::pair<offset_type, offset_type> &L =
332 Info::ReadKeyDataLength(Items);
333 offset_type ItemLen = L.first + L.second;
335 // Compare the hashes. If they are not the same, skip the entry entirely.
336 if (ItemHash != KeyHash) {
342 const internal_key_type &X =
343 InfoPtr->ReadKey((const unsigned char *const)Items, L.first);
345 // If the key doesn't match just skip reading the value.
346 if (!InfoPtr->EqualKey(X, IKey)) {
352 return iterator(X, Items + L.first, L.second, InfoPtr);
358 iterator end() const { return iterator(); }
360 Info &getInfoObj() { return InfoObj; }
362 /// \brief Create the hash table.
364 /// \param Buckets is the beginning of the hash table itself, which follows
365 /// the payload of entire structure. This is the value returned by
366 /// OnDiskHashTableGenerator::Emit.
368 /// \param Base is the point from which all offsets into the structure are
369 /// based. This is offset 0 in the stream that was used when Emitting the
371 static OnDiskChainedHashTable *Create(const unsigned char *Buckets,
372 const unsigned char *const Base,
373 const Info &InfoObj = Info()) {
374 assert(Buckets > Base);
375 auto NumBucketsAndEntries = readNumBucketsAndEntries(Buckets);
376 return new OnDiskChainedHashTable<Info>(NumBucketsAndEntries.first,
377 NumBucketsAndEntries.second,
378 Buckets, Base, InfoObj);
382 /// \brief Provides lookup and iteration over an on disk hash table.
384 /// \copydetails llvm::OnDiskChainedHashTable
385 template <typename Info>
386 class OnDiskIterableChainedHashTable : public OnDiskChainedHashTable<Info> {
387 const unsigned char *Payload;
390 typedef OnDiskChainedHashTable<Info> base_type;
391 typedef typename base_type::internal_key_type internal_key_type;
392 typedef typename base_type::external_key_type external_key_type;
393 typedef typename base_type::data_type data_type;
394 typedef typename base_type::hash_value_type hash_value_type;
395 typedef typename base_type::offset_type offset_type;
398 /// \brief Iterates over all of the keys in the table.
399 class iterator_base {
400 const unsigned char *Ptr;
401 offset_type NumItemsInBucketLeft;
402 offset_type NumEntriesLeft;
405 typedef external_key_type value_type;
407 iterator_base(const unsigned char *const Ptr, offset_type NumEntries)
408 : Ptr(Ptr), NumItemsInBucketLeft(0), NumEntriesLeft(NumEntries) {}
410 : Ptr(nullptr), NumItemsInBucketLeft(0), NumEntriesLeft(0) {}
412 friend bool operator==(const iterator_base &X, const iterator_base &Y) {
413 return X.NumEntriesLeft == Y.NumEntriesLeft;
415 friend bool operator!=(const iterator_base &X, const iterator_base &Y) {
416 return X.NumEntriesLeft != Y.NumEntriesLeft;
419 /// Move to the next item.
421 using namespace llvm::support;
422 if (!NumItemsInBucketLeft) {
423 // 'Items' starts with a 16-bit unsigned integer representing the
424 // number of items in this bucket.
425 NumItemsInBucketLeft =
426 endian::readNext<uint16_t, little, unaligned>(Ptr);
428 Ptr += sizeof(hash_value_type); // Skip the hash.
429 // Determine the length of the key and the data.
430 const std::pair<offset_type, offset_type> &L =
431 Info::ReadKeyDataLength(Ptr);
432 Ptr += L.first + L.second;
433 assert(NumItemsInBucketLeft);
434 --NumItemsInBucketLeft;
435 assert(NumEntriesLeft);
439 /// Get the start of the item as written by the trait (after the hash and
440 /// immediately before the key and value length).
441 const unsigned char *getItem() const {
442 return Ptr + (NumItemsInBucketLeft ? 0 : 2) + sizeof(hash_value_type);
447 OnDiskIterableChainedHashTable(offset_type NumBuckets, offset_type NumEntries,
448 const unsigned char *Buckets,
449 const unsigned char *Payload,
450 const unsigned char *Base,
451 const Info &InfoObj = Info())
452 : base_type(NumBuckets, NumEntries, Buckets, Base, InfoObj),
455 /// \brief Iterates over all of the keys in the table.
456 class key_iterator : public iterator_base {
460 typedef external_key_type value_type;
462 key_iterator(const unsigned char *const Ptr, offset_type NumEntries,
464 : iterator_base(Ptr, NumEntries), InfoObj(InfoObj) {}
465 key_iterator() : iterator_base(), InfoObj() {}
467 key_iterator &operator++() {
471 key_iterator operator++(int) { // Postincrement
472 key_iterator tmp = *this;
477 internal_key_type getInternalKey() const {
478 auto *LocalPtr = this->getItem();
480 // Determine the length of the key and the data.
481 auto L = Info::ReadKeyDataLength(LocalPtr);
484 return InfoObj->ReadKey(LocalPtr, L.first);
487 value_type operator*() const {
488 return InfoObj->GetExternalKey(getInternalKey());
492 key_iterator key_begin() {
493 return key_iterator(Payload, this->getNumEntries(), &this->getInfoObj());
495 key_iterator key_end() { return key_iterator(); }
497 iterator_range<key_iterator> keys() {
498 return make_range(key_begin(), key_end());
501 /// \brief Iterates over all the entries in the table, returning the data.
502 class data_iterator : public iterator_base {
506 typedef data_type value_type;
508 data_iterator(const unsigned char *const Ptr, offset_type NumEntries,
510 : iterator_base(Ptr, NumEntries), InfoObj(InfoObj) {}
511 data_iterator() : iterator_base(), InfoObj() {}
513 data_iterator &operator++() { // Preincrement
517 data_iterator operator++(int) { // Postincrement
518 data_iterator tmp = *this;
523 value_type operator*() const {
524 auto *LocalPtr = this->getItem();
526 // Determine the length of the key and the data.
527 auto L = Info::ReadKeyDataLength(LocalPtr);
530 const internal_key_type &Key = InfoObj->ReadKey(LocalPtr, L.first);
531 return InfoObj->ReadData(Key, LocalPtr + L.first, L.second);
535 data_iterator data_begin() {
536 return data_iterator(Payload, this->getNumEntries(), &this->getInfoObj());
538 data_iterator data_end() { return data_iterator(); }
540 iterator_range<data_iterator> data() {
541 return make_range(data_begin(), data_end());
544 /// \brief Create the hash table.
546 /// \param Buckets is the beginning of the hash table itself, which follows
547 /// the payload of entire structure. This is the value returned by
548 /// OnDiskHashTableGenerator::Emit.
550 /// \param Payload is the beginning of the data contained in the table. This
551 /// is Base plus any padding or header data that was stored, ie, the offset
552 /// that the stream was at when calling Emit.
554 /// \param Base is the point from which all offsets into the structure are
555 /// based. This is offset 0 in the stream that was used when Emitting the
557 static OnDiskIterableChainedHashTable *
558 Create(const unsigned char *Buckets, const unsigned char *const Payload,
559 const unsigned char *const Base, const Info &InfoObj = Info()) {
560 assert(Buckets > Base);
561 auto NumBucketsAndEntries =
562 OnDiskIterableChainedHashTable<Info>::readNumBucketsAndEntries(Buckets);
563 return new OnDiskIterableChainedHashTable<Info>(
564 NumBucketsAndEntries.first, NumBucketsAndEntries.second,
565 Buckets, Payload, Base, InfoObj);
569 } // end namespace llvm