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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@31288 91177308-0d34-0410-b5e6-96231b3b80d8
154 lines
5.2 KiB
C++
154 lines
5.2 KiB
C++
//===--- CStringMap.h - CString Hash table map interface --------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Chris Lattner and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the CStringMap class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_CSTRINGMAP_H
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#define LLVM_ADT_CSTRINGMAP_H
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#include "llvm/Support/Allocator.h"
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#include <cstring>
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namespace llvm {
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/// CStringMapVisitor - Subclasses of this class may be implemented to walk all
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/// of the items in a CStringMap.
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class CStringMapVisitor {
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public:
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virtual ~CStringMapVisitor();
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virtual void Visit(const char *Key, void *Value) const = 0;
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};
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/// CStringMapImpl - This is the base class of CStringMap that is shared among
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/// all of its instantiations.
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class CStringMapImpl {
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protected:
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/// ItemBucket - The hash table consists of an array of these. If Item is
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/// non-null, this is an extant entry, otherwise, it is a hole.
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struct ItemBucket {
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/// FullHashValue - This remembers the full hash value of the key for
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/// easy scanning.
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unsigned FullHashValue;
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/// Item - This is a pointer to the actual item object.
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void *Item;
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};
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ItemBucket *TheTable;
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unsigned NumBuckets;
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unsigned NumItems;
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unsigned ItemSize;
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protected:
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CStringMapImpl(unsigned InitSize, unsigned ItemSize);
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void RehashTable();
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/// LookupBucketFor - Look up the bucket that the specified string should end
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/// up in. If it already exists as a key in the map, the Item pointer for the
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/// specified bucket will be non-null. Otherwise, it will be null. In either
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/// case, the FullHashValue field of the bucket will be set to the hash value
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/// of the string.
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unsigned LookupBucketFor(const char *KeyStart, const char *KeyEnd);
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public:
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unsigned getNumBuckets() const { return NumBuckets; }
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unsigned getNumItems() const { return NumItems; }
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void VisitEntries(const CStringMapVisitor &Visitor) const;
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};
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/// CStringMap - This is an unconventional map that is specialized for handling
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/// keys that are "C strings", that is, null-terminated strings. This does some
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/// funky memory allocation and hashing things to make it extremely efficient,
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/// storing the string data *after* the value in the map.
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template<typename ValueTy, typename AllocatorTy = MallocAllocator>
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class CStringMap : public CStringMapImpl {
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AllocatorTy Allocator;
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public:
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CStringMap(unsigned InitialSize = 0)
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: CStringMapImpl(InitialSize, sizeof(ValueTy)) {}
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AllocatorTy &getAllocator() { return Allocator; }
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const AllocatorTy &getAllocator() const { return Allocator; }
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/// FindValue - Look up the specified key in the map. If it exists, return a
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/// pointer to the element, otherwise return null.
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ValueTy *FindValue(const char *KeyStart, const char *KeyEnd) {
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unsigned BucketNo = LookupBucketFor(KeyStart, KeyEnd);
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return static_cast<ValueTy*>(TheTable[BucketNo].Item);
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}
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/// GetKeyForValueInMap - Given a value that is inserted into this map, return
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/// the string that corresponds to it. This is an efficient operation that
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/// is provided by CStringMap. The string is live as long as the value is in
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/// the map.
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static const char *GetKeyForValueInMap(const ValueTy &Val) {
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return reinterpret_cast<const char*>(&Val+1);
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}
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/// GetOrCreateValue - Look up the specified key in the table. If a value
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/// exists, return it. Otherwise, default construct a value, insert it, and
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/// return.
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ValueTy &GetOrCreateValue(const char *KeyStart, const char *KeyEnd) {
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unsigned BucketNo = LookupBucketFor(KeyStart, KeyEnd);
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ItemBucket &Bucket = TheTable[BucketNo];
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if (Bucket.Item)
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return *static_cast<ValueTy*>(Bucket.Item);
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unsigned KeyLength = KeyEnd-KeyStart;
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// Okay, the item doesn't already exist, and Bucket is the bucket to fill
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// in. Allocate a new item with space for the null-terminated string at the
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// end.
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unsigned AllocSize = sizeof(ValueTy)+KeyLength+1;
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#ifdef __GNUC__
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unsigned Alignment = __alignof__(ValueTy);
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#else
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// FIXME: ugly.
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unsigned Alignment = 8;
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#endif
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ValueTy *NewItem = (ValueTy*)Allocator.Allocate(AllocSize, Alignment);
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new (NewItem) ValueTy();
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++NumItems;
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// Copy the string information.
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char *StrBuffer = (char*)(NewItem+1);
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memcpy(StrBuffer, KeyStart, KeyLength);
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StrBuffer[KeyLength] = 0; // Null terminate string.
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// Fill in the bucket for the hash table. The FullHashValue was already
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// filled in by LookupBucketFor.
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Bucket.Item = NewItem;
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// If the hash table is now more than 3/4 full, rehash into a larger table.
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if (NumItems > NumBuckets*3/4)
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RehashTable();
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return *NewItem;
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}
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~CStringMap() {
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for (ItemBucket *I = TheTable, *E = TheTable+NumBuckets; I != E; ++I) {
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if (ValueTy *Id = static_cast<ValueTy*>(I->Item)) {
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// Free memory referenced by the item.
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Id->~ValueTy();
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Allocator.Deallocate(Id);
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}
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}
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delete [] TheTable;
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}
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};
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}
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#endif
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