[llvm-commits] CVS: llvm/include/llvm/ADT/CStringMap.h

[Chris Lattner]

Changes in directory llvm/include/llvm/ADT:

CStringMap.h added (r1.1)
---
Log message:

add a highly efficient hash table that is specialized for mapping C strings
to some other type.


---
Diffs of the changes:  (+144 -0)

 CStringMap.h |  144 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 144 insertions(+)


Index: llvm/include/llvm/ADT/CStringMap.h
diff -c /dev/null llvm/include/llvm/ADT/CStringMap.h:1.1
*** /dev/null	Sun Oct 29 17:42:13 2006
--- llvm/include/llvm/ADT/CStringMap.h	Sun Oct 29 17:42:03 2006
***************
*** 0 ****
--- 1,144 ----
+ //===--- CStringMap.h - CString Hash table map interface --------*- C++ -*-===//
+ //
+ //                     The LLVM Compiler Infrastructure
+ //
+ // This file was developed by Chris Lattner and is distributed under
+ // the University of Illinois Open Source License. See LICENSE.TXT for details.
+ //
+ //===----------------------------------------------------------------------===//
+ //
+ // This file defines the CStringMap class.
+ //
+ //===----------------------------------------------------------------------===//
+ 
+ #ifndef LLVM_ADT_CSTRINGMAP_H
+ #define LLVM_ADT_CSTRINGMAP_H
+ 
+ #include "llvm/Support/Allocator.h"
+ #include <cstring>
+ 
+ namespace llvm {
+   
+ /// CStringMapVisitor - Subclasses of this class may be implemented to walk all
+ /// of the items in a CStringMap.
+ class CStringMapVisitor {
+ public:
+   virtual ~CStringMapVisitor();
+   virtual void Visit(const char *Key, void *Value) const = 0;
+ };
+   
+ /// CStringMapImpl - This is the base class of CStringMap that is shared among
+ /// all of its instantiations.
+ class CStringMapImpl {
+ protected:
+   /// ItemBucket - The hash table consists of an array of these.  If Item is
+   /// non-null, this is an extant entry, otherwise, it is a hole.
+   struct ItemBucket {
+     /// FullHashValue - This remembers the full hash value of the key for
+     /// easy scanning.
+     unsigned FullHashValue;
+     
+     /// Item - This is a pointer to the actual item object.
+     void *Item;
+   };
+   
+   ItemBucket *TheTable;
+   unsigned NumBuckets;
+   unsigned NumItems;
+   unsigned ItemSize;
+ protected:
+   CStringMapImpl(unsigned InitSize, unsigned ItemSize);
+   void RehashTable();
+   
+   /// LookupBucketFor - Look up the bucket that the specified string should end
+   /// up in.  If it already exists as a key in the map, the Item pointer for the
+   /// specified bucket will be non-null.  Otherwise, it will be null.  In either
+   /// case, the FullHashValue field of the bucket will be set to the hash value
+   /// of the string.
+   unsigned LookupBucketFor(const char *KeyStart, const char *KeyEnd);
+   
+ public:
+   unsigned getNumBuckets() const { return NumBuckets; }
+   unsigned getNumItems() const { return NumItems; }
+ 
+   void VisitEntries(const CStringMapVisitor &Visitor) const;
+ };
+ 
+ 
+ /// CStringMap - This is an unconventional map that is specialized for handling
+ /// keys that are "C strings", that is, null-terminated strings.  This does some
+ /// funky memory allocation and hashing things to make it extremely efficient,
+ /// storing the string data *after* the value in the map.
+ template<typename ValueTy, typename AllocatorTy = MallocAllocator>
+ class CStringMap : public CStringMapImpl {
+   AllocatorTy Allocator;
+ public:
+   CStringMap(unsigned InitialSize = 0)
+     : CStringMapImpl(InitialSize, sizeof(ValueTy)) {}
+   
+   AllocatorTy &getAllocator() { return Allocator; }
+   const AllocatorTy &getAllocator() const { return Allocator; }
+ 
+   /// FindValue - Look up the specified key in the map.  If it exists, return a
+   /// pointer to the element, otherwise return null.
+   ValueTy *FindValue(const char *KeyStart, const char *KeyEnd) {
+     unsigned BucketNo = LookupBucketFor(KeyStart, KeyEnd);
+     return static_cast<ValueTy*>(TheTable[BucketNo].Item);
+   }
+   
+   /// GetOrCreateValue - Look up the specified key in the table.  If a value
+   /// exists, return it.  Otherwise, default construct a value, insert it, and
+   /// return.
+   ValueTy &GetOrCreateValue(const char *KeyStart, const char *KeyEnd) {
+     unsigned BucketNo = LookupBucketFor(KeyStart, KeyEnd);
+     ItemBucket &Bucket = TheTable[BucketNo];
+     if (Bucket.Item)
+       return *static_cast<ValueTy*>(Bucket.Item);
+     
+     unsigned KeyLength = KeyEnd-KeyStart;
+     
+     // Okay, the item doesn't already exist, and Bucket is the bucket to fill
+     // in.  Allocate a new item with space for the null-terminated string at the
+     // end.
+     unsigned AllocSize = sizeof(ValueTy)+KeyLength+1;
+     
+ #ifdef __GNUC__
+     unsigned Alignment = __alignof__(ValueTy);
+ #else
+     // FIXME: ugly.
+     unsigned Alignment = 8;
+ #endif
+     ValueTy *NewItem = (ValueTy*)Allocator.Allocate(AllocSize, Alignment);
+     new (NewItem) ValueTy();
+     ++NumItems;
+     
+     // Copy the string information.
+     char *StrBuffer = (char*)(NewItem+1);
+     memcpy(StrBuffer, KeyStart, KeyLength);
+     StrBuffer[KeyLength] = 0;  // Null terminate string.
+     
+     // Fill in the bucket for the hash table.  The FullHashValue was already
+     // filled in by LookupBucketFor.
+     Bucket.Item = NewItem;
+     
+     // If the hash table is now more than 3/4 full, rehash into a larger table.
+     if (NumItems > NumBuckets*3/4)
+       RehashTable();
+     return *NewItem;
+   }
+   
+   ~CStringMap() {
+     for (ItemBucket *I = TheTable, *E = TheTable+NumBuckets; I != E; ++I) {
+       if (ValueTy *Id = static_cast<ValueTy*>(I->Item)) {
+         // Free memory referenced by the item.
+         Id->~ValueTy();
+         Allocator.Deallocate(Id);
+       }
+     }
+     delete [] TheTable;
+   }
+ };
+   
+ }
+ 
+ #endif
\ No newline at end of file