99 lines
3.9 KiB
C
99 lines
3.9 KiB
C
/**
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@file
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A reliable hashtable implementation. The implementation makes
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use of nested top actions, and is reentrant. Currently, all keys
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and values must be of the same length, although this restriction
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will eventually be removed.
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The implementation uses a linear hash function, allowing the
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bucket list to be resized dynamically. Because the bucket list is
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built on top of arrayList, all operations are O(1), assuming the
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hash function behaves correctly. Currently, linkedListNTA
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implements the bucket lists.
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@see nestedTopAction.h, linkedListNTA.h, arrayList.h
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@ingroup OPERATIONS
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$id$
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*/
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#ifndef __LINEAR_HASH_NTA_H
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#define __LINEAR_HASH_NTA_H
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/** Currently, only used in the type field of the iterators. */
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#define FIXED_LENGTH_HASH 0
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#define VARIABLE_LENGTH_HASH 1
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/** Pass this into the keySize and/or valueSize parameter of the
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constructor below if the hashtable should support variable length
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keys and/or values, respectively. */
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#define VARIABLE_LENGTH -1
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typedef struct {
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recordid hashHeader;
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recordid bucket;
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int numBuckets;
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int keySize;
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int valueSize;
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lladd_linkedList_iterator * it;
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lladd_pagedList_iterator * pit;
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} lladd_hash_iterator;
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compensated_function recordid ThashCreate(int xid, int keySize, int valSize);
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compensated_function void ThashDelete(int xid, recordid hash);
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/* @return 1 if the key was defined, 0 otherwise. */
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compensated_function int ThashInsert(int xid, recordid hash, const byte* key, int keySize, const byte* value, int valueSize);
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/* @return 1 if the key was defined, 0 otherwise. */
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compensated_function int ThashRemove(int xid, recordid hash, const byte* key, int keySize);
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/** @return size of the value associated with key, or -1 if key not found.
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(a return value of zero means the key is associated with an
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empty value.) */
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compensated_function int ThashLookup(int xid, recordid hash, const byte* key, int keySize, byte ** value);
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/**
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Allocate a new hash iterator. This API is designed to eventually be
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overloaded, and is subject to change. If the iterator is run to completion,
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it is automatically freed. Otherwise, it should be manually freed with free().
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@param xid transaction id
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@param hash the recordid returned by ThashAlloc
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@param keySize the same as the value passed into ThashAlloc.
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@param valueSize the same as the value passed into ThashAlloc
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*/
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lladd_hash_iterator * ThashIterator(int xid, recordid hash, int keySize, int valueSize);
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/**
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Obtain the next value in the hash table.
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@return 1 if another value exists; 0 if the iterator is done, and has been deallocated.
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@param keySize Currently, keySize and valueSize must
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be set to the correct sizes when ThashNext is called. Once hashtables with
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variable sized entries are supported, this restriction will be relaxed or removed
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entirely.
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@param key a pointer to an uninitialized pointer value. If another entry is
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encountered, then the uninitialized pointer value will be set to point
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to a malloc()'ed region of memory that contains the value's key. This
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region of memory should be manually free()'ed by the application. LLADD
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normally leaves memory management to the application. However, once
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hashes with variable size entries are supported, it would be extremely
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difficult for the application to malloc an appropriate buffer for the
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iterator, so this function call does not obey normal LLADD calling
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semantics.
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@param value analagous to value.
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@param valueSize analagous to keySize
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*/
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int ThashNext(int xid, lladd_hash_iterator * it, byte ** key, int * keySize, byte** value, int * valueSize);
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/** Free the hash iterator and its associated resources. */
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void ThashDone(int xid, lladd_hash_iterator * it);
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Operation getLinearHashInsert();
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Operation getLinearHashRemove();
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//Support 16 entries by default.
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#define HASH_INIT_BITS 4
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#define HASH_FILL_FACTOR 0.7
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#endif // __LINEAR_HASH_NTA_H
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