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author | jorlow@chromium.org <jorlow@chromium.org@62dab493-f737-651d-591e-8d6aee1b9529> | 2011-03-30 18:49:03 +0000 |
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committer | jorlow@chromium.org <jorlow@chromium.org@62dab493-f737-651d-591e-8d6aee1b9529> | 2011-03-30 18:49:03 +0000 |
commit | 9e33808a26cbbb38008fcd10b74c4d05d78d0aa1 (patch) | |
tree | aa5b999df95bf5949265ae55e167a82033a959d7 /include/leveldb/iterator.h | |
parent | 4671a695fca3a8fb00cdf4609cd8238cf12ed13d (diff) | |
download | leveldb-9e33808a26cbbb38008fcd10b74c4d05d78d0aa1.tar.gz |
Fix last commit
git-svn-id: https://leveldb.googlecode.com/svn/trunk@19 62dab493-f737-651d-591e-8d6aee1b9529
Diffstat (limited to 'include/leveldb/iterator.h')
-rw-r--r-- | include/leveldb/iterator.h | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/include/leveldb/iterator.h b/include/leveldb/iterator.h new file mode 100644 index 0000000..1866fb5 --- /dev/null +++ b/include/leveldb/iterator.h @@ -0,0 +1,95 @@ +// Copyright (c) 2011 The LevelDB Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. See the AUTHORS file for names of contributors. +// +// An iterator yields a sequence of key/value pairs from a source. +// The following class defines the interface. Multiple implementations +// are provided by this library. In particular, iterators are provided +// to access the contents of a Table or a DB. + +#ifndef STORAGE_LEVELDB_INCLUDE_ITERATOR_H_ +#define STORAGE_LEVELDB_INCLUDE_ITERATOR_H_ + +#include "leveldb/slice.h" +#include "leveldb/status.h" + +namespace leveldb { + +class Iterator { + public: + Iterator(); + virtual ~Iterator(); + + // An iterator is either positioned at a key/value pair, or + // not valid. This method returns true iff the iterator is valid. + virtual bool Valid() const = 0; + + // Position at the first key in the source. The iterator is Valid() + // after this call iff the source is not empty. + virtual void SeekToFirst() = 0; + + // Position at the last key in the source. The iterator is + // Valid() after this call iff the source is not empty. + virtual void SeekToLast() = 0; + + // Position at the first key in the source that at or past target + // The iterator is Valid() after this call iff the source contains + // an entry that comes at or past target. + virtual void Seek(const Slice& target) = 0; + + // Moves to the next entry in the source. After this call, Valid() is + // true iff the iterator was not positioned at the last entry in the source. + // REQUIRES: Valid() + virtual void Next() = 0; + + // Moves to the previous entry in the source. After this call, Valid() is + // true iff the iterator was not positioned at the first entry in source. + // REQUIRES: Valid() + virtual void Prev() = 0; + + // Return the key for the current entry. The underlying storage for + // the returned slice is valid only until the next modification of + // the iterator. + // REQUIRES: Valid() + virtual Slice key() const = 0; + + // Return the value for the current entry. The underlying storage for + // the returned slice is valid only until the next modification of + // the iterator. + // REQUIRES: !AtEnd() && !AtStart() + virtual Slice value() const = 0; + + // If an error has occurred, return it. Else return an ok status. + virtual Status status() const = 0; + + // Clients are allowed to register function/arg1/arg2 triples that + // will be invoked when this iterator is destroyed. + // + // Note that unlike all of the preceding methods, this method is + // not abstract and therefore clients should not override it. + typedef void (*CleanupFunction)(void* arg1, void* arg2); + void RegisterCleanup(CleanupFunction function, void* arg1, void* arg2); + + private: + struct Cleanup { + CleanupFunction function; + void* arg1; + void* arg2; + Cleanup* next; + }; + Cleanup cleanup_; + + // No copying allowed + Iterator(const Iterator&); + void operator=(const Iterator&); +}; + +// Return an empty iterator (yields nothing). +extern Iterator* NewEmptyIterator(); + +// Return an empty iterator with the specified status. +extern Iterator* NewErrorIterator(const Status& status); + +} + +#endif // STORAGE_LEVELDB_INCLUDE_ITERATOR_H_ |