add iterator for skiplist

src/util/inc/sskiplist.h

-/*
- * Copyright (c) 2019 TAOS Data, Inc. <jhtao@taosdata.com>
- *
- * This program is free software: you can use, redistribute, and/or modify
- * it under the terms of the GNU Affero General Public License, version 3
- * or later ("AGPL"), as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-#if 0
-
-#ifndef TBASE_TSKIPLIST_H
-#define TBASE_TSKIPLIST_H
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-#define MAX_SKIP_LIST_LEVEL 20
-
-#include <pthread.h>
-#include <stdint.h>
-#include <stdlib.h>
-
-#include "os.h"
-#include "taosdef.h"
-
-/*
- * key of each node
- * todo move to as the global structure in all search codes...
- */
-
-const static size_t SKIP_LIST_STR_KEY_LENGTH_THRESHOLD = 15;
-typedef tVariant    tSkipListKey;
-
-typedef enum tSkipListPointQueryType {
-  INCLUDE_POINT_QUERY,
-  EXCLUDE_POINT_QUERY,
-} tSkipListPointQueryType;
-
-typedef struct tSkipListNode {
-  uint16_t nLevel;
-  char *   pData;
-
-  struct tSkipListNode **pForward;
-  struct tSkipListNode **pBackward;
-
-  tSkipListKey key;
-} tSkipListNode;
-
-/*
- * @version 0.2
- * @date   2017/11/12
- * the simple version of SkipList.
- * for multi-thread safe purpose, we employ pthread_rwlock_t to guarantee to generate
- * deterministic result. Later, we will remove the lock in SkipList to further
- * enhance the performance. In this case, one should use the concurrent skip list (by
- * using michael-scott algorithm) instead of this simple version in a multi-thread
- * environment, to achieve higher performance of read/write operations.
- *
- * Note: Duplicated primary key situation.
- * In case of duplicated primary key, two ways can be employed to handle this situation:
- * 1. add as normal insertion with out special process.
- * 2. add an overflow pointer at each list node, all nodes with the same key will be added
- *    in the overflow pointer. In this case, the total steps of each search will be reduced significantly.
- *    Currently, we implement the skip list in a line with the first means, maybe refactor it soon.
- *
- *    Memory consumption: the memory alignment causes many memory wasted. So, employ a memory
- *    pool will significantly reduce the total memory consumption, as well as the calloc/malloc operation costs.
- *
- * 3. use the iterator pattern to refactor all routines to make it more clean
- */
-
-// state struct, record following information:
-// number of links in each level.
-// avg search steps, for latest 1000 queries
-// avg search rsp time, for latest 1000 queries
-// total memory size
-typedef struct tSkipListState {
-  // in bytes, sizeof(tSkipList)+sizeof(tSkipListNode)*tSkipList->nSize
-  uint64_t nTotalMemSize;
-  uint64_t nLevelNodeCnt[MAX_SKIP_LIST_LEVEL];
-  uint64_t queryCount;  // total query count
-
-  /*
-   * only record latest 1000 queries
-   * when the value==1000, = 0,
-   * nTotalStepsForQueries = 0,
-   * nTotalElapsedTimeForQueries = 0
-   */
-  uint64_t nRecQueries;
-  uint16_t nTotalStepsForQueries;
-  uint64_t nTotalElapsedTimeForQueries;
-
-  uint16_t nInsertObjs;
-  uint16_t nTotalStepsForInsert;
-  uint64_t nTotalElapsedTimeForInsert;
-} tSkipListState;
-
-typedef struct tSkipList {
-  tSkipListNode pHead;
-  uint64_t      nSize;
-  uint16_t      nMaxLevel;
-  uint16_t      nLevel;
-  uint16_t      keyType;
-  uint16_t      nMaxKeyLen;
-
-  __compar_fn_t    comparator;
-  pthread_rwlock_t lock;   // will be removed soon
-  tSkipListState   state;  // skiplist state
-} tSkipList;
-
-/*
- * iterate the skiplist
- * this will cause the multi-thread problem, when the skiplist is destroyed, the iterate may
- * continue iterating the skiplist, so add the reference count for skiplist
- * TODO add the ref for skiplist when one iterator is created
- */
-typedef struct SSkipListIterator {
-  tSkipList *    pSkipList;
-  tSkipListNode *cur;
-  int64_t        num;
-} SSkipListIterator;
-
-/*
- * query condition structure to denote the range query
- * todo merge the point query cond with range query condition
- */
-typedef struct tSKipListQueryCond {
-  // when the upper bounding == lower bounding, it is a point query
-  tSkipListKey lowerBnd;
-  tSkipListKey upperBnd;
-  int32_t      lowerBndRelOptr;  // relation operator to denote if lower bound is
-  int32_t      upperBndRelOptr;  // included or not
-} tSKipListQueryCond;
-
-tSkipList *SSkipListCreate(int16_t nMaxLevel, int16_t keyType, int16_t nMaxKeyLen);
-
-void *SSkipListDestroy(tSkipList *pSkipList);
-
-// create skip list key
-tSkipListKey SSkipListCreateKey(int32_t type, char *val, size_t keyLength);
-
-// destroy skip list key
-void tSkipListDestroyKey(tSkipListKey *pKey);
-
-// put data into skiplist
-tSkipListNode *SSkipListPut(tSkipList *pSkipList, void *pData, tSkipListKey *pKey, int32_t insertIdenticalKey);
-
-/*
- * get only *one* node of which key is equalled to pKey, even there are more
- * than one nodes are of the same key
- */
-tSkipListNode *tSkipListGetOne(tSkipList *pSkipList, tSkipListKey *pKey);
-
-/*
- * get all data with the same keys
- */
-int32_t tSkipListGets(tSkipList *pSkipList, tSkipListKey *pKey, tSkipListNode ***pRes);
-
-int32_t tSkipListIterateList(tSkipList *pSkipList, tSkipListNode ***pRes, bool (*fp)(tSkipListNode *, void *),
-                             void *param);
-
-/*
- * remove only one node of the pKey value.
- * If more than one node has the same value, any one will be removed
- *
- * @Return
- * true: one node has been removed
- * false: no node has been removed
- */
-bool tSkipListRemove(tSkipList *pSkipList, tSkipListKey *pKey);
-
-/*
- * remove the specified node in parameters
- */
-void tSkipListRemoveNode(tSkipList *pSkipList, tSkipListNode *pNode);
-
-// for debug purpose only
-void SSkipListPrint(tSkipList *pSkipList, int16_t nlevel);
-
-/*
- * range query & single point query function
- */
-int32_t tSkipListQuery(tSkipList *pSkipList, tSKipListQueryCond *pQueryCond, tSkipListNode ***pResult);
-
-/*
- * include/exclude point query
- */
-int32_t tSkipListPointQuery(tSkipList *pSkipList, tSkipListKey *pKey, int32_t numOfKey, tSkipListPointQueryType type,
-                            tSkipListNode ***pResult);
-
-int32_t tSkipListIteratorReset(tSkipList *pSkipList, SSkipListIterator *iter);
-bool tSkipListIteratorNext(SSkipListIterator *iter);
-tSkipListNode *tSkipListIteratorGet(SSkipListIterator *iter);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif  // TBASE_TSKIPLIST_H
-#endif
\ No newline at end of file

src/util/inc/tskiplist.h

@@ -185,15 +185,39 @@ SSkipListNode *tSkipListPut(SSkipList *pSkipList, SSkipListNode *pNode);
 SArray* tSkipListGet(SSkipList *pSkipList, SSkipListKey pKey, int16_t keyType);
 
 /**
- *
+ * get the size of skip list
  * @param pSkipList
- * @param pRes
- * @param fp
- * @param param
  * @return
  */
-int32_t tSkipListIterateList(SSkipList *pSkipList, SSkipListNode ***pRes, bool (*fp)(SSkipListNode *, void *),
-                             void *param);
+size_t tSkipListGetSize(const SSkipList* pSkipList);
+
+/**
+ * create skiplist iterator
+ * @param pSkipList
+ * @return
+ */
+SSkipListIterator* tSkipListCreateIter(SSkipList *pSkipList);
+
+/**
+ * forward the skip list iterator
+ * @param iter
+ * @return
+ */
+bool tSkipListIterNext(SSkipListIterator *iter);
+
+/**
+ * get the element of skip list node
+ * @param iter
+ * @return
+ */
+SSkipListNode *tSkipListIterGet(SSkipListIterator *iter);
+
+/**
+ * destroy the skip list node
+ * @param iter
+ * @return
+ */
+void* tSkipListDestroyIter(SSkipListIterator* iter);
 
 /*
  * remove only one node of the pKey value.
@@ -210,9 +234,6 @@ bool tSkipListRemove(SSkipList *pSkipList, SSkipListKey *pKey);
  */
 void tSkipListRemoveNode(SSkipList *pSkipList, SSkipListNode *pNode);
 
-int32_t        tSkipListIteratorReset(SSkipList *pSkipList, SSkipListIterator *iter);
-bool           tSkipListIteratorNext(SSkipListIterator *iter);
-SSkipListNode *tSkipListIteratorGet(SSkipListIterator *iter);
 
 #ifdef __cplusplus
 }

src/util/src/tskiplist.c

@@ -524,6 +524,71 @@ SArray* tSkipListGet(SSkipList *pSkipList, SSkipListKey pKey, int16_t keyType) {
   return sa;
 }
 
+size_t tSkipListGetSize(const SSkipList* pSkipList) {
+  if (pSkipList == NULL) {
+    return 0;
+  }
+  
+  return pSkipList->size;
+}
+
+SSkipListIterator* tSkipListCreateIter(SSkipList *pSkipList) {
+  if (pSkipList == NULL) {
+    return NULL;
+  }
+  
+  SSkipListIterator* iter = calloc(1, sizeof(SSkipListIterator));
+  
+  iter->pSkipList = pSkipList;
+  if (pSkipList->lock) {
+    pthread_rwlock_rdlock(pSkipList->lock);
+  }
+  
+  iter->cur = NULL;
+  iter->num = pSkipList->size;
+  
+  if (pSkipList->lock) {
+    pthread_rwlock_unlock(pSkipList->lock);
+  }
+  
+  return iter;
+}
+
+bool tSkipListIterNext(SSkipListIterator *iter) {
+  if (iter->num == 0 || iter->pSkipList == NULL) {
+    return false;
+  }
+  
+  SSkipList *pSkipList = iter->pSkipList;
+  
+  if (pSkipList->lock) {
+    pthread_rwlock_rdlock(pSkipList->lock);
+  }
+  
+  if (iter->cur == NULL) {
+    iter->cur = SL_GET_FORWARD_POINTER(pSkipList->pHead, 0);
+  } else {
+    iter->cur = SL_GET_FORWARD_POINTER(iter->cur, 0);
+  }
+  
+  if (pSkipList->lock) {
+    pthread_rwlock_unlock(pSkipList->lock);
+  }
+  
+  return iter->cur != NULL;
+}
+
+SSkipListNode *tSkipListIterGet(SSkipListIterator *iter) { return (iter == NULL)? NULL:iter->cur; }
+
+void* tSkipListDestroyIter(SSkipListIterator* iter) {
+  if (iter == NULL) {
+    return NULL;
+  }
+  
+  tfree(iter);
+  return NULL;
+}
+
 // static int32_t tSkipListEndParQuery(SSkipList *pSkipList, SSkipListNode *pStartNode, SSkipListKey *pEndKey,
 //                                    int32_t cond, SSkipListNode ***pRes) {
 //  pthread_rwlock_rdlock(&pSkipList->lock);