diff --git a/HISTORY b/HISTORY
index 54982ce..5483375 100644
--- a/HISTORY
+++ b/HISTORY
@@ -1,6 +1,7 @@
 
 Version 1.44  2020-01-19
   * add test file src/tests/test_pthread_lock.c
+  * add uniq_skiplist.[hc]
 
 Version 1.43  2019-12-25
   * replace function call system to getExecResult,
diff --git a/src/Makefile.in b/src/Makefile.in
index 9b75651..1202649 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -14,8 +14,8 @@ FAST_SHARED_OBJS = hash.lo chain.lo shared_func.lo ini_file_reader.lo \
                    fast_buffer.lo multi_skiplist.lo flat_skiplist.lo \
                    system_info.lo fast_blocked_queue.lo id_generator.lo \
 				   char_converter.lo char_convert_loader.lo common_blocked_queue.lo \
-                   multi_socket_client.lo skiplist_set.lo json_parser.lo \
-                   buffered_file_writer.lo
+                   multi_socket_client.lo skiplist_set.lo uniq_skiplist.lo \
+                   json_parser.lo buffered_file_writer.lo
 
 FAST_STATIC_OBJS = hash.o chain.o shared_func.o ini_file_reader.o \
                    logger.o sockopt.o base64.o sched_thread.o \
@@ -26,8 +26,8 @@ FAST_STATIC_OBJS = hash.o chain.o shared_func.o ini_file_reader.o \
                    fast_buffer.o multi_skiplist.o flat_skiplist.o  \
                    system_info.o fast_blocked_queue.o id_generator.o \
 				   char_converter.o char_convert_loader.o common_blocked_queue.o \
-                   multi_socket_client.o skiplist_set.o json_parser.o \
-                   buffered_file_writer.o
+                   multi_socket_client.o skiplist_set.o uniq_skiplist.o \
+                   json_parser.o buffered_file_writer.o
 
 HEADER_FILES = common_define.h hash.h chain.h logger.h base64.h \
                shared_func.h pthread_func.h ini_file_reader.h _os_define.h \
@@ -39,8 +39,8 @@ HEADER_FILES = common_define.h hash.h chain.h logger.h base64.h \
                skiplist_common.h system_info.h fast_blocked_queue.h \
                php7_ext_wrapper.h id_generator.h char_converter.h \
 			   char_convert_loader.h common_blocked_queue.h  \
-               multi_socket_client.h skiplist_set.h fc_list.h \
-               json_parser.h buffered_file_writer.h
+               multi_socket_client.h skiplist_set.h uniq_skiplist.h \
+               fc_list.h json_parser.h buffered_file_writer.h
 
 ALL_OBJS = $(FAST_STATIC_OBJS) $(FAST_SHARED_OBJS)
 
diff --git a/src/skiplist_common.h b/src/skiplist_common.h
index 59fe1c9..d5d5a79 100644
--- a/src/skiplist_common.h
+++ b/src/skiplist_common.h
@@ -15,6 +15,7 @@
 #include <string.h>
 #include "common_define.h"
 
+#define SKIPLIST_MAX_LEVEL_COUNT  30
 #define SKIPLIST_DEFAULT_MIN_ALLOC_ELEMENTS_ONCE 64
 
 typedef int (*skiplist_compare_func)(const void *p1, const void *p2);
diff --git a/src/skiplist_set.c b/src/skiplist_set.c
index c54bcf6..b138cf7 100644
--- a/src/skiplist_set.c
+++ b/src/skiplist_set.c
@@ -35,10 +35,10 @@ int skiplist_set_init_ex(SkiplistSet *sl, const int level_count,
         return EINVAL;
     }
 
-    if (level_count > 30) {
+    if (level_count > SKIPLIST_MAX_LEVEL_COUNT) {
         logError("file: "__FILE__", line: %d, "
-                "level count: %d is too large",
-                __LINE__, level_count);
+                "level count: %d is too large exceeds %d",
+                __LINE__, level_count, SKIPLIST_MAX_LEVEL_COUNT);
         return E2BIG;
     }
 
diff --git a/src/uniq_skiplist.c b/src/uniq_skiplist.c
new file mode 100644
index 0000000..459aabb
--- /dev/null
+++ b/src/uniq_skiplist.c
@@ -0,0 +1,417 @@
+/**
+* Copyright (C) 2015 Happy Fish / YuQing
+*
+* libfastcommon may be copied only under the terms of the GNU General
+* Public License V3, which may be found in the FastDFS source kit.
+* Please visit the FastDFS Home Page http://www.fastken.com/ for more detail.
+**/
+
+//uniq_skiplist.c
+
+#include <ctype.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+#include "logger.h"
+#include "uniq_skiplist.h"
+
+int uniq_skiplist_init_ex(UniqSkiplistFactory *factory,
+        const int max_level_count, skiplist_compare_func compare_func,
+        skiplist_free_func free_func, const int alloc_skiplist_once,
+        const int min_alloc_elements_once)
+{
+    int bytes;
+    int element_size;
+    int i;
+    int alloc_elements_once;
+    int result;
+
+    if (max_level_count <= 0) {
+        logError("file: "__FILE__", line: %d, "
+                "invalid max level count: %d",
+                __LINE__, max_level_count);
+        return EINVAL;
+    }
+
+    if (max_level_count > SKIPLIST_MAX_LEVEL_COUNT) {
+        logError("file: "__FILE__", line: %d, "
+                "max level count: %d is too large, exceeds %d",
+                __LINE__, max_level_count, SKIPLIST_MAX_LEVEL_COUNT);
+        return E2BIG;
+    }
+
+    bytes = sizeof(struct fast_mblock_man) * max_level_count;
+    factory->node_allocators = (struct fast_mblock_man *)malloc(bytes);
+    if (factory->node_allocators == NULL) {
+        logError("file: "__FILE__", line: %d, "
+                "malloc %d bytes fail, errno: %d, error info: %s",
+                __LINE__, bytes, errno, STRERROR(errno));
+        return errno != 0 ? errno : ENOMEM;
+    }
+    memset(factory->node_allocators, 0, bytes);
+
+    alloc_elements_once = min_alloc_elements_once;
+    if (alloc_elements_once <= 0) {
+        alloc_elements_once = SKIPLIST_DEFAULT_MIN_ALLOC_ELEMENTS_ONCE;
+    }
+    else if (alloc_elements_once > 1024) {
+        alloc_elements_once = 1024;
+    }
+
+    for (i=max_level_count-1; i>=0; i--) {
+        element_size = sizeof(UniqSkiplistNode) +
+            sizeof(UniqSkiplistNode *) * (i + 1);
+        if ((result=fast_mblock_init_ex(factory->node_allocators + i,
+            element_size, alloc_elements_once, NULL, false)) != 0)
+        {
+            return result;
+        }
+        if (i % 2 == 0 && alloc_elements_once < 64 * 1024) {
+            alloc_elements_once *= 2;
+        }
+    }
+
+    if ((result=fast_mblock_init_ex(&factory->skiplist_allocators,
+                    sizeof(UniqSkiplist), alloc_skiplist_once > 0 ?
+                    alloc_skiplist_once : 16 * 1024, NULL, false)) != 0)
+    {
+        return result;
+    }
+    
+    factory->max_level_count = max_level_count;
+    factory->compare_func = compare_func;
+    factory->free_func = free_func;
+
+    srand(time(NULL));
+    return 0;
+}
+
+void uniq_skiplist_destroy(UniqSkiplistFactory *factory)
+{
+    int i;
+
+    if (factory->node_allocators == NULL) {
+        return;
+    }
+
+    fast_mblock_destroy(&factory->skiplist_allocators);
+
+    for (i=0; i<factory->max_level_count; i++) {
+        fast_mblock_destroy(factory->node_allocators + i);
+    }
+
+    free(factory->node_allocators);
+    factory->node_allocators = NULL;
+}
+
+UniqSkiplist *uniq_skiplist_new(UniqSkiplistFactory *factory,
+        const int level_count)
+{
+    UniqSkiplist *sl;
+    struct fast_mblock_man *top_mblock;
+    int i;
+
+    if (level_count <= 0) {
+        logError("file: "__FILE__", line: %d, "
+                "invalid level count: %d",
+                __LINE__, level_count);
+        errno = EINVAL;
+        return NULL;
+    }
+
+    if (level_count > factory->max_level_count) {
+        logError("file: "__FILE__", line: %d, "
+                "level count: %d is too large, "
+                "exceeds max level count: %d",
+                __LINE__, level_count, factory->max_level_count);
+        errno = E2BIG;
+        return NULL;
+    }
+
+    sl = (UniqSkiplist *)fast_mblock_alloc_object(
+            &factory->skiplist_allocators);
+    sl->element_count = 0;
+    sl->factory = factory;
+
+    sl->top_level_index = level_count - 1;
+    top_mblock = sl->factory->node_allocators + sl->top_level_index;
+    sl->top = (UniqSkiplistNode *)fast_mblock_alloc_object(top_mblock);
+    if (sl->top == NULL) {
+        errno = ENOMEM;
+        return NULL;
+    }
+    memset(sl->top, 0, top_mblock->info.element_size);
+
+    sl->tail = (UniqSkiplistNode *)fast_mblock_alloc_object(
+            sl->factory->node_allocators + 0);
+    if (sl->tail == NULL) {
+        errno = ENOMEM;
+        return NULL;
+    }
+    memset(sl->tail, 0, sl->factory->node_allocators[0].info.element_size);
+
+    for (i=0; i<level_count; i++) {
+        sl->top->links[i] = sl->tail;
+    }
+
+    return sl;
+}
+
+void uniq_skiplist_free(UniqSkiplist *sl)
+{
+    UniqSkiplistNode *node;
+    UniqSkiplistNode *deleted;
+
+    if (sl->element_count == 0)
+    {
+        return;
+    }
+
+    node = sl->top->links[0];
+    if (sl->factory->free_func != NULL) {
+        while (node != sl->tail) {
+            deleted = node;
+            node = node->links[0];
+            sl->factory->free_func(deleted->data);
+            fast_mblock_free_object(sl->factory->node_allocators +
+                    deleted->level_index, deleted);
+        }
+    } else {
+        while (node != sl->tail) {
+            deleted = node;
+            node = node->links[0];
+            fast_mblock_free_object(sl->factory->node_allocators +
+                    deleted->level_index, deleted);
+        }
+    }
+
+    sl->element_count = 0;
+}
+
+static inline int uniq_skiplist_get_level_index(UniqSkiplist *sl)
+{
+    int i;
+
+    for (i=0; i<sl->top_level_index; i++) {
+        if (rand() < RAND_MAX / 2) {
+            break;
+        }
+    }
+
+    return i;
+}
+
+int uniq_skiplist_insert(UniqSkiplist *sl, void *data)
+{
+    int i;
+    int level_index;
+    int cmp;
+    UniqSkiplistNode *node;
+    UniqSkiplistNode *previous;
+    UniqSkiplistNode *tmp_previous[SKIPLIST_MAX_LEVEL_COUNT];
+
+    level_index = uniq_skiplist_get_level_index(sl);
+    previous = sl->top;
+    for (i=sl->top_level_index; i>level_index; i--) {
+        while (previous->links[i] != sl->tail) {
+            cmp = sl->factory->compare_func(data, previous->links[i]->data);
+            if (cmp < 0) {
+                break;
+            }
+            else if (cmp == 0) {
+                return EEXIST;
+            }
+
+            previous = previous->links[i];
+        }
+    }
+
+    while (i >= 0) {
+        while (previous->links[i] != sl->tail) {
+            cmp = sl->factory->compare_func(data, previous->links[i]->data);
+            if (cmp < 0) {
+                break;
+            }
+            else if (cmp == 0) {
+                return EEXIST;
+            }
+
+            previous = previous->links[i];
+        }
+
+        tmp_previous[i] = previous;
+        i--;
+    }
+
+    node = (UniqSkiplistNode *)fast_mblock_alloc_object(
+            sl->factory->node_allocators + level_index);
+    if (node == NULL) {
+        return ENOMEM;
+    }
+    node->level_index = level_index;
+    node->data = data;
+
+    //thread safe for one write with many read model
+    for (i=0; i<=level_index; i++) {
+        node->links[i] = tmp_previous[i]->links[i];
+        tmp_previous[i]->links[i] = node;
+    }
+
+    return 0;
+}
+
+static UniqSkiplistNode *uniq_skiplist_get_equal_previous(UniqSkiplist *sl,
+        void *data, int *level_index)
+{
+    int i;
+    int cmp;
+    UniqSkiplistNode *previous;
+
+    previous = sl->top;
+    for (i=sl->top_level_index; i>=0; i--) {
+        while (previous->links[i] != sl->tail) {
+            cmp = sl->factory->compare_func(data, previous->links[i]->data);
+            if (cmp < 0) {
+                break;
+            }
+            else if (cmp == 0) {
+                *level_index = i;
+                return previous;
+            }
+
+            previous = previous->links[i];
+        }
+    }
+
+    return NULL;
+}
+
+static UniqSkiplistNode *uniq_skiplist_get_first_larger_or_equal(
+        UniqSkiplist *sl, void *data)
+{
+    int i;
+    int cmp;
+    UniqSkiplistNode *previous;
+
+    previous = sl->top;
+    for (i=sl->top_level_index; i>=0; i--) {
+        while (previous->links[i] != sl->tail) {
+            cmp = sl->factory->compare_func(data, previous->links[i]->data);
+            if (cmp < 0) {
+                break;
+            }
+            else if (cmp == 0) {
+                return previous->links[i];
+            }
+
+            previous = previous->links[i];
+        }
+    }
+
+    return previous->links[0];
+}
+
+static UniqSkiplistNode *uniq_skiplist_get_first_larger(
+        UniqSkiplist *sl, void *data)
+{
+    int i;
+    int cmp;
+    UniqSkiplistNode *previous;
+
+    previous = sl->top;
+    for (i=sl->top_level_index; i>=0; i--) {
+        while (previous->links[i] != sl->tail) {
+            cmp = sl->factory->compare_func(data, previous->links[i]->data);
+            if (cmp < 0) {
+                break;
+            }
+            else if (cmp == 0) {
+                return previous->links[i]->links[0];
+            }
+
+            previous = previous->links[i];
+        }
+    }
+
+    return previous->links[0];
+}
+
+int uniq_skiplist_delete(UniqSkiplist *sl, void *data)
+{
+    int i;
+    int level_index;
+    UniqSkiplistNode *previous;
+    UniqSkiplistNode *deleted;
+
+    previous = uniq_skiplist_get_equal_previous(sl, data, &level_index);
+    if (previous == NULL) {
+        return ENOENT;
+    }
+
+    deleted = previous->links[level_index];
+    for (i=level_index; i>=0; i--) {
+        while (previous->links[i] != sl->tail && 
+                previous->links[i] != deleted)
+        {
+            previous = previous->links[i];
+        }
+
+        assert(previous->links[i] == deleted);
+        previous->links[i] = previous->links[i]->links[i];
+    }
+
+    if (sl->factory->free_func != NULL) {
+        sl->factory->free_func(deleted->data);
+    }
+    fast_mblock_free_object(sl->factory->node_allocators + level_index, deleted);
+    return 0;
+}
+
+void *uniq_skiplist_find(UniqSkiplist *sl, void *data)
+{
+    int level_index;
+    UniqSkiplistNode *previous;
+
+    previous = uniq_skiplist_get_equal_previous(sl, data, &level_index);
+    return (previous != NULL) ? previous->links[level_index]->data : NULL;
+}
+
+int uniq_skiplist_find_all(UniqSkiplist *sl, void *data,
+        UniqSkiplistIterator *iterator)
+{
+    int level_index;
+    UniqSkiplistNode *previous;
+
+    previous = uniq_skiplist_get_equal_previous(sl, data, &level_index);
+    if (previous == NULL) {
+        iterator->tail = sl->tail;
+        iterator->current = sl->tail;
+        return ENOENT;
+    }
+
+    iterator->current = previous->links[level_index];
+    iterator->tail = iterator->current->links[0];
+    return 0;
+}
+
+int uniq_skiplist_find_range(UniqSkiplist *sl, void *start_data,
+        void *end_data, UniqSkiplistIterator *iterator)
+{
+    if (sl->factory->compare_func(start_data, end_data) > 0) {
+        iterator->current = sl->tail;
+        iterator->tail = sl->tail;
+        return EINVAL;
+    }
+
+    iterator->current = uniq_skiplist_get_first_larger_or_equal(sl, start_data);
+    if (iterator->current == sl->tail) {
+        iterator->tail = sl->tail;
+        return ENOENT;
+    }
+
+    iterator->tail = uniq_skiplist_get_first_larger(sl, end_data);
+    return iterator->current != iterator->tail ? 0 : ENOENT;
+}
+
diff --git a/src/uniq_skiplist.h b/src/uniq_skiplist.h
new file mode 100644
index 0000000..d2804fd
--- /dev/null
+++ b/src/uniq_skiplist.h
@@ -0,0 +1,109 @@
+/**
+* Copyright (C) 2015 Happy Fish / YuQing
+*
+* libfastcommon may be copied only under the terms of the GNU General
+* Public License V3, which may be found in the FastDFS source kit.
+* Please visit the FastDFS Home Page http://www.fastken.com/ for more detail.
+**/
+
+//uniq_skiplist.h
+
+#ifndef _UNIQ_SKIPLIST_H
+#define _UNIQ_SKIPLIST_H
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "common_define.h"
+#include "skiplist_common.h"
+#include "fast_mblock.h"
+
+typedef struct uniq_skiplist_node
+{
+    void *data;
+    int level_index;
+    struct uniq_skiplist_node *links[0];
+} UniqSkiplistNode;
+
+typedef struct uniq_skiplist_factory
+{
+    int max_level_count;
+    skiplist_compare_func compare_func;
+    skiplist_free_func free_func;
+    struct fast_mblock_man skiplist_allocators;
+    struct fast_mblock_man *node_allocators;
+} UniqSkiplistFactory;
+
+typedef struct uniq_skiplist
+{
+    UniqSkiplistFactory *factory;
+    int top_level_index;
+    int element_count;
+    UniqSkiplistNode *top;   //the top node
+    UniqSkiplistNode *tail;  //the tail node for interator
+} UniqSkiplist;
+
+typedef struct uniq_skiplist_iterator {
+    UniqSkiplistNode *current;
+    UniqSkiplistNode *tail;
+} UniqSkiplistIterator;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define uniq_skiplist_init(factory, max_level_count, compare_func, free_func) \
+    uniq_skiplist_init_ex(factory, max_level_count,  \
+            compare_func, free_func, 64 * 1024, \
+            SKIPLIST_DEFAULT_MIN_ALLOC_ELEMENTS_ONCE)
+
+int uniq_skiplist_init_ex(UniqSkiplistFactory *factory,
+        const int max_level_count, skiplist_compare_func compare_func,
+        skiplist_free_func free_func, const int alloc_skiplist_once,
+        const int min_alloc_elements_once);
+
+void uniq_skiplist_destroy(UniqSkiplistFactory *factory);
+
+UniqSkiplist *uniq_skiplist_new(UniqSkiplistFactory *factory,
+        const int level_count);
+
+void uniq_skiplist_free(UniqSkiplist *sl);
+
+int uniq_skiplist_insert(UniqSkiplist *sl, void *data);
+int uniq_skiplist_delete(UniqSkiplist *sl, void *data);
+void *uniq_skiplist_find(UniqSkiplist *sl, void *data);
+int uniq_skiplist_find_all(UniqSkiplist *sl, void *data,
+        UniqSkiplistIterator *iterator);
+int uniq_skiplist_find_range(UniqSkiplist *sl, void *start_data,
+        void *end_data, UniqSkiplistIterator *iterator);
+
+static inline void uniq_skiplist_iterator(UniqSkiplist *sl, UniqSkiplistIterator *iterator)
+{
+    iterator->current = sl->top->links[0];
+    iterator->tail = sl->tail;
+}
+
+static inline void *uniq_skiplist_next(UniqSkiplistIterator *iterator)
+{
+    void *data;
+
+    if (iterator->current == iterator->tail) {
+        return NULL;
+    }
+
+    data = iterator->current->data;
+    iterator->current = iterator->current->links[0];
+    return data;
+}
+
+static inline bool uniq_skiplist_empty(UniqSkiplist *sl)
+{
+    return sl->top->links[0] == sl->tail;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+