diff --git a/source/libs/index/inc/index_fst_counting_writer.h b/source/libs/index/inc/index_fst_counting_writer.h
index 86bc0d07d5..ea090389bb 100644
--- a/source/libs/index/inc/index_fst_counting_writer.h
+++ b/source/libs/index/inc/index_fst_counting_writer.h
@@ -45,7 +45,7 @@ static int writeCtxDoWrite(WriterCtx *ctx, uint8_t *buf, int len);
 static int writeCtxDoRead(WriterCtx *ctx, uint8_t *buf, int len);
 static int writeCtxDoFlush(WriterCtx *ctx);
 
-WriterCtx* writerCtxCreate(WriterType type);
+WriterCtx* writerCtxCreate(WriterType type, bool readOnly);
 void writerCtxDestroy(WriterCtx *w);
 
 typedef uint32_t CheckSummer;
@@ -57,14 +57,16 @@ typedef struct FstCountingWriter {
   CheckSummer summer;  
 } FstCountingWriter;
 
-int fstCountingWriterWrite(FstCountingWriter *write, uint8_t *buf, uint32_t bufLen); 
+int fstCountingWriterWrite(FstCountingWriter *write, uint8_t *buf, uint32_t len); 
+
+int fstCountingWriterRead(FstCountingWriter *write, uint8_t *buf, uint32_t len);
 
 int fstCountingWriterFlush(FstCountingWriter *write);
 
 
 uint32_t fstCountingWriterMaskedCheckSum(FstCountingWriter *write);
 
-FstCountingWriter *fstCountingWriterCreate(void *wtr);
+FstCountingWriter *fstCountingWriterCreate(void *wtr, bool readOnly);
 void fstCountingWriterDestroy(FstCountingWriter *w); 
 
 
diff --git a/source/libs/index/src/index_fst.c b/source/libs/index/src/index_fst.c
index 76dbe24b2a..0cc95b738d 100644
--- a/source/libs/index/src/index_fst.c
+++ b/source/libs/index/src/index_fst.c
@@ -404,7 +404,7 @@ CompiledAddr fstStateTransAddr(FstState *s, FstNode *node) {
   assert(s->state == OneTransNext || s->state == OneTrans);
   FstSlice *slice = &node->data;
   if (s->state == OneTransNext) {
-    return (CompiledAddr)(node->end);      
+    return (CompiledAddr)(node->end) - 1;      
   } else {
     PackSizes sizes = node->sizes; 
     uint8_t tSizes = FST_GET_TRANSITION_PACK_SIZE(sizes);  
@@ -459,7 +459,7 @@ Output fstStateOutput(FstState *s, FstNode *node) {
   uint8_t tSizes = FST_GET_TRANSITION_PACK_SIZE(node->sizes);
 
   uint64_t i = node->start 
-                - fstStateInputLen(s);
+                - fstStateInputLen(s)
                 - 1
                 - tSizes 
                 - oSizes;
@@ -620,7 +620,7 @@ FstNode *fstNodeCreate(int64_t version, CompiledAddr addr, FstSlice *slice) {
      n->version = version;
      n->state   = st;  
      n->start   = addr;
-     n->end     = fstStateEndAddrForOneTransNext(&st, slice); //? s.end_addr(data); 
+     n->end     = fstStateEndAddrForOneTransNext(&st, &n->data); //? s.end_addr(data); 
      n->isFinal = false;
      n->sizes   = 0;
      n->nTrans  = 1;
@@ -632,23 +632,24 @@ FstNode *fstNodeCreate(int64_t version, CompiledAddr addr, FstSlice *slice) {
      n->version = version; 
      n->state   = st; 
      n->start   = addr;
-     n->end     = fstStateEndAddrForOneTrans(&st, slice, sz); // s.end_addr(data, sz);
+     n->end     = fstStateEndAddrForOneTrans(&st, &data, sz); // s.end_addr(data, sz);
      n->isFinal = false; 
      n->nTrans  = 1; 
      n->sizes   = sz;   
      n->finalOutput = 0; 
   } else {
-     uint64_t sz = fstStateSizes(&st, slice);    // s.sizes(data)
-     uint32_t nTrans = fstStateNtrans(&st, slice); // s.ntrans(data)  
-     n->data    = *slice; 
+     FstSlice data = fstSliceCopy(slice, 0, addr);
+     uint64_t sz = fstStateSizes(&st, &data);    // s.sizes(data)
+     uint32_t nTrans = fstStateNtrans(&st, &data); // s.ntrans(data)  
+     n->data    = data; 
      n->version = version;
      n->state   = st;
      n->start   = addr;
-     n->end     = fstStateEndAddrForAnyTrans(&st, version, slice, sz, nTrans); // s.end_addr(version, data, sz, ntrans);
+     n->end     = fstStateEndAddrForAnyTrans(&st, version, &data, sz, nTrans); // s.end_addr(version, data, sz, ntrans);
      n->isFinal = fstStateIsFinalState(&st); // s.is_final_state();
      n->nTrans  = nTrans;
      n->sizes   = sz;
-     n->finalOutput = fstStateFinalOutput(&st, version, slice, sz, nTrans); // s.final_output(version, data, sz, ntrans);
+     n->finalOutput = fstStateFinalOutput(&st, version, &data, sz, nTrans); // s.final_output(version, data, sz, ntrans);
   }
    return n; 
 }
@@ -771,7 +772,7 @@ FstBuilder *fstBuilderCreate(void *w, FstType ty) {
   if (NULL == b) { return b; }
 
    
-  b->wrt = fstCountingWriterCreate(w);
+  b->wrt = fstCountingWriterCreate(w, false);
   b->unfinished = fstUnFinishedNodesCreate();   
   b->registry   = fstRegistryCreate(10000, 2) ;
   b->last       = fstSliceCreate(NULL, 0);
@@ -1043,8 +1044,9 @@ bool fstGet(Fst *fst, FstSlice *b, Output *out) {
   for (uint32_t i = 0; i < len; i++) {
     uint8_t inp = data[i];
     Output  res = 0;
-    bool null = fstNodeFindInput(root, inp, &res);    
-    if (null) { return false; }    
+    if (false == fstNodeFindInput(root, inp, &res)) {
+      return false; 
+    }   
 
     FstTransition trn; 
     fstNodeGetTransitionAt(root, res, &trn);
diff --git a/source/libs/index/src/index_fst_counting_writer.c b/source/libs/index/src/index_fst_counting_writer.c
index 9c1a0b9f5d..9ec346cebc 100644
--- a/source/libs/index/src/index_fst_counting_writer.c
+++ b/source/libs/index/src/index_fst_counting_writer.c
@@ -31,17 +31,19 @@ static int writeCtxDoWrite(WriterCtx *ctx, uint8_t *buf, int len) {
   return len;
 }
 static int writeCtxDoRead(WriterCtx *ctx, uint8_t *buf, int len) {
+  int nRead = 0; 
   if (ctx->type == TFile) {
-    tfRead(ctx->fd, buf, len);
+    nRead = tfRead(ctx->fd, buf, len);
   } else {
     memcpy(buf, ctx->mem + ctx->offset, len);
   }
-  ctx->offset += len;
+  ctx->offset += nRead;
 
-  return 1;
+  return nRead;
 } 
 static int writeCtxDoFlush(WriterCtx *ctx) {
   if (ctx->type == TFile) {
+    //tfFsync(ctx->fd);
     //tfFlush(ctx->fd);
   } else {
     // do nothing
@@ -49,14 +51,19 @@ static int writeCtxDoFlush(WriterCtx *ctx) {
   return 1;
 }
 
-WriterCtx* writerCtxCreate(WriterType type) {     
+WriterCtx* writerCtxCreate(WriterType type, bool readOnly) {     
   WriterCtx *ctx = calloc(1, sizeof(WriterCtx));
   if (ctx == NULL) { return NULL; }
 
   ctx->type = type;
   if (ctx->type == TFile) {
     tfInit();
-    ctx->fd = tfOpenCreateWriteAppend(tmpFile);  
+    // ugly code, refactor later
+    if (readOnly == false) {
+      ctx->fd = tfOpenCreateWriteAppend(tmpFile);  
+    } else {
+      ctx->fd = tfOpenReadWrite(tmpFile);
+    } 
     if (ctx->fd < 0) {
       indexError("open file error %d", errno);       
     }
@@ -76,35 +83,44 @@ void writerCtxDestroy(WriterCtx *ctx) {
   if (ctx->type == TMemory) {
     free(ctx->mem);
   } else {
-    tfCleanup();
     tfClose(ctx->fd);    
+    tfCleanup();
   }
   free(ctx);
 }
 
 
-FstCountingWriter *fstCountingWriterCreate(void *wrt) {
+FstCountingWriter *fstCountingWriterCreate(void *wrt, bool readOnly) {
   FstCountingWriter *cw = calloc(1, sizeof(FstCountingWriter)); 
   if (cw == NULL) { return NULL; }
   
-  cw->wrt = (void *)(writerCtxCreate(TFile)); 
+  cw->wrt = (void *)(writerCtxCreate(TFile, readOnly)); 
   return cw; 
 }
 void fstCountingWriterDestroy(FstCountingWriter *cw) {
   // free wrt object: close fd or free mem 
+  fstCountingWriterFlush(cw);
   writerCtxDestroy((WriterCtx *)(cw->wrt));
   free(cw);
 }
 
-int fstCountingWriterWrite(FstCountingWriter *write, uint8_t *buf, uint32_t bufLen) {
+int fstCountingWriterWrite(FstCountingWriter *write, uint8_t *buf, uint32_t len) {
   if (write == NULL) { return 0; } 
   // update checksum 
   // write data to file/socket or mem
   WriterCtx *ctx = write->wrt;
 
-  int nWrite = ctx->write(ctx, buf, bufLen); 
-  write->count += nWrite;
-  return bufLen; 
+  int nWrite = ctx->write(ctx, buf, len); 
+  assert(nWrite == len);
+  write->count += len;
+  return len; 
+} 
+int fstCountingWriterRead(FstCountingWriter *write, uint8_t *buf, uint32_t len) {
+  if (write == NULL) { return 0; }
+  WriterCtx *ctx = write->wrt;
+  int nRead = ctx->read(ctx, buf, len);
+  //assert(nRead == len);
+  return nRead; 
 } 
 
 uint32_t fstCountingWriterMaskedCheckSum(FstCountingWriter *write) {
diff --git a/source/libs/index/src/index_fst_util.c b/source/libs/index/src/index_fst_util.c
index ab74a76eb9..c933c6d23b 100644
--- a/source/libs/index/src/index_fst_util.c
+++ b/source/libs/index/src/index_fst_util.c
@@ -67,7 +67,7 @@ uint8_t packSize(uint64_t n) {
 }
 
 uint64_t unpackUint64(uint8_t *ch, uint8_t sz) {
-  uint64_t n;
+  uint64_t n = 0;
   for (uint8_t i = 0; i < sz; i++) {
     n = n | (ch[i] << (8 * i));
   }
diff --git a/source/libs/index/test/indexTests.cpp b/source/libs/index/test/indexTests.cpp
index 5164209922..858861529d 100644
--- a/source/libs/index/test/indexTests.cpp
+++ b/source/libs/index/test/indexTests.cpp
@@ -63,6 +63,7 @@
 //}
 
 int main(int argc, char** argv) {
+  // test write
   FstBuilder *b = fstBuilderCreate(NULL, 0);
   {
     std::string str("aaa");
@@ -87,9 +88,42 @@ int main(int argc, char** argv) {
     }
     
   } 
-  //fstBuilderInsert(b, key1, val2); 
   fstBuilderFinish(b);
   fstBuilderDestroy(b);
+
+
+  char buf[64 * 1024] = {0};     
+
+  FstSlice s; 
+
+  FstCountingWriter *w = fstCountingWriterCreate(NULL, true);
+  int nRead = fstCountingWriterRead(w, (uint8_t *)buf, sizeof(buf)); 
+  assert(nRead <= sizeof(buf));  
+  s = fstSliceCreate((uint8_t *)buf, nRead);
+  fstCountingWriterDestroy(w);
+
+
+  // test reader
+  
+      
+  Fst *fst = fstCreate(&s); 
+  {
+    std::string str("aaa"); 
+    uint64_t out;
+    
+   
+    FstSlice key = fstSliceCreate((uint8_t *)str.c_str(), str.size());
+    bool ok = fstGet(fst, &key, &out); 
+    if (ok == true) {
+      //indexInfo("Get key-value success, %s, %d", str.c_str(), out); 
+    } else {
+      //indexError("Get key-value failed, %s", str.c_str()); 
+    }
+  }
+  fstSliceDestroy(&s);
+  
+
+  
   return 1;
 }