fix(query): add hex encoding/decoding for transmitting nchar constant

from client to server in JSON

include/os/osString.h

@@ -59,6 +59,8 @@ bool    taosMbsToUcs4(const char *mbs, size_t mbs_len, TdUcs4 *ucs4, int32_t ucs
 int32_t tasoUcs4Compare(TdUcs4 *f1_ucs4, TdUcs4 *f2_ucs4, int32_t bytes);
 TdUcs4* tasoUcs4Copy(TdUcs4 *target_ucs4, TdUcs4 *source_ucs4, int32_t len_ucs4);
 bool    taosValidateEncodec(const char *encodec);
+int32_t taosHexEncode(const char *src, char *dst, int32_t len);
+int32_t taosHexDecode(const char *src, char *dst, int32_t len);
 
 int32_t taosWcharWidth(TdWchar wchar);
 int32_t taosWcharsWidth(TdWchar *pWchar, int32_t size);

source/libs/nodes/src/nodesCodeFuncs.c

@@ -1699,7 +1699,18 @@ static int32_t datumToJson(const void* pObj, SJson* pJson) {
     case TSDB_DATA_TYPE_DOUBLE:
       code = tjsonAddDoubleToObject(pJson, jkValueDatum, pNode->datum.d);
       break;
-    case TSDB_DATA_TYPE_NCHAR:
+    case TSDB_DATA_TYPE_NCHAR: {
+      //cJSON only support utf-8 encoding. Convert memory content to hex string.
+      char *buf = taosMemoryCalloc(varDataLen(pNode->datum.p) * 2 + 1, sizeof(char));
+      code = taosHexEncode(varDataVal(pNode->datum.p), buf, varDataLen(pNode->datum.p));
+      if(code != TSDB_CODE_SUCCESS) {
+        taosMemoryFree(buf);
+        return TSDB_CODE_TSC_INVALID_VALUE;
+      }
+      code = tjsonAddStringToObject(pJson, jkValueDatum, buf);
+      taosMemoryFree(buf);
+      break;
+    }
     case TSDB_DATA_TYPE_VARCHAR:
     case TSDB_DATA_TYPE_VARBINARY:
       code = tjsonAddStringToObject(pJson, jkValueDatum, varDataVal(pNode->datum.p));
@@ -1773,8 +1784,27 @@ static int32_t jsonToDatum(const SJson* pJson, void* pObj) {
         code = TSDB_CODE_OUT_OF_MEMORY;
         break;
       }
-      varDataSetLen(pNode->datum.p, pNode->node.resType.bytes);
-      code = tjsonGetStringValue(pJson, jkValueDatum, varDataVal(pNode->datum.p));
+      varDataSetLen(pNode->datum.p, pNode->node.resType.bytes - VARSTR_HEADER_SIZE);
+      if (TSDB_DATA_TYPE_NCHAR == pNode->node.resType.type) {
+        char *buf = taosMemoryCalloc(1, pNode->node.resType.bytes * 2 + VARSTR_HEADER_SIZE + 1);
+        if (NULL == buf) {
+          code = TSDB_CODE_OUT_OF_MEMORY;
+          break;
+        }
+        code = tjsonGetStringValue(pJson, jkValueDatum, buf);
+        if (code != TSDB_CODE_SUCCESS) {
+          taosMemoryFree(buf);
+          break;
+        }
+        code = taosHexDecode(buf, varDataVal(pNode->datum.p), pNode->node.resType.bytes - VARSTR_HEADER_SIZE);
+        if (code != TSDB_CODE_SUCCESS) {
+          taosMemoryFree(buf);
+          break;
+        }
+        taosMemoryFree(buf);
+      } else {
+        code = tjsonGetStringValue(pJson, jkValueDatum, varDataVal(pNode->datum.p));
+      }
       break;
     }
     case TSDB_DATA_TYPE_JSON:

source/os/src/osString.c

@@ -195,6 +195,36 @@ int32_t taosUcs4len(TdUcs4 *ucs4) {
   return n;
 }
 
+//dst buffer size should be at least 2*len + 1
+int32_t taosHexEncode(const char *src, char *dst, int32_t len) {
+  if (!dst) {
+    return -1;
+  }
+
+  for (int32_t i = 0; i < len; ++i) {
+    sprintf(dst + i * 2, "%02x", src[i] & 0xff);
+  }
+
+  return 0;
+}
+
+int32_t taosHexDecode(const char *src, char *dst, int32_t len) {
+  if (!dst) {
+    return -1;
+  }
+
+  uint16_t hn, ln, out;
+  for (int i = 0, j = 0; i < len * 2; i += 2, ++j ) {
+    hn = src[i] > '9' ? src[i] - 'A' + 10 : src[i] - '0';
+    ln = src[i + 1] > '9' ? src[i + 1] - 'A' + 10 : src[i + 1] - '0';
+
+    out = (hn << 4) | ln;
+    memcpy(dst + j, &out, 1);
+  }
+
+  return 0;
+}
+
 int32_t taosWcharWidth(TdWchar wchar) { return wcwidth(wchar); }
 
 int32_t taosWcharsWidth(TdWchar *pWchar, int32_t size) { return wcswidth(pWchar, size); }