Add RedisModule_CreateStringFromString().

src/module.c

@@ -673,6 +673,17 @@ RedisModuleString *RM_CreateStringFromLongLong(RedisModuleCtx *ctx, long long ll
     return RM_CreateString(ctx,buf,len);
 }
 
+/* Like RedisModule_CreatString(), but creates a string starting from another
+ * RedisModuleString.
+ *
+ * The returned string must be released with RedisModule_FreeString() or by
+ * enabling automatic memory management. */
+RedisModuleString *RM_CreateStringFromString(RedisModuleCtx *ctx, const RedisModuleString *str) {
+    RedisModuleString *o = dupStringObject(str);
+    autoMemoryAdd(ctx,REDISMODULE_AM_STRING,o);
+    return o;
+}
+
 /* Free a module string object obtained with one of the Redis modules API calls
  * that return new string objects.
  *
@@ -2828,6 +2839,7 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(CreateStringFromCallReply);
     REGISTER_API(CreateString);
     REGISTER_API(CreateStringFromLongLong);
+    REGISTER_API(CreateStringFromString);
     REGISTER_API(FreeString);
     REGISTER_API(StringPtrLen);
     REGISTER_API(AutoMemory);

src/modules/API.md

@@ -179,6 +179,16 @@ integer instead of taking a buffer and its length.
 The returned string must be released with `RedisModule_FreeString()` or by
 enabling automatic memory management.
 
+## `RM_CreateStringFromString`
+
+    RedisModuleString *RM_CreateStringFromString(RedisModuleCtx *ctx, const RedisModuleString *str);
+
+Like `RedisModule_CreatString()`, but creates a string starting from an existing
+RedisModuleString.
+
+The returned string must be released with `RedisModule_FreeString()` or by
+enabling automatic memory management.
+
 ## `RM_FreeString`
 
     void RM_FreeString(RedisModuleCtx *ctx, RedisModuleString *str);

src/object.c

@@ -147,7 +147,7 @@ robj *createStringObjectFromLongDouble(long double value, int humanfriendly) {
  * will always result in a fresh object that is unshared (refcount == 1).
  *
  * The resulting object always has refcount set to 1. */
-robj *dupStringObject(robj *o) {
+robj *dupStringObject(const robj *o) {
     robj *d;
 
     serverAssert(o->type == OBJ_STRING);

src/redismodule.h

@@ -122,6 +122,7 @@ size_t REDISMODULE_API_FUNC(RedisModule_CallReplyLength)(RedisModuleCallReply *r
 RedisModuleCallReply *REDISMODULE_API_FUNC(RedisModule_CallReplyArrayElement)(RedisModuleCallReply *reply, size_t idx);
 RedisModuleString *REDISMODULE_API_FUNC(RedisModule_CreateString)(RedisModuleCtx *ctx, const char *ptr, size_t len);
 RedisModuleString *REDISMODULE_API_FUNC(RedisModule_CreateStringFromLongLong)(RedisModuleCtx *ctx, long long ll);
+RedisModuleString *REDISMODULE_API_FUNC(RedisModule_CreateStringFromString)(RedisModuleCtx *ctx, const RedisModuleString *str);
 void REDISMODULE_API_FUNC(RedisModule_FreeString)(RedisModuleCtx *ctx, RedisModuleString *str);
 const char *REDISMODULE_API_FUNC(RedisModule_StringPtrLen)(RedisModuleString *str, size_t *len);
 int REDISMODULE_API_FUNC(RedisModule_ReplyWithError)(RedisModuleCtx *ctx, const char *err);
@@ -225,6 +226,7 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(CreateStringFromCallReply);
     REDISMODULE_GET_API(CreateString);
     REDISMODULE_GET_API(CreateStringFromLongLong);
+    REDISMODULE_GET_API(CreateStringFromString);
     REDISMODULE_GET_API(FreeString);
     REDISMODULE_GET_API(StringPtrLen);
     REDISMODULE_GET_API(AutoMemory);

src/server.h

@@ -1285,7 +1285,7 @@ robj *createObject(int type, void *ptr);
 robj *createStringObject(const char *ptr, size_t len);
 robj *createRawStringObject(const char *ptr, size_t len);
 robj *createEmbeddedStringObject(const char *ptr, size_t len);
-robj *dupStringObject(robj *o);
+robj *dupStringObject(const robj *o);
 int isSdsRepresentableAsLongLong(sds s, long long *llval);
 int isObjectRepresentableAsLongLong(robj *o, long long *llongval);
 robj *tryObjectEncoding(robj *o);