Add module data-type support for COPY. (#8112)

This adds a copy callback for module data types, in order to make
modules compatible with the new COPY command.

The callback is optional and COPY will fail for keys with data types
that do not implement it.

1 files changed, 34 insertions, 3 deletions

diff --git a/tests/modules/datatype.c b/tests/modules/datatype.c
index 6596f9368..0c6f95551 100644
--- a/tests/modules/datatype.c
+++ b/tests/modules/datatype.c
@@ -41,6 +41,32 @@ static void datatype_free(void *value) {
     }
 }
 
+static void *datatype_copy(RedisModuleString *fromkey, RedisModuleString *tokey, const void *value) {
+    const DataType *old = value;
+
+    /* Answers to ultimate questions cannot be copied! */
+    if (old->intval == 42)
+        return NULL;
+
+    DataType *new = (DataType *) RedisModule_Alloc(sizeof(DataType));
+
+    new->intval = old->intval;
+    new->strval = RedisModule_CreateStringFromString(NULL, old->strval);
+
+    /* Breaking the rules here! We return a copy that also includes traces
+     * of fromkey/tokey to confirm we get what we expect.
+     */
+    size_t len;
+    const char *str = RedisModule_StringPtrLen(fromkey, &len);
+    RedisModule_StringAppendBuffer(NULL, new->strval, "/", 1);
+    RedisModule_StringAppendBuffer(NULL, new->strval, str, len);
+    RedisModule_StringAppendBuffer(NULL, new->strval, "/", 1);
+    str = RedisModule_StringPtrLen(tokey, &len);
+    RedisModule_StringAppendBuffer(NULL, new->strval, str, len);
+
+    return new;
+}
+
 static int datatype_set(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
     if (argc != 4) {
         RedisModule_WrongArity(ctx);
@@ -97,9 +123,13 @@ static int datatype_get(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
     DataType *dt = RedisModule_ModuleTypeGetValue(key);
     RedisModule_CloseKey(key);
 
-    RedisModule_ReplyWithArray(ctx, 2);
-    RedisModule_ReplyWithLongLong(ctx, dt->intval);
-    RedisModule_ReplyWithString(ctx, dt->strval);
+    if (!dt) {
+        RedisModule_ReplyWithNullArray(ctx);
+    } else {
+        RedisModule_ReplyWithArray(ctx, 2);
+        RedisModule_ReplyWithLongLong(ctx, dt->intval);
+        RedisModule_ReplyWithString(ctx, dt->strval);
+    }
     return REDISMODULE_OK;
 }
 
@@ -161,6 +191,7 @@ int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
         .rdb_load = datatype_load,
         .rdb_save = datatype_save,
         .free = datatype_free,
+        .copy = datatype_copy
     };
 
     datatype = RedisModule_CreateDataType(ctx, "test___dt", 1, &datatype_methods);