Add ModuleDataType to/from string serialization.

Add two new functions that leverage the RedisModuleDataType mechanism
for RDB serialization/deserialization and make it possible to use it
to/from arbitrary strings:

* RM_SaveDataTypeToString()
* RM_LoadDataTypeFromString()

runtest-moduleapi

@@ -22,4 +22,5 @@ $TCLSH tests/test_helper.tcl \
 --single unit/moduleapi/hooks \
 --single unit/moduleapi/misc \
 --single unit/moduleapi/blockonkeys \
+--single unit/moduleapi/datatype
 "${@}"

src/module.c

@@ -3884,6 +3884,59 @@ void RM_DigestEndSequence(RedisModuleDigest *md) {
     memset(md->o,0,sizeof(md->o));
 }
 
+/* Decode a serialized representation of a module data type 'mt' from string
+ * 'str' and return a newly allocated value, or NULL if decoding failed.
+ *
+ * This call basically reuses the 'rdb_load' callback which module data types
+ * implement in order to allow a module to arbitrarily serialize/de-serialize
+ * keys, similar to how the Redis 'DUMP' and 'RESTORE' commands are implemented.
+ *
+ * Modules should generally use the REDISMODULE_OPTIONS_HANDLE_IO_ERRORS flag and
+ * make sure the de-serialization code properly checks and handles IO errors
+ * (freeing allocated buffers and returning a NULL).
+ *
+ * If this is NOT done, Redis will handle corrupted (or just truncated) serialized
+ * data by producing an error message and terminating the process.
+ */
+
+void *RM_LoadDataTypeFromString(const RedisModuleString *str, const moduleType *mt) {
+    rio payload;
+    RedisModuleIO io;
+
+    rioInitWithBuffer(&payload, str->ptr);
+    moduleInitIOContext(io,(moduleType *)mt,&payload,NULL);
+
+    /* All RM_Save*() calls always write a version 2 compatible format, so we
+     * need to make sure we read the same.
+     */
+    io.ver = 2;
+    return mt->rdb_load(&io,0);
+}
+
+/* Encode a module data type 'mt' value 'data' into serialized form, and return it
+ * as a newly allocated RedisModuleString.
+ *
+ * This call basically reuses the 'rdb_save' callback which module data types
+ * implement in order to allow a module to arbitrarily serialize/de-serialize
+ * keys, similar to how the Redis 'DUMP' and 'RESTORE' commands are implemented.
+ */
+
+RedisModuleString *RM_SaveDataTypeToString(RedisModuleCtx *ctx, void *data, const moduleType *mt) {
+    rio payload;
+    RedisModuleIO io;
+
+    rioInitWithBuffer(&payload,sdsempty());
+    moduleInitIOContext(io,(moduleType *)mt,&payload,NULL);
+    mt->rdb_save(&io,data);
+    if (io.error) {
+        return NULL;
+    } else {
+        robj *str = createObject(OBJ_STRING,payload.io.buffer.ptr);
+        autoMemoryAdd(ctx,REDISMODULE_AM_STRING,str);
+        return str;
+    }
+}
+
 /* --------------------------------------------------------------------------
  * AOF API for modules data types
  * -------------------------------------------------------------------------- */
@@ -6876,6 +6929,8 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(LoadFloat);
     REGISTER_API(SaveLongDouble);
     REGISTER_API(LoadLongDouble);
+    REGISTER_API(SaveDataTypeToString);
+    REGISTER_API(LoadDataTypeFromString);
     REGISTER_API(EmitAOF);
     REGISTER_API(Log);
     REGISTER_API(LogIOError);

src/redismodule.h

@@ -537,6 +537,8 @@ void REDISMODULE_API_FUNC(RedisModule_SaveFloat)(RedisModuleIO *io, float value)
 float REDISMODULE_API_FUNC(RedisModule_LoadFloat)(RedisModuleIO *io);
 void REDISMODULE_API_FUNC(RedisModule_SaveLongDouble)(RedisModuleIO *io, long double value);
 long double REDISMODULE_API_FUNC(RedisModule_LoadLongDouble)(RedisModuleIO *io);
+void *REDISMODULE_API_FUNC(RedisModule_LoadDataTypeFromString)(const RedisModuleString *str, const RedisModuleType *mt);
+RedisModuleString *REDISMODULE_API_FUNC(RedisModule_SaveDataTypeToString)(RedisModuleCtx *ctx, void *data, const RedisModuleType *mt);
 void REDISMODULE_API_FUNC(RedisModule_Log)(RedisModuleCtx *ctx, const char *level, const char *fmt, ...);
 void REDISMODULE_API_FUNC(RedisModule_LogIOError)(RedisModuleIO *io, const char *levelstr, const char *fmt, ...);
 void REDISMODULE_API_FUNC(RedisModule__Assert)(const char *estr, const char *file, int line);
@@ -745,6 +747,8 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(LoadFloat);
     REDISMODULE_GET_API(SaveLongDouble);
     REDISMODULE_GET_API(LoadLongDouble);
+    REDISMODULE_GET_API(SaveDataTypeToString);
+    REDISMODULE_GET_API(LoadDataTypeFromString);
     REDISMODULE_GET_API(EmitAOF);
     REDISMODULE_GET_API(Log);
     REDISMODULE_GET_API(LogIOError);

tests/modules/Makefile

@@ -19,7 +19,8 @@ TEST_MODULES = \
     propagate.so \
     misc.so \
     hooks.so \
-    blockonkeys.so
+    blockonkeys.so \
+    datatype.so
 
 .PHONY: all
 

tests/modules/datatype.c

@@ -0,0 +1,161 @@
+/* This module current tests a small subset but should be extended in the future
+ * for general ModuleDataType coverage.
+ */
+
+#include "redismodule.h"
+
+static RedisModuleType *datatype = NULL;
+
+typedef struct {
+    long long intval;
+    RedisModuleString *strval;
+} DataType;
+
+static void *datatype_load(RedisModuleIO *io, int encver) {
+    (void) encver;
+
+    int intval = RedisModule_LoadSigned(io);
+    if (RedisModule_IsIOError(io)) return NULL;
+
+    RedisModuleString *strval = RedisModule_LoadString(io);
+    if (RedisModule_IsIOError(io)) return NULL;
+
+    DataType *dt = (DataType *) RedisModule_Alloc(sizeof(DataType));
+    dt->intval = intval;
+    dt->strval = strval;
+    return dt;
+}
+
+static void datatype_save(RedisModuleIO *io, void *value) {
+    DataType *dt = (DataType *) value;
+    RedisModule_SaveSigned(io, dt->intval);
+    RedisModule_SaveString(io, dt->strval);
+}
+
+static void datatype_free(void *value) {
+    if (value) {
+        DataType *dt = (DataType *) value;
+
+        if (dt->strval) RedisModule_FreeString(NULL, dt->strval);
+        RedisModule_Free(dt);
+    }
+}
+
+static int datatype_set(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    if (argc != 4) {
+        RedisModule_WrongArity(ctx);
+        return REDISMODULE_OK;
+    }
+
+    long long intval;
+
+    if (RedisModule_StringToLongLong(argv[2], &intval) != REDISMODULE_OK) {
+        RedisModule_ReplyWithError(ctx, "Invalid integr value");
+        return REDISMODULE_OK;
+    }
+
+    RedisModuleKey *key = RedisModule_OpenKey(ctx, argv[1], REDISMODULE_WRITE);
+    DataType *dt = RedisModule_Calloc(sizeof(DataType), 1);
+    dt->intval = intval;
+    dt->strval = argv[3];
+    RedisModule_RetainString(ctx, dt->strval);
+
+    RedisModule_ModuleTypeSetValue(key, datatype, dt);
+    RedisModule_CloseKey(key);
+    RedisModule_ReplyWithSimpleString(ctx, "OK");
+
+    return REDISMODULE_OK;
+}
+
+static int datatype_restore(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    if (argc != 3) {
+        RedisModule_WrongArity(ctx);
+        return REDISMODULE_OK;
+    }
+
+    DataType *dt = RedisModule_LoadDataTypeFromString(argv[2], datatype);
+    if (!dt) {
+        RedisModule_ReplyWithError(ctx, "Invalid data");
+        return REDISMODULE_OK;
+    }
+
+    RedisModuleKey *key = RedisModule_OpenKey(ctx, argv[1], REDISMODULE_WRITE);
+    RedisModule_ModuleTypeSetValue(key, datatype, dt);
+    RedisModule_CloseKey(key);
+    RedisModule_ReplyWithSimpleString(ctx, "OK");
+
+    return REDISMODULE_OK;
+}
+
+static int datatype_get(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    if (argc != 2) {
+        RedisModule_WrongArity(ctx);
+        return REDISMODULE_OK;
+    }
+
+    RedisModuleKey *key = RedisModule_OpenKey(ctx, argv[1], REDISMODULE_READ);
+    DataType *dt = RedisModule_ModuleTypeGetValue(key);
+    RedisModule_CloseKey(key);
+
+    RedisModule_ReplyWithArray(ctx, 2);
+    RedisModule_ReplyWithLongLong(ctx, dt->intval);
+    RedisModule_ReplyWithString(ctx, dt->strval);
+    return REDISMODULE_OK;
+}
+
+static int datatype_dump(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    if (argc != 2) {
+        RedisModule_WrongArity(ctx);
+        return REDISMODULE_OK;
+    }
+
+    RedisModuleKey *key = RedisModule_OpenKey(ctx, argv[1], REDISMODULE_READ);
+    DataType *dt = RedisModule_ModuleTypeGetValue(key);
+    RedisModule_CloseKey(key);
+
+    RedisModuleString *reply = RedisModule_SaveDataTypeToString(ctx, dt, datatype);
+    if (!reply) {
+        RedisModule_ReplyWithError(ctx, "Failed to save");
+        return REDISMODULE_OK;
+    }
+
+    RedisModule_ReplyWithString(ctx, reply);
+    RedisModule_FreeString(ctx, reply);
+    return REDISMODULE_OK;
+}
+
+
+int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    REDISMODULE_NOT_USED(argv);
+    REDISMODULE_NOT_USED(argc);
+
+    if (RedisModule_Init(ctx,"datatype",1,REDISMODULE_APIVER_1) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
+    RedisModule_SetModuleOptions(ctx, REDISMODULE_OPTIONS_HANDLE_IO_ERRORS);
+
+    RedisModuleTypeMethods datatype_methods = {
+        .version = REDISMODULE_TYPE_METHOD_VERSION,
+        .rdb_load = datatype_load,
+        .rdb_save = datatype_save,
+        .free = datatype_free,
+    };
+
+    datatype = RedisModule_CreateDataType(ctx, "test___dt", 1, &datatype_methods);
+    if (datatype == NULL)
+        return REDISMODULE_ERR;
+
+    if (RedisModule_CreateCommand(ctx,"datatype.set", datatype_set,"deny-oom",1,1,1) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
+    if (RedisModule_CreateCommand(ctx,"datatype.get", datatype_get,"",1,1,1) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
+    if (RedisModule_CreateCommand(ctx,"datatype.restore", datatype_restore,"deny-oom",1,1,1) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
+    if (RedisModule_CreateCommand(ctx,"datatype.dump", datatype_dump,"",1,1,1) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
+    return REDISMODULE_OK;
+}

tests/unit/moduleapi/datatype.tcl

@@ -0,0 +1,27 @@
+set testmodule [file normalize tests/modules/datatype.so]
+
+start_server {tags {"modules"}} {
+    r module load $testmodule
+
+    test {DataType: Test module is sane, GET/SET work.} {
+        r datatype.set dtkey 100 stringval
+        assert {[r datatype.get dtkey] eq {100 stringval}}
+    }
+
+    test {DataType: RM_SaveDataTypeToString(), RM_LoadDataTypeFromString() work} {
+        r datatype.set dtkey -1111 MyString
+        set encoded [r datatype.dump dtkey]
+
+        r datatype.restore dtkeycopy $encoded
+        assert {[r datatype.get dtkeycopy] eq {-1111 MyString}}
+    }
+
+    test {DataType: Handle truncated RM_LoadDataTypeFromString()} {
+        r datatype.set dtkey -1111 MyString
+        set encoded [r datatype.dump dtkey]
+        set truncated [string range $encoded 0 end-1]
+
+        catch {r datatype.restore dtkeycopy $truncated} e
+        set e
+    } {*Invalid*}
+}