Modules: API to save/load single precision floating point numbers.

When double precision is not needed, to take 2x space in the
serialization is not good.

src/module.c

@@ -2849,6 +2849,31 @@ double RM_LoadDouble(RedisModuleIO *io) {
     return value;
 }
 
+/* In the context of the rdb_save method of a module data type, saves a float 
+ * value to the RDB file. The float can be a valid number, a NaN or infinity.
+ * It is possible to load back the value with RedisModule_LoadFloat(). */
+void RM_SaveFloat(RedisModuleIO *io, float value) {
+    if (io->error) return;
+    int retval = rdbSaveBinaryFloatValue(io->rio, value);
+    if (retval == -1) {
+        io->error = 1;
+    } else {
+        io->bytes += retval;
+    }
+}
+
+/* In the context of the rdb_save method of a module data type, loads back the
+ * float value saved by RedisModule_SaveFloat(). */
+float RM_LoadFloat(RedisModuleIO *io) {
+    float value;
+    int retval = rdbLoadBinaryFloatValue(io->rio, &value);
+    if (retval == -1) {
+        moduleRDBLoadError(io);
+        return 0; /* Never reached. */
+    }
+    return value;
+}
+
 /* --------------------------------------------------------------------------
  * AOF API for modules data types
  * -------------------------------------------------------------------------- */
@@ -3280,6 +3305,8 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(LoadStringBuffer);
     REGISTER_API(SaveDouble);
     REGISTER_API(LoadDouble);
+    REGISTER_API(SaveFloat);
+    REGISTER_API(LoadFloat);
     REGISTER_API(EmitAOF);
     REGISTER_API(Log);
     REGISTER_API(LogIOError);

src/rdb.c

@@ -567,17 +567,30 @@ int rdbLoadDoubleValue(rio *rdb, double *val) {
  * Return -1 on error, the size of the serialized value on success. */
 int rdbSaveBinaryDoubleValue(rio *rdb, double val) {
     memrev64ifbe(&val);
-    return rdbWriteRaw(rdb,&val,8);
+    return rdbWriteRaw(rdb,&val,sizeof(val));
 }
 
 /* Loads a double from RDB 8 or greater. See rdbSaveBinaryDoubleValue() for
  * more info. On error -1 is returned, otherwise 0. */
 int rdbLoadBinaryDoubleValue(rio *rdb, double *val) {
-    if (rioRead(rdb,val,8) == 0) return -1;
+    if (rioRead(rdb,val,sizeof(*val)) == 0) return -1;
     memrev64ifbe(val);
     return 0;
 }
 
+/* Like rdbSaveBinaryDoubleValue() but single precision. */
+int rdbSaveBinaryFloatValue(rio *rdb, float val) {
+    memrev32ifbe(&val);
+    return rdbWriteRaw(rdb,&val,sizeof(val));
+}
+
+/* Like rdbLoadBinaryDoubleValue() but single precision. */
+int rdbLoadBinaryFloatValue(rio *rdb, float *val) {
+    if (rioRead(rdb,val,sizeof(*val)) == 0) return -1;
+    memrev32ifbe(val);
+    return 0;
+}
+
 /* Save the object type of object "o". */
 int rdbSaveObjectType(rio *rdb, robj *o) {
     switch (o->type) {

src/rdb.h

@@ -134,6 +134,8 @@ ssize_t rdbSaveRawString(rio *rdb, unsigned char *s, size_t len);
 void *rdbGenericLoadStringObject(rio *rdb, int flags, size_t *lenptr);
 int rdbSaveBinaryDoubleValue(rio *rdb, double val);
 int rdbLoadBinaryDoubleValue(rio *rdb, double *val);
+int rdbSaveBinaryFloatValue(rio *rdb, float val);
+int rdbLoadBinaryFloatValue(rio *rdb, float *val);
 int rdbLoadRio(rio *rdb);
 
 #endif

src/redismodule.h

@@ -184,6 +184,8 @@ RedisModuleString *REDISMODULE_API_FUNC(RedisModule_LoadString)(RedisModuleIO *i
 char *REDISMODULE_API_FUNC(RedisModule_LoadStringBuffer)(RedisModuleIO *io, size_t *lenptr);
 void REDISMODULE_API_FUNC(RedisModule_SaveDouble)(RedisModuleIO *io, double value);
 double REDISMODULE_API_FUNC(RedisModule_LoadDouble)(RedisModuleIO *io);
+void REDISMODULE_API_FUNC(RedisModule_SaveFloat)(RedisModuleIO *io, float value);
+float REDISMODULE_API_FUNC(RedisModule_LoadFloat)(RedisModuleIO *io);
 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, ...);
 int REDISMODULE_API_FUNC(RedisModule_StringAppendBuffer)(RedisModuleCtx *ctx, RedisModuleString *str, const char *buf, size_t len);
@@ -281,6 +283,8 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(LoadStringBuffer);
     REDISMODULE_GET_API(SaveDouble);
     REDISMODULE_GET_API(LoadDouble);
+    REDISMODULE_GET_API(SaveFloat);
+    REDISMODULE_GET_API(LoadFloat);
     REDISMODULE_GET_API(EmitAOF);
     REDISMODULE_GET_API(Log);
     REDISMODULE_GET_API(LogIOError);