Modules API reference

RM_Alloc

void *RM_Alloc(size_t bytes);

Use like malloc(). Memory allocated with this function is reported in Redis INFO memory, used for keys eviction according to maxmemory settings and in general is taken into account as memory allocated by Redis. You should avoid to use malloc().

RM_Realloc

void* RM_Realloc(void *ptr, size_t bytes);

Use like realloc() for memory obtained with RedisModule_Alloc().

RM_Free

void RM_Free(void *ptr);

Use like free() for memory obtained by RedisModule_Alloc() and RedisModule_Realloc(). However you should never try to free with RedisModule_Free() memory allocated with malloc() inside your module.

RM_Strdup

char *RM_Strdup(const char *str);

Like strdup() but returns memory allocated with RedisModule_Alloc().

RM_PoolAlloc

void *RM_PoolAlloc(RedisModuleCtx *ctx, size_t bytes);

Return heap allocated memory that will be freed automatically when the module callback function returns. Mostly suitable for small allocations that are short living and must be released when the callback returns anyway. The returned memory is aligned to the architecture word size if at least word size bytes are requested, otherwise it is just aligned to the next power of two, so for example a 3 bytes request is 4 bytes aligned while a 2 bytes request is 2 bytes aligned.

There is no realloc style function since when this is needed to use the pool allocator is not a good idea.

The function returns NULL if bytes is 0.

RM_GetApi

int RM_GetApi(const char *funcname, void **targetPtrPtr);

Lookup the requested module API and store the function pointer into the target pointer. The function returns REDISMODULE_ERR if there is no such named API, otherwise REDISMODULE_OK.

This function is not meant to be used by modules developer, it is only used implicitly by including redismodule.h.

RM_IsKeysPositionRequest

int RM_IsKeysPositionRequest(RedisModuleCtx *ctx);

Return non-zero if a module command, that was declared with the flag "getkeys-api", is called in a special way to get the keys positions and not to get executed. Otherwise zero is returned.

RM_KeyAtPos

void RM_KeyAtPos(RedisModuleCtx *ctx, int pos);

When a module command is called in order to obtain the position of keys, since it was flagged as "getkeys-api" during the registration, the command implementation checks for this special call using the RedisModule_IsKeysPositionRequest() API and uses this function in order to report keys, like in the following example:

if (RedisModule_IsKeysPositionRequest(ctx)) { RedisModule_KeyAtPos(ctx,1); RedisModule_KeyAtPos(ctx,2); }

Note: in the example below the get keys API would not be needed since keys are at fixed positions. This interface is only used for commands with a more complex structure.

RM_CreateCommand

int RM_CreateCommand(RedisModuleCtx *ctx, const char *name, RedisModuleCmdFunc cmdfunc, const char *strflags, int firstkey, int lastkey, int keystep);

Register a new command in the Redis server, that will be handled by calling the function pointer 'func' using the RedisModule calling convention. The function returns REDISMODULE_ERR if the specified command name is already busy or a set of invalid flags were passed, otherwise REDISMODULE_OK is returned and the new command is registered.

This function must be called during the initialization of the module inside the RedisModule_OnLoad() function. Calling this function outside of the initialization function is not defined.

The command function type is the following:

 int MyCommand_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc);

And is supposed to always return REDISMODULE_OK.

The set of flags 'strflags' specify the behavior of the command, and should be passed as a C string compoesd of space separated words, like for example "write deny-oom". The set of flags are:

RM_SetModuleAttribs

void RM_SetModuleAttribs(RedisModuleCtx *ctx, const char *name, int ver, int apiver);

Called by RM_Init() to setup the ctx->module structure.

This is an internal function, Redis modules developers don't need to use it.

RM_AutoMemory

void RM_AutoMemory(RedisModuleCtx *ctx);

Enable automatic memory management. See API.md for more information.

The function must be called as the first function of a command implementation that wants to use automatic memory.

RM_CreateString

RedisModuleString *RM_CreateString(RedisModuleCtx *ctx, const char *ptr, size_t len);

Create a new module string object. The returned string must be freed with RedisModule_FreeString(), unless automatic memory is enabled.

The string is created by copying the len bytes starting at ptr. No reference is retained to the passed buffer.

RM_CreateStringFromLongLong

RedisModuleString *RM_CreateStringFromLongLong(RedisModuleCtx *ctx, long long ll);

Like RedisModule_CreatString(), but creates a string starting from a long long 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);

Free a module string object obtained with one of the Redis modules API calls that return new string objects.

It is possible to call this function even when automatic memory management is enabled. In that case the string will be released ASAP and removed from the pool of string to release at the end.

RM_StringPtrLen

const char *RM_StringPtrLen(RedisModuleString *str, size_t *len);

Given a string module object, this function returns the string pointer and length of the string. The returned pointer and length should only be used for read only accesses and never modified.

RM_StringToLongLong

int RM_StringToLongLong(RedisModuleString *str, long long *ll);

Convert the string into a long long integer, storing it at *ll. Returns REDISMODULE_OK on success. If the string can't be parsed as a valid, strict long long (no spaces before/after), REDISMODULE_ERR is returned.

RM_StringToDouble

int RM_StringToDouble(RedisModuleString *str, double *d);

Convert the string into a double, storing it at *d. Returns REDISMODULE_OK on success or REDISMODULE_ERR if the string is not a valid string representation of a double value.

RM_WrongArity

int RM_WrongArity(RedisModuleCtx *ctx);

Send an error about the number of arguments given to the command, citing the command name in the error message.

Example:

if (argc != 3) return RedisModule_WrongArity(ctx);

RM_ReplyWithLongLong

int RM_ReplyWithLongLong(RedisModuleCtx *ctx, long long ll);

Send an integer reply to the client, with the specified long long value. The function always returns REDISMODULE_OK.

RM_ReplyWithError

int RM_ReplyWithError(RedisModuleCtx *ctx, const char *err);

Reply with the error 'err'.

Note that 'err' must contain all the error, including the initial error code. The function only provides the initial "-", so the usage is, for example:

RM_ReplyWithError(ctx,"ERR Wrong Type");

and not just:

RM_ReplyWithError(ctx,"Wrong Type");

The function always returns REDISMODULE_OK.

RM_ReplyWithSimpleString

int RM_ReplyWithSimpleString(RedisModuleCtx *ctx, const char *msg);

Reply with a simple string (+... \r\n in RESP protocol). This replies are suitable only when sending a small non-binary string with small overhead, like "OK" or similar replies.

The function always returns REDISMODULE_OK.

RM_ReplyWithArray

int RM_ReplyWithArray(RedisModuleCtx *ctx, long len);

Reply with an array type of 'len' elements. However 'len' other calls to ReplyWith* style functions must follow in order to emit the elements of the array.

When producing arrays with a number of element that is not known beforehand the function can be called with the special count REDISMODULE_POSTPONED_ARRAY_LEN, and the actual number of elements can be later set with RedisModule_ReplySetArrayLength() (which will set the latest "open" count if there are multiple ones).

The function always returns REDISMODULE_OK.

RM_ReplySetArrayLength

void RM_ReplySetArrayLength(RedisModuleCtx *ctx, long len);

When RedisModule_ReplyWithArray() is used with the argument REDISMODULE_POSTPONED_ARRAY_LEN, because we don't know beforehand the number of items we are going to output as elements of the array, this function will take care to set the array length.

Since it is possible to have multiple array replies pending with unknown length, this function guarantees to always set the latest array length that was created in a postponed way.

For example in order to output an array like [1,[10,20,30]] we could write:

RedisModule_ReplyWithArray(ctx,REDISMODULE_POSTPONED_ARRAY_LEN); RedisModule_ReplyWithLongLong(ctx,1); RedisModule_ReplyWithArray(ctx,REDISMODULE_POSTPONED_ARRAY_LEN); RedisModule_ReplyWithLongLong(ctx,10); RedisModule_ReplyWithLongLong(ctx,20); RedisModule_ReplyWithLongLong(ctx,30); RedisModule_ReplySetArrayLength(ctx,3); // Set len of 10,20,30 array. RedisModule_ReplySetArrayLength(ctx,2); // Set len of top array

Note that in the above example there is no reason to postpone the array length, since we produce a fixed number of elements, but in the practice the code may use an interator or other ways of creating the output so that is not easy to calculate in advance the number of elements.

RM_ReplyWithStringBuffer

int RM_ReplyWithStringBuffer(RedisModuleCtx *ctx, const char *buf, size_t len);

Reply with a bulk string, taking in input a C buffer pointer and length.

The function always returns REDISMODULE_OK.

RM_ReplyWithString

int RM_ReplyWithString(RedisModuleCtx *ctx, RedisModuleString *str);

Reply with a bulk string, taking in input a RedisModuleString object.

The function always returns REDISMODULE_OK.

RM_ReplyWithNull

int RM_ReplyWithNull(RedisModuleCtx *ctx);

Reply to the client with a NULL. In the RESP protocol a NULL is encoded as the string "$-1\r\n".

The function always returns REDISMODULE_OK.

RM_ReplyWithCallReply

int RM_ReplyWithCallReply(RedisModuleCtx *ctx, RedisModuleCallReply *reply);

Reply exactly what a Redis command returned us with RedisModule_Call(). This function is useful when we use RedisModule_Call() in order to execute some command, as we want to reply to the client exactly the same reply we obtained by the command.

The function always returns REDISMODULE_OK.

RM_ReplyWithDouble

int RM_ReplyWithDouble(RedisModuleCtx *ctx, double d);

Send a string reply obtained converting the double 'd' into a bulk string. This function is basically equivalent to converting a double into a string into a C buffer, and then calling the function RedisModule_ReplyWithStringBuffer() with the buffer and length.

The function always returns REDISMODULE_OK.

RM_Replicate

int RM_Replicate(RedisModuleCtx *ctx, const char *cmdname, const char *fmt, ...);

Replicate the specified command and arguments to slaves and AOF, as effect of execution of the calling command implementation.

The replicated commands are always wrapped into the MULTI/EXEC that contains all the commands replicated in a given module command execution. However the commands replicated with RedisModule_Call() are the first items, the ones replicated with RedisModule_Replicate() will all follow before the EXEC.

Modules should try to use one interface or the other.

This command follows exactly the same interface of RedisModule_Call(), so a set of format specifiers must be passed, followed by arguments matching the provided format specifiers.

Please refer to RedisModule_Call() for more information.

The command returns REDISMODULE_ERR if the format specifiers are invalid or the command name does not belong to a known command.

RM_ReplicateVerbatim

int RM_ReplicateVerbatim(RedisModuleCtx *ctx);

This function will replicate the command exactly as it was invoked by the client. Note that this function will not wrap the command into a MULTI/EXEC stanza, so it should not be mixed with other replication commands.

Basically this form of replication is useful when you want to propagate the command to the slaves and AOF file exactly as it was called, since the command can just be re-executed to deterministically re-create the new state starting from the old one.

The function always returns REDISMODULE_OK.

RM_GetClientId

unsigned long long RM_GetClientId(RedisModuleCtx *ctx);

Return the ID of the current client calling the currently active module command. The returned ID has a few guarantees:

  1. The ID is different for each different client, so if the same client executes a module command multiple times, it can be recognized as having the same ID, otherwise the ID will be different.
  2. The ID increases monotonically. Clients connecting to the server later are guaranteed to get IDs greater than any past ID previously seen.

Valid IDs are from 1 to 2^64-1. If 0 is returned it means there is no way to fetch the ID in the context the function was currently called.

RM_GetSelectedDb

int RM_GetSelectedDb(RedisModuleCtx *ctx);

Return the currently selected DB.

RM_SelectDb

int RM_SelectDb(RedisModuleCtx *ctx, int newid);

Change the currently selected DB. Returns an error if the id is out of range.

Note that the client will retain the currently selected DB even after the Redis command implemented by the module calling this function returns.

If the module command wishes to change something in a different DB and returns back to the original one, it should call RedisModule_GetSelectedDb() before in order to restore the old DB number before returning.

RM_OpenKey

void *RM_OpenKey(RedisModuleCtx *ctx, robj *keyname, int mode);

Return an handle representing a Redis key, so that it is possible to call other APIs with the key handle as argument to perform operations on the key.

The return value is the handle repesenting the key, that must be closed with RM_CloseKey().

If the key does not exist and WRITE mode is requested, the handle is still returned, since it is possible to perform operations on a yet not existing key (that will be created, for example, after a list push operation). If the mode is just READ instead, and the key does not exist, NULL is returned. However it is still safe to call RedisModule_CloseKey() and RedisModule_KeyType() on a NULL value.

RM_CloseKey

void RM_CloseKey(RedisModuleKey *key);

Close a key handle.

RM_KeyType

int RM_KeyType(RedisModuleKey *key);

Return the type of the key. If the key pointer is NULL then REDISMODULE_KEYTYPE_EMPTY is returned.

RM_ValueLength

size_t RM_ValueLength(RedisModuleKey *key);

Return the length of the value associated with the key. For strings this is the length of the string. For all the other types is the number of elements (just counting keys for hashes).

If the key pointer is NULL or the key is empty, zero is returned.

RM_DeleteKey

int RM_DeleteKey(RedisModuleKey *key);

If the key is open for writing, remove it, and setup the key to accept new writes as an empty key (that will be created on demand). On success REDISMODULE_OK is returned. If the key is not open for writing REDISMODULE_ERR is returned.

RM_GetExpire

mstime_t RM_GetExpire(RedisModuleKey *key);

Return the key expire value, as milliseconds of remaining TTL. If no TTL is associated with the key or if the key is empty, REDISMODULE_NO_EXPIRE is returned.

RM_SetExpire

int RM_SetExpire(RedisModuleKey *key, mstime_t expire);

Set a new expire for the key. If the special expire REDISMODULE_NO_EXPIRE is set, the expire is cancelled if there was one (the same as the PERSIST command).

Note that the expire must be provided as a positive integer representing the number of milliseconds of TTL the key should have.

The function returns REDISMODULE_OK on success or REDISMODULE_ERR if the key was not open for writing or is an empty key.

RM_StringSet

int RM_StringSet(RedisModuleKey *key, RedisModuleString *str);

If the key is open for writing, set the specified string 'str' as the value of the key, deleting the old value if any. On success REDISMODULE_OK is returned. If the key is not open for writing or there is an active iterator, REDISMODULE_ERR is returned.

RM_StringDMA

char *RM_StringDMA(RedisModuleKey *key, size_t *len, int mode);

Prepare the key associated string value for DMA access, and returns a pointer and size (by reference), that the user can use to read or modify the string in-place accessing it directly via pointer.

The 'mode' is composed by bitwise OR-ing the following flags:

REDISMODULE_READ -- Read access REDISMODULE_WRITE -- Write access

If the DMA is not requested for writing, the pointer returned should only be accessed in a read-only fashion.

On error (wrong type) NULL is returned.

DMA access rules:

  1. No other key writing function should be called since the moment the pointer is obtained, for all the time we want to use DMA access to read or modify the string.

  2. Each time RM_StringTruncate() is called, to continue with the DMA access, RM_StringDMA() should be called again to re-obtain a new pointer and length.

  3. If the returned pointer is not NULL, but the length is zero, no byte can be touched (the string is empty, or the key itself is empty) so a RM_StringTruncate() call should be used if there is to enlarge the string, and later call StringDMA() again to get the pointer.

RM_StringTruncate

int RM_StringTruncate(RedisModuleKey *key, size_t newlen);

If the string is open for writing and is of string type, resize it, padding with zero bytes if the new length is greater than the old one.

After this call, RM_StringDMA() must be called again to continue DMA access with the new pointer.

The function returns REDISMODULE_OK on success, and REDISMODULE_ERR on error, that is, the key is not open for writing, is not a string or resizing for more than 512 MB is requested.

If the key is empty, a string key is created with the new string value unless the new length value requested is zero.

RM_ListPush

int RM_ListPush(RedisModuleKey *key, int where, RedisModuleString *ele);

Push an element into a list, on head or tail depending on 'where' argumnet. If the key pointer is about an empty key opened for writing, the key is created. On error (key opened for read-only operations or of the wrong type) REDISMODULE_ERR is returned, otherwise REDISMODULE_OK is returned.

RM_ListPop

RedisModuleString *RM_ListPop(RedisModuleKey *key, int where);

Pop an element from the list, and returns it as a module string object that the user should be free with RM_FreeString() or by enabling automatic memory. 'where' specifies if the element should be popped from head or tail. The command returns NULL if: 1) The list is empty. 2) The key was not open for writing. 3) The key is not a list.

RM_ZsetAddFlagsToCoreFlags

int RM_ZsetAddFlagsToCoreFlags(int flags);

Conversion from/to public flags of the Modules API and our private flags, so that we have everything decoupled.

RM_ZsetAddFlagsFromCoreFlags

int RM_ZsetAddFlagsFromCoreFlags(int flags);

See previous function comment.

RM_ZsetAdd

int RM_ZsetAdd(RedisModuleKey *key, double score, RedisModuleString *ele, int *flagsptr);

Add a new element into a sorted set, with the specified 'score'. If the element already exists, the score is updated.

A new sorted set is created at value if the key is an empty open key setup for writing.

Additional flags can be passed to the function via a pointer, the flags are both used to receive input and to communicate state when the function returns. 'flagsptr' can be NULL if no special flags are used.

The input flags are:

REDISMODULE_ZADD_XX: Element must already exist. Do nothing otherwise. REDISMODULE_ZADD_NX: Element must not exist. Do nothing otherwise.

The output flags are:

REDISMODULE_ZADD_ADDED: The new element was added to the sorted set. REDISMODULE_ZADD_UPDATED: The score of the element was updated. REDISMODULE_ZADD_NOP: No operation was performed because XX or NX flags.

On success the function returns REDISMODULE_OK. On the following errors REDISMODULE_ERR is returned:

RM_ZsetIncrby

int RM_ZsetIncrby(RedisModuleKey *key, double score, RedisModuleString *ele, int *flagsptr, double *newscore);

This function works exactly like RM_ZsetAdd(), but instead of setting a new score, the score of the existing element is incremented, or if the element does not already exist, it is added assuming the old score was zero.

The input and output flags, and the return value, have the same exact meaning, with the only difference that this function will return REDISMODULE_ERR even when 'score' is a valid double number, but adding it to the existing score resuts into a NaN (not a number) condition.

This function has an additional field 'newscore', if not NULL is filled with the new score of the element after the increment, if no error is returned.

RM_ZsetRem

int RM_ZsetRem(RedisModuleKey *key, RedisModuleString *ele, int *deleted);

Remove the specified element from the sorted set. The function returns REDISMODULE_OK on success, and REDISMODULE_ERR on one of the following conditions:

The return value does NOT indicate the fact the element was really removed (since it existed) or not, just if the function was executed with success.

In order to know if the element was removed, the additional argument 'deleted' must be passed, that populates the integer by reference setting it to 1 or 0 depending on the outcome of the operation. The 'deleted' argument can be NULL if the caller is not interested to know if the element was really removed.

Empty keys will be handled correctly by doing nothing.

RM_ZsetScore

int RM_ZsetScore(RedisModuleKey *key, RedisModuleString *ele, double *score);

On success retrieve the double score associated at the sorted set element 'ele' and returns REDISMODULE_OK. Otherwise REDISMODULE_ERR is returned to signal one of the following conditions:

RM_ZsetRangeStop

void RM_ZsetRangeStop(RedisModuleKey *key);

Stop a sorted set iteration.

RM_ZsetRangeEndReached

int RM_ZsetRangeEndReached(RedisModuleKey *key);

Return the "End of range" flag value to signal the end of the iteration.

RM_ZsetFirstInScoreRange

int RM_ZsetFirstInScoreRange(RedisModuleKey *key, double min, double max, int minex, int maxex);

Setup a sorted set iterator seeking the first element in the specified range. Returns REDISMODULE_OK if the iterator was correctly initialized otherwise REDISMODULE_ERR is returned in the following conditions:

  1. The value stored at key is not a sorted set or the key is empty.

The range is specified according to the two double values 'min' and 'max'. Both can be infinite using the following two macros:

REDISMODULE_POSITIVE_INFINITE for positive infinite value REDISMODULE_NEGATIVE_INFINITE for negative infinite value

'minex' and 'maxex' parameters, if true, respectively setup a range where the min and max value are exclusive (not included) instead of inclusive.

RM_ZsetLastInScoreRange

int RM_ZsetLastInScoreRange(RedisModuleKey *key, double min, double max, int minex, int maxex);

Exactly like RedisModule_ZsetFirstInScoreRange() but the last element of the range is selected for the start of the iteration instead.

RM_ZsetFirstInLexRange

int RM_ZsetFirstInLexRange(RedisModuleKey *key, RedisModuleString *min, RedisModuleString *max);

Setup a sorted set iterator seeking the first element in the specified lexicographical range. Returns REDISMODULE_OK if the iterator was correctly initialized otherwise REDISMODULE_ERR is returned in the following conditions:

  1. The value stored at key is not a sorted set or the key is empty.
  2. The lexicographical range 'min' and 'max' format is invalid.

'min' and 'max' should be provided as two RedisModuleString objects in the same format as the parameters passed to the ZRANGEBYLEX command. The function does not take ownership of the objects, so they can be released ASAP after the iterator is setup.

RM_ZsetLastInLexRange

int RM_ZsetLastInLexRange(RedisModuleKey *key, RedisModuleString *min, RedisModuleString *max);

Exactly like RedisModule_ZsetFirstInLexRange() but the last element of the range is selected for the start of the iteration instead.

RM_ZsetRangeCurrentElement

RedisModuleString *RM_ZsetRangeCurrentElement(RedisModuleKey *key, double *score);

Return the current sorted set element of an active sorted set iterator or NULL if the range specified in the iterator does not include any element.

RM_ZsetRangeNext

int RM_ZsetRangeNext(RedisModuleKey *key);

Go to the next element of the sorted set iterator. Returns 1 if there was a next element, 0 if we are already at the latest element or the range does not include any item at all.

RM_ZsetRangePrev

int RM_ZsetRangePrev(RedisModuleKey *key);

Go to the previous element of the sorted set iterator. Returns 1 if there was a previous element, 0 if we are already at the first element or the range does not include any item at all.

RM_HashSet

int RM_HashSet(RedisModuleKey *key, int flags, ...);

Set the field of the specified hash field to the specified value. If the key is an empty key open for writing, it is created with an empty hash value, in order to set the specified field.

The function is variadic and the user must specify pairs of field names and values, both as RedisModuleString pointers (unless the CFIELD option is set, see later).

Example to set the hash argv[1] to the value argv[2]:

RedisModule_HashSet(key,REDISMODULE_HASH_NONE,argv[1],argv[2],NULL);

The function can also be used in order to delete fields (if they exist) by setting them to the specified value of REDISMODULE_HASH_DELETE:

RedisModule_HashSet(key,REDISMODULE_HASH_NONE,argv[1], REDISMODULE_HASH_DELETE,NULL);

The behavior of the command changes with the specified flags, that can be set to REDISMODULE_HASH_NONE if no special behavior is needed.

REDISMODULE_HASH_NX: The operation is performed only if the field was not already existing in the hash. REDISMODULE_HASH_XX: The operation is performed only if the field was already existing, so that a new value could be associated to an existing filed, but no new fields are created. REDISMODULE_HASH_CFIELDS: The field names passed are null terminated C strings instead of RedisModuleString objects.

Unless NX is specified, the command overwrites the old field value with the new one.

When using REDISMODULE_HASH_CFIELDS, field names are reported using normal C strings, so for example to delete the field "foo" the following code can be used:

RedisModule_HashSet(key,REDISMODULE_HASH_CFIELDS,"foo", REDISMODULE_HASH_DELETE,NULL);

Return value:

The number of fields updated (that may be less than the number of fields specified because of the XX or NX options).

In the following case the return value is always zero:

RM_HashGet

int RM_HashGet(RedisModuleKey *key, int flags, ...);

Get fields from an hash value. This function is called using a variable number of arguments, alternating a field name (as a StringRedisModule pointer) with a pointer to a StringRedisModule pointer, that is set to the value of the field if the field exist, or NULL if the field did not exist. At the end of the field/value-ptr pairs, NULL must be specified as last argument to signal the end of the arguments in the variadic function.

This is an example usage:

 RedisModuleString *first, *second;
 `RedisModule_HashGet(mykey`,`REDISMODULE_HASH_NONE`,argv[1],&first,
                 argv[2],&second,NULL);

As with RedisModule_HashSet() the behavior of the command can be specified passing flags different than REDISMODULE_HASH_NONE:

REDISMODULE_HASH_CFIELD: field names as null terminated C strings.

REDISMODULE_HASH_EXISTS: instead of setting the value of the field expecting a RedisModuleString pointer to pointer, the function just reports if the field esists or not and expects an integer pointer as the second element of each pair.

Example of REDISMODULE_HASH_CFIELD:

 RedisModuleString *username, *hashedpass;
 `RedisModule_HashGet(mykey`,"username",&username,"hp",&hashedpass, NULL);

Example of REDISMODULE_HASH_EXISTS:

 int exists;
 `RedisModule_HashGet(mykey`,argv[1],&exists,NULL);

The function returns REDISMODULE_OK on success and REDISMODULE_ERR if the key is not an hash value.

Memory management:

The returned RedisModuleString objects should be released with RedisModule_FreeString(), or by enabling automatic memory management.

RM_FreeCallReply_Rec

void RM_FreeCallReply_Rec(RedisModuleCallReply *reply, int freenested);

Free a Call reply and all the nested replies it contains if it's an array.

RM_FreeCallReply

void RM_FreeCallReply(RedisModuleCallReply *reply);

Wrapper for the recursive free reply function. This is needed in order to have the first level function to return on nested replies, but only if called by the module API.

RM_CallReplyType

int RM_CallReplyType(RedisModuleCallReply *reply);

Return the reply type.

RM_CallReplyLength

size_t RM_CallReplyLength(RedisModuleCallReply *reply);

Return the reply type length, where applicable.

RM_CallReplyArrayElement

RedisModuleCallReply *RM_CallReplyArrayElement(RedisModuleCallReply *reply, size_t idx);

Return the 'idx'-th nested call reply element of an array reply, or NULL if the reply type is wrong or the index is out of range.

RM_CallReplyInteger

long long RM_CallReplyInteger(RedisModuleCallReply *reply);

Return the long long of an integer reply.

RM_CallReplyStringPtr

const char *RM_CallReplyStringPtr(RedisModuleCallReply *reply, size_t *len);

Return the pointer and length of a string or error reply.

RM_CreateStringFromCallReply

RedisModuleString *RM_CreateStringFromCallReply(RedisModuleCallReply *reply);

Return a new string object from a call reply of type string, error or integer. Otherwise (wrong reply type) return NULL.

RM_Call

RedisModuleCallReply *RM_Call(RedisModuleCtx *ctx, const char *cmdname, const char *fmt, ...);

Exported API to call any Redis command from modules. On success a RedisModuleCallReply object is returned, otherwise NULL is returned and errno is set to the following values:

EINVAL: command non existing, wrong arity, wrong format specifier. EPERM: operation in Cluster instance with key in non local slot.

RM_CallReplyProto

const char *RM_CallReplyProto(RedisModuleCallReply *reply, size_t *len);

Return a pointer, and a length, to the protocol returned by the command that returned the reply object.

RM_CreateDataType

moduleType *RM_CreateDataType(RedisModuleCtx *ctx, const char *name, int encver, moduleTypeLoadFunc rdb_load, moduleTypeSaveFunc rdb_save, moduleTypeRewriteFunc aof_rewrite, moduleTypeDigestFunc digest, moduleTypeFreeFunc free);

Register a new data type exported by the module. The parameters are the following. Please for in depth documentation check the modules API documentation, especially the INTRO.md file.

Note: the module name "AAAAAAAAA" is reserved and produces an error, it happens to be pretty lame as well.

If there is already a module registering a type with the same name, and if the module name or encver is invalid, NULL is returned. Otherwise the new type is registered into Redis, and a reference of type RedisModuleType is returned: the caller of the function should store this reference into a gobal variable to make future use of it in the modules type API, since a single module may register multiple types. Example code fragment:

 static RedisModuleType *BalancedTreeType;

 int `RedisModule_OnLoad(RedisModuleCtx` *ctx) {
     // some code here ...
     BalancedTreeType = `RM_CreateDataType(`...);
 }

RM_ModuleTypeSetValue

int RM_ModuleTypeSetValue(RedisModuleKey *key, moduleType *mt, void *value);

If the key is open for writing, set the specified module type object as the value of the key, deleting the old value if any. On success REDISMODULE_OK is returned. If the key is not open for writing or there is an active iterator, REDISMODULE_ERR is returned.

RM_ModuleTypeGetType

moduleType *RM_ModuleTypeGetType(RedisModuleKey *key);

Assuming RedisModule_KeyType() returned REDISMODULE_KEYTYPE_MODULE on the key, returns the moduel type pointer of the value stored at key.

If the key is NULL, is not associated with a module type, or is empty, then NULL is returned instead.

RM_ModuleTypeGetValue

void *RM_ModuleTypeGetValue(RedisModuleKey *key);

Assuming RedisModule_KeyType() returned REDISMODULE_KEYTYPE_MODULE on the key, returns the module type low-level value stored at key, as it was set by the user via RedisModule_ModuleTypeSet().

If the key is NULL, is not associated with a module type, or is empty, then NULL is returned instead.

RM_SaveUnsigned

void RM_SaveUnsigned(RedisModuleIO *io, uint64_t value);

Save an unsigned 64 bit value into the RDB file. This function should only be called in the context of the rdb_save method of modules implementing new data types.

RM_LoadUnsigned

uint64_t RM_LoadUnsigned(RedisModuleIO *io);

Load an unsigned 64 bit value from the RDB file. This function should only be called in the context of the rdb_load method of modules implementing new data types.

RM_SaveSigned

void RM_SaveSigned(RedisModuleIO *io, int64_t value);

Like RedisModule_SaveUnsigned() but for signed 64 bit values.

RM_LoadSigned

int64_t RM_LoadSigned(RedisModuleIO *io);

Like RedisModule_LoadUnsigned() but for signed 64 bit values.

RM_SaveString

void RM_SaveString(RedisModuleIO *io, RedisModuleString *s);

In the context of the rdb_save method of a module type, saves a string into the RDB file taking as input a RedisModuleString.

The string can be later loaded with RedisModule_LoadString() or other Load family functions expecting a serialized string inside the RDB file.

RM_SaveStringBuffer

void RM_SaveStringBuffer(RedisModuleIO *io, const char *str, size_t len);

Like RedisModule_SaveString() but takes a raw C pointer and length as input.

RM_LoadString

RedisModuleString *RM_LoadString(RedisModuleIO *io);

In the context of the rdb_load method of a module data type, loads a string from the RDB file, that was previously saved with RedisModule_SaveString() functions family.

The returned string is a newly allocated RedisModuleString object, and the user should at some point free it with a call to RedisModule_FreeString().

If the data structure does not store strings as RedisModuleString objects, the similar function RedisModule_LoadStringBuffer() could be used instead.

RM_LoadStringBuffer

char *RM_LoadStringBuffer(RedisModuleIO *io, size_t *lenptr);

Like RedisModule_LoadString() but returns an heap allocated string that was allocated with RedisModule_Alloc(), and can be resized or freed with RedisModule_Realloc() or RedisModule_Free().

The size of the string is stored at '*lenptr' if not NULL. The returned string is not automatically NULL termianted, it is loaded exactly as it was stored inisde the RDB file.

RM_SaveDouble

void RM_SaveDouble(RedisModuleIO *io, double value);

In the context of the rdb_save method of a module data type, saves a double value to the RDB file. The double can be a valid number, a NaN or infinity. It is possible to load back the value with RedisModule_LoadDouble().

RM_LoadDouble

double RM_LoadDouble(RedisModuleIO *io);

In the context of the rdb_save method of a module data type, loads back the double value saved by RedisModule_SaveDouble().

RM_EmitAOF

void RM_EmitAOF(RedisModuleIO *io, const char *cmdname, const char *fmt, ...);

Emits a command into the AOF during the AOF rewriting process. This function is only called in the context of the aof_rewrite method of data types exported by a module. The command works exactly like RedisModule_Call() in the way the parameters are passed, but it does not return anything as the error handling is performed by Redis itself.

RM_Log

void RM_Log(RedisModuleCtx *ctx, const char *levelstr, const char *fmt, ...);

Produces a log message to the standard Redis log, the format accepts printf-alike specifiers, while level is a string describing the log level to use when emitting the log, and must be one of the following:

If the specified log level is invalid, verbose is used by default. There is a fixed limit to the length of the log line this function is able to emit, this limti is not specified but is guaranteed to be more than a few lines of text.