From d27d41d2b885a7d4f00dae935882adf4a4a4b558 Mon Sep 17 00:00:00 2001 From: Guus Sliepen Date: Tue, 29 Jul 2014 17:00:13 +0200 Subject: [PATCH] Document how memory management is handled in the API. --- src/meshlink.h | 71 ++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 60 insertions(+), 11 deletions(-) diff --git a/src/meshlink.h b/src/meshlink.h index e06a5906..a21af570 100644 --- a/src/meshlink.h +++ b/src/meshlink.h @@ -75,20 +75,29 @@ struct meshlink_channel { */ extern const char *meshlink_strerror(meshlink_errno_t errno); -/// Initialize MeshLink's configuration directory. -/** This function causes MeshLink to initialize its configuration directory, - * if it hasn't already been initialized. - * It only has to be run the first time the application starts, - * but it is not a problem if it is run more than once, as long as - * the arguments given are the same. +/// Open or create a MeshLink instance. +/** This function opens or creates a MeshLink instance. + * The state is stored in the configuration directory passed in the variable @a confbase @a. + * If the configuration directory does not exist yet, for example when it is the first time + * this instance is opened, the configuration directory will be automatically created and initialized. + * However, the parent directory should already exist, otherwise an error will be returned. + * + * The name given should be a unique identifier for this instance. + * + * This function returns a pointer to a struct meshlink_handle that will be allocated by MeshLink. + * When the application does no longer need to use this handle, it must call meshlink_close() to + * free its resources. * * This function does not start any network I/O yet. The application should * first set callbacks, and then call meshlink_start(). * * @param confbase The directory in which MeshLink will store its configuration files. + * After the function returns, the application is free to overwrite or free @a confbase @a. * @param name The name which this instance of the application will use in the mesh. + * After the function returns, the application is free to overwrite or free @a name @a. * - * @return This function will return true if MeshLink has succesfully set up its configuration files, false otherwise. + * @return A pointer to a meshlink_handle_t which represents this instance of MeshLink. + * The pointer is valid until meshlink_close() is called. */ extern meshlink_handle_t *meshlink_open(const char *confbase, const char *name); @@ -112,8 +121,8 @@ extern void meshlink_stop(meshlink_handle_t *mesh); /// Close the MeshLink handle. /** This function calls meshlink_stop() if necessary, - * and frees all memory allocated by MeshLink. - * Afterwards, the handle and any pointers to a struct meshlink_node are invalid. + * and frees the struct meshlink_handle and all associacted memory allocated by MeshLink. + * Afterwards, the handle and any pointers to a struct meshlink_node or struct meshlink_channel are invalid. * * @param mesh A handle which represents an instance of MeshLink. */ @@ -123,6 +132,8 @@ extern void meshlink_close(meshlink_handle_t *mesh); /** @param mesh A handle which represents an instance of MeshLink. * @param source A pointer to a meshlink_node_t describing the source of the data. * @param data A pointer to a buffer containing the data sent by the source. + * The pointer is only valid during the lifetime of the callback. + * The callback should mempcy() the data if it needs to be available outside the callback. * @param len The length of the received data. */ typedef void (*meshlink_receive_cb_t)(meshlink_handle_t *mesh, meshlink_node_t *source, const void *data, size_t len); @@ -136,6 +147,7 @@ typedef void (*meshlink_receive_cb_t)(meshlink_handle_t *mesh, meshlink_node_t * * * @param mesh A handle which represents an instance of MeshLink. * @param cb A pointer to the function which will be called when another node sends data to the local node. + * If a NULL pointer is given, the callback will be disabled. */ extern void meshlink_set_receive_cb(meshlink_handle_t *mesh, meshlink_receive_cb_t cb); @@ -155,6 +167,7 @@ typedef void (*meshlink_node_status_cb_t)(meshlink_handle_t *mesh, meshlink_node * * @param mesh A handle which represents an instance of MeshLink. * @param cb A pointer to the function which will be called when another node's status changes. + * If a NULL pointer is given, the callback will be disabled. */ extern void meshlink_set_node_status_cb(meshlink_handle_t *mesh, meshlink_node_status_cb_t cb); @@ -171,6 +184,8 @@ typedef enum { /** @param mesh A handle which represents an instance of MeshLink. * @param level An enum describing the severity level of the message. * @param text A pointer to a string containing the textual log message. + * This pointer is only valid for the duration of the callback. + * The application should strdup() the text if it has to be available outside the callback. */ typedef void (*meshlink_log_cb_t)(meshlink_handle_t *mesh, meshlink_log_level_t level, const char *text); @@ -184,6 +199,7 @@ typedef void (*meshlink_log_cb_t)(meshlink_handle_t *mesh, meshlink_log_level_t * @param mesh A handle which represents an instance of MeshLink. * @param level An enum describing the minimum severity level. Debugging information with a lower level will not trigger the callback. * @param cb A pointer to the function which will be called when another node sends data to the local node. + * If a NULL pointer is given, the callback will be disabled. */ extern void meshlink_set_log_cb(meshlink_handle_t *mesh, meshlink_log_level_t level, meshlink_log_cb_t cb); @@ -197,6 +213,7 @@ extern void meshlink_set_log_cb(meshlink_handle_t *mesh, meshlink_log_level_t le * @param mesh A handle which represents an instance of MeshLink. * @param destination A pointer to a meshlink_node_t describing the destination for the data. * @param data A pointer to a buffer containing the data to be sent to the source. + * After meshlink_send() returns, the application is free to overwrite or free this buffer. * @param len The length of the data. * @return This function will return true if MeshLink has queued the message for transmission, and false otherwise. * A return value of true does not guarantee that the message will actually arrive at the destination. @@ -208,9 +225,11 @@ extern bool meshlink_send(meshlink_handle_t *mesh, meshlink_node_t *destination, * * @param mesh A handle which represents an instance of MeshLink. * @param name The name of the node for which a handle is requested. + * After this function returns, the application is free to overwrite or free @a name @a. * * @return A pointer to a meshlink_node_t which represents the requested node, * or NULL if the requested node does not exist. + * The pointer is guaranteed to be valid until meshlink_close() is called. */ extern meshlink_node_t *meshlink_get_node(meshlink_handle_t *mesh, const char *name); @@ -219,6 +238,7 @@ extern meshlink_node_t *meshlink_get_node(meshlink_handle_t *mesh, const char *n * * @param mesh A handle which represents an instance of MeshLink. * @param nodes A pointer to an array of pointers to meshlink_node_t, which should be allocated by the application. + * The pointers are valid until meshlink_close() is called. * @param nmemb The maximum number of pointers that can be stored in the nodes array. * * @return The number of known nodes, or -1 in case of an error. @@ -234,6 +254,7 @@ extern ssize_t meshlink_get_all_nodes(meshlink_handle_t *mesh, meshlink_node_t * * @param data A pointer to a buffer containing the data to be signed. * @param len The length of the data to be signed. * @param signature A pointer to a buffer where the signature will be stored. + * The buffer must be allocated by the application, and should be at least MESHLINK_SIGLEN bytes big. * @param siglen The size of the signature buffer. Will be changed after the call to match the size of the signature itself. * * @return This function returns true if the signature was correctly generated, false otherwise. @@ -247,8 +268,9 @@ extern bool meshlink_sign(meshlink_handle_t *mesh, const void *data, size_t len, * @param source A pointer to a meshlink_node_t describing the source of the signature. * @param data A pointer to a buffer containing the data to be verified. * @param len The length of the data to be verified. - * @param signature A pointer to a string containing the signature. - * @param siglen The size of the signature. + * @param signature A pointer to a buffer where the signature will be stored. + * @param siglen A pointer to a variable holding the size of the signature buffer. + * The contents of the variable will be changed by meshlink_sign() to reflect the actual size of the signature. * * @return This function returns true if the signature is valid, false otherwise. */ @@ -272,6 +294,7 @@ extern bool meshlink_add_address(meshlink_handle_t *mesh, const char *address); * * @param mesh A handle which represents an instance of MeshLink. * @param name The name that the invitee will use in the mesh. + * After this function returns, the application is free to overwrite or free @a name @a. * * @return This function returns a string that contains the invitation URL. * The application should call free() after it has finished using the URL. @@ -285,6 +308,7 @@ extern char *meshlink_invite(meshlink_handle_t *mesh, const char *name); * * @param mesh A handle which represents an instance of MeshLink. * @param invitation A string containing the invitation URL. + * After this function returns, the application is free to overwrite or free @a invitation @a. * * @return This function returns true if the local node joined the mesh it was invited to, false otherwise. */ @@ -308,6 +332,7 @@ extern char *meshlink_export(meshlink_handle_t *mesh); * * @param mesh A handle which represents an instance of MeshLink. * @param data A string containing the other node's exported key and addresses. + * After this function returns, the application is free to overwrite or free @a data @a. * * @return This function returns true if the data was valid and the other node has been granted access to the mesh, false otherwise. */ @@ -329,9 +354,17 @@ extern void meshlink_blacklist(meshlink_handle_t *mesh, meshlink_node_t *node); * * @param mesh A handle which represents an instance of MeshLink. * @param channel A handle for the incoming channel. + * If the application accepts the incoming channel by returning true, + * then this handle is valid until meshlink_channel_close() is called on it. + * If the application rejects the incoming channel by returning false, + * then this handle is invalid after the callback returns + * (the callback does not need to call meshlink_channel_close() itself in this case). * @param node The node from which this channel is being initiated. + * The pointer is guaranteed to be valid until meshlink_close() is called. * @param port The port number the peer wishes to connect to. * @param data A pointer to a buffer containing data already received. (Not yet used.) + * The pointer is only valid during the lifetime of the callback. + * The callback should mempcy() the data if it needs to be available outside the callback. * @param len The length of the data. (Not yet used.) * * @return This function should return true if the application accepts the incoming channel, false otherwise. @@ -346,6 +379,8 @@ typedef bool (*meshlink_channel_accept_cb_t)(meshlink_handle_t *mesh, meshlink_c * @param mesh A handle which represents an instance of MeshLink. * @param channel A handle for the channel. * @param data A pointer to a buffer containing data sent by the source. + * The pointer is only valid during the lifetime of the callback. + * The callback should mempcy() the data if it needs to be available outside the callback. * @param len The length of the data. */ typedef void (*meshlink_channel_receive_cb_t)(meshlink_handle_t *mesh, meshlink_channel_t *channel, const void *data, size_t len); @@ -357,8 +392,11 @@ typedef void (*meshlink_channel_receive_cb_t)(meshlink_handle_t *mesh, meshlink_ * to hand the data over to the application's thread. * The callback should also not block itself and return as quickly as possible. * + * If no accept callback is set, incoming channels are rejected. + * * @param mesh A handle which represents an instance of MeshLink. * @param cb A pointer to the function which will be called when another node sends data to the local node. + * If a NULL pointer is given, the callback will be disabled. */ extern void meshlink_set_channel_accept_cb(meshlink_handle_t *mesh, meshlink_channel_accept_cb_t cb); @@ -372,6 +410,7 @@ extern void meshlink_set_channel_accept_cb(meshlink_handle_t *mesh, meshlink_cha * @param mesh A handle which represents an instance of MeshLink. * @param channel A handle for the channel. * @param cb A pointer to the function which will be called when another node sends data to the local node. + * If a NULL pointer is given, the callback will be disabled. */ extern void meshlink_set_channel_receive_cb(meshlink_handle_t *mesh, meshlink_channel_t *channel, meshlink_channel_receive_cb_t cb); @@ -379,14 +418,20 @@ extern void meshlink_set_channel_receive_cb(meshlink_handle_t *mesh, meshlink_ch /** This function is called whenever a remote node wants to open a channel to the local node. * The application then has to decide whether to accept or reject this channel. * + * This function returns a pointer to a struct meshlink_channel that will be allocated by MeshLink. + * When the application does no longer need to use this channel, it must call meshlink_close() + * to free its resources. + * * @param mesh A handle which represents an instance of MeshLink. * @param node The node to which this channel is being initiated. * @param port The port number the peer wishes to connect to. * @param cb A pointer to the function which will be called when the remote node sends data to the local node. * @param data A pointer to a buffer containing data to already queue for sending. + * After meshlink_send() returns, the application is free to overwrite or free this buffer. * @param len The length of the data. * * @return A handle for the channel, or NULL in case of an error. + * The handle is valid until meshlink_channel_close() is called. */ extern meshlink_channel_t *meshlink_channel_open(meshlink_handle_t *mesh, meshlink_node_t *node, uint16_t port, meshlink_channel_receive_cb_t cb, const void *data, size_t len); @@ -395,6 +440,8 @@ extern meshlink_channel_t *meshlink_channel_open(meshlink_handle_t *mesh, meshli * It can be used to inform the remote node that the local node has finished sending all data on the channel, * but still allows waiting for incoming data from the remote node. * + * Shutting down the receive direction is also possible, and is equivalent to setting the receive callback to NULL. + * * @param mesh A handle which represents an instance of MeshLink. * @param channel A handle for the channel. * @param direction Must be one of SHUT_RD, SHUT_WR or SHUT_RDWR. @@ -404,6 +451,7 @@ extern void meshlink_channel_shutdown(meshlink_handle_t *mesh, meshlink_channel_ /// Close a reliable stream channel. /** This informs the remote node that the local node has finished sending all data on the channel. * It also causes the local node to stop accepting incoming data from the remote node. + * It will free the struct meshlink_channel and all associated resources. * Afterwards, the channel handle is invalid and must not be used any more. * * @param mesh A handle which represents an instance of MeshLink. @@ -417,6 +465,7 @@ extern void meshlink_channel_close(meshlink_handle_t *mesh, meshlink_channel_t * * @param mesh A handle which represents an instance of MeshLink. * @param channel A handle for the channel. * @param data A pointer to a buffer containing data sent by the source. + * After meshlink_send() returns, the application is free to overwrite or free this buffer. * @param len The length of the data. * * @return The amount of data that was queued, which can be less than len, or a negative value in case of an error. -- 2.39.5