X-Git-Url: https://gerrit.automotivelinux.org/gerrit/gitweb?a=blobdiff_plain;f=docs%2Fafb-binding-writing.md;h=aad422c456584cd44cbb545703269f372b8fc46b;hb=refs%2Fheads%2Feel;hp=dd9a8b563072b55708b26ea61c4c31c50a520220;hpb=f6bc48698587758fb764bae66302002fe148e978;p=src%2Fapp-framework-binder.git diff --git a/docs/afb-binding-writing.md b/docs/afb-binding-writing.md index dd9a8b56..aad422c4 100644 --- a/docs/afb-binding-writing.md +++ b/docs/afb-binding-writing.md @@ -1,12 +1,10 @@ - -Overview of the bindings -======================== +# Overview of the bindings The ***binder*** serves files through HTTP protocol and offers to developers the capability to offer application API methods through HTTP or WebSocket protocol. -The ***bindings*** are used to add **API** to ***binders***. +The ***bindings*** are used to add **API** to ***binders***. This part describes how to write a ***binding*** for ***binder*** or in other words how to add a new **API** to the system. @@ -16,75 +14,73 @@ This section shortly explain how to write a binding using the C programming language. It is convenient to install the ***binder*** on the -desktop used for writing the binding. It allows easy -debug and test. +desktop used for writing the binding. +It allows easy debug and test. -Nature of a binding -------------------- +## Nature of a binding A ***binding*** is an independent piece of software compiled as a shared -library and dynamically loaded by a ***binder***. - +library and dynamically loaded by a ***binder***. It is intended to provide one **API** (**A**pplication **P**rogramming **I**nterface). -The **API** is designated and accessed through its name. +The **API** is designated and accessed through its name. It contains several **verbs** that implement the ***binding*** -functionnalities. Each of these **verbs** is a **method** that +functionalities. +Each of these **verbs** is a **method** that processes requests of applications and sends result. -The ***binding***'s methods is invoqued by HTTP or websocket +The ***binding***'s methods are invoked by HTTP or websocket requests. The **methods** of the ***bindings*** are noted **api/verb** where **api** is the **API** name of the binding and **verb** is -the **method**'s name within the **API**. +the **method**'s name within the **API**. This notation comes from HTTP invocations that rely on URL path terminated with **api/verb**. The name of an **API** can be made of any characters except: - - the control characters (\u0000 .. \u001f) - - the characters of the set { ' ', '"', '#', '%', '&', +- the control characters (\u0000 .. \u001f) +- the characters of the set { ' ', '"', '#', '%', '&', '\'', '/', '?', '`', '\x7f' } -The names if the **verbs** can be any character. +The names of the **verbs** can be any character. -The binder mkes no distinctions between upper case and lower case -latin letters. So **API/VERB** matches **Api/Verb** or **api/verb**. +The binder makes no distinctions between upper case and lower case +latin letters. +So **API/VERB** matches **Api/Verb** or **api/verb**. Actually it exists 2 ways of writing ***bindings***. You can either write: - - a binding version 1 (not recommanded); - - a binding version 2 (RECOMMANDED). - -A ***binder*** loads and runs any of these version -in any combination. +- a binding version 1 (not recommended); +- a binding version 2 (RECOMMENDED). +A ***binder*** loads and runs any of these version in any combination. This document explain how to write bindings version 2. + -Sample binding: tuto-1 -====================== +## Sample binding: tuto-1 This is the code of the binding **tuto-1.c**: ```C 1 #define AFB_BINDING_VERSION 2 2 #include - 3 + 3 4 void hello(afb_req req) 5 { 6 AFB_REQ_DEBUG(req, "hello world"); 7 afb_req_success(req, NULL, "hello world"); 8 } - 9 + 9 10 const afb_verb_v2 verbs[] = { 11 { .verb="hello", .callback=hello }, 12 { .verb=NULL } 13 }; - 14 + 14 15 const afb_binding_v2 afbBindingV2 = { 16 .api = "tuto-1", 17 .verbs = verbs @@ -94,13 +90,13 @@ This is the code of the binding **tuto-1.c**: Compiling: ```bash -$ gcc -fPIC -shared tuto-1.c -o tuto-1.so $(pkg-config --cflags-only-I afb-daemon) +gcc -fPIC -shared tuto-1.c -o tuto-1.so $(pkg-config --cflags-only-I afb-daemon) ``` Running: ```bash -$ afb-daemon --binding tuto-1.so --port 3333 --token '' +afb-daemon --binding tuto-1.so --port 3333 --token '' ``` Testing using **curl**: @@ -128,10 +124,9 @@ ON-REPLY 1:tuto-1/hello: OK This shows basic things: - - The include to get for creating a binding - - How to declare the API offered by the binding - - How to handle request made to the binding - +- The include to get for creating a binding +- How to declare the API offered by the binding +- How to handle request made to the binding ### Getting declarations for the binding @@ -142,29 +137,31 @@ The lines 1 and 2 show how to get the include file **afb-binding.h**. 2 #include ``` -You must define the version of ***binding*** that you are using. +You must define the version of ***binding*** that you are using. This is done line 1 where we define that this is the version 2. If you don't define it, a warning message is prompted by the compiler -and the version is switched to version 1. This behaviour is -temporarily and enables to continue to use previously written +and the version is switched to version 1. +This behaviour is temporarily and enables to continue to use previously written ***binding*** without change but it will change in some future when ***bindings*** V1 will become obsoletes. -To include **afb-binding.h** successfuly, the include search path -should be set correctly if needed (not needed only if installed in +To include **afb-binding.h** successfully, the include search path +should be set correctly if needed (not needed only if installed in /usr/include/afb directory that is the default). Setting the include path is easy using **pkg-config**: ```bash -$ pkg-config --cflags-only-I afb-daemon +pkg-config --cflags-only-I afb-daemon ``` -Note for **C++** developers: The ***binder*** currently expose -only **C** language **API**. The file **afb/afb-binding.h** -isn't **C++** ready. You should use the construct **extern "C"** -as below: +Note for **C++** developers: + +- The ***binder*** currently expose only **C** language **API**. + The file **afb/afb-binding.h** isn't **C++** ready. + +You should use the construct **extern "C"** as below: ```C #define AFB_BINDING_VERSION 2 @@ -174,8 +171,8 @@ as below: ``` Future version of the ***binder*** will include a **C++** -interface. Until it is available, please, use the above -construct. +interface. +Until it is available, please, use the above construct. ### Declaring the API of the binding @@ -190,7 +187,7 @@ a structure of type **afb_binding_v2**. 11 { .verb="hello", .callback=hello }, 12 { .verb=NULL } 13 }; - 14 + 14 15 const afb_binding_v2 afbBindingV2 = { 16 .api = "tuto-1", 17 .verbs = verbs @@ -199,8 +196,8 @@ a structure of type **afb_binding_v2**. The structure **afbBindingV2** actually tells that: - - the exported **API** name is **tuto-1** (line 16) - - the array of verbs is the above defined one +- the exported **API** name is **tuto-1** (line 16) +- the array of verbs is the above defined one The exported list of verb is specified by an array of structures, each describing a verb, ended with a verb NULL (line 12). @@ -209,7 +206,7 @@ The only defined verb here (line 11) is named **hello** (field **.verb**) and the function that handle the related request is **hello** (field **.callback**). -Note that you can explicitely mark the fact that these are +Note that you can explicitly mark the fact that these are struct by typing the **struct** as below: ```C @@ -217,7 +214,7 @@ struct by typing the **struct** as below: 11 { .verb="hello", .callback=hello }, 12 { .verb=NULL } 13 }; - 14 + 14 15 const struct afb_binding_v2 afbBindingV2 = { 16 .api = "tuto-1", 17 .verbs = verbs @@ -238,48 +235,50 @@ the AGL stuff is installed. ``` When the ***binder*** receives a request for the verb **hello** of -of the api **tuto-1**, it invoque the callback **hello** of the **binding** +of the api **tuto-1**, it invoke the callback **hello** of the **binding** with the argument **req** that handles the client request. The callback has to treat synchronously or asynchronously the request and should at the end emit a reply for the request. Here, the callback for **tuto-1/hello** replies a successful answer -(ligne 7) to the request **req**. The second parameter (here NULL) -is a json object that is sent to the client with the reply. +(line 7) to the request **req**. +The second parameter (here NULL) is a json object that is sent to the client with the reply. The third parameter is also sent with the reply and is a string called info that can be used as some meta data. -Here again, you can explicitely mark the fact that +Here again, you can explicitly mark the fact that **afb_req** is a structure by declaring **hello** as below: ```C 4 void hello(struct afb_req req) ``` -Sample binding: tuto-2 -====================== + + +## Sample binding: tuto-2 The second tutorial shows many important feature that can -commonly be used when writting a ***binding***: initialisation, -getting arguments, sending replies, pushing events. +commonly be used when writing a ***binding***: + +- initialization, getting arguments, sending replies, pushing events. This is the code of the binding **tuto-2.c**: ```C 1 #include 2 #include - 3 + 3 4 #define AFB_BINDING_VERSION 2 5 #include - 6 + 6 7 afb_event event_login, event_logout; - 8 + 8 9 void login(afb_req req) 10 { 11 json_object *args, *user, *passwd; 12 char *usr; - 13 + 13 14 args = afb_req_json(req); 15 if (!json_object_object_get_ex(args, "user", &user) 16 || !json_object_object_get_ex(args, "password", &passwd)) { @@ -300,12 +299,12 @@ This is the code of the binding **tuto-2.c**: 31 afb_event_push(event_login, json_object_new_string(usr)); 32 } 33 } - 34 + 34 35 void action(afb_req req) 36 { 37 json_object *args, *val; 38 char *usr; - 39 + 39 40 args = afb_req_json(req); 41 usr = afb_req_context_get(req); 42 AFB_REQ_NOTICE(req, "action for user %s: %s", usr, json_object_get_string(args)); @@ -322,11 +321,11 @@ This is the code of the binding **tuto-2.c**: 53 } 54 afb_req_success(req, json_object_get(args), NULL); 55 } - 56 + 56 57 void logout(afb_req req) 58 { 59 char *usr; - 60 + 60 61 usr = afb_req_context_get(req); 62 AFB_REQ_NOTICE(req, "login user %s out", usr); 63 afb_event_push(event_logout, json_object_new_string(usr)); @@ -334,13 +333,13 @@ This is the code of the binding **tuto-2.c**: 65 afb_req_context_clear(req); 66 afb_req_success(req, NULL, NULL); 67 } - 68 + 68 69 int preinit() 70 { 71 AFB_NOTICE("preinit"); 72 return 0; 73 } - 74 + 74 75 int init() 76 { 77 AFB_NOTICE("init"); @@ -351,14 +350,14 @@ This is the code of the binding **tuto-2.c**: 82 AFB_ERROR("Can't create events"); 83 return -1; 84 } - 85 + 85 86 const afb_verb_v2 verbs[] = { 87 { .verb="login", .callback=login }, 88 { .verb="action", .callback=action, .session=AFB_SESSION_LOA_1 }, 89 { .verb="logout", .callback=logout, .session=AFB_SESSION_LOA_1 }, 90 { .verb=NULL } 91 }; - 92 + 92 93 const afb_binding_v2 afbBindingV2 = { 94 .api = "tuto-2", 95 .specification = NULL, @@ -372,13 +371,13 @@ This is the code of the binding **tuto-2.c**: Compiling: ```bash -$ gcc -fPIC -shared tuto-2.c -o tuto-2.so $(pkg-config --cflags --libs afb-daemon) +gcc -fPIC -shared tuto-2.c -o tuto-2.so $(pkg-config --cflags --libs afb-daemon) ``` Running: ```bash -$ afb-daemon --binding tuto-2.so --port 3333 --token '' +afb-daemon --binding tuto-2.so --port 3333 --token '' ``` Testing: @@ -462,4 +461,3 @@ ON-EVENT tuto-2/logout: "jtype":"afb-event" } ``` -