-
-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.
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.
+<!-- pagebreak -->
-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 <afb/afb-binding.h>
- 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
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**:
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
2 #include <afb/afb-binding.h>
```
-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
```
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
11 { .verb="hello", .callback=hello },
12 { .verb=NULL }
13 };
- 14
+ 14
15 const afb_binding_v2 afbBindingV2 = {
16 .api = "tuto-1",
17 .verbs = verbs
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).
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
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
```
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
-======================
+<!-- pagebreak -->
+
+## 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 <string.h>
2 #include <json-c/json.h>
- 3
+ 3
4 #define AFB_BINDING_VERSION 2
5 #include <afb/afb-binding.h>
- 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)) {
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));
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));
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");
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,
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:
"jtype":"afb-event"
}
```
-
Code Review / src / app-framework-binder.git / blobdiff