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Boost the power of C with these open source libraries 使用开源库提升 C 语言编程能力
开源库 GObject 和 libsoup 已经做了很多工作，因此你可以专注于使用 C 语言开发神奇的应用。 GObject and libsoup do a lot of work for you, so you can turn your attention to inventing amazing applications in C.
（Image by: Image from Unsplash.com, Creative Commons Zero）
GLib Object System (GObject) 为 C 语言提供了灵活可扩展的面向对象框架。在这篇文章中，我将使用该库的 2.4 版本进行演示。 The GLib Object System (GObject) is a library providing a flexible and extensible object-oriented framework for C. In this article, I demonstrate using the 2.4 version of the library.
GObject 库继承了 ANSI C 标准，拥有一些常见的数据类型，例如： The GObject libraries extend the ANSI C standard, with typedefs for common types such as:
- gchar: 字符型
- guchar: 无符号字符型
- gunichar: 宽为 32 比特的 Unicode 字符型
- gboolean: 布尔型
- gint8, gint16, gint32, gint64: 8, 16, 32 和 64 比特有符号整数
- guint8, guint16, guint32, guint64: 无符号 8, 16, 32 和 64 比特整数
- gfloat: IEEE 754 标准单精度浮点数
- gdouble: IEEE 754 标准 双精度浮点数
- gpointer: 泛指针
函数指针
GObject 库还引入了类和接口的类型和对象体系。这是可能的，因为 ANSI C 语言理解函数指针。
你可以这样做来声明函数指针：
void (*my_callback)(gpointer data);
首先，你需要给变量 my_callback 赋值：
void my_callback_func(gpointer data)
{
//do something
}
my_callback = my_callback_func;
函数指针 my_callback 可以这样来调用：
gpointer data;
data = g_malloc(512 * sizeof(gint16));
my_callback(data);
对象类
GObject 基类由 2 个结构（GObject 和 GObjectClass）组成，你可以继承它们以实现你自己的对象。
你需要在结构体中先嵌入 GObject 和 GObjectClass ：
struct _MyObject
{
GObject gobject;
//your fields
};
struct _MyObjectClass
{
GObjectClass gobject;
//your class methods
};
GType my_object_get_type(void);
对象的实现包含了公有成员（译注：理解为 public 修饰符）。GObject 也提供了私有成员的方法。这实际上是 C 源文件中的一个结构，而不是头文件。该类通常只包含函数指针。
一个接口不能派生自另一个接口，比如：
struct _MyInterface
{
GInterface ginterface;
//your interface methods
};
Properties are accessed by g_object_get() and g_object_set() function calls. To get a property, you must provide the return location of the specific type. It’s recommended that you initialize the return location first:
gchar *str
str = NULL;
g_object_get(gobject,
"my-name", &str,
NULL);
Or you might want to set the property:
g_object_set(gobject,
"my-name", "Anderson",
NULL);
libsoup HTTP 库
The libsoup project provides an HTTP client and server library for GNOME. It uses GObjects and the glib main loop to integrate with GNOME applications, and also has a synchronous API for use in command-line tools. First, create a libsoup session with an authentication callback specified. You can also make use of cookies.
SoupSession *soup_session;
SoupCookieJar *jar;
soup_session = soup_session_new_with_options(SOUP_SESSION_ADD_FEATURE_BY_TYPE, SOUP_TYPE_AUTH_BASIC,
SOUP_SESSION_ADD_FEATURE_BY_TYPE, SOUP_TYPE_AUTH_DIGEST,
NULL);
jar = soup_cookie_jar_text_new("cookies.txt",
FALSE);
soup_session_add_feature(soup_session, jar);
g_signal_connect(soup_session, "authenticate",
G_CALLBACK(my_authenticate_callback), NULL);
Then you can create a HTTP GET request like the following:
SoupMessage *msg;
SoupMessageHeaders *response_headers;
SoupMessageBody *response_body;
guint status;
GError *error;
msg = soup_form_request_new("GET",
"http://127.0.0.1:8080/my-xmlrpc",
NULL);
status = soup_session_send_message(soup_session,
msg);
response_headers = NULL;
response_body = NULL;
g_object_get(msg,
"response-headers", &response_headers,
"response-body", &response_body,
NULL);
g_message("status %d", status);
cookie = NULL;
soup_message_headers_iter_init(&iter,
response_headers);
while(soup_message_headers_iter_next(&iter, &name, &value)){
g_message("%s: %s", name, value);
}
g_message("%s", response_body->data);
if(status == 200){
cookie = soup_cookies_from_response(msg);
while(cookie != NULL){
char *cookie_name;
cookie_name = soup_cookie_get_name(cookie->data);
//parse cookies
cookie = cookie->next;
}
}
The authentication callback is called as the web server asks for authentication.
Here’s a function signature:
#define MY_AUTHENTICATE_LOGIN "my-username"
#define MY_AUTHENTICATE_PASSWORD "my-password"
void my_authenticate_callback(SoupSession *session,
SoupMessage *msg,
SoupAuth *auth,
gboolean retrying,
gpointer user_data)
{
g_message("authenticate: ****");
soup_auth_authenticate(auth,
MY_AUTHENTICATE_LOGIN,
MY_AUTHENTICATE_PASSWORD);
}
A libsoup server
For basic HTTP authentication to work, you must specify a callback and server context path. Then you add a handler with another callback.
This example listens to any IPv4 address on localhost port 8080:
SoupServer *soup_server;
SoupAuthDomain *auth_domain;
GSocket *ip4_socket;
GSocketAddress *ip4_address;
MyObject *my_object;
GError *error;
soup_server = soup_server_new(NULL);
auth_domain = soup_auth_domain_basic_new(SOUP_AUTH_DOMAIN_REALM, "my-realm",
SOUP_AUTH_DOMAIN_BASIC_AUTH_CALLBACK, my_xmlrpc_server_auth_callback,
SOUP_AUTH_DOMAIN_BASIC_AUTH_DATA, my_object,
SOUP_AUTH_DOMAIN_ADD_PATH, "my-xmlrpc",
NULL);
soup_server_add_auth_domain(soup_server, auth_domain);
soup_server_add_handler(soup_server,
"my-xmlrpc",
my_xmlrpc_server_callback,
my_object,
NULL);
ip4_socket = g_socket_new(G_SOCKET_FAMILY_IPV4,
G_SOCKET_TYPE_STREAM,
G_SOCKET_PROTOCOL_TCP,
&error);
ip4_address = g_inet_socket_address_new(g_inet_address_new_any(G_SOCKET_FAMILY_IPV4),
8080);
error = NULL;
g_socket_bind(ip4_socket,
ip4_address,
TRUE,
&error);
error = NULL;
g_socket_listen(ip4_socket, &error);
error = NULL;
soup_server_listen_socket(soup_server,
ip4_socket, 0, &error);
示例代码中，有两个回调函数。一个处理身份认证，另一个处理对它的请求。
假设你想要网页服务器运行一个用户名为 my-username 和口令为 my-password 的用户登录，并且用一个随机独一用户 ID 字符串设置会话 cookie 。
gboolean my_xmlrpc_server_auth_callback(SoupAuthDomain *domain,
SoupMessage *msg,
const char *username,
const char *password,
MyObject *my_object)
{
if(username == NULL || password == NULL){
return(FALSE);
}
if(!strcmp(username, "my-username") &&
!strcmp(password, "my-password")){
SoupCookie *session_cookie;
GSList *cookie;
gchar *security_token;
cookie = NULL;
security_token = g_uuid_string_random();
session_cookie = soup_cookie_new("my-srv-security-token",
security_token,
"localhost",
"my-xmlrpc",
-1);
cookie = g_slist_prepend(cookie,
session_cookie);
soup_cookies_to_request(cookie,
msg);
return(TRUE);
}
return(FALSE);
}
对内容路径 my-xmlrpc 的处理函数：
void my_xmlrpc_server_callback(SoupServer *soup_server,
SoupMessage *msg,
const char *path,
GHashTable *query,
SoupClientContext *client,
MyObject *my_object)
{
GSList *cookie;
cookie = soup_cookies_from_request(msg);
//check cookies
}
更加强大的 C 语言
I hope my examples show how the GObject and libsoup projects give C a very real boost. Libraries like these extend C in a literal sense, and by doing so they make C more approachable. They do a lot of work for you, so you can turn your attention to inventing amazing applications in the simple, direct, and timeless C language.
via: https://opensource.com/article/22/5/libsoup-gobject-c
作者：Joël Krähemann 选题：lkxed 译者：Donkey-Hao 校对：校对者ID