实战：Zig 编写高性能 Web 服务（1）

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1.1  认识 std.http

std.http 是 Zig 标准库中用于处理 HTTP 相关操作的类库。以我学习新的编程语言的经历来看，编写web程序是最常见的技术场景，所以熟练掌握 HTTP server/client 服务相关的编程知识是比较重要的。

std.http 主要包含以下API:

• Client: HTTP client implementation.
• Server: HTTP server implementation.
• protocol：headers parse methods.
• Connection: Connection type (keep_alive, close)
• ContentEncoding: Content encoding options (compress, deflate, gzip and zstd)
• Field: Common type for name and value
• Headers: HTTP headers
• Method: HTTP methods such as GET and POST
• Status: HTTP status codes (not_found = 404, teapot = 418, etc.)
• TransferEncoding: Form of encoding used to transfer the body (chunked)
• Version: Currently HTTP/1.0 and HTTP/1.1

1.2 编写一个HTTP client程序

先创建一个开工项目：

$ mkdir -p httpz
$ cd httpz
$ zig init$ ls -ls
total 20
4 -rw-r--r-- 1 xiaods xiaods 3879 Jun  3 11:53 build.zig
4 -rw-r--r-- 1 xiaods xiaods 3080 Jun  3 11:50 build.zig.zon
4 drwxr-xr-x 2 xiaods xiaods 4096 Jun  3 13:33 src
4 drwxr-xr-x 6 xiaods xiaods 4096 Jun  3 11:51 zig-cache
4 drwxr-xr-x 4 xiaods xiaods 4096 Jun  3 11:51 zig-out

编辑 src/main.zig，我们将使用 std.heap.GeneralPurposeAllocator，这是一个安全的分配器，可以防止双重释放（double-free）、使用后释放（use-after-free），并且能够检测内存泄漏。

const std = @import("std");
const print = std.debug.print;
const http = std.http;var gpa = std.heap.GeneralPurposeAllocator(.{}){};defer _ = gpa.deinit();const allocator = gpa.allocator();

下一步，为了发送一个请求，我们需要几样东西：

• client.open 函数
• 一个从URL解析而来的 std.Uri

下面是我们如何将这些参数组合在一起的方法：

    const uri = try std.Uri.parse("http://httpbin.org/headers");const buf = try allocator.alloc(u8, 1024 * 1024 * 4);defer allocator.free(buf);var req = try client.open(.GET, uri, .{.server_header_buffer = buf,});defer req.deinit();

为了真正的发送请求，需要通过send,finish,wait来完成：

 try req.send();try req.finish();try req.wait();

打印返回的服务器headers 信息：

var iter = req.response.iterateHeaders();while (iter.next()) |header| {std.debug.print("Name:{s}, Value:{s}\n", .{ header.name, header.value });}try std.testing.expectEqual(req.response.status, .ok);

打印返回的服务端内容：

    var rdr = req.reader();const body = try rdr.readAllAlloc(allocator, 1024 * 1024 * 4);defer allocator.free(body);print("Body:\n{s}\n", .{body});

把上面的代码所有内容放在一起，并打印出响应内容：

const std = @import("std");
const print = std.debug.print;
const http = std.http;pub fn main() !void {var gpa = std.heap.GeneralPurposeAllocator(.{}){};defer _ = gpa.deinit();const allocator = gpa.allocator();var client = http.Client{ .allocator = allocator };defer client.deinit();const uri = try std.Uri.parse("http://httpbin.org/headers");const buf = try allocator.alloc(u8, 1024 * 1024 * 4);defer allocator.free(buf);var req = try client.open(.GET, uri, .{.server_header_buffer = buf,});defer req.deinit();try req.send();try req.finish();try req.wait();var iter = req.response.iterateHeaders();while (iter.next()) |header| {std.debug.print("Name:{s}, Value:{s}\n", .{ header.name, header.value });}try std.testing.expectEqual(req.response.status, .ok);var rdr = req.reader();const body = try rdr.readAllAlloc(allocator, 1024 * 1024 * 4);defer allocator.free(body);print("Body:\n{s}\n", .{body});
}

跑一下：

 $ zig build run
Name:Date, Value:Mon, 03 Jun 2024 08:24:19 GMT
Name:Content-Type, Value:application/json
Name:Content-Length, Value:202
Name:Connection, Value:keep-alive
Name:Server, Value:gunicorn/19.9.0
Name:Access-Control-Allow-Origin, Value:*
Name:Access-Control-Allow-Credentials, Value:true
Body:
{"headers": {"Accept-Encoding": "gzip, deflate","Host": "httpbin.org","User-Agent": "zig/0.12.0 (std.http)","X-Amzn-Trace-Id": "Root=1-665d7db3-258c846d0fcca0912fadfa8b"}
}

成功了！我们成功地向服务器发送了一个GET请求并打印出了响应。

GET请求的例子我们看到了，那么如何发起POST请求呢？让我们继续拿例子说话。

准备好发送内容：

const uri = try std.Uri.parse("http://httpbin.org/anything");const payload =\\ {\\  "name": "zig-learning",\\  "author": "xiaods"\\ };

发送POST 请求：

var buf: [1024]u8 = undefined;var req = try client.open(.POST, uri, .{ .server_header_buffer = &buf });defer req.deinit();req.transfer_encoding = .{ .content_length = payload.len };try req.send();var wtr = req.writer();try wtr.writeAll(payload);try req.finish();try req.wait();try std.testing.expectEqual(req.response.status, .ok);

打印返回内容：

var rdr = req.reader();const body = try rdr.readAllAlloc(allocator, 1024 * 1024 * 4);defer allocator.free(body);print("Body:\n{s}\n", .{body});

完整的Post代码如下：

const std = @import("std");
const print = std.debug.print;
const http = std.http;pub fn main() !void {var gpa = std.heap.GeneralPurposeAllocator(.{}){};defer _ = gpa.deinit();const allocator = gpa.allocator();var client = http.Client{ .allocator = allocator };defer client.deinit();const uri = try std.Uri.parse("http://httpbin.org/anything");const payload =\\ {\\  "name": "zig-learning",\\  "author": "xiaods"\\ };var buf: [1024]u8 = undefined;var req = try client.open(.POST, uri, .{ .server_header_buffer = &buf });defer req.deinit();req.transfer_encoding = .{ .content_length = payload.len };try req.send();var wtr = req.writer();try wtr.writeAll(payload);try req.finish();try req.wait();try std.testing.expectEqual(req.response.status, .ok);var rdr = req.reader();const body = try rdr.readAllAlloc(allocator, 1024 * 1024 * 4);defer allocator.free(body);print("Body:\n{s}\n", .{body});
}

 运行结果：

$ zig run src/http-post.zig 
Body:
{"args": {}, "data": " {\n  \"name\": \"zig-learning\",\n  \"author\": \"xiaods\"\n }", "files": {}, "form": {}, "headers": {"Accept-Encoding": "gzip, deflate", "Content-Length": "52", "Host": "httpbin.org", "User-Agent": "zig/0.12.0 (std.http)", "X-Amzn-Trace-Id": "Root=1-665d8114-01b0167844d8d101012e6d6a"}, "json": {"author": "xiaods", "name": "zig-learning"}, "method": "POST", "origin": "219.133.170.77", "url": "http://httpbin.org/anything"
}

请消化消化以上代码，别着急，我们后面继续前行，编写web server

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