FIDL 範例：計算機

這個計算機範例說明如何建構具備最基本功能的 FIDL 通訊協定。您將在此範例中進行建構，修改可能會傳回錯誤的方法、使用其他方法組合 FIDL 通訊協定，以及顯示其他基本元素的用法。

開始使用

在這個範例中，您將建立基本計算機伺服器和用戶端，說明先定義，然後提供及使用 FIDL 通訊協定所需的基本設定。

首先，您將定義介面定義和測試裝置。介面定義 (.fidl 檔案本身) 是任何新 FIDL 通訊協定的起點。此外，計算機還包含必要的 CML 和領域定義，可用於建立用戶端-伺服器模式，並用作任意實作項目的專案架構。

請參閱以下 FIDL 程式碼：

FIDL

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// The namespace for this FIDL protocol. This namespace is how both consumers (clients) and providers (servers) reference this protocol.
library examples.calculator.baseline;

// @discoverable indicates 'Calculator' is a protocol that will be served under the examples.calculator.baseline libarary namespace. https://fuchsia.dev/fuchsia-src/reference/fidl/language/attributes#discoverable . If @discoverable is missing, it will lead to a compile time error when trying to import the library.
@discoverable
// A limited-functionality calculator 'protocol' that adds and subtracts integers.
open protocol Calculator {
    // Takes as input a struct with two integers, and returns their sum: (a+b)=sum.  This method is infallible (no errors can be generated) as two int32's cannot overflow a result type of int64.
    flexible Add(struct {
        a int32;
        b int32;
    }) -> (struct {
        sum int64;
    });
    // Takes as input a struct with two integers, and returns their difference: (a-b)=difference.  This method is infallible (no errors can be generated) as two int32's cannot overflow a result type of int64.
    flexible Subtract(struct {
        a int32;
        b int32;
    }) -> (struct {
        difference int64;
    });
};

CML

用戶端

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
{
    include: [ "syslog/client.shard.cml" ],
    program: {
        runner: "elf",
        binary: "bin/client_bin",
    },
    use: [
        { protocol: "examples.calculator.baseline.Calculator" },
    ],
    config: {},
}

伺服器

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
{
    include: [ "syslog/client.shard.cml" ],
    program: {
        runner: "elf",
        binary: "bin/server_bin",
    },
    capabilities: [
        { protocol: "examples.calculator.baseline.Calculator" },
    ],
    expose: [
        {
            protocol: "examples.calculator.baseline.Calculator",
            from: "self",
        },
    ],
}

運作範圍

// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
{
    children: [
        {
            name: "client",
            url: "#meta/client.cm",
        },
        {
            name: "server",
            url: "#meta/server.cm",
        },
    ],
    offer: [
        // Route the protocol under test from the server to the client.
        {
            protocol: "examples.calculator.baseline.Calculator",
            from: "#server",
            to: "#client",
        },

        // Route diagnostics support to both children.
        {
            dictionary: "diagnostics",
            from: "parent",
            to: [
                "#client",
                "#server",
            ],
        },
    ],
}

接著，您可以使用任何支援的語言編寫用戶端和伺服器實作項目：

荒漠油廠

用戶端

// TODO(https://fxbug.dev/42063075): Rust implementation.

伺服器

// TODO(https://fxbug.dev/42063075): Rust implementation.

C++ (自然)

用戶端

// TODO(https://fxbug.dev/42063075): C++ (Natural) implementation.

伺服器

// TODO(https://fxbug.dev/42063075): C++ (Natural) implementation.

C++ (Wire)

用戶端

// TODO(https://fxbug.dev/42063075): C++ (Wire) implementation.

伺服器

// TODO(https://fxbug.dev/42063075): C++ (Wire) implementation.

HLCPP

用戶端

// TODO(https://fxbug.dev/42063075): HLCPP implementation.

伺服器

// TODO(https://fxbug.dev/42063075): HLCPP implementation.

對於平台開發人員等特定開發人員而言，從頭開始建立 FIDL 通訊協定 (如本範例所示) 可能更常見。不過，其他類型的開發人員也能從學習如何建構 FIDL 通訊協定中受益，即使他們通常不會這麼做也一樣。這有助您瞭解 FIDL 的所有內容如何搭配運作，包括語法、文法、語言功能、如何提供及使用特定 FIDL 通訊協定，以及建構系統的運作方式。在後續步驟中，我們會根據這個基準提供範例，說明如何擴充現有的 FIDL 通訊協定，這應該是相當常見的做法。

改善設計

以下各節將探討可用於原始設計的疊代方法。每個案例都會以獨立的方式呈現，而非依序建立，以便修改或改善上述基本案例。