sdk/fidl/fuchsia.component.resolution/component.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.
library fuchsia.component.resolution;

using fuchsia.mem;
using fuchsia.version;

/// A component is a unit of executable software.
///
/// This object provides the component's declaration, access to its package's
/// content, and relevant metadata as resolved `fuchsia.component.resolution.Resolver`.
type Component = resource table {
    /// The resolved URL of the component.
    /// This is the canonical URL obtained by the component resolver after
    /// following redirects and resolving relative paths.
    1: url string:MAX_COMPONENT_URL_LENGTH;

    /// Binary representation of the component's declaration (`fuchsia.component.decl.Component`).
    /// This information is typically obtained from the component's manifest
    /// or generated by the component resolver.
    2: decl fuchsia.mem.Data;

    /// The package that contains the component.
    /// By convention, the component's package is mapped to "/pkg" in its
    /// namespace at runtime.
    ///
    /// This is null if the component is not represented as a package.
    /// In that case, it is the runner's responsibility to load the component's
    /// resource from the `resolved_url`.  This mechanism is used for web
    /// applications.
    ///
    /// Most runners, including but not limited to the builtin ELF runner,
    /// require the package's directory connection to have OPEN_RIGHT_EXECUTABLE
    /// rights in order to run the resolved component.
    3: package Package;

    /// Binary representation of the component's configuration values
    /// (`fuchsia.component.config.ValuesData`).
    4: config_values fuchsia.mem.Data;

    /// The context used to resolve `component_url`s relative to this
    /// component. Pass this value to `Resolver::ResolveWithContext()` when
    /// resolving a component URL that _may_ be relative to this `Component`.
    ///
    /// The `resolution_context` is an opaque value (from the perspective of
    /// component resolution) that is provided by a component `Resolver` to save
    /// with a parent `Component`.
    ///
    /// `Resolver`s that can resolve relative path component URLs, via
    /// `ResolveWithContext`, should return a `resolution_context` from both
    /// `Resolve` and `ResolveWithContext`. Relative path component URLs can
    /// only be resolved via `ResolveWithContext`, which requires a valid
    /// resolution `Context`.
    5: resolution_context Context;

    /// The target ABI revision of the resolved component.
    @available(added=10)
    6: abi_revision fuchsia.version.AbiRevision;
};

// TODO(https://fxbug.dev/42050722): Change this length to something smaller once
// fuchsia.pkg implements subpackages, assuming fuchsia.pkg implements the
// package context value as a much smaller lookup key (such as a package hash to
// the package containing the subpackage map).

// Note the context length, in bytes, must be at least the size of
// fuchsia.pkg.MAX_RESOLUTION_CONTEXT_SIZE, plus the size required to
// accommodate additional component context information, if any.

/// The maximum number of bytes for a `Context`.
@available(added=9)
const MAX_RESOLUTION_CONTEXT_SIZE uint32 = 8192;
@available(removed=9)
const MAX_RESOLUTION_CONTEXT_LENGTH uint32 = 8192;

/// A component resolution context, used when resolving component URLs relative
/// to another component. The context is stored in a byte array that persists a
/// value used by the target `Resolver` to locate and resolve a component by
/// relative path (for example, by a subpackage name).
@available(added=9)
type Context = struct {
    bytes vector<uint8>:MAX_RESOLUTION_CONTEXT_SIZE;
};
@available(replaced=9)
alias Context = vector<uint8>:MAX_RESOLUTION_CONTEXT_LENGTH;