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97 lines
3.2 KiB
97 lines
3.2 KiB
/* Distributed under the OSI-approved BSD 3-Clause License. See accompanying
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file Copyright.txt or https://cmake.org/licensing for details. */
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#pragma once
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#include "cmConfigure.h" // IWYU pragma: keep
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#include <functional>
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#include <memory>
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#include <cm/optional>
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#include <cm3p/uv.h>
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/** \class cmUVJobServerClient
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* \brief Job server client that can integrate with a libuv event loop.
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*
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* Use the \a Connect method to connect to an ambient job server as
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* described by the MAKEFLAGS environment variable, if any. Request
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* a token using the \a RequestToken method. The \a onToken callback
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* will be invoked asynchronously when the token is received. Act
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* on the token, and then use \a ReleaseToken to release it.
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*
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* The job server protocol states that a client process implicitly
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* has one free token available, corresponding to the token its
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* parent used to start it. \a cmUVJobServerClient will use the
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* implicit token whenever it is available instead of requesting
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* an explicit token from the job server. However, clients of
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* this class must still request and receive the token before
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* acting on it, and cannot assume that it is always held.
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*
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* If the job server connection breaks, \a onDisconnect will be
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* called with the libuv error. No further tokens can be received
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* from the job server, but progress can still be made serially
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* using the implicit token.
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*/
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class cmUVJobServerClient
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{
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public:
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class Impl;
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private:
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std::unique_ptr<Impl> Impl_;
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cmUVJobServerClient(std::unique_ptr<Impl> impl);
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public:
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/**
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* Disconnect from the job server.
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*/
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~cmUVJobServerClient();
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cmUVJobServerClient(cmUVJobServerClient&&) noexcept;
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cmUVJobServerClient(cmUVJobServerClient const&) = delete;
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cmUVJobServerClient& operator=(cmUVJobServerClient&&) noexcept;
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cmUVJobServerClient& operator=(cmUVJobServerClient const&) = delete;
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/**
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* Request a token from the job server.
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* When the token is held, the \a onToken callback will be invoked.
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*/
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void RequestToken();
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/**
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* Release a token to the job server.
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* This may be called only after a corresponding \a onToken callback.
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*/
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void ReleaseToken();
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/**
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* Get the number of implicit and explicit tokens currently held.
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* This is the number of times \a onToken has been called but not
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* yet followed by a call to \a ReleaseToken.
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* This is meant for testing and debugging.
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*/
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int GetHeldTokens() const;
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/**
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* Get the number of explicit tokens currently requested from the
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* job server but not yet received. If the implicit token becomes
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* available, it is used in place of a requested token, and this
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* is decremented without receiving an explicit token.
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* This is meant for testing and debugging.
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*/
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int GetNeedTokens() const;
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/**
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* Connect to an ambient job server, if any.
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* \param loop The libuv event loop on which to schedule events.
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* \param onToken Function to call when a new token is held.
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* \param onDisconnect Function to call on disconnect, with libuv error.
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* \returns Connected instance, or cm::nullopt.
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*/
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static cm::optional<cmUVJobServerClient> Connect(
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uv_loop_t& loop, std::function<void()> onToken,
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std::function<void(int)> onDisconnect);
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};
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