mirror of
https://github.com/foxcpp/maddy.git
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99 lines
2.1 KiB
Go
99 lines
2.1 KiB
Go
/*
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Maddy Mail Server - Composable all-in-one email server.
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Copyright © 2019-2020 Max Mazurov <fox.cpp@disroot.org>, Maddy Mail Server contributors
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package future
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import (
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"context"
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"sync"
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)
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// The Future object implements a container for (value, error) pair that "will
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// be populated later" and allows multiple users to wait for it to be set.
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//
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// It should not be copied after first use.
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type Future struct {
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mu sync.RWMutex
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set bool
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val interface{}
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err error
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notify chan struct{}
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}
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func New() *Future {
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return &Future{notify: make(chan struct{})}
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}
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// Set sets the Future (value, error) pair. All currently blocked and future
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// Get calls will return it.
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func (f *Future) Set(val interface{}, err error) {
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if f == nil {
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panic("nil future used")
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}
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f.mu.Lock()
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defer f.mu.Unlock()
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if f.set {
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panic("Future.Set called multiple times")
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}
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f.set = true
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f.val = val
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f.err = err
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close(f.notify)
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}
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func (f *Future) Get() (interface{}, error) {
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if f == nil {
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panic("nil future used")
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}
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return f.GetContext(context.Background())
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}
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func (f *Future) GetContext(ctx context.Context) (interface{}, error) {
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if f == nil {
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panic("nil future used")
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}
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f.mu.RLock()
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if f.set {
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val := f.val
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err := f.err
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f.mu.RUnlock()
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return val, err
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}
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f.mu.RUnlock()
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select {
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case <-f.notify:
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case <-ctx.Done():
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return nil, ctx.Err()
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}
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f.mu.RLock()
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defer f.mu.RUnlock()
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if !f.set {
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panic("future: Notification received, but value is not set")
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}
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return f.val, f.err
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}
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