73 lines
2.1 KiB
Go
73 lines
2.1 KiB
Go
// Package memorylocker provides an in-memory locking mechanism.
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//
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// When multiple processes are attempting to access an upload, whether it be
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// by reading or writing, a synchronization mechanism is required to prevent
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// data corruption, especially to ensure correct offset values and the proper
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// order of chunks inside a single upload.
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//
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// MemoryLocker persists locks using memory and therefore allowing a simple and
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// cheap mechanism. Locks will only exist as long as this object is kept in
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// reference and will be erased if the program exits.
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package memorylocker
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import (
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"sync"
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"github.com/tus/tusd"
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)
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// MemoryLocker persists locks using memory and therefore allowing a simple and
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// cheap mechanism. Locks will only exist as long as this object is kept in
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// reference and will be erased if the program exits.
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type MemoryLocker struct {
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locks map[string]bool
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mutex *sync.Mutex
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}
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// NewMemoryLocker creates a new in-memory locker. The DataStore parameter
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// is only presented for back-wards compatibility and is ignored. Please
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// use the New() function instead.
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func NewMemoryLocker(_ tusd.DataStore) *MemoryLocker {
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return New()
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}
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// New creates a new in-memory locker.
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func New() *MemoryLocker {
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return &MemoryLocker{
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locks: make(map[string]bool),
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mutex: new(sync.Mutex),
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}
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}
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// UseIn adds this locker to the passed composer.
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func (locker *MemoryLocker) UseIn(composer *tusd.StoreComposer) {
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composer.UseLocker(locker)
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}
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// LockUpload tries to obtain the exclusive lock.
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func (locker *MemoryLocker) LockUpload(id string) error {
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locker.mutex.Lock()
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defer locker.mutex.Unlock()
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// Ensure file is not locked
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if _, ok := locker.locks[id]; ok {
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return tusd.ErrFileLocked
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}
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locker.locks[id] = true
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return nil
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}
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// UnlockUpload releases a lock. If no such lock exists, no error will be returned.
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func (locker *MemoryLocker) UnlockUpload(id string) error {
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locker.mutex.Lock()
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defer locker.mutex.Unlock()
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// Deleting a non-existing key does not end in unexpected errors or panic
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// since this operation results in a no-op
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delete(locker.locks, id)
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return nil
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}
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