mirror of
https://github.com/ceph/go-ceph
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b0ffc1afe8
The former code assumed a LIFO usage, and otherwise always produced collisions. This change uses unique IDs instead, that as a side-effect might make debugging easier. Signed-off-by: Sven Anderson <sven@redhat.com>
66 lines
1.7 KiB
Go
66 lines
1.7 KiB
Go
package callbacks
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import (
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"sync"
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)
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// The logic of this file is largely adapted from:
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// https://github.com/golang/go/wiki/cgo#function-variables
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//
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// Also helpful:
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// https://eli.thegreenplace.net/2019/passing-callbacks-and-pointers-to-cgo/
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// Callbacks provides a tracker for data that is to be passed between Go
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// and C callback functions. The Go callback/object may not be passed
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// by a pointer to C code and so instead integer IDs into an internal
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// map are used.
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// Typically the item being added will either be a callback function or
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// a data structure containing a callback function. It is up to the caller
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// to control and validate what "callbacks" get used.
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type Callbacks struct {
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mutex sync.RWMutex
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cmap map[uintptr]interface{}
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lastID uintptr
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}
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// New returns a new callbacks tracker.
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func New() *Callbacks {
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return &Callbacks{cmap: make(map[uintptr]interface{})}
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}
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// getID returns a unique ID.
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// NOTE: cb.mutex must be locked already!
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func (cb *Callbacks) getID() uintptr {
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for exists := true; exists; {
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cb.lastID++
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// Sanity check for the very unlikely case of an integer overflow in long
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// running processes.
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_, exists = cb.cmap[cb.lastID]
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}
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return cb.lastID
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}
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// Add a callback/object to the tracker and return a new ID
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// for the object.
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func (cb *Callbacks) Add(v interface{}) uintptr {
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cb.mutex.Lock()
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defer cb.mutex.Unlock()
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id := cb.getID()
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cb.cmap[id] = v
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return id
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}
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// Remove a callback/object given it's ID.
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func (cb *Callbacks) Remove(id uintptr) {
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cb.mutex.Lock()
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defer cb.mutex.Unlock()
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delete(cb.cmap, id)
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}
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// Lookup returns a mapped callback/object given an ID.
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func (cb *Callbacks) Lookup(id uintptr) interface{} {
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cb.mutex.RLock()
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defer cb.mutex.RUnlock()
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return cb.cmap[id]
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}
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