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// Copyright (C) 2019 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
//
// Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file.
// +build cgo
// +build sqlite_unlock_notify
package sqlite3
/*
#cgo CFLAGS: -DSQLITE_ENABLE_UNLOCK_NOTIFY
#include <stdlib.h>
#include "sqlite3-binding.h"
extern void unlock_notify_callback(void *arg, int argc);
*/
import "C"
import (
"fmt"
"math"
"sync"
"unsafe"
)
type unlock_notify_table struct {
sync.Mutex
seqnum uint
table map[uint]chan struct{}
}
var unt unlock_notify_table = unlock_notify_table{table: make(map[uint]chan struct{})}
func (t *unlock_notify_table) add(c chan struct{}) uint {
t.Lock()
defer t.Unlock()
h := t.seqnum
t.table[h] = c
t.seqnum++
return h
}
func (t *unlock_notify_table) remove(h uint) {
t.Lock()
defer t.Unlock()
delete(t.table, h)
}
func (t *unlock_notify_table) get(h uint) chan struct{} {
t.Lock()
defer t.Unlock()
c, ok := t.table[h]
if !ok {
panic(fmt.Sprintf("Non-existent key for unlcok-notify channel: %d", h))
}
return c
}
//export unlock_notify_callback
func unlock_notify_callback(argv unsafe.Pointer, argc C.int) {
for i := 0; i < int(argc); i++ {
parg := ((*(*[(math.MaxInt32 - 1) / unsafe.Sizeof((*C.uint)(nil))]*[1]uint)(argv))[i])
arg := *parg
h := arg[0]
c := unt.get(h)
c <- struct{}{}
}
}
//export unlock_notify_wait
func unlock_notify_wait(db *C.sqlite3) C.int {
// It has to be a bufferred channel to not block in sqlite_unlock_notify
// as sqlite_unlock_notify could invoke the callback before it returns.
c := make(chan struct{}, 1)
defer close(c)
h := unt.add(c)
defer unt.remove(h)
pargv := C.malloc(C.sizeof_uint)
defer C.free(pargv)
argv := (*[1]uint)(pargv)
argv[0] = h
if rv := C.sqlite3_unlock_notify(db, (*[0]byte)(C.unlock_notify_callback), unsafe.Pointer(pargv)); rv != C.SQLITE_OK {
return rv
}
<-c
return C.SQLITE_OK
}
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