Create sqlite3_opt_unlock_notify.go

src/github.com/mattn/go-sqlite3/sqlite3_opt_unlock_notify.go

@@ -0,0 +1,93 @@
+// Copyright (C) 2018 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
+}