sqlite3_opt_unlock_notify.go raw

   1  // Copyright (C) 2019 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
   2  //
   3  // Use of this source code is governed by an MIT-style
   4  // license that can be found in the LICENSE file.
   5  
   6  //go:build cgo && sqlite_unlock_notify
   7  // +build cgo,sqlite_unlock_notify
   8  
   9  package sqlite3
  10  
  11  /*
  12  #cgo CFLAGS: -DSQLITE_ENABLE_UNLOCK_NOTIFY
  13  
  14  #include <stdlib.h>
  15  #ifndef USE_LIBSQLITE3
  16  #include "sqlite3-binding.h"
  17  #else
  18  #include <sqlite3.h>
  19  #endif
  20  
  21  extern void unlock_notify_callback(void *arg, int argc);
  22  */
  23  import "C"
  24  import (
  25  	"fmt"
  26  	"math"
  27  	"sync"
  28  	"unsafe"
  29  )
  30  
  31  type unlock_notify_table struct {
  32  	sync.Mutex
  33  	seqnum uint
  34  	table  map[uint]chan struct{}
  35  }
  36  
  37  var unt unlock_notify_table = unlock_notify_table{table: make(map[uint]chan struct{})}
  38  
  39  func (t *unlock_notify_table) add(c chan struct{}) uint {
  40  	t.Lock()
  41  	defer t.Unlock()
  42  	h := t.seqnum
  43  	t.table[h] = c
  44  	t.seqnum++
  45  	return h
  46  }
  47  
  48  func (t *unlock_notify_table) remove(h uint) {
  49  	t.Lock()
  50  	defer t.Unlock()
  51  	delete(t.table, h)
  52  }
  53  
  54  func (t *unlock_notify_table) get(h uint) chan struct{} {
  55  	t.Lock()
  56  	defer t.Unlock()
  57  	c, ok := t.table[h]
  58  	if !ok {
  59  		panic(fmt.Sprintf("Non-existent key for unlcok-notify channel: %d", h))
  60  	}
  61  	return c
  62  }
  63  
  64  //export unlock_notify_callback
  65  func unlock_notify_callback(argv unsafe.Pointer, argc C.int) {
  66  	for i := 0; i < int(argc); i++ {
  67  		parg := ((*(*[(math.MaxInt32 - 1) / unsafe.Sizeof((*C.uint)(nil))]*[1]uint)(argv))[i])
  68  		arg := *parg
  69  		h := arg[0]
  70  		c := unt.get(h)
  71  		c <- struct{}{}
  72  	}
  73  }
  74  
  75  //export unlock_notify_wait
  76  func unlock_notify_wait(db *C.sqlite3) C.int {
  77  	// It has to be a bufferred channel to not block in sqlite_unlock_notify
  78  	// as sqlite_unlock_notify could invoke the callback before it returns.
  79  	c := make(chan struct{}, 1)
  80  	defer close(c)
  81  
  82  	h := unt.add(c)
  83  	defer unt.remove(h)
  84  
  85  	pargv := C.malloc(C.sizeof_uint)
  86  	defer C.free(pargv)
  87  
  88  	argv := (*[1]uint)(pargv)
  89  	argv[0] = h
  90  	if rv := C.sqlite3_unlock_notify(db, (*[0]byte)(C.unlock_notify_callback), unsafe.Pointer(pargv)); rv != C.SQLITE_OK {
  91  		return rv
  92  	}
  93  
  94  	<-c
  95  
  96  	return C.SQLITE_OK
  97  }
  98