feat: Waku v2 bridge

Issue #12610

vendor/zombiezen.com/go/sqlite/blocking_step.go

@@ -0,0 +1,102 @@
+// Copyright (c) 2018 David Crawshaw <david@zentus.com>
+// Copyright (c) 2021 Ross Light <ross@zombiezen.com>
+//
+// Permission to use, copy, modify, and distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+// SPDX-License-Identifier: ISC
+
+package sqlite
+
+import (
+	"fmt"
+	"sync"
+	"unsafe"
+
+	"modernc.org/libc"
+	"modernc.org/libc/sys/types"
+	lib "modernc.org/sqlite/lib"
+)
+
+// See https://sqlite.org/unlock_notify.html for detailed explanation.
+
+// unlockNote is a C-allocated struct used as a condition variable.
+type unlockNote struct {
+	mu    sync.Mutex
+	wait  sync.Mutex // held while fired == false
+	fired bool
+}
+
+func allocUnlockNote(tls *libc.TLS) (uintptr, error) {
+	ptr := libc.Xcalloc(tls, 1, types.Size_t(unsafe.Sizeof(unlockNote{})))
+	if ptr == 0 {
+		return 0, fmt.Errorf("out of memory for unlockNote")
+	}
+	un := (*unlockNote)(unsafe.Pointer(ptr))
+	un.wait.Lock()
+	return ptr, nil
+}
+
+func fireUnlockNote(tls *libc.TLS, ptr uintptr) {
+	un := (*unlockNote)(unsafe.Pointer(ptr))
+	un.mu.Lock()
+	if !un.fired {
+		un.fired = true
+		un.wait.Unlock()
+	}
+	un.mu.Unlock()
+}
+
+func unlockNotifyCallback(tls *libc.TLS, apArg uintptr, nArg int32) {
+	for ; nArg > 0; nArg-- {
+		fireUnlockNote(tls, *(*uintptr)(unsafe.Pointer(apArg)))
+		// apArg is a C array of pointers.
+		apArg += unsafe.Sizeof(uintptr(0))
+	}
+}
+
+func waitForUnlockNotify(tls *libc.TLS, db uintptr, unPtr uintptr) ResultCode {
+	un := (*unlockNote)(unsafe.Pointer(unPtr))
+	if un.fired {
+		un.wait.Lock()
+	}
+	un.fired = false
+
+	// The following is a conversion from function value to uintptr. It assumes
+	// the memory representation described in https://golang.org/s/go11func.
+	//
+	// It does this by doing the following in order:
+	// 1) Create a Go struct containing a pointer to a pointer to
+	//    unlockNotifyCallback. It is assumed that the pointer to
+	//    unlockNotifyCallback will be stored in the read-only data section and
+	//    thus will not move.
+	// 2) Convert the pointer to the Go struct to a pointer to uintptr through
+	//    unsafe.Pointer. This is permitted via Rule #1 of unsafe.Pointer.
+	// 3) Dereference the pointer to uintptr to obtain the function value as a
+	//    uintptr. This is safe as long as function values are passed as pointers.
+	cbPtr := *(*uintptr)(unsafe.Pointer(&struct {
+		f func(*libc.TLS, uintptr, int32)
+	}{unlockNotifyCallback}))
+
+	res := ResultCode(lib.Xsqlite3_unlock_notify(tls, db, cbPtr, unPtr))
+
+	if res == ResultOK {
+		un.mu.Lock()
+		fired := un.fired
+		un.mu.Unlock()
+		if !fired {
+			un.wait.Lock()
+			un.wait.Unlock()
+		}
+	}
+	return res
+}