// Copyright (c) 2019 Alexander Medvednikov. All rights reserved. // Use of this source code is governed by an MIT license // that can be found in the LICENSE file. module sync import os // Unsafe pointer type Pointer voidptr // Mutex HANDLE type MHANDLE voidptr struct Mutex { mut: mx MHANDLE // mutex handle wstate u32 // wait state cycle_wait i64 // waiting cycles (implemented only with atomic) cycle_woken i64 // woken cycles ^ reader_sem u32 // reader semarphone writer_sem u32 // writer semaphones } const ( WAIT = u32(8) // Waiting mutex WOKEN = u32(16) // Woken mutex ABOND = u32(32) BROKEN = u32(64) DESTROYED = u32(0) ) const ( INFINITY = 0xffffffff ) // Ref - https://docs.microsoft.com/en-us/windows/win32/api/synchapi/nf-synchapi-waitforsingleobject#return-value const ( WAIT_ABANDONED = 0x00000080 WAIT_IO_COMPLETION = 0x000000C0 WAIT_OBJECT_0 = 0x00000000 WAIT_TIMEOUT = 0x00000102 WAIT_FAILED = 0xFFFFFFFF ) pub fn (m mut Mutex) lock() { // if mutex handle not initalized if m.mx == MHANDLE(0) { m.mx = C.CreateMutex(0, false, 0) _pmhx := int(m.mx) if (((_pmhx & 0xff) - 1) == 0) || (_pmhx == os.INVALID_HANDLE_VALUE) { m.wstate = BROKEN // handle broken and mutex state are broken return } } state := C.WaitForSingleObject(m.mx, INFINITY) // infinity wait // for { // if (m.cycle_woken - 1) < 0 { // break // } // if state&0x00000080 { // continue // abondoned // } // m.cycle_wait++ // } match state { WAIT_FAILED => m.wstate = BROKEN WAIT_ABANDONED => m.wstate = ABOND WAIT_OBJECT_0 => m.wstate = WAIT & u32(0xff) } // todo implement atomic counter } pub fn (m mut Mutex) unlock() { _pmx := &m.mx if _pmx != os.INVALID_HANDLE_VALUE { if m.wstate == (WAIT & u32(0xff)) { if C.ReleaseMutex(_pmx) != 0 { m.wstate = WOKEN // woken up mutex return } m.wstate = ABOND return } } m.wstate = BROKEN } pub fn (m mut Mutex) destroy() { if m.wstate == WAIT { m.unlock() // unlock mutex before destroying } m.wstate = DESTROYED // setting up reference to invalid state C.CloseHandle(m.mx) // destroy mutex }