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