runtime: Select/TrySelect

README.md

@@ -59,6 +59,7 @@ You can import a Python library in LLGo!
 
 And you can import any Python library into `llgo` through a program called `llpyg` (see [Development tools](#development-tools)). The following libraries have been included in `llgo`:
 
+* [py](https://pkg.go.dev/github.com/goplus/llgo/py) (abi)
 * [py/std](https://pkg.go.dev/github.com/goplus/llgo/py/std) (builtins)
 * [py/sys](https://pkg.go.dev/github.com/goplus/llgo/py/sys)
 * [py/os](https://pkg.go.dev/github.com/goplus/llgo/py/os)

_demo/cchan/cchan.go

@@ -36,6 +36,7 @@ func main() {
 	runtime.ChanClose(c)
 
 	v = 10
+
 	if runtime.ChanTrySend(c, unsafe.Pointer(&v), eltSize) {
 		println("error: chan send to closed chan")
 	}

_demo/cchansel/cchansel.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/internal/runtime"
+)
+
+const (
+	eltSize = int(unsafe.Sizeof(0))
+)
+
+func fibonacci(c, quit *runtime.Chan) {
+	x, y := 0, 1
+	for {
+		isel, _ := runtime.Select(
+			runtime.ChanOp{C: c, Send: true, Val: unsafe.Pointer(&x), Size: int32(eltSize)},
+			runtime.ChanOp{C: quit},
+		)
+		if isel == 0 {
+			x, y = y, x+y
+		} else {
+			println("quit")
+			return
+		}
+	}
+}
+
+func main() {
+	c := runtime.NewChan(eltSize, 0)
+	quit := runtime.NewChan(eltSize, 0)
+	go func() {
+		for i := 0; i < 10; i++ {
+			val := 0
+			runtime.ChanRecv(c, unsafe.Pointer(&val), eltSize)
+			println(val)
+		}
+		runtime.ChanClose(quit)
+	}()
+	fibonacci(c, quit)
+}

_demo/chansel/chansel.go

@@ -0,0 +1,26 @@
+package main
+
+func fibonacci(c, quit chan int) {
+	x, y := 0, 1
+	for {
+		select {
+		case c <- x:
+			x, y = y, x+y
+		case <-quit:
+			println("quit")
+			return
+		}
+	}
+}
+
+func main() {
+	c := make(chan int)
+	quit := make(chan int)
+	go func() {
+		for i := 0; i < 10; i++ {
+			println(<-c)
+		}
+		close(quit)
+	}()
+	fibonacci(c, quit)
+}

c/c.go

@@ -68,6 +68,10 @@ func Alloca(size uintptr) Pointer
 //go:linkname AllocaCStr llgo.allocaCStr
 func AllocaCStr(s string) *Char
 
+// TODO(xsw):
+// llgo:link AllocaNew llgo.allocaNew
+func AllocaNew[T any]() *T { return nil }
+
 //go:linkname Malloc C.malloc
 func Malloc(size uintptr) Pointer
 

c/pthread/sync/_sema.go

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package sync
+
+// #include <semaphore.h>
+import "C"
+
+import (
+	_ "unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+// Sem represents a semaphore.
+type Sem C.sem_t
+
+// initializes the unnamed semaphore at the address
+// pointed to by sem.  The value argument specifies the initial
+// value for the semaphore.
+//
+// The pshared argument indicates whether this semaphore is to be
+// shared between the threads of a process, or between processes.
+//
+// If pshared has the value 0, then the semaphore is shared between
+// the threads of a process, and should be located at some address
+// that is visible to all threads (e.g., a global variable, or a
+// variable allocated dynamically on the heap).
+//
+// If pshared is nonzero, then the semaphore is shared between
+// processes, and should be located in a region of shared memory
+// (see shm_open(3), mmap(2), and shmget(2)).  (Since a child
+// created by fork(2) inherits its parent's memory mappings, it can
+// also access the semaphore.)  Any process that can access the
+// shared memory region can operate on the semaphore using
+// sem_post(3), sem_wait(3), and so on.
+//
+// Initializing a semaphore that has already been initialized
+// results in undefined behavior.
+//
+// llgo:link (*Sem).Init C.sem_init
+func (*Sem) Init(pshared c.Int, value c.Uint) c.Int { return 0 }
+
+// llgo:link (*Sem).Destroy C.sem_destroy
+func (*Sem) Destroy() c.Int { return 0 }
+
+// llgo:link (*Sem).Post C.sem_post
+func (*Sem) Post() c.Int { return 0 }
+
+// llgo:link (*Sem).Wait C.sem_wait
+func (*Sem) Wait() c.Int { return 0 }
+
+// llgo:link (*Sem).TryWait C.sem_trywait
+func (*Sem) TryWait() c.Int { return 0 }
+
+// llgo:link (*Sem).GetValue C.sem_getvalue
+func (*Sem) GetValue(sval *c.Int) c.Int { return 0 }

c/sync/atomic/atomic.go

@@ -18,7 +18,6 @@ package atomic
 
 import (
 	"unsafe"
-	_ "unsafe"
 )
 
 const (

internal/runtime/z_chan.go

@@ -26,7 +26,8 @@ import (
 // -----------------------------------------------------------------------------
 
 const (
-	chanFull = 1
+	chanNoSendRecv = 0
+	chanHasRecv    = 1
 )
 
 type Chan struct {
@@ -36,6 +37,7 @@ type Chan struct {
 	getp  int
 	len   int
 	cap   int
+	sops  *selectOp
 	close bool
 }
 
@@ -60,9 +62,16 @@ func ChanCap(p *Chan) int {
 	return p.cap
 }
 
+func notifyOps(p *Chan) {
+	for sop := p.sops; sop != nil; sop = sop.next {
+		sop.notify()
+	}
+}
+
 func ChanClose(p *Chan) {
 	p.mutex.Lock()
 	p.close = true
+	notifyOps(p)
 	p.mutex.Unlock()
 	p.cond.Broadcast()
 }
@@ -71,12 +80,14 @@ func ChanTrySend(p *Chan, v unsafe.Pointer, eltSize int) bool {
 	n := p.cap
 	p.mutex.Lock()
 	if n == 0 {
-		if p.getp == chanFull || p.close {
+		if p.getp != chanHasRecv || p.close {
 			p.mutex.Unlock()
 			return false
 		}
-		p.data = v
-		p.getp = chanFull
+		if p.data != nil {
+			c.Memcpy(p.data, v, uintptr(eltSize))
+		}
+		p.getp = chanNoSendRecv
 	} else {
 		if p.len == n || p.close {
 			p.mutex.Unlock()
@@ -86,6 +97,7 @@ func ChanTrySend(p *Chan, v unsafe.Pointer, eltSize int) bool {
 		c.Memcpy(c.Advance(p.data, off*eltSize), v, uintptr(eltSize))
 		p.len++
 	}
+	notifyOps(p)
 	p.mutex.Unlock()
 	p.cond.Broadcast()
 	return true
@@ -95,15 +107,17 @@ func ChanSend(p *Chan, v unsafe.Pointer, eltSize int) bool {
 	n := p.cap
 	p.mutex.Lock()
 	if n == 0 {
-		for p.getp == chanFull {
+		for p.getp != chanHasRecv && !p.close {
 			p.cond.Wait(&p.mutex)
 		}
 		if p.close {
 			p.mutex.Unlock()
 			return false
 		}
-		p.data = v
-		p.getp = chanFull
+		if p.data != nil {
+			c.Memcpy(p.data, v, uintptr(eltSize))
+		}
+		p.getp = chanNoSendRecv
 	} else {
 		for p.len == n {
 			p.cond.Wait(&p.mutex)
@@ -116,48 +130,50 @@ func ChanSend(p *Chan, v unsafe.Pointer, eltSize int) bool {
 		c.Memcpy(c.Advance(p.data, off*eltSize), v, uintptr(eltSize))
 		p.len++
 	}
+	notifyOps(p)
 	p.mutex.Unlock()
 	p.cond.Broadcast()
 	return true
 }
 
-func ChanTryRecv(p *Chan, v unsafe.Pointer, eltSize int) bool {
+func ChanTryRecv(p *Chan, v unsafe.Pointer, eltSize int) (recvOK bool, tryOK bool) {
 	n := p.cap
 	p.mutex.Lock()
 	if n == 0 {
-		if p.getp == 0 {
-			p.mutex.Unlock()
-			return false
-		}
-		c.Memcpy(v, p.data, uintptr(eltSize))
-		p.getp = 0
+		tryOK = p.close
+		p.mutex.Unlock()
+		return
 	} else {
 		if p.len == 0 {
+			tryOK = p.close
 			p.mutex.Unlock()
-			return false
+			return
+		}
+		if v != nil {
+			c.Memcpy(v, c.Advance(p.data, p.getp*eltSize), uintptr(eltSize))
 		}
-		c.Memcpy(v, c.Advance(p.data, p.getp*eltSize), uintptr(eltSize))
 		p.getp = (p.getp + 1) % n
 		p.len--
 	}
+	notifyOps(p)
 	p.mutex.Unlock()
 	p.cond.Broadcast()
-	return true
+	return true, true
 }
 
-func ChanRecv(p *Chan, v unsafe.Pointer, eltSize int) bool {
+func ChanRecv(p *Chan, v unsafe.Pointer, eltSize int) (recvOK bool) {
 	n := p.cap
 	p.mutex.Lock()
 	if n == 0 {
-		for p.getp == 0 {
-			if p.close {
-				p.mutex.Unlock()
-				return false
-			}
+		for p.getp == chanHasRecv && !p.close {
 			p.cond.Wait(&p.mutex)
 		}
-		c.Memcpy(v, p.data, uintptr(eltSize))
-		p.getp = 0
+		if p.close {
+			p.mutex.Unlock()
+			return false
+		}
+		p.getp = chanHasRecv
+		p.data = v
 	} else {
 		for p.len == 0 {
 			if p.close {
@@ -166,13 +182,124 @@ func ChanRecv(p *Chan, v unsafe.Pointer, eltSize int) bool {
 			}
 			p.cond.Wait(&p.mutex)
 		}
-		c.Memcpy(v, c.Advance(p.data, p.getp*eltSize), uintptr(eltSize))
+		if v != nil {
+			c.Memcpy(v, c.Advance(p.data, p.getp*eltSize), uintptr(eltSize))
+		}
 		p.getp = (p.getp + 1) % n
 		p.len--
 	}
+	notifyOps(p)
 	p.mutex.Unlock()
 	p.cond.Broadcast()
-	return true
+	if n == 0 {
+		p.mutex.Lock()
+		for p.getp == chanHasRecv && !p.close {
+			p.cond.Wait(&p.mutex)
+		}
+		recvOK = !p.close
+		p.mutex.Unlock()
+	} else {
+		recvOK = true
+	}
+	return
+}
+
+// -----------------------------------------------------------------------------
+
+type selectOp struct {
+	mutex sync.Mutex
+	cond  sync.Cond
+	next  *selectOp
+
+	sem bool
+}
+
+func (p *selectOp) init() {
+	p.mutex.Init(nil)
+	p.cond.Init(nil)
+	p.next = nil
+	p.sem = false
+}
+
+func (p *selectOp) notify() {
+	p.mutex.Lock()
+	p.sem = true
+	p.mutex.Unlock()
+	p.cond.Signal()
+}
+
+func (p *selectOp) wait() {
+	p.mutex.Lock()
+	if !p.sem {
+		p.cond.Wait(&p.mutex)
+	}
+	p.sem = false
+	p.mutex.Unlock()
+}
+
+// ChanOp represents a channel operation.
+type ChanOp struct {
+	C *Chan
+
+	Val  unsafe.Pointer
+	Size int32
+
+	Send bool
+}
+
+// TrySelect executes a non-blocking select operation.
+func TrySelect(ops ...ChanOp) (isel int, recvOK, tryOK bool) {
+	for isel = range ops {
+		op := ops[isel]
+		if op.Send {
+			if tryOK = ChanTrySend(op.C, op.Val, int(op.Size)); tryOK {
+				return
+			}
+		} else {
+			if recvOK, tryOK = ChanTryRecv(op.C, op.Val, int(op.Size)); tryOK {
+				return
+			}
+		}
+	}
+	return
+}
+
+// Select executes a blocking select operation.
+func Select(ops ...ChanOp) (isel int, recvOK bool) {
+	selOp := new(selectOp) // TODO(xsw): use c.AllocaNew[selectOp]()
+	selOp.init()
+	for _, op := range ops {
+		prepareSelect(op.C, selOp)
+	}
+	var tryOK bool
+	for {
+		if isel, recvOK, tryOK = TrySelect(ops...); tryOK {
+			break
+		}
+		selOp.wait()
+	}
+	for _, op := range ops {
+		endSelect(op.C, selOp)
+	}
+	return
+}
+
+func prepareSelect(c *Chan, selOp *selectOp) {
+	c.mutex.Lock()
+	selOp.next = c.sops
+	c.sops = selOp
+	c.mutex.Unlock()
+}
+
+func endSelect(c *Chan, selOp *selectOp) {
+	c.mutex.Lock()
+	pp := &c.sops
+	for *pp != selOp {
+		pp = &(*pp).next
+	}
+	*pp = selOp.next
+	c.mutex.Unlock()
+	selOp.next = nil
 }
 
 // -----------------------------------------------------------------------------