ch3.6: 增加闭包函数的例子代码

examples/ch3.6/closure/main.go

@@ -0,0 +1,34 @@
+// Copyright © 2018 ChaiShushan <chaishushan{AT}gmail.com>.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+package main
+
+import (
+	"unsafe"
+)
+
+type FunTwiceClosure struct {
+	F uintptr
+	X int
+}
+
+func NewTwiceFunClosure(x int) func() int {
+	var p = &FunTwiceClosure{
+		F: asmFunTwiceClosureAddr(),
+		X: x,
+	}
+	return ptrToFunc(unsafe.Pointer(p))
+}
+
+func ptrToFunc(p unsafe.Pointer) func() int
+
+func asmFunTwiceClosureAddr() uintptr
+func asmFunTwiceClosureBody()
+
+func main() {
+	fnTwice := NewTwiceFunClosure(1)
+
+	println(fnTwice()) // 1*2 => 2
+	println(fnTwice()) // 2*2 => 4
+	println(fnTwice()) // 4*2 => 8
+}

examples/ch3.6/closure/main_amd64.s

@@ -0,0 +1,22 @@
+// Copyright © 2018 ChaiShushan <chaishushan{AT}gmail.com>.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+#include "textflag.h"
+
+TEXT ·ptrToFunc(SB), NOSPLIT, $0-16
+	MOVQ ptr+0(FP), AX // AX = ptr
+	MOVQ AX, ret+8(FP) // return AX
+	RET
+
+TEXT ·asmFunTwiceClosureAddr(SB), NOSPLIT, $0-8
+	LEAQ ·asmFunTwiceClosureBody(SB), AX // AX = ·asmFunTwiceClosureBody(SB)
+	MOVQ AX, ret+0(FP)                   // return AX
+	RET
+
+TEXT ·asmFunTwiceClosureBody(SB), NOSPLIT|NEEDCTXT, $0-8
+	MOVQ 8(DX), AX
+	ADDQ AX   , AX        // AX *= 2
+	MOVQ AX   , 8(DX)     // ctx.X = AX
+	MOVQ AX   , ret+0(FP) // return AX
+	RET
+