Cgo add cbytes implementation (rebased version of #3318) (#4470)

cgo: added CBytes implementation

Author: leongross

cgo/cgo.go

@@ -162,6 +162,13 @@ func __GoBytes(unsafe.Pointer, uintptr) []byte
 func GoBytes(ptr unsafe.Pointer, length C.int) []byte {
 	return C.__GoBytes(ptr, uintptr(length))
 }
+
+//go:linkname C.__CBytes runtime.cgo_CBytes
+func __CBytes([]byte) unsafe.Pointer
+
+func CBytes(b []byte) unsafe.Pointer {
+	return C.__CBytes(b)
+}
 `
 
 // Process extracts `import "C"` statements from the AST, parses the comment
@@ -218,7 +225,7 @@ func Process(files []*ast.File, dir, importPath string, fset *token.FileSet, cfl
 		switch decl := decl.(type) {
 		case *ast.FuncDecl:
 			switch decl.Name.Name {
-			case "CString", "GoString", "GoStringN", "__GoStringN", "GoBytes", "__GoBytes":
+			case "CString", "GoString", "GoStringN", "__GoStringN", "GoBytes", "__GoBytes", "CBytes", "__CBytes":
 				// Adjust the name to have a "C." prefix so it is correctly
 				// resolved.
 				decl.Name.Name = "C." + decl.Name.Name

cgo/testdata/basic.out.go

@@ -24,6 +24,13 @@ func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
 	return C.__GoBytes(ptr, uintptr(length))
 }
 
+//go:linkname C.__CBytes runtime.cgo_CBytes
+func C.__CBytes([]byte) unsafe.Pointer
+
+func C.CBytes(b []byte) unsafe.Pointer {
+	return C.__CBytes(b)
+}
+
 type (
 	C.char      uint8
 	C.schar     int8

cgo/testdata/const.out.go

@@ -24,6 +24,13 @@ func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
 	return C.__GoBytes(ptr, uintptr(length))
 }
 
+//go:linkname C.__CBytes runtime.cgo_CBytes
+func C.__CBytes([]byte) unsafe.Pointer
+
+func C.CBytes(b []byte) unsafe.Pointer {
+	return C.__CBytes(b)
+}
+
 type (
 	C.char      uint8
 	C.schar     int8

cgo/testdata/errors.out.go

@@ -44,6 +44,13 @@ func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
 	return C.__GoBytes(ptr, uintptr(length))
 }
 
+//go:linkname C.__CBytes runtime.cgo_CBytes
+func C.__CBytes([]byte) unsafe.Pointer
+
+func C.CBytes(b []byte) unsafe.Pointer {
+	return C.__CBytes(b)
+}
+
 type (
 	C.char      uint8
 	C.schar     int8

cgo/testdata/flags.out.go

@@ -29,6 +29,13 @@ func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
 	return C.__GoBytes(ptr, uintptr(length))
 }
 
+//go:linkname C.__CBytes runtime.cgo_CBytes
+func C.__CBytes([]byte) unsafe.Pointer
+
+func C.CBytes(b []byte) unsafe.Pointer {
+	return C.__CBytes(b)
+}
+
 type (
 	C.char      uint8
 	C.schar     int8

cgo/testdata/symbols.out.go

@@ -24,6 +24,13 @@ func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
 	return C.__GoBytes(ptr, uintptr(length))
 }
 
+//go:linkname C.__CBytes runtime.cgo_CBytes
+func C.__CBytes([]byte) unsafe.Pointer
+
+func C.CBytes(b []byte) unsafe.Pointer {
+	return C.__CBytes(b)
+}
+
 type (
 	C.char      uint8
 	C.schar     int8

cgo/testdata/types.out.go

@@ -24,6 +24,13 @@ func C.GoBytes(ptr unsafe.Pointer, length C.int) []byte {
 	return C.__GoBytes(ptr, uintptr(length))
 }
 
+//go:linkname C.__CBytes runtime.cgo_CBytes
+func C.__CBytes([]byte) unsafe.Pointer
+
+func C.CBytes(b []byte) unsafe.Pointer {
+	return C.__CBytes(b)
+}
+
 type (
 	C.char      uint8
 	C.schar     int8

src/runtime/string.go

@@ -283,3 +283,10 @@ func cgo_GoBytes(ptr unsafe.Pointer, length uintptr) []byte {
 	}
 	return buf
 }
+
+func cgo_CBytes(b []byte) unsafe.Pointer {
+	p := malloc(uintptr(len(b)))
+	s := unsafe.Slice((*byte)(p), len(b))
+	copy(s, b)
+	return p
+}

testdata/cgo/main.go

@@ -165,6 +165,8 @@ func main() {
 	println("C.GoString(nil):", C.GoString(nil))
 	println("len(C.GoStringN(nil, 0)):", len(C.GoStringN(nil, 0)))
 	println("len(C.GoBytes(nil, 0)):", len(C.GoBytes(nil, 0)))
+	println("len(C.GoBytes(C.CBytes(nil),0)):", len(C.GoBytes(C.CBytes(nil), 0)))
+	println(`rountrip CBytes:`, C.GoString((*C.char)(C.CBytes([]byte("hello\000")))))
 
 	// libc: test whether C functions work at all.
 	buf1 := []byte("foobar\x00")

testdata/cgo/out.txt

@@ -73,6 +73,8 @@ C.CStringN: 4 2 0 4 8
 C.GoString(nil): 
 len(C.GoStringN(nil, 0)): 0
 len(C.GoBytes(nil, 0)): 0
+len(C.GoBytes(C.CBytes(nil),0)): 0
+rountrip CBytes: hello
 copied string: foobar
 CGo sqrt(3): +1.732051e+000
 C   sqrt(3): +1.732051e+000