os,internal/syscall/windows: use ReadFile/MultiByteToWideChar to read from console

Fixes #6303

Change-Id: Ib2cd15ac6106ef8e6b975943db8efc8d8ab21052
Reviewed-on: https://go-review.googlesource.com/4310
Reviewed-by: Russ Cox <rsc@golang.org>

src/internal/syscall/windows/syscall_windows.go

@@ -138,3 +138,6 @@ func Rename(oldpath, newpath string) error {
 	}
 	return MoveFileEx(from, to, MOVEFILE_REPLACE_EXISTING)
 }
+
+//sys	GetACP() (acp uint, err error) = kernel32.GetACP
+//sys	MultiByteToWideChar(codePage uint, dwFlags uint32, str *byte, nstr int32, wchar *uint16, nwchar int32) (nwrite int, err error) = kernel32.MultiByteToWideChar

src/internal/syscall/windows/zsyscall_windows.go

@@ -14,6 +14,8 @@ var (
 	procGetAdaptersAddresses = modiphlpapi.NewProc("GetAdaptersAddresses")
 	procGetComputerNameExW   = modkernel32.NewProc("GetComputerNameExW")
 	procMoveFileExW          = modkernel32.NewProc("MoveFileExW")
+	procGetACP               = modkernel32.NewProc("GetACP")
+	procMultiByteToWideChar  = modkernel32.NewProc("MultiByteToWideChar")
 )
 
 func GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizePointer *uint32) (errcode error) {
@@ -47,3 +49,29 @@ func MoveFileEx(from *uint16, to *uint16, flags uint32) (err error) {
 	}
 	return
 }
+
+func MultiByteToWideChar(codePage uint, dwFlags uint32, str *byte, nstr int32, wchar *uint16, nwchar int32) (nwrite int, err error) {
+	r0, _, e1 := syscall.Syscall6(procMultiByteToWideChar.Addr(), 6, uintptr(codePage), uintptr(dwFlags), uintptr(unsafe.Pointer(str)), uintptr(nstr), uintptr(unsafe.Pointer(wchar)), uintptr(nwchar))
+	nwrite = int(r0)
+	if nwrite == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
+func GetACP() (acp uint, err error) {
+	r0, _, e1 := syscall.Syscall(procGetACP.Addr(), 0, 0, 0, 0)
+	acp = uint(r0)
+	if acp == 0 {
+		if e1 != 0 {
+			err = error(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}

src/os/file_windows.go

@@ -257,24 +257,38 @@ func (f *File) readConsole(b []byte) (n int, err error) {
 		return 0, nil
 	}
 	if len(f.readbuf) == 0 {
-		// syscall.ReadConsole seems to fail, if given large buffer.
-		// So limit the buffer to 16000 characters.
 		numBytes := len(b)
-		if numBytes > 16000 {
-			numBytes = 16000
+		// Windows  can't read bytes over max of int16.
+		if numBytes > 32767 {
+			numBytes = 32767
 		}
-		// get more input data from os
-		wchars := make([]uint16, numBytes)
-		var p *uint16
-		if len(b) > 0 {
-			p = &wchars[0]
-		}
-		var nw uint32
-		err := syscall.ReadConsole(f.fd, p, uint32(len(wchars)), &nw, nil)
+		mbytes := make([]byte, numBytes)
+		var nmb uint32
+		err := syscall.ReadFile(f.fd, mbytes, &nmb, nil)
 		if err != nil {
 			return 0, err
 		}
-		f.readbuf = utf16.Decode(wchars[:nw])
+		if nmb > 0 {
+			var pmb *byte
+			if len(b) > 0 {
+				pmb = &mbytes[0]
+			}
+			acp, err := windows.GetACP()
+			if err != nil {
+				return 0, err
+			}
+			nwc, err := windows.MultiByteToWideChar(acp, 2, pmb, int32(nmb), nil, 0)
+			if err != nil {
+				return 0, err
+			}
+			wchars := make([]uint16, nwc)
+			pwc := &wchars[0]
+			nwc, err = windows.MultiByteToWideChar(acp, 2, pmb, int32(nmb), pwc, int32(nwc))
+			if err != nil {
+				return 0, err
+			}
+			f.readbuf = utf16.Decode(wchars[:nwc])
+		}
 	}
 	for i, r := range f.readbuf {
 		if utf8.RuneLen(r) > len(b) {