runtime: add several os package stubs

2 files changed, 163 insertions, 4 deletions

diff --git a/src/os/file.go b/src/os/file.go
index c275a39ed..9f247dc6e 100644
--- a/src/os/file.go
+++ b/src/os/file.go
@@ -11,7 +11,8 @@ import (
 
 // Portable analogs of some common system call errors.
 var (
-	ErrUnsupported = errors.New("operation not supported")
+	errUnsupported = errors.New("operation not supported")
+	notImplemented = errors.New("os: not implemented")
 )
 
 // Stdin, Stdout, and Stderr are open Files pointing to the standard input,
@@ -28,6 +29,21 @@ type File struct {
 	name string
 }
 
+// Readdir is a stub, not yet implemented
+func (f *File) Readdir(n int) ([]FileInfo, error) {
+	return nil, notImplemented
+}
+
+// Readdirnames is a stub, not yet implemented
+func (f *File) Readdirnames(n int) (names []string, err error) {
+	return nil, notImplemented
+}
+
+// Stat is a stub, not yet implemented
+func (f *File) Stat() (FileInfo, error) {
+	return nil, notImplemented
+}
+
 // NewFile returns a new File with the given file descriptor and name.
 func NewFile(fd uintptr, name string) *File {
 	return &File{fd, name}
@@ -38,3 +54,146 @@ func NewFile(fd uintptr, name string) *File {
 func (f *File) Fd() uintptr {
 	return f.fd
 }
+
+const (
+	PathSeparator     = '/' // OS-specific path separator
+	PathListSeparator = ':' // OS-specific path list separator
+)
+
+// IsPathSeparator reports whether c is a directory separator character.
+func IsPathSeparator(c uint8) bool {
+	return PathSeparator == c
+}
+
+// PathError records an error and the operation and file path that caused it.
+type PathError struct {
+	Op   string
+	Path string
+	Err  error
+}
+
+func (e *PathError) Error() string { return e.Op + " " + e.Path + ": " + e.Err.Error() }
+
+// Open is a super simple stub function (for now), only capable of opening stdin, stdout, and stderr
+func Open(name string) (*File, error) {
+	fd := uintptr(999)
+	switch name {
+	case "/dev/stdin":
+		fd = 0
+	case "/dev/stdout":
+		fd = 1
+	case "/dev/stderr":
+		fd = 2
+	default:
+		return nil, &PathError{"open", name, notImplemented}
+	}
+	return &File{fd, name}, nil
+}
+
+// OpenFile is a stub, passing through to the stub Open() call
+func OpenFile(name string, flag int, perm FileMode) (*File, error) {
+	return Open(name)
+}
+
+// Create is a stub, passing through to the stub Open() call
+func Create(name string) (*File, error) {
+	return Open(name)
+}
+
+type FileMode uint32
+
+// Mode constants, copied from the mainline Go source
+// https://github.com/golang/go/blob/4ce6a8e89668b87dce67e2f55802903d6eb9110a/src/os/types.go#L35-L63
+const (
+	// The single letters are the abbreviations used by the String method's formatting.
+	ModeDir        FileMode = 1 << (32 - 1 - iota) // d: is a directory
+	ModeAppend                                     // a: append-only
+	ModeExclusive                                  // l: exclusive use
+	ModeTemporary                                  // T: temporary file; Plan 9 only
+	ModeSymlink                                    // L: symbolic link
+	ModeDevice                                     // D: device file
+	ModeNamedPipe                                  // p: named pipe (FIFO)
+	ModeSocket                                     // S: Unix domain socket
+	ModeSetuid                                     // u: setuid
+	ModeSetgid                                     // g: setgid
+	ModeCharDevice                                 // c: Unix character device, when ModeDevice is set
+	ModeSticky                                     // t: sticky
+	ModeIrregular                                  // ?: non-regular file; nothing else is known about this file
+
+	// Mask for the type bits. For regular files, none will be set.
+	ModeType = ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice | ModeCharDevice | ModeIrregular
+
+	ModePerm FileMode = 0777 // Unix permission bits
+)
+
+// IsDir is a stub, always returning false
+func (m FileMode) IsDir() bool {
+	return false
+}
+
+// Stub constants
+const (
+	O_RDONLY int = 1
+	O_WRONLY int = 2
+	O_RDWR   int = 4
+	O_APPEND int = 8
+	O_CREATE int = 16
+	O_EXCL   int = 32
+	O_SYNC   int = 64
+	O_TRUNC  int = 128
+)
+
+// A FileInfo describes a file and is returned by Stat and Lstat.
+type FileInfo interface {
+	Name() string       // base name of the file
+	Size() int64        // length in bytes for regular files; system-dependent for others
+	Mode() FileMode     // file mode bits
+	// ModTime() time.Time // modification time
+	IsDir() bool        // abbreviation for Mode().IsDir()
+	Sys() interface{}   // underlying data source (can return nil)
+}
+
+// Stat is a stub, not yet implemented
+func Stat(name string) (FileInfo, error) {
+	return nil, notImplemented
+}
+
+// Lstat is a stub, not yet implemented
+func Lstat(name string) (FileInfo, error) {
+	return nil, notImplemented
+}
+
+// Getwd is a stub (for now), always returning an empty string
+func Getwd() (string, error) {
+	return "", nil
+}
+
+// Readlink is a stub (for now), always returning the string it was given
+func Readlink(name string) (string, error) {
+	return name, nil
+}
+
+// TempDir is a stub (for now), always returning the string "/tmp"
+func TempDir() string {
+	return "/tmp"
+}
+
+// Mkdir is a stub, not yet implemented
+func Mkdir(name string, perm FileMode) error {
+	return notImplemented
+}
+
+// IsExist is a stub (for now), always returning false
+func IsExist(err error) bool {
+	return false
+}
+
+// IsNotExist is a stub (for now), always returning false
+func IsNotExist(err error) bool {
+	return false
+}
+
+// Getpid is a stub (for now), always returning 1
+func Getpid() int {
+	return 1
+}
diff --git a/src/os/file_other.go b/src/os/file_other.go
index abe90868c..8d168ebc4 100644
--- a/src/os/file_other.go
+++ b/src/os/file_other.go
@@ -8,7 +8,7 @@ import (
 
 // Read is unsupported on this system.
 func (f *File) Read(b []byte) (n int, err error) {
-	return 0, ErrUnsupported
+	return 0, errUnsupported
 }
 
 // Write writes len(b) bytes to the output. It returns the number of bytes
@@ -21,13 +21,13 @@ func (f *File) Write(b []byte) (n int, err error) {
 		}
 		return len(b), nil
 	default:
-		return 0, ErrUnsupported
+		return 0, errUnsupported
 	}
 }
 
 // Close is unsupported on this system.
 func (f *File) Close() error {
-	return ErrUnsupported
+	return errUnsupported
 }
 
 //go:linkname putchar runtime.putchar