Kludge: work around lack of syscall.seek on 386 and arm, tinygo-org#1906

Revert this once syscall.seek is implemented
cf. tinygo-org#1906

Author: dkegel-fastly

src/os/file.go

@@ -176,19 +176,6 @@ func (f *File) Readdirnames(n int) (names []string, err error) {
 	return nil, &PathError{"readdirnames", f.name, ErrNotImplemented}
 }
 
-// Seek sets the offset for the next Read or Write on file to offset, interpreted
-// according to whence: 0 means relative to the origin of the file, 1 means
-// relative to the current offset, and 2 means relative to the end.
-// It returns the new offset and an error, if any.
-// The behavior of Seek on a file opened with O_APPEND is not specified.
-//
-// If f is a directory, the behavior of Seek varies by operating
-// system; you can seek to the beginning of the directory on Unix-like
-// operating systems, but not on Windows.
-func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
-	return f.handle.Seek(offset, whence)
-}
-
 func (f *File) SyscallConn() (syscall.RawConn, error) {
 	return nil, ErrNotImplemented
 }

src/os/file_windows.go

@@ -72,6 +72,20 @@ func (f unixFileHandle) Seek(offset int64, whence int) (int64, error) {
 	return newoffset, handleSyscallError(err)
 }
 
+// Seek sets the offset for the next Read or Write on file to offset, interpreted
+// according to whence: 0 means relative to the origin of the file, 1 means
+// relative to the current offset, and 2 means relative to the end.
+// It returns the new offset and an error, if any.
+// The behavior of Seek on a file opened with O_APPEND is not specified.
+//
+// If f is a directory, the behavior of Seek varies by operating
+// system; you can seek to the beginning of the directory on Unix-like
+// operating systems, but not on Windows.
+// TODO: move this back to file.go once syscall.seek is implemented on 386 and arm.
+func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
+	return f.handle.Seek(offset, whence)
+}
+
 // isWindowsNulName reports whether name is os.DevNull ('NUL') on Windows.
 // True is returned if name is 'NUL' whatever the case.
 func isWindowsNulName(name string) bool {

src/os/seek_unix_bad.go

@@ -0,0 +1,31 @@
+// +build linux,!baremetal,386 linux,!baremetal,arm
+
+// Functions broken by lack of seek().
+// Stat is broken because it uses Time, which has a preadn function that uses seek :-(
+//
+// TODO: remove this file once tinygo gets syscall.Seek support on i386
+
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package os
+
+// Seek sets the offset for the next Read or Write on file to offset, interpreted
+// according to whence: 0 means relative to the origin of the file, 1 means
+// relative to the current offset, and 2 means relative to the end.
+// It returns the new offset and an error, if any.
+// The behavior of Seek on a file opened with O_APPEND is not specified.
+//
+// If f is a directory, the behavior of Seek varies by operating
+// system; you can seek to the beginning of the directory on Unix-like
+// operating systems, but not on Windows.
+func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
+	return f.handle.Seek(offset, whence)
+}
+
+// Stat returns the FileInfo structure describing file.
+// If there is an error, it will be of type *PathError.
+func (f *File) Stat() (FileInfo, error) {
+	return nil, &PathError{Op: "fstat", Path: f.name, Err: ErrNotImplemented}
+}

src/os/seek_unix_good.go

@@ -0,0 +1,39 @@
+// +build darwin linux,!baremetal,!386,!arm
+
+// Functions broken by lack of seek().
+// Stat is broken because it uses Time, which has a preadn function that uses seek :-(
+//
+// TODO: merge these functions back where they belong once tinygo gets syscall.Seek support on i386
+
+package os
+
+import (
+	"syscall"
+)
+
+// Seek sets the offset for the next Read or Write on file to offset, interpreted
+// according to whence: 0 means relative to the origin of the file, 1 means
+// relative to the current offset, and 2 means relative to the end.
+// It returns the new offset and an error, if any.
+// The behavior of Seek on a file opened with O_APPEND is not specified.
+//
+// If f is a directory, the behavior of Seek varies by operating
+// system; you can seek to the beginning of the directory on Unix-like
+// operating systems, but not on Windows.
+func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
+	return f.handle.Seek(offset, whence)
+}
+
+// Stat returns the FileInfo structure describing file.
+// If there is an error, it will be of type *PathError.
+func (f *File) Stat() (FileInfo, error) {
+	var fs fileStat
+	err := ignoringEINTR(func() error {
+		return syscall.Fstat(int(f.handle.(unixFileHandle)), &fs.sys)
+	})
+	if err != nil {
+		return nil, &PathError{Op: "fstat", Path: f.name, Err: err}
+	}
+	fillFileStatFromSys(&fs, f.name)
+	return &fs, nil
+}

src/os/stat_unix.go

@@ -15,20 +15,6 @@ func (f *File) Sync() error {
 	return ErrNotImplemented
 }
 
-// Stat returns the FileInfo structure describing file.
-// If there is an error, it will be of type *PathError.
-func (f *File) Stat() (FileInfo, error) {
-	var fs fileStat
-	err := ignoringEINTR(func() error {
-		return syscall.Fstat(int(f.handle.(unixFileHandle)), &fs.sys)
-	})
-	if err != nil {
-		return nil, &PathError{Op: "fstat", Path: f.name, Err: err}
-	}
-	fillFileStatFromSys(&fs, f.name)
-	return &fs, nil
-}
-
 // statNolog stats a file with no test logging.
 func statNolog(name string) (FileInfo, error) {
 	var fs fileStat