Step 2 of the Big Error Shift.

Change the representation of errors in "os" to be cleaner.
(But they are not really representative of the power of the new scheme.)
Step 3 will be to remove all references to os.NewError.
Step 4 will be to delete the second half of lib/os/error.go.

R=rsc
OCL=27587
CL=27587

src/lib/os/error.go

@@ -18,6 +18,67 @@ func (e *ErrorString) String() string {
 	return *e
 }
 
+// Errno is the Unix error number.  Names such as EINVAL are simple
+// wrappers to convert the error number into an Error.
+type Errno int64
+func (e Errno) String() string {
+	return syscall.Errstr(e)
+}
+
+// ErrnoToError calls NewError to create an _Error object for the string
+// associated with Unix error code errno.
+func ErrnoToError(errno int64) Error {
+	if errno == 0 {
+		return nil
+	}
+	return Errno(errno)
+}
+
+// Commonly known Unix errors.
+var (
+	ENONE Error = Errno(syscall.ENONE);
+	EPERM Error = Errno(syscall.EPERM);
+	ENOENT Error = Errno(syscall.ENOENT);
+	ESRCH Error = Errno(syscall.ESRCH);
+	EINTR Error = Errno(syscall.EINTR);
+	EIO Error = Errno(syscall.EIO);
+	ENXIO Error = Errno(syscall.ENXIO);
+	E2BIG Error = Errno(syscall.E2BIG);
+	ENOEXEC Error = Errno(syscall.ENOEXEC);
+	EBADF Error = Errno(syscall.EBADF);
+	ECHILD Error = Errno(syscall.ECHILD);
+	EDEADLK Error = Errno(syscall.EDEADLK);
+	ENOMEM Error = Errno(syscall.ENOMEM);
+	EACCES Error = Errno(syscall.EACCES);
+	EFAULT Error = Errno(syscall.EFAULT);
+	ENOTBLK Error = Errno(syscall.ENOTBLK);
+	EBUSY Error = Errno(syscall.EBUSY);
+	EEXIST Error = Errno(syscall.EEXIST);
+	EXDEV Error = Errno(syscall.EXDEV);
+	ENODEV Error = Errno(syscall.ENODEV);
+	ENOTDIR Error = Errno(syscall.ENOTDIR);
+	EISDIR Error = Errno(syscall.EISDIR);
+	EINVAL Error = Errno(syscall.EINVAL);
+	ENFILE Error = Errno(syscall.ENFILE);
+	EMFILE Error = Errno(syscall.EMFILE);
+	ENOTTY Error = Errno(syscall.ENOTTY);
+	ETXTBSY Error = Errno(syscall.ETXTBSY);
+	EFBIG Error = Errno(syscall.EFBIG);
+	ENOSPC Error = Errno(syscall.ENOSPC);
+	ESPIPE Error = Errno(syscall.ESPIPE);
+	EROFS Error = Errno(syscall.EROFS);
+	EMLINK Error = Errno(syscall.EMLINK);
+	EPIPE Error = Errno(syscall.EPIPE);
+	EAGAIN Error = Errno(syscall.EAGAIN);
+	EDOM Error = Errno(syscall.EDOM);
+	ERANGE Error = Errno(syscall.ERANGE);
+)
+
+// -----------------------
+// Everything below here is deprecated.
+// Delete when all callers of NewError are gone and their uses converted
+// to the new error scheme (for an example, see template).
+
 // _Error is a structure wrapping a string describing an error.
 // Errors are singleton structures, created by NewError, so their addresses can
 // be compared to test for equality. A nil Error pointer means ``no error''.
@@ -28,11 +89,6 @@ type _Error struct {
 	s string
 }
 
-// Indexed by errno.
-// If we worry about syscall speed (only relevant on failure), we could
-// make it an array, but it's probably not important.
-var errorTab = make(map[int64] Error);
-
 // Table of all known errors in system.  Use the same error string twice,
 // get the same *os._Error.
 var errorStringTab = make(map[string] Error);
@@ -55,66 +111,6 @@ func NewError(s string) Error {
 	return err;
 }
 
-// ErrnoToError calls NewError to create an _Error object for the string
-// associated with Unix error code errno.
-func ErrnoToError(errno int64) Error {
-	if errno == 0 {
-		return nil
-	}
-	// Quick lookup by errno.
-	err, ok := errorTab[errno];
-	if ok {
-		return err
-	}
-	err = NewError(syscall.Errstr(errno));
-	errorTab[errno] = err;
-	return err;
-}
-
-// Commonly known Unix errors.
-var (
-	// TODO(r):
-	// 1. these become type ENONE struct { ErrorString }
-	// 2. create private instances of each type: var eNONE ENONE(ErrnoToString(syscall.ENONE));
-	// 3. put them in a table
-	// 4. ErrnoToError uses the table. its error case ECATCHALL("%d")
-	ENONE = ErrnoToError(syscall.ENONE);
-	EPERM = ErrnoToError(syscall.EPERM);
-	ENOENT = ErrnoToError(syscall.ENOENT);
-	ESRCH = ErrnoToError(syscall.ESRCH);
-	EINTR = ErrnoToError(syscall.EINTR);
-	EIO = ErrnoToError(syscall.EIO);
-	ENXIO = ErrnoToError(syscall.ENXIO);
-	E2BIG = ErrnoToError(syscall.E2BIG);
-	ENOEXEC = ErrnoToError(syscall.ENOEXEC);
-	EBADF = ErrnoToError(syscall.EBADF);
-	ECHILD = ErrnoToError(syscall.ECHILD);
-	EDEADLK = ErrnoToError(syscall.EDEADLK);
-	ENOMEM = ErrnoToError(syscall.ENOMEM);
-	EACCES = ErrnoToError(syscall.EACCES);
-	EFAULT = ErrnoToError(syscall.EFAULT);
-	ENOTBLK = ErrnoToError(syscall.ENOTBLK);
-	EBUSY = ErrnoToError(syscall.EBUSY);
-	EEXIST = ErrnoToError(syscall.EEXIST);
-	EXDEV = ErrnoToError(syscall.EXDEV);
-	ENODEV = ErrnoToError(syscall.ENODEV);
-	ENOTDIR = ErrnoToError(syscall.ENOTDIR);
-	EISDIR = ErrnoToError(syscall.EISDIR);
-	EINVAL = ErrnoToError(syscall.EINVAL);
-	ENFILE = ErrnoToError(syscall.ENFILE);
-	EMFILE = ErrnoToError(syscall.EMFILE);
-	ENOTTY = ErrnoToError(syscall.ENOTTY);
-	ETXTBSY = ErrnoToError(syscall.ETXTBSY);
-	EFBIG = ErrnoToError(syscall.EFBIG);
-	ENOSPC = ErrnoToError(syscall.ENOSPC);
-	ESPIPE = ErrnoToError(syscall.ESPIPE);
-	EROFS = ErrnoToError(syscall.EROFS);
-	EMLINK = ErrnoToError(syscall.EMLINK);
-	EPIPE = ErrnoToError(syscall.EPIPE);
-	EDOM = ErrnoToError(syscall.EDOM);
-	ERANGE = ErrnoToError(syscall.ERANGE);
-	EAGAIN = ErrnoToError(syscall.EAGAIN);
-)
 
 // String returns the string associated with the _Error.
 func (e *_Error) String() string {