A FileWr.T, or file writer, is a writer on a File.T. \index{buffered file I/O} \index{file!buffered I/O}

INTERFACE FileWr;

IMPORT Wr, File, OSError, Pathname;

TYPE
  T <: Public;
  Public = Wr.T OBJECT METHODS
    init(h: File.T; buffered: BOOLEAN := TRUE): T
      RAISES {OSError.E}
  END;

If w is a file writer and h is a file handle, the call w.init(h) initializes w so that characters output to w are written to h and so that closing w closes h.

For any other file handle h, w.init(h, b) causes w to be a nonseekable writer, buffered if and only if b is TRUE, and initializes cur(w) to zero.

If a subsequent writer operation on w raises Wr.Failure, the associated exception argument is the AtomList.T argument accompanying an OSError.E exception from a file operation on h.

PROCEDURE Open(p: Pathname.T): T RAISES {OSError.E};

Return a file writer whose target is the file named p. If the file does not exist, it is created. If the file exists, it is truncated to a size of zero.

      RETURN NEW(T).init(FS.OpenFile(p))

PROCEDURE OpenAppend(p: Pathname.T): T RAISES {OSError.E};

Return a file writer whose target is the file named p. If the file does not exist, it is created. If the file exists, the writer is positioned to append to the existing contents of the file.

      WITH h = FS.OpenFile(p, truncate := FALSE) DO
        EVAL h.seek(RegularFile.Origin.End, 0);
        RETURN NEW(T).init(h)
      END

END FileWr.