1 files changed, 123 insertions, 0 deletions
diff --git a/src/lib/go/ast/format.go b/src/lib/go/ast/format.go
new file mode 100644
index 000000000..db7be71ce
--- /dev/null
+++ b/src/lib/go/ast/format.go
@@ -0,0 +1,123 @@
+// Copyright 2009 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 ast
+
+import (
+	"datafmt";
+	"go/ast";
+	"go/token";
+	"io";
+	"os";
+)
+
+
+// Format is a customized datafmt.Format for printing of ASTs.
+type Format datafmt.Format;
+
+
+// ----------------------------------------------------------------------------
+// Custom formatters
+
+// The AST-specific formatting state is maintained by a state variable.
+type state struct {
+	// for now we have very little state
+	// TODO maintain list of unassociated comments
+	optSemi *bool
+}
+
+
+func (s *state) Copy() datafmt.Environment {
+	optSemi := *s.optSemi;
+	return &state{&optSemi};
+}
+
+
+func isValidPos(s *datafmt.State, value interface{}, ruleName string) bool {
+	pos := value.(token.Position);
+	return pos.IsValid();
+}
+
+
+func isSend(s *datafmt.State, value interface{}, ruleName string) bool {
+	return value.(ast.ChanDir) & ast.SEND != 0;
+}
+
+
+func isRecv(s *datafmt.State, value interface{}, ruleName string) bool {
+	return value.(ast.ChanDir) & ast.RECV != 0;
+}
+
+
+func isMultiLineComment(s *datafmt.State, value interface{}, ruleName string) bool {
+	return value.([]byte)[1] == '*';
+}
+
+
+func clearOptSemi(s *datafmt.State, value interface{}, ruleName string) bool {
+	*s.Env().(*state).optSemi = false;
+	return true;
+}
+
+
+func setOptSemi(s *datafmt.State, value interface{}, ruleName string) bool {
+	*s.Env().(*state).optSemi = true;
+	return true;
+}
+
+
+func optSemi(s *datafmt.State, value interface{}, ruleName string) bool {
+	if !*s.Env().(*state).optSemi {
+		s.Write([]byte{';'});
+	}
+	return true;
+}
+
+
+var fmap = datafmt.FormatterMap {
+	"isValidPos": isValidPos,
+	"isSend": isSend,
+	"isRecv": isRecv,
+	"isMultiLineComment": isMultiLineComment,
+	"/": clearOptSemi,
+	"clearOptSemi": clearOptSemi,
+	"setOptSemi": setOptSemi,
+	"optSemi": optSemi,
+}
+
+
+// ----------------------------------------------------------------------------
+// Printing
+
+// NewFormat parses a datafmt format specification from a file
+// and adds AST-specific custom formatter rules. The result is
+// the customized format or an os.Error, if any.
+//
+func NewFormat(filename string) (Format, os.Error) {
+	src, err := io.ReadFile(filename);
+	if err != nil {
+		return nil, err;
+	}
+	f, err := datafmt.Parse(src, fmap);
+	return Format(f), err;
+}
+
+
+// Fprint formats each AST node provided as argument according to the
+// format f and writes to standard output. The result is the total number
+// of bytes written and an os.Error, if any.
+//
+func (f Format) Fprint(w io.Writer, nodes ...) (int, os.Error) {
+	s := state{new(bool)};
+	return datafmt.Format(f).Fprint(w, &s, nodes);
+}
+
+
+// Fprint formats each AST node provided as argument according to the
+// format f and writes to w. The result is the total number of bytes
+// written and an os.Error, if any.
+//
+func (f Format) Print(nodes ...) (int, os.Error) {
+	return f.Fprint(os.Stdout, nodes);
+}