cmd/compile/internal/syntax: fast Go syntax trees, initial commit.

Syntax tree nodes, scanner, parser, basic printers.

Builds syntax trees for entire Go std lib at a rate of ~1.8M lines/s
in warmed up state (MacMini, 2.3 GHz Intel Core i7, 8GB RAM):

$ go test -run StdLib -fast
parsed 1074617 lines (2832 files) in 579.66364ms (1853863 lines/s)
allocated 282.212Mb (486.854Mb/s)
PASS

Change-Id: Ie26d9a7bf4e5ff07457aedfcc9b89f0eba72ae3f
Reviewed-on: https://go-review.googlesource.com/27195
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/cmd/compile/internal/syntax/syntax.go

@@ -0,0 +1,61 @@
+// 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 syntax
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+type Mode uint
+
+type ErrorHandler func(pos, line int, msg string)
+
+// TODO(gri) These need a lot more work.
+
+func ReadFile(filename string, errh ErrorHandler, mode Mode) (*File, error) {
+	src, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	defer src.Close()
+	return Read(src, errh, mode)
+}
+
+type bytesReader struct {
+	data []byte
+}
+
+func (r *bytesReader) Read(p []byte) (int, error) {
+	if len(r.data) > 0 {
+		n := copy(p, r.data)
+		r.data = r.data[n:]
+		return n, nil
+	}
+	return 0, io.EOF
+}
+
+func ReadBytes(src []byte, errh ErrorHandler, mode Mode) (*File, error) {
+	return Read(&bytesReader{src}, errh, mode)
+}
+
+func Read(src io.Reader, errh ErrorHandler, mode Mode) (*File, error) {
+	var p parser
+	p.init(src, errh)
+
+	p.next()
+	ast := p.file()
+
+	if errh == nil && p.nerrors > 0 {
+		return nil, fmt.Errorf("%d syntax errors", p.nerrors)
+	}
+
+	return ast, nil
+}
+
+func Write(w io.Writer, n *File) error {
+	panic("unimplemented")
+}