1 files changed, 186 insertions, 0 deletions
diff --git a/libgo/go/go/scanner/errors.go b/libgo/go/go/scanner/errors.go
new file mode 100644
index 000000000..47e35a710
--- /dev/null
+++ b/libgo/go/go/scanner/errors.go
@@ -0,0 +1,186 @@
+// 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 scanner
+
+import (
+	"container/vector"
+	"fmt"
+	"go/token"
+	"io"
+	"os"
+	"sort"
+)
+
+
+// An implementation of an ErrorHandler may be provided to the Scanner.
+// If a syntax error is encountered and a handler was installed, Error
+// is called with a position and an error message. The position points
+// to the beginning of the offending token.
+//
+type ErrorHandler interface {
+	Error(pos token.Position, msg string)
+}
+
+
+// ErrorVector implements the ErrorHandler interface. It maintains a list
+// of errors which can be retrieved with GetErrorList and GetError. The
+// zero value for an ErrorVector is an empty ErrorVector ready to use.
+//
+// A common usage pattern is to embed an ErrorVector alongside a
+// scanner in a data structure that uses the scanner. By passing a
+// reference to an ErrorVector to the scanner's Init call, default
+// error handling is obtained.
+//
+type ErrorVector struct {
+	errors vector.Vector
+}
+
+
+// Reset resets an ErrorVector to no errors.
+func (h *ErrorVector) Reset() { h.errors.Resize(0, 0) }
+
+
+// ErrorCount returns the number of errors collected.
+func (h *ErrorVector) ErrorCount() int { return h.errors.Len() }
+
+
+// Within ErrorVector, an error is represented by an Error node. The
+// position Pos, if valid, points to the beginning of the offending
+// token, and the error condition is described by Msg.
+//
+type Error struct {
+	Pos token.Position
+	Msg string
+}
+
+
+func (e *Error) String() string {
+	if e.Pos.Filename != "" || e.Pos.IsValid() {
+		// don't print "<unknown position>"
+		// TODO(gri) reconsider the semantics of Position.IsValid
+		return e.Pos.String() + ": " + e.Msg
+	}
+	return e.Msg
+}
+
+
+// An ErrorList is a (possibly sorted) list of Errors.
+type ErrorList []*Error
+
+
+// ErrorList implements the sort Interface.
+func (p ErrorList) Len() int      { return len(p) }
+func (p ErrorList) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
+
+
+func (p ErrorList) Less(i, j int) bool {
+	e := &p[i].Pos
+	f := &p[j].Pos
+	// Note that it is not sufficient to simply compare file offsets because
+	// the offsets do not reflect modified line information (through //line
+	// comments).
+	if e.Filename < f.Filename {
+		return true
+	}
+	if e.Filename == f.Filename {
+		if e.Line < f.Line {
+			return true
+		}
+		if e.Line == f.Line {
+			return e.Column < f.Column
+		}
+	}
+	return false
+}
+
+
+func (p ErrorList) String() string {
+	switch len(p) {
+	case 0:
+		return "unspecified error"
+	case 1:
+		return p[0].String()
+	}
+	return fmt.Sprintf("%s (and %d more errors)", p[0].String(), len(p)-1)
+}
+
+
+// These constants control the construction of the ErrorList
+// returned by GetErrors.
+//
+const (
+	Raw         = iota // leave error list unchanged
+	Sorted             // sort error list by file, line, and column number
+	NoMultiples        // sort error list and leave only the first error per line
+)
+
+
+// GetErrorList returns the list of errors collected by an ErrorVector.
+// The construction of the ErrorList returned is controlled by the mode
+// parameter. If there are no errors, the result is nil.
+//
+func (h *ErrorVector) GetErrorList(mode int) ErrorList {
+	if h.errors.Len() == 0 {
+		return nil
+	}
+
+	list := make(ErrorList, h.errors.Len())
+	for i := 0; i < h.errors.Len(); i++ {
+		list[i] = h.errors.At(i).(*Error)
+	}
+
+	if mode >= Sorted {
+		sort.Sort(list)
+	}
+
+	if mode >= NoMultiples {
+		var last token.Position // initial last.Line is != any legal error line
+		i := 0
+		for _, e := range list {
+			if e.Pos.Filename != last.Filename || e.Pos.Line != last.Line {
+				last = e.Pos
+				list[i] = e
+				i++
+			}
+		}
+		list = list[0:i]
+	}
+
+	return list
+}
+
+
+// GetError is like GetErrorList, but it returns an os.Error instead
+// so that a nil result can be assigned to an os.Error variable and
+// remains nil.
+//
+func (h *ErrorVector) GetError(mode int) os.Error {
+	if h.errors.Len() == 0 {
+		return nil
+	}
+
+	return h.GetErrorList(mode)
+}
+
+
+// ErrorVector implements the ErrorHandler interface.
+func (h *ErrorVector) Error(pos token.Position, msg string) {
+	h.errors.Push(&Error{pos, msg})
+}
+
+
+// PrintError is a utility function that prints a list of errors to w,
+// one error per line, if the err parameter is an ErrorList. Otherwise
+// it prints the err string.
+//
+func PrintError(w io.Writer, err os.Error) {
+	if list, ok := err.(ErrorList); ok {
+		for _, e := range list {
+			fmt.Fprintf(w, "%s\n", e)
+		}
+	} else {
+		fmt.Fprintf(w, "%s\n", err)
+	}
+}