1 files changed, 82 insertions, 0 deletions
diff --git a/libgo/go/debug/gosym/pclntab.go b/libgo/go/debug/gosym/pclntab.go
new file mode 100644
index 000000000..9d7b0d15f
--- /dev/null
+++ b/libgo/go/debug/gosym/pclntab.go
@@ -0,0 +1,82 @@
+// 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.
+
+/*
+ * Line tables
+ */
+
+package gosym
+
+import "encoding/binary"
+
+type LineTable struct {
+	Data []byte
+	PC   uint64
+	Line int
+}
+
+// TODO(rsc): Need to pull in quantum from architecture definition.
+const quantum = 1
+
+func (t *LineTable) parse(targetPC uint64, targetLine int) (b []byte, pc uint64, line int) {
+	// The PC/line table can be thought of as a sequence of
+	//  <pc update>* <line update>
+	// batches.  Each update batch results in a (pc, line) pair,
+	// where line applies to every PC from pc up to but not
+	// including the pc of the next pair.
+	//
+	// Here we process each update individually, which simplifies
+	// the code, but makes the corner cases more confusing.
+	b, pc, line = t.Data, t.PC, t.Line
+	for pc <= targetPC && line != targetLine && len(b) > 0 {
+		code := b[0]
+		b = b[1:]
+		switch {
+		case code == 0:
+			if len(b) < 4 {
+				b = b[0:0]
+				break
+			}
+			val := binary.BigEndian.Uint32(b)
+			b = b[4:]
+			line += int(val)
+		case code <= 64:
+			line += int(code)
+		case code <= 128:
+			line -= int(code - 64)
+		default:
+			pc += quantum * uint64(code-128)
+			continue
+		}
+		pc += quantum
+	}
+	return b, pc, line
+}
+
+func (t *LineTable) slice(pc uint64) *LineTable {
+	data, pc, line := t.parse(pc, -1)
+	return &LineTable{data, pc, line}
+}
+
+func (t *LineTable) PCToLine(pc uint64) int {
+	_, _, line := t.parse(pc, -1)
+	return line
+}
+
+func (t *LineTable) LineToPC(line int, maxpc uint64) uint64 {
+	_, pc, line1 := t.parse(maxpc, line)
+	if line1 != line {
+		return 0
+	}
+	// Subtract quantum from PC to account for post-line increment
+	return pc - quantum
+}
+
+// NewLineTable returns a new PC/line table
+// corresponding to the encoded data.
+// Text must be the start address of the
+// corresponding text segment.
+func NewLineTable(data []byte, text uint64) *LineTable {
+	return &LineTable{data, text, 0}
+}