1 files changed, 134 insertions, 0 deletions
diff --git a/src/debug/dwarf/unit.go b/src/debug/dwarf/unit.go
new file mode 100644
index 0000000..9b3d6e9
--- /dev/null
+++ b/src/debug/dwarf/unit.go
@@ -0,0 +1,134 @@
+// 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 dwarf
+
+import (
+	"sort"
+	"strconv"
+)
+
+// DWARF debug info is split into a sequence of compilation units.
+// Each unit has its own abbreviation table and address size.
+
+type unit struct {
+	base   Offset // byte offset of header within the aggregate info
+	off    Offset // byte offset of data within the aggregate info
+	data   []byte
+	atable abbrevTable
+	asize  int
+	vers   int
+	utype  uint8 // DWARF 5 unit type
+	is64   bool  // True for 64-bit DWARF format
+}
+
+// Implement the dataFormat interface.
+
+func (u *unit) version() int {
+	return u.vers
+}
+
+func (u *unit) dwarf64() (bool, bool) {
+	return u.is64, true
+}
+
+func (u *unit) addrsize() int {
+	return u.asize
+}
+
+func (d *Data) parseUnits() ([]unit, error) {
+	// Count units.
+	nunit := 0
+	b := makeBuf(d, unknownFormat{}, "info", 0, d.info)
+	for len(b.data) > 0 {
+		len, _ := b.unitLength()
+		if len != Offset(uint32(len)) {
+			b.error("unit length overflow")
+			break
+		}
+		b.skip(int(len))
+		if len > 0 {
+			nunit++
+		}
+	}
+	if b.err != nil {
+		return nil, b.err
+	}
+
+	// Again, this time writing them down.
+	b = makeBuf(d, unknownFormat{}, "info", 0, d.info)
+	units := make([]unit, nunit)
+	for i := range units {
+		u := &units[i]
+		u.base = b.off
+		var n Offset
+		for n == 0 {
+			n, u.is64 = b.unitLength()
+		}
+		dataOff := b.off
+		vers := b.uint16()
+		if vers < 2 || vers > 5 {
+			b.error("unsupported DWARF version " + strconv.Itoa(int(vers)))
+			break
+		}
+		u.vers = int(vers)
+		if vers >= 5 {
+			u.utype = b.uint8()
+			u.asize = int(b.uint8())
+		}
+		var abbrevOff uint64
+		if u.is64 {
+			abbrevOff = b.uint64()
+		} else {
+			abbrevOff = uint64(b.uint32())
+		}
+		atable, err := d.parseAbbrev(abbrevOff, u.vers)
+		if err != nil {
+			if b.err == nil {
+				b.err = err
+			}
+			break
+		}
+		u.atable = atable
+		if vers < 5 {
+			u.asize = int(b.uint8())
+		}
+
+		switch u.utype {
+		case utSkeleton, utSplitCompile:
+			b.uint64() // unit ID
+		case utType, utSplitType:
+			b.uint64()  // type signature
+			if u.is64 { // type offset
+				b.uint64()
+			} else {
+				b.uint32()
+			}
+		}
+
+		u.off = b.off
+		u.data = b.bytes(int(n - (b.off - dataOff)))
+	}
+	if b.err != nil {
+		return nil, b.err
+	}
+	return units, nil
+}
+
+// offsetToUnit returns the index of the unit containing offset off.
+// It returns -1 if no unit contains this offset.
+func (d *Data) offsetToUnit(off Offset) int {
+	// Find the unit after off
+	next := sort.Search(len(d.unit), func(i int) bool {
+		return d.unit[i].off > off
+	})
+	if next == 0 {
+		return -1
+	}
+	u := &d.unit[next-1]
+	if u.off <= off && off < u.off+Offset(len(u.data)) {
+		return next - 1
+	}
+	return -1
+}