cmd/objdump: copy gosym.PCValue into internal package

... so we don't have to export gosym.PCValue.

Change-Id: Ie8f196d5e5ab63e3e69d1d7b4bfbbf32b7b5e4f5
Reviewed-on: https://go-review.googlesource.com/33791
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

api/go1.8.txt

@@ -155,7 +155,6 @@ pkg database/sql, type IsolationLevel int
 pkg database/sql, type NamedArg struct
 pkg database/sql, type NamedArg struct, Name string
 pkg database/sql, type NamedArg struct, Value interface{}
-pkg debug/gosym, func PCValue([]uint8, uint64, int) int
 pkg debug/pe, method (*COFFSymbol) FullName(StringTable) (string, error)
 pkg debug/pe, method (StringTable) String(uint32) (string, error)
 pkg debug/pe, type File struct, COFFSymbols []COFFSymbol

src/cmd/internal/objfile/goobj.go

@@ -114,14 +114,14 @@ func (f *goobjFile) PCToLine(pc uint64) (string, int, *gosym.Func) {
 		if err != nil {
 			return "", 0, nil
 		}
-		fileID := gosym.PCValue(pcfile, pc-uint64(s.Data.Offset), arch.MinLC)
+		fileID := int(pcValue(pcfile, pc-uint64(s.Data.Offset), arch))
 		fileName := s.Func.File[fileID]
 		pcline := make([]byte, s.Func.PCLine.Size)
 		_, err = f.f.ReadAt(pcline, s.Func.PCLine.Offset)
 		if err != nil {
 			return "", 0, nil
 		}
-		line := gosym.PCValue(pcline, pc-uint64(s.Data.Offset), arch.MinLC)
+		line := int(pcValue(pcline, pc-uint64(s.Data.Offset), arch))
 		// Note: we provide only the name in the Func structure.
 		// We could provide more if needed.
 		return fileName, line, &gosym.Func{Sym: &gosym.Sym{Name: s.Name}}
@@ -129,6 +129,53 @@ func (f *goobjFile) PCToLine(pc uint64) (string, int, *gosym.Func) {
 	return "", 0, nil
 }
 
+// pcValue looks up the given PC in a pc value table. target is the
+// offset of the pc from the entry point.
+func pcValue(tab []byte, target uint64, arch *sys.Arch) int32 {
+	val := int32(-1)
+	var pc uint64
+	for step(&tab, &pc, &val, pc == 0, arch) {
+		if target < pc {
+			return val
+		}
+	}
+	return -1
+}
+
+// step advances to the next pc, value pair in the encoded table.
+func step(p *[]byte, pc *uint64, val *int32, first bool, arch *sys.Arch) bool {
+	uvdelta := readvarint(p)
+	if uvdelta == 0 && !first {
+		return false
+	}
+	if uvdelta&1 != 0 {
+		uvdelta = ^(uvdelta >> 1)
+	} else {
+		uvdelta >>= 1
+	}
+	vdelta := int32(uvdelta)
+	pcdelta := readvarint(p) * uint32(arch.MinLC)
+	*pc += uint64(pcdelta)
+	*val += vdelta
+	return true
+}
+
+// readvarint reads, removes, and returns a varint from *p.
+func readvarint(p *[]byte) uint32 {
+	var v, shift uint32
+	s := *p
+	for shift = 0; ; shift += 7 {
+		b := s[0]
+		s = s[1:]
+		v |= (uint32(b) & 0x7F) << shift
+		if b&0x80 == 0 {
+			break
+		}
+	}
+	*p = s
+	return v
+}
+
 // We treat the whole object file as the text section.
 func (f *goobjFile) text() (textStart uint64, text []byte, err error) {
 	var info os.FileInfo

src/debug/gosym/pclntab.go

@@ -291,13 +291,6 @@ func (t *LineTable) step(p *[]byte, pc *uint64, val *int32, first bool) bool {
 	return true
 }
 
-// PCValue looks up the given PC in a pc value table. target is the
-// offset of the pc from the entry point.
-func PCValue(tab []byte, target uint64, quantum int) int {
-	t := LineTable{Data: tab, quantum: uint32(quantum)}
-	return int(t.pcvalue(0, 0, target))
-}
-
 // pcvalue reports the value associated with the target pc.
 // off is the offset to the beginning of the pc-value table,
 // and entry is the start PC for the corresponding function.