Improve .debug_line parser performance

dwarf/line/line_parser.go

@@ -50,20 +50,17 @@ func Parse(data []byte) *DebugLineInfo {
 func parseDebugLinePrologue(dbl *DebugLineInfo, buf *bytes.Buffer) {
 	p := &DebugLinePrologue{}
 
-	binary.Read(buf, binary.LittleEndian, &p.Length)
+	p.Length = binary.LittleEndian.Uint32(buf.Next(4))
-	binary.Read(buf, binary.LittleEndian, &p.Version)
+	p.Version = binary.LittleEndian.Uint16(buf.Next(2))
-	binary.Read(buf, binary.LittleEndian, &p.PrologueLength)
+	p.PrologueLength = binary.LittleEndian.Uint32(buf.Next(4))
-	binary.Read(buf, binary.LittleEndian, &p.MinInstrLength)
+	p.MinInstrLength = uint8(buf.Next(1)[0])
-	binary.Read(buf, binary.LittleEndian, &p.InitialIsStmt)
+	p.InitialIsStmt = uint8(buf.Next(1)[0])
-	binary.Read(buf, binary.LittleEndian, &p.LineBase)
+	p.LineBase = int8(buf.Next(1)[0])
-	binary.Read(buf, binary.LittleEndian, &p.LineRange)
+	p.LineRange = uint8(buf.Next(1)[0])
-	binary.Read(buf, binary.LittleEndian, &p.OpcodeBase)
+	p.OpcodeBase = uint8(buf.Next(1)[0])
-	binary.Read(buf, binary.LittleEndian, &p.StdOpLengths)
 
 	p.StdOpLengths = make([]uint8, p.OpcodeBase-1)
-	for i := uint8(0); i < p.OpcodeBase-1; i++ {
+	binary.Read(buf, binary.LittleEndian, &p.StdOpLengths)
-		binary.Read(buf, binary.LittleEndian, &p.StdOpLengths[i])
-	}
 
 	dbl.Prologue = p
 }

dwarf/line/line_parser_test.go

@@ -6,6 +6,8 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+
+	"github.com/davecheney/profile"
 )
 
 func grabDebugLineSection(fp string, t *testing.T) []byte {
@@ -91,3 +93,13 @@ func TestDebugLinePrologueParser(t *testing.T) {
 		t.Fatal("First entry not parsed correctly")
 	}
 }
+
+func BenchmarkLineParser(b *testing.B) {
+	defer profile.Start(profile.MemProfile).Stop()
+	data := grabDebugLineSection("../../_fixtures/testnextprog", nil)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = Parse(data)
+	}
+}

dwarf/util/util.go

@@ -1,9 +1,6 @@
 package util
 
-import (
+import "bytes"
-	"bytes"
-	"unicode/utf8"
-)
 
 // DecodeULEB128 decodes an unsigned Little Endian Base 128
 // represented number.
@@ -67,36 +64,10 @@ func DecodeSLEB128(buf *bytes.Buffer) (int64, uint32) {
 }
 
 func ParseString(data *bytes.Buffer) (string, uint32) {
-	var (
+	str, err := data.ReadString(0x0)
-		size uint32
+	if err != nil {
-		str  []rune
+		panic("Could not parse string")
-		strb []byte
-	)
-
-	for {
-		b, err := data.ReadByte()
-		if err != nil {
-			panic("parseString(): Could not read byte")
-		}
-		size++
-
-		if b == 0x0 {
-			if size == 1 {
-				return "", size
-			}
-
-			break
-		}
-
-		strb = append(strb, b)
-
-		if utf8.FullRune(strb) {
-			r, _ := utf8.DecodeRune(strb)
-			str = append(str, r)
-			size++
-			strb = strb[0:0]
-		}
 	}
 
-	return string(str), size
+	return str[:len(str)-1], uint32(len(str))
 }

dwarf/util/util_test.go

@@ -32,6 +32,6 @@ func TestParseString(t *testing.T) {
 	str, _ := ParseString(bstr)
 
 	if str != "hi" {
-		t.Fatal("String was not parsed correctly")
+		t.Fatalf("String was not parsed correctly %#v", str)
 	}
 }