archive/tar: simplify toASCII and parseString

Use a simple []byte instead of bytes.Buffer to create a string.
Use bytes.IndexByte instead of our own for loop.

Change-Id: Ic4a1161d79017fd3af086a05c53d5f20a5f09326
Reviewed-on: https://go-review.googlesource.com/54752
Reviewed-by: Avelino <t@avelino.xxx>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Joe Tsai <thebrokentoaster@gmail.com>

diff --git a/src/archive/tar/strconv.go b/src/archive/tar/strconv.go
index 929770c25c4575775e2e261025f11a38803e1d2b..16d060c231ea9c06a59075e8b054ca9d6101bef8 100644 (file)
--- a/src/archive/tar/strconv.go
+++ b/src/archive/tar/strconv.go
@@ -27,13 +27,13 @@ func toASCII(s string) string {
        if isASCII(s) {
                return s
        }
-       var buf bytes.Buffer
+       b := make([]byte, 0, len(s))
        for _, c := range s {
                if c < 0x80 && c != 0x00 {
-                       buf.WriteByte(byte(c))
+                       b = append(b, byte(c))
                }
        }
-       return buf.String()
+       return string(b)
 }
 
 type parser struct {
@@ -47,11 +47,10 @@ type formatter struct {
 // parseString parses bytes as a NUL-terminated C-style string.
 // If a NUL byte is not found then the whole slice is returned as a string.
 func (*parser) parseString(b []byte) string {
-       n := 0
-       for n < len(b) && b[n] != 0 {
-               n++
+       if i := bytes.IndexByte(b, 0); i >= 0 {
+               return string(b[:i])
        }
-       return string(b[0:n])
+       return string(b)
 }
 
 // Write s into b, terminating it with a NUL if there is room.
@@ -75,7 +74,7 @@ func (f *formatter) formatString(b []byte, s string) {
 // that the first byte can only be either 0x80 or 0xff. Thus, the first byte is
 // equivalent to the sign bit in two's complement form.
 func fitsInBase256(n int, x int64) bool {
-       var binBits = uint(n-1) * 8
+       binBits := uint(n-1) * 8
        return n >= 9 || (x >= -1<<binBits && x < 1<<binBits)
 }