cmd/internal: remove duplicate pathToPrefix function

goobj.importPathToPrefix is 3x faster than gc.pathToPrefix so rename and
move it to cmd/internal/objabi which is already imported by both goobj and
gc.

Change-Id: I10eda5bce95ef6d5d888818c5c47258c2833ea45
Reviewed-on: https://go-review.googlesource.com/40875
Run-TryBot: Todd Neal <todd@tneal.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

2 files changed, 74 insertions, 0 deletions

diff --git a/src/cmd/internal/objabi/path.go b/src/cmd/internal/objabi/path.go
new file mode 100644
index 0000000000..2a42179a36
--- /dev/null
+++ b/src/cmd/internal/objabi/path.go
@@ -0,0 +1,41 @@
+// Copyright 2017 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 objabi
+
+import "strings"
+
+// PathToPrefix converts raw string to the prefix that will be used in the
+// symbol table. All control characters, space, '%' and '"', as well as
+// non-7-bit clean bytes turn into %xx. The period needs escaping only in the
+// last segment of the path, and it makes for happier users if we escape that as
+// little as possible.
+func PathToPrefix(s string) string {
+	slash := strings.LastIndex(s, "/")
+	// check for chars that need escaping
+	n := 0
+	for r := 0; r < len(s); r++ {
+		if c := s[r]; c <= ' ' || (c == '.' && r > slash) || c == '%' || c == '"' || c >= 0x7F {
+			n++
+		}
+	}
+
+	// quick exit
+	if n == 0 {
+		return s
+	}
+
+	// escape
+	const hex = "0123456789abcdef"
+	p := make([]byte, 0, len(s)+2*n)
+	for r := 0; r < len(s); r++ {
+		if c := s[r]; c <= ' ' || (c == '.' && r > slash) || c == '%' || c == '"' || c >= 0x7F {
+			p = append(p, '%', hex[c>>4], hex[c&0xF])
+		} else {
+			p = append(p, c)
+		}
+	}
+
+	return string(p)
+}
diff --git a/src/cmd/internal/objabi/path_test.go b/src/cmd/internal/objabi/path_test.go
new file mode 100644
index 0000000000..05d7fb436e
--- /dev/null
+++ b/src/cmd/internal/objabi/path_test.go
@@ -0,0 +1,33 @@
+// Copyright 2017 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 objabi
+
+import "testing"
+
+func TestPathToPrefix(t *testing.T) {
+	tests := []struct {
+		Path     string
+		Expected string
+	}{{"foo/bar/v1", "foo/bar/v1"},
+		{"foo/bar/v.1", "foo/bar/v%2e1"},
+		{"f.o.o/b.a.r/v1", "f.o.o/b.a.r/v1"},
+		{"f.o.o/b.a.r/v.1", "f.o.o/b.a.r/v%2e1"},
+		{"f.o.o/b.a.r/v..1", "f.o.o/b.a.r/v%2e%2e1"},
+		{"f.o.o/b.a.r/v..1.", "f.o.o/b.a.r/v%2e%2e1%2e"},
+		{"f.o.o/b.a.r/v%1", "f.o.o/b.a.r/v%251"},
+		{"runtime", "runtime"},
+		{"sync/atomic", "sync/atomic"},
+		{"golang.org/x/tools/godoc", "golang.org/x/tools/godoc"},
+		{"foo.bar/baz.quux", "foo.bar/baz%2equux"},
+		{"", ""},
+		{"%foo%bar", "%25foo%25bar"},
+		{"\x01\x00\x7F☺", "%01%00%7f%e2%98%ba"},
+	}
+	for _, tc := range tests {
+		if got := PathToPrefix(tc.Path); got != tc.Expected {
+			t.Errorf("expected PathToPrefix(%s) = %s, got %s", tc.Path, tc.Expected, got)
+		}
+	}
+}