.

t/neo/storage/fs1/cmd/fstail/xstrconv.go

@@ -10,18 +10,21 @@ import (
 	"lab.nexedi.com/kirr/go123/mem"
 )
 
+
+const hex = "0123456789abcdef"
+
 // pyQuote quotes string the way python repr(str) would do
 func pyQuote(s string) string {
 	out := pyQuoteBytes(mem.Bytes(s))
 	return mem.String(out)
 }
 
-
-const hex = "0123456789abcdef"
-
 func pyQuoteBytes(b []byte) []byte {
 	buf := make([]byte, 0, (len(b) + 2) /* to reduce allocations when quoting */ * 2)
+	return pyAppendQuoteBytes(buf, b)
+}
 
+func pyAppendQuoteBytes(buf, b []byte) []byte {
 	// smartquotes: choose ' or " as quoting character
 	// https://github.com/python/cpython/blob/v2.7.13-116-g1aa1803b3d/Objects/stringobject.c#L947
 	quote := byte('\'')
@@ -58,16 +61,19 @@ func pyQuoteBytes(b []byte) []byte {
 				// we already converted to \<letter> what python represents as such above
 				buf = append(buf, '\\', 'x', hex[b[0]>>4], hex[b[0]&0xf])
 
+			case r < utf8.RuneSelf /* RuneSelf itself is not printable */ - 1:
+				// we already escaped all < RuneSelf runes
+				buf = append(buf, byte(r))
+
 			case strconv.IsPrint(r):
-				// shortcut to avoid calling QuoteRune
+				// printable utf-8 characters go as is
 				buf = append(buf, b[:size]...)
 
 			default:
-				// we already handled ', " and (< ' ') above, so now it
-				// should be safe to reuse strconv.QuoteRune
-				rq := strconv.QuoteRune(r)	// "'\x01'"
-				rq = rq[1:len(rq)-1]		//  "\x01"
-				buf = append(buf, rq...)
+				// everything else goes in numeric byte escapes
+				for i := 0; i < size; i++ {
+					buf = append(buf, '\\', 'x', hex[b[i]>>4], hex[b[i]&0xf])
+				}
 			}
 		}
 

t/neo/storage/fs1/cmd/fstail/xstrconv_test.go

@@ -4,6 +4,8 @@ package main
 
 import (
 	"testing"
+
+	"lab.nexedi.com/kirr/go123/mem"
 )
 
 // byterange returns []byte with element [start,stop)
@@ -39,21 +41,27 @@ var pyQuoteTestv = []struct {in, quoted string} {
 
 	// invalid utf-8
 	{"\xd0a", `'\xd0a'`},
+
+	// non-printable utf-8
+	{"\u007f\u0080\u0081\u0082\u0083\u0084\u0085\u0086\u0087", `'\x7f\xc2\x80\xc2\x81\xc2\x82\xc2\x83\xc2\x84\xc2\x85\xc2\x86\xc2\x87'`},
 }
 
 func TestPyQuote(t *testing.T) {
 	for _, tt := range pyQuoteTestv {
 		quoted := pyQuote(tt.in)
 		if quoted != tt.quoted {
-			t.Errorf("pyQuote(%q) -> %s  ; want %s", tt.in, quoted, tt.quoted)
+			t.Errorf("pyQuote(%q) ->\nhave: %s\nwant: %s", tt.in, quoted, tt.quoted)
 		}
 	}
 }
 
 func BenchmarkPyQuote(b *testing.B) {
+	buf := []byte{}
+
 	for i := 0; i < b.N; i++ {
 		for _, tt := range pyQuoteTestv {
-			pyQuote(tt.in)
+			buf = buf[:0]
+			buf = pyAppendQuoteBytes(buf, mem.Bytes(tt.in))
 		}
 	}
 }