utf8: add InString routines for decoding in strings

reflect: add InterfaceValue.Get(), remove Empty
strconv: add Quote, CanBackquote
fmt:
	* %q go-quoted " string
	* %#q go-quoted ` string if possible, " string otherwise
	* %x hexadecimal string
	* anywhere a string is okay, *[]byte is okay
	* flags # 0 - + space
	* print value inside interface, not interface itself
	* tests

R=r
DELTA=756  (597 added, 121 deleted, 38 changed)
OCL=19888
CL=19916

4 files changed, 167 insertions, 2 deletions

diff --git a/src/lib/strconv/Makefile b/src/lib/strconv/Makefile
index 399360a936..cf74d58f73 100644
--- a/src/lib/strconv/Makefile
+++ b/src/lib/strconv/Makefile
@@ -33,8 +33,9 @@ coverage: packages
 
 O1=\
 	atoi.$O\
-	decimal.$O\
 	itoa.$O\
+	decimal.$O\
+	quote.$O\
 
 O2=\
 	ftoa.$O\
@@ -45,7 +46,7 @@ O3=\
 strconv.a: a1 a2 a3
 
 a1:	$(O1)
-	$(AR) grc strconv.a atoi.$O decimal.$O itoa.$O
+	$(AR) grc strconv.a atoi.$O itoa.$O decimal.$O quote.$O
 	rm -f $(O1)
 
 a2:	$(O2)
diff --git a/src/lib/strconv/ftoa_test.go b/src/lib/strconv/ftoa_test.go
index 914ecd9e33..643abb0dd4 100644
--- a/src/lib/strconv/ftoa_test.go
+++ b/src/lib/strconv/ftoa_test.go
@@ -25,6 +25,7 @@ var ftests = []Test {
 	Test{ 1, 'g', 5, "1" },
 	Test{ 1, 'g', -1, "1" },
 	Test{ 20, 'g', -1, "20" },
+	Test{ 1234567.8, 'g', -1, "1.2345678e+06" },
 	Test{ 200000, 'g', -1, "200000" },
 	Test{ 2000000, 'g', -1, "2e+06" },
 
diff --git a/src/lib/strconv/quote.go b/src/lib/strconv/quote.go
new file mode 100644
index 0000000000..122af92d72
--- /dev/null
+++ b/src/lib/strconv/quote.go
@@ -0,0 +1,76 @@
+// Copyright 2009 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 strconv
+
+import (
+	"utf8";
+)
+
+const ldigits = "0123456789abcdef"
+const udigits = "0123456789ABCDEF"
+
+export func Quote(s string) string {
+	t := `"`;
+	for i := 0; i < len(s); i++ {
+		switch {
+		case s[i] == '"':
+			t += `\"`;
+		case s[i] == '\\':
+			t += `\\`;
+		case ' ' <= s[i] && s[i] <= '~':
+			t += string(s[i]);
+		case s[i] == '\a':
+			t += `\a`;
+		case s[i] == '\b':
+			t += `\b`;
+		case s[i] == '\f':
+			t += `\f`;
+		case s[i] == '\n':
+			t += `\n`;
+		case s[i] == '\r':
+			t += `\r`;
+		case s[i] == '\t':
+			t += `\t`;
+		case s[i] == '\v':
+			t += `\v`;
+
+		case utf8.FullRuneInString(s, i):
+			r, size := utf8.DecodeRuneInString(s, i);
+			if r == utf8.RuneError && size == 1 {
+				goto EscX;
+			}
+			i += size-1;  // i++ on next iteration
+			if r < 0x10000 {
+				t += `\u`;
+				for j:=uint(0); j<4; j++ {
+					t += string(ldigits[(r>>(12-4*j))&0xF]);
+				}
+			} else {
+				t += `\U`;
+				for j:=uint(0); j<8; j++ {
+					t += string(ldigits[(r>>(28-4*j))&0xF]);
+				}
+			}
+
+		default:
+		EscX:
+			t += `\x`;
+			t += string(ldigits[s[i]>>4]);
+			t += string(ldigits[s[i]&0xF]);
+		}
+	}
+	t += `"`;
+	return t;
+}
+
+export func CanBackquote(s string) bool {
+	for i := 0; i < len(s); i++ {
+		if s[i] < ' ' || s[i] == '`' {
+			return false;
+		}
+	}
+	return true;
+}
+
diff --git a/src/lib/strconv/quote_test.go b/src/lib/strconv/quote_test.go
new file mode 100644
index 0000000000..2c0e98ed52
--- /dev/null
+++ b/src/lib/strconv/quote_test.go
@@ -0,0 +1,87 @@
+// Copyright 2009 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 strconv
+
+import (
+	"strconv";
+	"testing";
+)
+
+type QuoteTest struct {
+	in string;
+	out string;
+}
+
+var quotetests = []QuoteTest {
+	QuoteTest{ "\a\b\f\r\n\t\v", `"\a\b\f\r\n\t\v"` },
+	QuoteTest{ "\\", `"\\"` },
+	QuoteTest{ "abc\xffdef", `"abc\xffdef"` },
+	QuoteTest{ "\u263a", `"\u263a"` },
+	QuoteTest{ "\U0010ffff", `"\U0010ffff"` },
+}
+
+export func TestQuote(t *testing.T) {
+	for i := 0; i < len(quotetests); i++ {
+		tt := quotetests[i];
+		if out := Quote(tt.in); out != tt.out {
+			t.Errorf("Quote(%s) = %s, want %s", tt.in, out, tt.out);
+		}
+	}
+}
+
+type CanBackquoteTest struct {
+	in string;
+	out bool;
+}
+
+var canbackquotetests = []CanBackquoteTest {
+	CanBackquoteTest{ "`", false },
+	CanBackquoteTest{ string(0), false },
+	CanBackquoteTest{ string(1), false },
+	CanBackquoteTest{ string(2), false },
+	CanBackquoteTest{ string(3), false },
+	CanBackquoteTest{ string(4), false },
+	CanBackquoteTest{ string(5), false },
+	CanBackquoteTest{ string(6), false },
+	CanBackquoteTest{ string(7), false },
+	CanBackquoteTest{ string(8), false },
+	CanBackquoteTest{ string(9), false },
+	CanBackquoteTest{ string(10), false },
+	CanBackquoteTest{ string(11), false },
+	CanBackquoteTest{ string(12), false },
+	CanBackquoteTest{ string(13), false },
+	CanBackquoteTest{ string(14), false },
+	CanBackquoteTest{ string(15), false },
+	CanBackquoteTest{ string(16), false },
+	CanBackquoteTest{ string(17), false },
+	CanBackquoteTest{ string(18), false },
+	CanBackquoteTest{ string(19), false },
+	CanBackquoteTest{ string(20), false },
+	CanBackquoteTest{ string(21), false },
+	CanBackquoteTest{ string(22), false },
+	CanBackquoteTest{ string(23), false },
+	CanBackquoteTest{ string(24), false },
+	CanBackquoteTest{ string(25), false },
+	CanBackquoteTest{ string(26), false },
+	CanBackquoteTest{ string(27), false },
+	CanBackquoteTest{ string(28), false },
+	CanBackquoteTest{ string(29), false },
+	CanBackquoteTest{ string(30), false },
+	CanBackquoteTest{ string(31), false },
+	CanBackquoteTest{ `' !"#$%&'()*+,-./:;<=>?@[\]^_{|}~`, true },
+	CanBackquoteTest{ `0123456789`, true },
+	CanBackquoteTest{ `ABCDEFGHIJKLMNOPQRSTUVWXYZ`, true },
+	CanBackquoteTest{ `abcdefghijklmnopqrstuvwxyz`, true },
+	CanBackquoteTest{ `☺`, true },
+}
+
+export func TestCanBackquote(t *testing.T) {
+	for i := 0; i < len(canbackquotetests); i++ {
+		tt := canbackquotetests[i];
+		if out := CanBackquote(tt.in); out != tt.out {
+			t.Errorf("CanBackquote(%q) = %v, want %v", tt.in, out, tt.out);
+		}
+	}
+}