FIX: do not pad output when used enbase/url

resolves: Oldes/Rebol-issues#2548

Author: Oldes

src/core/f-enbase.c

@@ -973,15 +973,25 @@ static REBU64 base36_powers[BASE36_LENGTH] = {
 	}
 
 	if ((len % 3) != 0) {
-		p[2] = p[3] = '=';
-		*p++ = table[src[x] >> 2];
-		if ((len - x) >= 1)
-			*p++ = table[((src[x] & 0x3) << 4) + ((len - x) == 1 ? 0 : src[x + 1] >> 4)];
-		else p++;
-		if ((len - x) == 2)
-			*p++ = table[(src[x + 1] & 0xF) << 2];
-		else p++;
-		p++;
+		if (urlSafe) {
+			// no padding
+			*p++ = table[src[x] >> 2];
+			if ((len - x) >= 1)
+				*p++ = table[((src[x] & 0x3) << 4) + ((len - x) == 1 ? 0 : src[x + 1] >> 4)];
+			if ((len - x) == 2)
+				*p++ = table[(src[x + 1] & 0xF) << 2];
+		}
+		else {
+			p[2] = p[3] = '=';
+			*p++ = table[src[x] >> 2];
+			if ((len - x) >= 1)
+				*p++ = table[((src[x] & 0x3) << 4) + ((len - x) == 1 ? 0 : src[x + 1] >> 4)];
+			else p++;
+			if ((len - x) == 2)
+				*p++ = table[(src[x + 1] & 0xF) << 2];
+			else p++;
+			p++;
+		}
 	}
 
 	//if (*(p-1) != LF && x > 49 && brk) *p++ = LF; // adds LF before closing bracket

src/tests/units/enbase-test.r3

@@ -107,14 +107,25 @@ AAACAAIAAAMDCCGTADs=}
 		} 64]
 	--test-- "debase 64 url 3"
 		key1: "qL8R4QIcQ_ZsRqOAbeRfcZhilN_MksRtDaErMA=="
+		key2: "qL8R4QIcQ_ZsRqOAbeRfcZhilN_MksRtDaErMA"
 		bin: try [debase/url key1 64]
-		--assert true? all [binary? bin key1 = enbase/url bin 64]
+		--assert true? all [binary? bin key2 = enbase/url bin 64]
 		;debase is working also when input is missing the padding
-		key2: "qL8R4QIcQ_ZsRqOAbeRfcZhilN_MksRtDaErMA"
 		--assert bin = try [debase/url key2 64]
 
 ===end-group===
 
+
+===start-group=== "enbase 64 - safe URL variant"
+	--test "enbase/url"
+	;@@ https://github.com/Oldes/Rebol-issues/issues/2548
+	--assert "YQ==" == enbase "a" 64
+	--assert "YWE=" == enbase "aa" 64
+	--assert "YQ"   == enbase/url "a" 64
+	--assert "YWE"  == enbase/url "aa" 64
+===end-group===
+
+
 ===start-group=== "debase 16"
 
 	--test-- "debase 16 1"