tweak base64_encode() a bit

src/base64.c

@@ -52,17 +52,6 @@ decode(char *restrict *restrict dest, char *restrict const buf,
 	return 1;
 }
 
-/*
- * Base64-encode *in (size: inlen) into the blob supplied as rblob. If
- * there is insufficient space, it will bail out and return
- * NULL. Otherwise, it will null-terminate and return the blob.
- * The enc argument specifies the alphabet and whether padding is used.
- * Inspired heavily by gnulib/Simon Josefsson (as referenced in RFC4648)
- *
- * XXX: tmp[] and idx are used to ensure the reader (and author) retains
- * XXX: a limited amount of sanity. They are strictly speaking not
- * XXX: necessary, if you don't mind going crazy.
- */
 ssize_t
 base64_encode(const enum encoding enc, char *restrict const buf,
 	      const size_t maxlen, const char *restrict const inbuf,
@@ -71,68 +60,46 @@ base64_encode(const enum encoding enc, char *restrict const buf,
 	const struct b64_alphabet *alpha = &b64_alphabet[enc];
 	char *p = buf;
 	const char *in = inbuf;
-	size_t outlen = maxlen, inlen = inlength;
-	unsigned char tmp[3], idx;
 
 	AN(buf);
 	AN(alpha);
-	if (in == NULL || inlen == 0)
+	if (in == NULL || inlength == 0)
 		return 0;
-	if ((enc != BASE64URLNOPAD && outlen < base64_encode_l(inlen))
-	    || outlen < base64nopad_encode_l(inlen))
+	if ((enc != BASE64URLNOPAD && maxlen < base64_encode_l(inlength))
+	    || maxlen < base64nopad_encode_l(inlength))
 		return -1;
 
-	while (1) {
-		assert(inlen);
-		assert(outlen > 3);
+	while (in < inbuf + inlength) {
+		unsigned char *tmp, idx;
+		size_t rest = (inbuf + inlength) - in;
 
-		tmp[0] = (unsigned char) in[0];
-		tmp[1] = (unsigned char) in[1];
-		tmp[2] = (unsigned char) in[2];
+		tmp = (unsigned char *) in;
 
 		*p++ = alpha->b64[(tmp[0] >> 2) & 0x3f];
 
 		idx = (tmp[0] << 4);
-		if (inlen > 1)
+		if (rest > 1)
 			idx += (tmp[1] >> 4);
-		idx &= 0x3f;
-		*p++ = alpha->b64[idx];
+		*p++ = alpha->b64[idx & 0x3f];
 
-		if (inlen > 1) {
+		if (rest > 1) {
 			idx = (tmp[1] << 2);
-			if (inlen > 2)
+			if (rest > 2)
 				idx += tmp[2] >> 6;
-			idx &= 0x3f;
-
-			*p++ = alpha->b64[idx];
-		} else {
-			if (alpha->padding)
-				*p++ = alpha->padding;
+			*p++ = alpha->b64[idx & 0x3f];
 		}
+		else if (alpha->padding)
+			*p++ = alpha->padding;
 
-		if (inlen > 2) {
+		if (rest > 2)
 			*p++ = alpha->b64[tmp[2] & 0x3f];
-		} else {
-			if (alpha->padding)
-				*p++ = alpha->padding;
-		}
-
-		/*
-		 * XXX: Only consume 4 bytes, but since we need a fifth for
-		 * XXX: NULL later on, we might as well test here.
-		 */
-		assert(outlen >= 5);
-
-		outlen -= 4;
-
-		if (inlen < 4)
-			break;
+		else if (alpha->padding)
+			*p++ = alpha->padding;
 
-		inlen -= 3;
 		in += 3;
 	}
 
-	assert(outlen > 0);
+	assert(p >= buf && p - buf <= maxlen);
 	return p - buf;
 }
 

src/base64.h

@@ -32,7 +32,7 @@
 #define PAD -2
 
 static const struct b64_alphabet {
-	const char *b64;
+	const char b64[64];
 	const int8_t i64[256];
 	const int padding;
 } b64_alphabet[] = {
@@ -46,7 +46,7 @@ static const struct b64_alphabet {
 			ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL,
 			ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL,
 			ILL, ILL, ILL,  62, ILL, ILL, ILL,  63, /* +, -    */
-			 52,  53,  54,  55,  56,  57,  58,  59, /* 0 -7    */
+			 52,  53,  54,  55,  56,  57,  58,  59, /* 0 - 7   */
 			 60,  61, ILL, ILL, ILL, PAD, ILL, ILL, /* 8, 9, = */ 
 			ILL,   0,   1,   2,   3,   4,   5,   6, /* A - G   */
 			  7,   8,   9,  10,  11,  12,  13,  14, /* H - O   */
@@ -85,7 +85,7 @@ static const struct b64_alphabet {
 			ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL,
 			ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL,
 			ILL, ILL, ILL, ILL, ILL,  62, ILL, ILL, /* -       */
-			 52,  53,  54,  55,  56,  57,  58,  59, /* 0 -7    */
+			 52,  53,  54,  55,  56,  57,  58,  59, /* 0 - 7   */
 			 60,  61, ILL, ILL, ILL, PAD, ILL, ILL, /* 8, 9, = */ 
 			ILL,   0,   1,   2,   3,   4,   5,   6, /* A - G   */
 			  7,   8,   9,  10,  11,  12,  13,  14, /* H - O   */
@@ -124,7 +124,7 @@ static const struct b64_alphabet {
 			ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL,
 			ILL, ILL, ILL, ILL, ILL, ILL, ILL, ILL,
 			ILL, ILL, ILL, ILL, ILL,  62, ILL, ILL, /* -       */
-			 52,  53,  54,  55,  56,  57,  58,  59, /* 0 -7    */
+			 52,  53,  54,  55,  56,  57,  58,  59, /* 0 - 7   */
 			 60,  61, ILL, ILL, ILL, ILL, ILL, ILL, /* 8, 9    */ 
 			ILL,   0,   1,   2,   3,   4,   5,   6, /* A - G   */
 			  7,   8,   9,  10,  11,  12,  13,  14, /* H - O   */