set ENOMEM consistently (I hope everywhere)

src/hex.c

@@ -84,8 +84,10 @@ hex_encode(const enum encoding enc, char *restrict const buf,
 	assert(enc == HEXUC || enc == HEXLC);
 	if (in == NULL || inlen == 0)
 		return 0;
-	if (buflen < hex_encode_l(inlen))
+	if (buflen < hex_encode_l(inlen)) {
+		errno = ENOMEM;
 		return -1;
+	}
 
 	if (enc != HEXLC)
 		alphabet = hex_alphabet[1];

src/id.c

@@ -55,8 +55,10 @@ id_encode(const enum encoding enc, char *restrict const buf,
 	(void) enc;
 	AN(buf);
 
-	if (buflen < inlen + 1)
+	if (buflen < inlen + 1) {
+		errno = ENOMEM;
 		return -1;
+	}
 	if (in == NULL || inlen == 0)
 		return 0;
 

src/url.c

@@ -95,13 +95,17 @@ url_encode(const enum encoding enc, char *restrict const buf,
 
 	for (int i = 0; i < inlen; i++) {
 		if (isunreserved(in[i])) {
-			if (p == end)
+			if (p == end) {
+				errno = ENOMEM;
 				return -1;
+			}
 			*p++ = in[i];
 		}
 		else {
-			if (p + 3 > end)
+			if (p + 3 > end) {
+				errno = ENOMEM;
 				return -1;
+			}
 			*p++ = '%';
 			*p++ = alphabet[(in[i] & 0xf0) >> 4];
 			*p++ = alphabet[in[i] & 0x0f];