MINOR: standard: add function "encode_chunk"

This function has the same behavior as encode_string(), except it
takes a "struct chunk" instead of a "char *" on input.

include/common/standard.h

@@ -29,6 +29,7 @@
 #include <sys/socket.h>
 #include <sys/un.h>
 #include <netinet/in.h>
+#include <common/chunk.h>
 #include <common/config.h>
 #include <eb32tree.h>
 
@@ -282,6 +283,14 @@ char *encode_string(char *start, char *stop,
 		    const char escape, const fd_set *map,
 		    const char *string);
 
+/*
+ * Same behavior, except that it encodes chunk <chunk> instead of a string.
+ */
+char *encode_chunk(char *start, char *stop,
+                   const char escape, const fd_set *map,
+                   const struct chunk *chunk);
+
+
 /* Decode an URL-encoded string in-place. The resulting string might
  * be shorter. If some forbidden characters are found, the conversion is
  * aborted, the string is truncated before the issue and non-zero is returned,

src/standard.c

@@ -21,6 +21,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 
+#include <common/chunk.h>
 #include <common/config.h>
 #include <common/standard.h>
 #include <eb32tree.h>
@@ -1045,6 +1046,36 @@ char *encode_string(char *start, char *stop,
 	return start;
 }
 
+/*
+ * Same behavior as encode_string() above, except that it encodes chunk
+ * <chunk> instead of a string.
+ */
+char *encode_chunk(char *start, char *stop,
+		    const char escape, const fd_set *map,
+		    const struct chunk *chunk)
+{
+	char *str = chunk->str;
+	char *end = chunk->str + chunk->len;
+
+	if (start < stop) {
+		stop--; /* reserve one byte for the final '\0' */
+		while (start < stop && str < end) {
+			if (!FD_ISSET((unsigned char)(*str), map))
+				*start++ = *str;
+			else {
+				if (start + 3 >= stop)
+					break;
+				*start++ = escape;
+				*start++ = hextab[(*str >> 4) & 15];
+				*start++ = hextab[*str & 15];
+			}
+			str++;
+		}
+		*start = '\0';
+	}
+	return start;
+}
+
 /* Decode an URL-encoded string in-place. The resulting string might
  * be shorter. If some forbidden characters are found, the conversion is
  * aborted, the string is truncated before the issue and a negative value is