Support username and password authentication when talking to HTTP

proxies.

[originally from svn r1971]

misc.c

@@ -50,6 +50,35 @@ char *dupcat(char *s1, ...)
     return p;
 }
 
+/* ----------------------------------------------------------------------
+ * Base64 encoding routine. This is required in public-key writing
+ * but also in HTTP proxy handling, so it's centralised here.
+ */
+
+void base64_encode_atom(unsigned char *data, int n, char *out)
+{
+    static const char base64_chars[] =
+	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+    unsigned word;
+
+    word = data[0] << 16;
+    if (n > 1)
+	word |= data[1] << 8;
+    if (n > 2)
+	word |= data[2];
+    out[0] = base64_chars[(word >> 18) & 0x3F];
+    out[1] = base64_chars[(word >> 12) & 0x3F];
+    if (n > 1)
+	out[2] = base64_chars[(word >> 6) & 0x3F];
+    else
+	out[2] = '=';
+    if (n > 2)
+	out[3] = base64_chars[word & 0x3F];
+    else
+	out[3] = '=';
+}
+
 /* ----------------------------------------------------------------------
  * Generic routines to deal with send buffers: a linked list of
  * smallish blocks, with the operations