common: Add z-base-32 encoder.

* common/zb32.c: New.
* common/t-zb32.c: New.
* common/Makefile.am (common_sources): Add zb82.c
--
(cherry picked from commit b8a91ebf46a927801866e99bb5a66ab00651424e)

Resolved conflicts:
	common/Makefile.am

common/Makefile.am

@@ -52,6 +52,7 @@ common_sources = \
 	gettime.c \
 	yesno.c \
 	b64enc.c b64dec.c \
+	zb32.c \
 	convert.c \
 	percent.c \
 	miscellaneous.c \

common/util.h

@@ -182,6 +182,8 @@ gpg_error_t b64dec_proc (struct b64state *state, void *buffer, size_t length,
 gpg_error_t b64dec_finish (struct b64state *state);
 
 
+/*-- zb32.c --*/
+char *zb32_encode (const void *data, unsigned int databits);
 
 
 /*-- sexputil.c */

common/zb32.c

@@ -0,0 +1,120 @@
+/* zb32.c - z-base-32 functions
+ * Copyright (C) 2014  Werner Koch
+ *
+ * This file is part of GnuPG.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either
+ *
+ *   - the GNU Lesser General Public License as published by the Free
+ *     Software Foundation; either version 3 of the License, or (at
+ *     your option) any later version.
+ *
+ * or
+ *
+ *   - the GNU General Public License as published by the Free
+ *     Software Foundation; either version 2 of the License, or (at
+ *     your option) any later version.
+ *
+ * or both in parallel, as here.
+ *
+ * This file is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+
+#include "util.h"
+
+
+/* Zooko's base32 variant. See RFC-6189 and
+   http://philzimmermann.com/docs/human-oriented-base-32-encoding.txt
+   Caller must xfree the returned string.  Returns NULL and sets ERRNO
+   on error.  To avoid integer overflow DATALEN is limited to 2^16
+   bytes.  Note, that DATABITS is measured in bits!.  */
+char *
+zb32_encode (const void *data, unsigned int databits)
+{
+  static char const zb32asc[32] = {'y','b','n','d','r','f','g','8',
+                                   'e','j','k','m','c','p','q','x',
+                                   'o','t','1','u','w','i','s','z',
+                                   'a','3','4','5','h','7','6','9' };
+  const unsigned char *s;
+  char *output, *d;
+  size_t datalen;
+
+  datalen = (databits + 7) / 8;
+  if (datalen > (1 << 16))
+    {
+      errno = EINVAL;
+      return NULL;
+    }
+
+  d = output = xtrymalloc (8 * (datalen / 5)
+                           + 2 * (datalen % 5)
+                           - ((datalen%5)>2)
+                           + 1);
+  if (!output)
+    return NULL;
+
+  /* I use straightforward code.  The compiler should be able to do a
+     better job on optimization than me and it is easier to read.  */
+  for (s = data; datalen >= 5; s += 5, datalen -= 5)
+    {
+      *d++ = zb32asc[((s[0]      ) >> 3)               ];
+      *d++ = zb32asc[((s[0] &   7) << 2) | (s[1] >> 6) ];
+      *d++ = zb32asc[((s[1] &  63) >> 1)               ];
+      *d++ = zb32asc[((s[1] &   1) << 4) | (s[2] >> 4) ];
+      *d++ = zb32asc[((s[2] &  15) << 1) | (s[3] >> 7) ];
+      *d++ = zb32asc[((s[3] & 127) >> 2)               ];
+      *d++ = zb32asc[((s[3] &   3) << 3) | (s[4] >> 5) ];
+      *d++ = zb32asc[((s[4] &  31)     )               ];
+    }
+
+  switch (datalen)
+    {
+    case 4:
+      *d++ = zb32asc[((s[0]      ) >> 3)               ];
+      *d++ = zb32asc[((s[0] &   7) << 2) | (s[1] >> 6) ];
+      *d++ = zb32asc[((s[1] &  63) >> 1)               ];
+      *d++ = zb32asc[((s[1] &   1) << 4) | (s[2] >> 4) ];
+      *d++ = zb32asc[((s[2] &  15) << 1) | (s[3] >> 7) ];
+      *d++ = zb32asc[((s[3] & 127) >> 2)               ];
+      *d++ = zb32asc[((s[3] &   3) << 3)               ];
+      break;
+    case 3:
+      *d++ = zb32asc[((s[0]      ) >> 3)               ];
+      *d++ = zb32asc[((s[0] &   7) << 2) | (s[1] >> 6) ];
+      *d++ = zb32asc[((s[1] &  63) >> 1)               ];
+      *d++ = zb32asc[((s[1] &   1) << 4) | (s[2] >> 4) ];
+      *d++ = zb32asc[((s[2] &  15) << 1)               ];
+      break;
+    case 2:
+      *d++ = zb32asc[((s[0]      ) >> 3)               ];
+      *d++ = zb32asc[((s[0] &   7) << 2) | (s[1] >> 6) ];
+      *d++ = zb32asc[((s[1] &  63) >> 1)               ];
+      *d++ = zb32asc[((s[1] &   1) << 4)               ];
+      break;
+    case 1:
+      *d++ = zb32asc[((s[0]      ) >> 3)               ];
+      *d++ = zb32asc[((s[0] &   7) << 2)               ];
+      break;
+    default:
+      break;
+    }
+  *d = 0;
+
+  /* Need to strip some bytes if not a multiple of 40.  */
+  output[(databits + 5 - 1) / 5] = 0;
+  return output;
+}