start moving code to the library, and add error codes

lib/error.c

@@ -0,0 +1,95 @@
+ /*
+ * Copyright (c) 2014 Yubico AB
+ * All rights reserved.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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/>.
+ *
+ * Additional permission under GNU GPL version 3 section 7
+ *
+ * If you modify this program, or any covered work, by linking or
+ * combining it with the OpenSSL project's OpenSSL library (or a
+ * modified version of that library), containing parts covered by the
+ * terms of the OpenSSL or SSLeay licenses, We grant you additional 
+ * permission to convey the resulting work. Corresponding Source for a
+ * non-source form of such a combination shall include the source code
+ * for the parts of OpenSSL used as well as that of the covered work.
+ *
+ */
+
+#include "ykpiv.h"
+
+#include <stddef.h>
+
+#define ERR(name, desc) { name, #name, desc }
+
+typedef struct
+{
+  ykpiv_rc rc;
+  const char *name;
+  const char *description;
+} err_t;
+
+static const err_t errors[] = {
+  ERR (YKPIV_OK, "Successful return"),
+  ERR (YKPIV_MEMORY_ERROR, "Error allocating memory"),
+  ERR (YKPIV_PCSC_ERROR, "Error in PCSC call"),
+};
+
+/**
+ * ykpiv_strerror:
+ * @err: error code
+ *
+ * Convert return code to human readable string explanation of the
+ * reason for the particular error code.
+ *
+ * This string can be used to output a diagnostic message to the user.
+ *
+ * Return value: Returns a pointer to a statically allocated string
+ *   containing an explanation of the error code @err.
+ **/
+const char *ykpiv_strerror(ykpiv_rc err) {
+  static const char *unknown = "Unknown ykpiv error";
+  const char *p;
+
+  if (-err < 0 || -err >= (int) (sizeof (errors) / sizeof (errors[0])))
+    return unknown;
+
+  p = errors[-err].description;
+  if (!p)
+    p = unknown;
+
+  return p;
+}
+
+
+/**
+ * ykpiv_strerror_name:
+ * @err: error code
+ *
+ * Convert return code to human readable string representing the error
+ * code symbol itself.  For example, ykpiv_strerror_name(%YKPIV_OK)
+ * returns the string "YKPIV_OK".
+ *
+ * This string can be used to output a diagnostic message to the user.
+ *
+ * Return value: Returns a pointer to a statically allocated string
+ *   containing a string version of the error code @err, or NULL if
+ *   the error code is not known.
+ **/
+const char *ykpiv_strerror_name(ykpiv_rc err) {
+  if (-err < 0 || -err >= (int) (sizeof (errors) / sizeof (errors[0])))
+    return NULL;
+
+  return errors[-err].name;
+}