add strerror and variants

Signed-off-by: Mattias Andrée <maandree@operamail.com>

1 files changed, 125 insertions, 0 deletions

diff --git a/src/string/strerror.c b/src/string/strerror.c
new file mode 100644
index 0000000..417d622
--- /dev/null
+++ b/src/string/strerror.c
@@ -0,0 +1,125 @@
+/**
+ * slibc — Yet another C library
+ * Copyright © 2015  Mattias Andrée (maandree@member.fsf.org)
+ * 
+ * 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/>.
+ */
+#include <string.h>
+
+
+/**
+ * Return a textual representation of an error code.
+ * This error code must from `errno`.
+ * 
+ * This implementation of `strerror` cannot fail. however
+ * POSIX specifies that it can fail, any may only set `errno`
+ * if it does fail. You should therefore, set `errno` to
+ * zero before calling this function, and inspect `errno`
+ * when it returns, as there is no reserved return value
+ * that indicates and error.
+ * 
+ * The returned value must not be modified or freed.
+ * 
+ * As a slibc-specific modification, this function is MT-Safe.
+ * 
+ * @param   errnum  The error code.
+ * @return          A description of the error.
+ */
+char* strerror(int errnum)
+{
+  return strerror_l(errnum, CURRENT_LOCALE /* TODO not defined */);
+}
+
+
+/**
+ * Return a textual representation of an error code.
+ * This error code must from `errno`.
+ * 
+ * POSIX specifies `errno` may only be set on failure,
+ * and reserves no return value to indicate such.
+ * You should therefore, set `errno` to zero before calling
+ * this function, and inspect `errno` when it returns.
+ * 
+ * The returned value must not be modified or freed.
+ * 
+ * As a slibc-specific modification, this function is MT-Safe.
+ * 
+ * @param   errnum  The error code.
+ * @param   locale  The locale, must be a valid locale and not
+ *                  `LC_GLOBAL_LOCALE`, lest the behaviour is undefined.
+ * @return          A description of the error.
+ */
+char* strerror_l(int errnum, locale_t locale)
+{
+  /* TODO implement strerror_l */
+  return (void) errnum, (void) locale, NULL:
+}
+
+
+/**
+ * Reenterant variant of `stderror`.
+ * 
+ * This is an XSI-compliant extension. However the name
+ * is not part of the XSI specification, `strerror_r`
+ * should be used. It is defined to this function if
+ * `(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && !_GNU_SOURCE`.
+ * 
+ * @param   errnum  The error code.
+ * @param   buf     Buffer where the description shall be stored.
+ * @param   buflen  The allocation size of `buf`.
+ * @return          Zero on success, value for `errno` on error
+ * 
+ * @throws  ERANGE  `buf` was too small to store the description.
+ */
+int __xsi_strerror_r(int errnum, char* buf, size_t buflen)
+{
+  char* description = strerror(errnum);
+  size_t length = strlen(description);
+  
+  if (buflen == 0)
+    return ERANGE;
+  
+  if (buflen <= length)
+    {
+      memcpy(buf, description, buflen - 1);
+      buf[buflen - 1] = 0;
+      return ERANGE;
+    }
+  
+  return memcpy(buf, description, length + 1), 0;
+}
+
+
+/**
+ * Reenterant variant of `stderror`.
+ * 
+ * This is a GNU-specific extension. However the name
+ * is not part of the GNU specification, `strerror_r` should
+ * be used. It is defined to this function unless
+ * `(_POSIX_C_SOURCE >= 200112L || _XOPEN_SOURCE >= 600) && !_GNU_SOURCE`.
+ * 
+ * @param   errnum  The error code.
+ * @param   buf     Buffer where the description shall be stored.
+ * @param   buflen  The allocation size of `buf`.
+ * @return          `buf` on success, `NULL` on error. On error, `errno`
+ *                  is set to indicate the error.
+ * 
+ * @throws  ERANGE  `buf` was too small to store the description.
+ */
+char* __gnu_strerror_r(int errnum, char* buf, size_t buflen)
+{
+  errno = __xsi_strerror_r(errnum, buf, buflen);
+  return errno ? NULL : buf;
+}
+