1 files changed, 85 insertions, 0 deletions
diff --git a/lib/checkargs.c b/lib/checkargs.c
new file mode 100644
index 0000000..e1c97be
--- /dev/null
+++ b/lib/checkargs.c
@@ -0,0 +1,85 @@
+/*  datedif - calculates the difference in days between two dates
+ *  Copyright (C) 2000 Micael Widell     contact: xeniac@linux.nu
+ *
+ *  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 2 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, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+int isDateArgument(char* dateString) {
+  
+  const int MONTHS[] = {31,0,31,30,31,30,31,31,30,31,30,31};
+  int i, day, month, year;
+  char buffer[5];
+  
+  /* 'today' is a valid date */ 
+  if (strcmp(dateString, "today") == 0)
+    return 1;
+  
+  /* Numeric dates must be eight characters long */
+  if (8 != strlen(dateString))
+    return 0;
+  
+  /* Check that the date is entirely formed of numbers */
+  for (i = 0; i < 8; i++) {
+    if (dateString[i] < '0' || dateString[i] > '9')
+      return 0;
+  }
+  
+  /* Check that the date exists */
+  memset(buffer, 0, 5);
+  strncpy(buffer, dateString + 6, 2);
+  day = atoi(buffer);
+  strncpy(buffer, dateString + 4, 2); 
+  month = atoi(buffer);
+  month -= 1;
+  strncpy(buffer, dateString, 4);
+  year = atoi(buffer);
+  
+  /* Validate month */
+  if (month < 0 || month > 11)
+    return 0;
+  
+  /* Validating dates is simple when the date does not fall into February */
+  if (1 != month) {
+    if (day < 1 || day > MONTHS[month])
+      return 0;
+  } else {
+    int feb = 28;
+    
+    /* Februarys are a bit tougher issue */
+    if (0 == year % 4) {
+      if (0 == year % 100) {
+	if (0 == year % 400) {
+	  feb = 29;
+	} else {
+	  feb = 28;
+	}
+      } else {
+	feb = 29;
+      }
+    }
+    if (day < 1 || day > feb)
+      return 0;
+  }
+
+  /* Avoid user from using dates before 16000301, since those will result in
+     incorrect output */
+  if(16000301 > atoi(dateString))
+    return 0;
+  
+  return 1;
+}