Added a build script.

The build script was added to obtain the correct values of the
errno C preprocessor definitions. This way no matter what the platform
has defined them as, they will be correct in the libraries code.

src/c/errno.rs

@@ -0,0 +1,167 @@
+use weave::Error;
+use binding::CInt;
+
+
+
+/// This signifies that there is no current error.
+/// This can be used for clearing an error.
+pub const NO_ERROR: CInt = 0;
+
+/// Include the generated C error values.
+include!(concat!(env!("OUT_DIR"), "/errno_values.rs"));
+
+
+
+///
+#[derive(Copy, Clone, Eq, Ord, PartialEq, PartialOrd)]
+pub enum CError
+{
+   /// There is no Error.
+   None,
+
+   /// Some mathematical functions are only defined
+   /// for certain real values, which is called its domain,
+   /// for example the square root function is only defined for
+   /// non-negative numbers, therefore the sqrt function sets
+   /// errno to EDOM if called with a negative argument.
+   Domain,
+
+   /// The range of values that can be represented
+   /// with a variable is limited. For example, mathematical functions
+   /// such as pow can easily outbound the range representable by a
+   /// floating point variable, or functions such as strtod can
+   /// encounter sequences of digits longer than the range
+   /// representable values. In these cases, errno is set to ERANGE.
+   Range,
+
+   /// Multibyte character sequence may have a
+   /// restricted set of valid sequences. When a set of multibyte
+   /// characters is translated by functions such as mbrtowc,
+   /// errno is set to EILSEQ when an invalid sequence is encountered.
+   IllegalSequence,
+
+   /// There was a detected error, but it
+   /// is not one handled by CError.
+   Unhandled
+}
+
+
+
+impl CError
+{
+   /// Returns if the given value is a handled CError.
+   pub fn is_handled_error(errno: i32) -> bool
+   {
+      let error: CError;
+
+      // Turn the error value into a CError and
+      // check if it is an Unhandled error.
+      error = CError::from(errno);
+      if error != CError::Unhandled
+      {
+         true
+      }
+      else
+      {
+         false
+      }
+   }
+
+   /// Check the last Error that was posted.
+   pub fn get_current_error() -> CError
+   {
+      CError::from(get_errno())
+   }
+
+   /// Set the current Error for the system.
+   pub fn set_current_error(error: CError)
+   {
+      set_errno(error as i32);
+   }
+
+   /// Clear the current Error.
+   pub fn clear()
+   {
+      CError::set_current_error(CError::None);
+   }
+}
+
+impl ::std::fmt::Debug for CError
+{
+   fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result
+   {
+      ::std::fmt::Display::fmt(self, f)
+   }
+}
+
+impl ::std::fmt::Display for CError
+{
+   fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result
+   {
+      //write!(f, "{}", self.to_str())
+      write!(f, "{}", self.get_description())
+   }
+}
+
+impl From<i32> for CError
+{
+   fn from(val: i32) -> CError
+   {
+      match val
+      {
+         NO_ERROR => { CError::None }
+         EDOM => { CError::Domain }
+         ERANGE => { CError::Range }
+         EILSEQ => { CError::IllegalSequence }
+         _ => { CError::Unhandled }
+      }
+   }
+}
+
+impl Error for CError
+{
+   fn get_description(&self) -> &str
+   {
+      match *self
+      {
+         CError::None => { "There was no error" }
+         CError::Domain => { "Math argument out of domain of function" }
+         CError::Range => { "Math result not representable" }
+         CError::IllegalSequence => { "Illegal byte sequence" }
+         CError::Unhandled => { "Detected an Error not handled by CError" }
+      }
+   }
+
+   fn get_cause(&self) -> Option<&Error>
+   {
+      None
+   }
+}
+
+
+
+/// A helper function for getting the current error.
+fn get_errno() -> i32
+{
+   unsafe
+   {  
+      *__errno_location() as i32
+   }
+}
+
+/// A helper function for setting the current error.
+fn set_errno(errnum: i32)
+{
+   unsafe
+   {
+      *__errno_location() = errnum as CInt;
+   }
+}
+
+
+
+// The function to get the errno memory location.
+extern
+{
+   fn __errno_location() -> *mut CInt;
+}

src/c/mod.rs

@@ -3,10 +3,12 @@
 //! this library is as up-to-date as it can be.
 
 
+mod errno;
 mod string;
 mod time;
 
 
 
+pub use self::errno::*;
 pub use self::string::*;
 pub use self::time::*;