Implement Integer type binding for DER Reader and Writer

src/rw/der.rs

@@ -84,9 +84,15 @@ impl<W: BasicWrite> Writer for BasicWriter<W> {
 
     fn write_number<T: Number, C: crate::descriptor::numbers::Constraint<T>>(
         &mut self,
-        _value: T,
+        value: T,
     ) -> Result<(), Self::Error> {
-        todo!()
+        self.write.write_identifier(C::TAG)?;
+        let value = value.to_i64();
+        let offset = value.leading_zeros() / u8::BITS;
+        let len = value.to_be_bytes().len() as u64 - offset as u64;
+        self.write.write_length(len)?;
+        self.write.write_integer_i64(value)?;
+        Ok(())
     }
 
     fn write_utf8string<C: crate::descriptor::utf8string::Constraint>(
@@ -227,7 +233,12 @@ impl<R: BasicRead> Reader for BasicReader<R> {
     fn read_number<T: Number, C: crate::descriptor::numbers::Constraint<T>>(
         &mut self,
     ) -> Result<T, Self::Error> {
-        todo!()
+        let identifier = self.read.read_identifier()?;
+        if identifier.value() != Tag::DEFAULT_INTEGER.value() {
+            return Err(Error::unexpected_tag(Tag::DEFAULT_INTEGER, identifier));
+        }
+        let len = self.read.read_length()?;
+        self.read.read_integer_i64(len as u32).map(T::from_i64)
     }
 
     fn read_utf8string<C: crate::descriptor::utf8string::Constraint>(

tests/der_basic_number.rs

@@ -0,0 +1,50 @@
+use asn1rs::descriptor::numbers::NoConstraint;
+use asn1rs::descriptor::numbers::Number;
+use asn1rs::descriptor::{Integer, ReadableType, WritableType};
+use asn1rs::prelude::basic::DER;
+use std::fmt::Debug;
+
+fn write_read_integer<T: Number + Debug + PartialEq>(len: T) {
+    let mut buffer = Vec::new();
+    let mut writer = DER::writer(&mut buffer);
+
+    Integer::<T, NoConstraint>::write_value(&mut writer, &len).unwrap();
+
+    let mut reader = DER::reader(&buffer[..]);
+    let read = Integer::<T, NoConstraint>::read_value(&mut reader).unwrap();
+
+    assert_eq!(len, read);
+}
+
+#[test]
+pub fn test_length_bounds() {
+    write_read_integer(0);
+    write_read_integer(u8::MAX as u64 - 1);
+    write_read_integer(u8::MAX as u64);
+    write_read_integer(u8::MAX as u64 + 1);
+    write_read_integer(u16::MAX as u64 - 1);
+    write_read_integer(u16::MAX as u64);
+    write_read_integer(u16::MAX as u64 + 1);
+    write_read_integer(u32::MAX as u64 - 1);
+    write_read_integer(u32::MAX as u64);
+    write_read_integer(u32::MAX as u64 + 1);
+    write_read_integer(u64::MAX - 1);
+    write_read_integer(u64::MAX);
+}
+
+#[inline]
+pub fn test_letsencrypt_point_numbers() {
+    const BYTES: &'static [u8] = &[0x80, 0x01, 0x09, 0x81, 0x01, 0x09];
+
+    let mut reader = DER::reader(BYTES);
+
+    assert_eq!(
+        9,
+        Integer::<i64, NoConstraint>::read_value(&mut reader).unwrap()
+    );
+
+    assert_eq!(
+        9,
+        Integer::<i64, NoConstraint>::read_value(&mut reader).unwrap()
+    );
+}