1 files changed, 149 insertions, 0 deletions
diff --git a/vendor/der/src/writer/slice.rs b/vendor/der/src/writer/slice.rs
new file mode 100644
index 0000000..5dafe99
--- /dev/null
+++ b/vendor/der/src/writer/slice.rs
@@ -0,0 +1,149 @@
+//! Slice writer.
+
+use crate::{
+    asn1::*, Encode, EncodeValue, ErrorKind, Header, Length, Result, Tag, TagMode, TagNumber,
+    Tagged, Writer,
+};
+
+/// [`Writer`] which encodes DER into a mutable output byte slice.
+#[derive(Debug)]
+pub struct SliceWriter<'a> {
+    /// Buffer into which DER-encoded message is written
+    bytes: &'a mut [u8],
+
+    /// Has the encoding operation failed?
+    failed: bool,
+
+    /// Total number of bytes written to buffer so far
+    position: Length,
+}
+
+impl<'a> SliceWriter<'a> {
+    /// Create a new encoder with the given byte slice as a backing buffer.
+    pub fn new(bytes: &'a mut [u8]) -> Self {
+        Self {
+            bytes,
+            failed: false,
+            position: Length::ZERO,
+        }
+    }
+
+    /// Encode a value which impls the [`Encode`] trait.
+    pub fn encode<T: Encode>(&mut self, encodable: &T) -> Result<()> {
+        if self.is_failed() {
+            self.error(ErrorKind::Failed)?;
+        }
+
+        encodable.encode(self).map_err(|e| {
+            self.failed = true;
+            e.nested(self.position)
+        })
+    }
+
+    /// Return an error with the given [`ErrorKind`], annotating it with
+    /// context about where the error occurred.
+    pub fn error<T>(&mut self, kind: ErrorKind) -> Result<T> {
+        self.failed = true;
+        Err(kind.at(self.position))
+    }
+
+    /// Did the decoding operation fail due to an error?
+    pub fn is_failed(&self) -> bool {
+        self.failed
+    }
+
+    /// Finish encoding to the buffer, returning a slice containing the data
+    /// written to the buffer.
+    pub fn finish(self) -> Result<&'a [u8]> {
+        let position = self.position;
+
+        if self.is_failed() {
+            return Err(ErrorKind::Failed.at(position));
+        }
+
+        self.bytes
+            .get(..usize::try_from(position)?)
+            .ok_or_else(|| ErrorKind::Overlength.at(position))
+    }
+
+    /// Encode a `CONTEXT-SPECIFIC` field with the provided tag number and mode.
+    pub fn context_specific<T>(
+        &mut self,
+        tag_number: TagNumber,
+        tag_mode: TagMode,
+        value: &T,
+    ) -> Result<()>
+    where
+        T: EncodeValue + Tagged,
+    {
+        ContextSpecificRef {
+            tag_number,
+            tag_mode,
+            value,
+        }
+        .encode(self)
+    }
+
+    /// Encode an ASN.1 `SEQUENCE` of the given length.
+    ///
+    /// Spawns a nested slice writer which is expected to be exactly the
+    /// specified length upon completion.
+    pub fn sequence<F>(&mut self, length: Length, f: F) -> Result<()>
+    where
+        F: FnOnce(&mut SliceWriter<'_>) -> Result<()>,
+    {
+        Header::new(Tag::Sequence, length).and_then(|header| header.encode(self))?;
+
+        let mut nested_encoder = SliceWriter::new(self.reserve(length)?);
+        f(&mut nested_encoder)?;
+
+        if nested_encoder.finish()?.len() == usize::try_from(length)? {
+            Ok(())
+        } else {
+            self.error(ErrorKind::Length { tag: Tag::Sequence })
+        }
+    }
+
+    /// Reserve a portion of the internal buffer, updating the internal cursor
+    /// position and returning a mutable slice.
+    fn reserve(&mut self, len: impl TryInto<Length>) -> Result<&mut [u8]> {
+        if self.is_failed() {
+            return Err(ErrorKind::Failed.at(self.position));
+        }
+
+        let len = len
+            .try_into()
+            .or_else(|_| self.error(ErrorKind::Overflow))?;
+
+        let end = (self.position + len).or_else(|e| self.error(e.kind()))?;
+        let slice = self
+            .bytes
+            .get_mut(self.position.try_into()?..end.try_into()?)
+            .ok_or_else(|| ErrorKind::Overlength.at(end))?;
+
+        self.position = end;
+        Ok(slice)
+    }
+}
+
+impl<'a> Writer for SliceWriter<'a> {
+    fn write(&mut self, slice: &[u8]) -> Result<()> {
+        self.reserve(slice.len())?.copy_from_slice(slice);
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::SliceWriter;
+    use crate::{Encode, ErrorKind, Length};
+
+    #[test]
+    fn overlength_message() {
+        let mut buffer = [];
+        let mut writer = SliceWriter::new(&mut buffer);
+        let err = false.encode(&mut writer).err().unwrap();
+        assert_eq!(err.kind(), ErrorKind::Overlength);
+        assert_eq!(err.position(), Some(Length::ONE));
+    }
+}