Move visitors to a shared module

serdect/src/array.rs

@@ -1,6 +1,6 @@
 //! Serialization primitives for arrays.
 
-// Unfortunately, we currently cannot assert generically that we are serializing
+// Unfortunately, we currently cannot tell `serde` in a uniform fashion that we are serializing
 // a fixed-size byte array.
 // See https://github.com/serde-rs/serde/issues/2120 for the discussion.
 // Therefore we have to fall back to the slice methods,
@@ -9,11 +9,12 @@
 // to be exactly equal to the size of the buffer during deserialization,
 // while for slices the buffer can be larger than the deserialized data.
 
+use core::fmt;
 use core::marker::PhantomData;
 
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 
-use crate::slice;
+use crate::common::{self, LengthCheck, SliceVisitor, StrIntoBufVisitor};
 
 #[cfg(feature = "zeroize")]
 use zeroize::Zeroize;
@@ -25,7 +26,7 @@ where
     S: Serializer,
     T: AsRef<[u8]>,
 {
-    slice::serialize_hex_lower_or_bin(value, serializer)
+    common::serialize_hex_lower_or_bin(value, serializer)
 }
 
 /// Serialize the given type as upper case hex when using human-readable
@@ -35,7 +36,22 @@ where
     S: Serializer,
     T: AsRef<[u8]>,
 {
-    slice::serialize_hex_upper_or_bin(value, serializer)
+    common::serialize_hex_upper_or_bin(value, serializer)
+}
+
+struct ExactLength;
+
+impl LengthCheck for ExactLength {
+    fn length_check(buffer_length: usize, data_length: usize) -> bool {
+        buffer_length == data_length
+    }
+    fn expecting(
+        formatter: &mut fmt::Formatter<'_>,
+        data_type: &str,
+        data_length: usize,
+    ) -> fmt::Result {
+        write!(formatter, "{} of length {}", data_type, data_length)
+    }
 }
 
 /// Deserialize from hex when using human-readable formats or binary if the
@@ -46,12 +62,9 @@ where
     D: Deserializer<'de>,
 {
     if deserializer.is_human_readable() {
-        deserializer.deserialize_str(slice::StrVisitor::<slice::ExactLength>(buffer, PhantomData))
+        deserializer.deserialize_str(StrIntoBufVisitor::<ExactLength>(buffer, PhantomData))
     } else {
-        deserializer.deserialize_byte_buf(slice::SliceVisitor::<slice::ExactLength>(
-            buffer,
-            PhantomData,
-        ))
+        deserializer.deserialize_byte_buf(SliceVisitor::<ExactLength>(buffer, PhantomData))
     }
 }
 

serdect/src/common.rs

@@ -0,0 +1,181 @@
+use core::fmt;
+use core::marker::PhantomData;
+
+use serde::{
+    de::{Error, Visitor},
+    Serializer,
+};
+
+#[cfg(feature = "alloc")]
+use ::{alloc::vec::Vec, serde::Serialize};
+
+#[cfg(not(feature = "alloc"))]
+use serde::ser::Error as SerError;
+
+pub(crate) fn serialize_hex<S, T, const UPPERCASE: bool>(
+    value: &T,
+    serializer: S,
+) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+    T: AsRef<[u8]>,
+{
+    #[cfg(feature = "alloc")]
+    if UPPERCASE {
+        return base16ct::upper::encode_string(value.as_ref()).serialize(serializer);
+    } else {
+        return base16ct::lower::encode_string(value.as_ref()).serialize(serializer);
+    }
+    #[cfg(not(feature = "alloc"))]
+    {
+        let _ = value;
+        let _ = serializer;
+        return Err(S::Error::custom(
+            "serializer is human readable, which requires the `alloc` crate feature",
+        ));
+    }
+}
+
+pub(crate) fn serialize_hex_lower_or_bin<S, T>(value: &T, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+    T: AsRef<[u8]>,
+{
+    if serializer.is_human_readable() {
+        serialize_hex::<_, _, false>(value, serializer)
+    } else {
+        serializer.serialize_bytes(value.as_ref())
+    }
+}
+
+/// Serialize the given type as upper case hex when using human-readable
+/// formats or binary if the format is binary.
+pub(crate) fn serialize_hex_upper_or_bin<S, T>(value: &T, serializer: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+    T: AsRef<[u8]>,
+{
+    if serializer.is_human_readable() {
+        serialize_hex::<_, _, true>(value, serializer)
+    } else {
+        serializer.serialize_bytes(value.as_ref())
+    }
+}
+
+pub(crate) trait LengthCheck {
+    fn length_check(buffer_length: usize, data_length: usize) -> bool;
+    fn expecting(
+        formatter: &mut fmt::Formatter<'_>,
+        data_type: &str,
+        data_length: usize,
+    ) -> fmt::Result;
+}
+
+pub(crate) struct StrIntoBufVisitor<'b, T: LengthCheck>(pub &'b mut [u8], pub PhantomData<T>);
+
+impl<'de, 'b, T: LengthCheck> Visitor<'de> for StrIntoBufVisitor<'b, T> {
+    type Value = ();
+
+    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        T::expecting(formatter, "a string", self.0.len() * 2)
+    }
+
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        if !T::length_check(self.0.len() * 2, v.len()) {
+            return Err(Error::invalid_length(v.len(), &self));
+        }
+        // TODO: Map `base16ct::Error::InvalidLength` to `Error::invalid_length`.
+        base16ct::mixed::decode(v, self.0)
+            .map(|_| ())
+            .map_err(E::custom)
+    }
+}
+
+#[cfg(feature = "alloc")]
+pub(crate) struct StrIntoVecVisitor;
+
+#[cfg(feature = "alloc")]
+impl<'de> Visitor<'de> for StrIntoVecVisitor {
+    type Value = Vec<u8>;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(formatter, "a string")
+    }
+
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        base16ct::mixed::decode_vec(v).map_err(E::custom)
+    }
+}
+
+pub(crate) struct SliceVisitor<'b, T: LengthCheck>(pub &'b mut [u8], pub PhantomData<T>);
+
+impl<'de, 'b, T: LengthCheck> Visitor<'de> for SliceVisitor<'b, T> {
+    type Value = ();
+
+    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        T::expecting(formatter, "an array", self.0.len())
+    }
+
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        // Workaround for
+        // https://github.com/rust-lang/rfcs/blob/b1de05846d9bc5591d753f611ab8ee84a01fa500/text/2094-nll.md#problem-case-3-conditional-control-flow-across-functions
+        if T::length_check(self.0.len(), v.len()) {
+            let buffer = &mut self.0[..v.len()];
+            buffer.copy_from_slice(v);
+            return Ok(());
+        }
+
+        Err(E::invalid_length(v.len(), &self))
+    }
+
+    #[cfg(feature = "alloc")]
+    fn visit_byte_buf<E>(self, mut v: Vec<u8>) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        // Workaround for
+        // https://github.com/rust-lang/rfcs/blob/b1de05846d9bc5591d753f611ab8ee84a01fa500/text/2094-nll.md#problem-case-3-conditional-control-flow-across-functions
+        if T::length_check(self.0.len(), v.len()) {
+            let buffer = &mut self.0[..v.len()];
+            buffer.swap_with_slice(&mut v);
+            return Ok(());
+        }
+
+        Err(E::invalid_length(v.len(), &self))
+    }
+}
+
+#[cfg(feature = "alloc")]
+pub(crate) struct VecVisitor;
+
+#[cfg(feature = "alloc")]
+impl<'de> Visitor<'de> for VecVisitor {
+    type Value = Vec<u8>;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(formatter, "a bytestring")
+    }
+
+    fn visit_bytes<E>(self, v: &[u8]) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(v.into())
+    }
+
+    fn visit_byte_buf<E>(self, v: Vec<u8>) -> Result<Self::Value, E>
+    where
+        E: Error,
+    {
+        Ok(v)
+    }
+}

serdect/src/lib.rs

@@ -131,35 +131,7 @@
 extern crate alloc;
 
 pub mod array;
+mod common;
 pub mod slice;
 
 pub use serde;
-
-use serde::Serializer;
-
-#[cfg(not(feature = "alloc"))]
-use serde::ser::Error;
-
-#[cfg(feature = "alloc")]
-use serde::Serialize;
-
-fn serialize_hex<S, T, const UPPERCASE: bool>(value: &T, serializer: S) -> Result<S::Ok, S::Error>
-where
-    S: Serializer,
-    T: AsRef<[u8]>,
-{
-    #[cfg(feature = "alloc")]
-    if UPPERCASE {
-        return base16ct::upper::encode_string(value.as_ref()).serialize(serializer);
-    } else {
-        return base16ct::lower::encode_string(value.as_ref()).serialize(serializer);
-    }
-    #[cfg(not(feature = "alloc"))]
-    {
-        let _ = value;
-        let _ = serializer;
-        return Err(S::Error::custom(
-            "serializer is human readable, which requires the `alloc` crate feature",
-        ));
-    }
-}