der: optimize compile-time: code reuse with encode_value_to_slice (#1940)

Author: dishmaker

der/src/asn1/any.rs

@@ -8,9 +8,6 @@ use crate::{
 };
 use core::cmp::Ordering;
 
-#[cfg(feature = "alloc")]
-use crate::SliceWriter;
-
 /// ASN.1 `ANY`: represents any explicitly tagged ASN.1 value.
 ///
 /// This is a zero-copy reference type which borrows from the input data.
@@ -179,7 +176,7 @@ pub use self::allocating::Any;
 #[cfg(feature = "alloc")]
 mod allocating {
     use super::*;
-    use crate::{BytesOwned, reader::read_value, referenced::*};
+    use crate::{BytesOwned, encode::encode_value_to_slice, reader::read_value, referenced::*};
     use alloc::boxed::Box;
 
     /// ASN.1 `ANY`: represents any explicitly tagged ASN.1 value.
@@ -242,9 +239,7 @@ mod allocating {
         {
             let encoded_len = usize::try_from(msg.value_len()?)?;
             let mut buf = vec![0u8; encoded_len];
-            let mut writer = SliceWriter::new(&mut buf);
-            msg.encode_value(&mut writer)?;
-            writer.finish()?;
+            encode_value_to_slice(&mut buf, msg)?;
             Any::new(msg.tag(), buf)
         }
 

der/src/asn1/integer.rs

@@ -5,7 +5,7 @@ pub(super) mod uint;
 
 use core::{cmp::Ordering, mem::size_of};
 
-use crate::{EncodeValue, Result, SliceWriter};
+use crate::{EncodeValue, Result, encode::encode_value_to_slice};
 
 /// Is the highest bit of the first byte in the slice set to `1`? (if present)
 #[inline]
@@ -25,14 +25,12 @@ where
     debug_assert!(size_of::<T>() <= MAX_INT_SIZE);
 
     let mut buf1 = [0u8; MAX_INT_SIZE];
-    let mut encoder1 = SliceWriter::new(&mut buf1);
-    a.encode_value(&mut encoder1)?;
-
     let mut buf2 = [0u8; MAX_INT_SIZE];
-    let mut encoder2 = SliceWriter::new(&mut buf2);
-    b.encode_value(&mut encoder2)?;
 
-    Ok(encoder1.finish()?.cmp(encoder2.finish()?))
+    let buf1 = encode_value_to_slice(&mut buf1, &a)?;
+    let buf2 = encode_value_to_slice(&mut buf2, &b)?;
+
+    Ok(buf1.cmp(buf2))
 }
 
 #[cfg(test)]

der/src/asn1/integer/int.rs

@@ -311,9 +311,7 @@ mod allocating {
 
                     fn try_from(value: $int) -> $crate::Result<Self> {
                         let mut buf  = [0u8; 16];
-                        let mut writer = $crate::SliceWriter::new(&mut buf[..]);
-                        value.encode_value(&mut writer)?;
-                        let buf = writer.finish()?;
+                        let buf = $crate::encode::encode_value_to_slice(&mut buf, &value)?;
                         Int::new(buf)
                     }
                 }

der/src/asn1/integer/uint.rs

@@ -284,9 +284,7 @@ mod allocating {
 
                     fn try_from(value: $uint) -> $crate::Result<Self> {
                         let mut buf  = [0u8; 17];
-                        let mut writer = $crate::SliceWriter::new(&mut buf[..]);
-                        value.encode_value(&mut writer)?;
-                        let buf = writer.finish()?;
+                        let buf = $crate::encode::encode_value_to_slice(&mut buf, &value)?;
                         Uint::new(buf)
                     }
                 }

der/src/encode.rs

@@ -164,3 +164,13 @@ where
         T::encode_value(self, writer)
     }
 }
+
+/// Encodes value only (without tag + length) to a slice.
+pub(crate) fn encode_value_to_slice<'a, T>(buf: &'a mut [u8], value: &T) -> Result<&'a [u8]>
+where
+    T: EncodeValue,
+{
+    let mut encoder = SliceWriter::new(buf);
+    value.encode_value(&mut encoder)?;
+    encoder.finish()
+}

der/src/length.rs

@@ -3,10 +3,7 @@
 pub(crate) mod indefinite;
 
 use self::indefinite::INDEFINITE_LENGTH_OCTET;
-use crate::{
-    Decode, DerOrd, Encode, EncodingRules, Error, ErrorKind, Reader, Result, SliceWriter, Tag,
-    Writer,
-};
+use crate::{Decode, DerOrd, Encode, EncodingRules, Error, ErrorKind, Reader, Result, Tag, Writer};
 use core::{
     cmp::Ordering,
     fmt,
@@ -327,13 +324,10 @@ impl DerOrd for Length {
         let mut buf1 = [0u8; Self::MAX_SIZE];
         let mut buf2 = [0u8; Self::MAX_SIZE];
 
-        let mut encoder1 = SliceWriter::new(&mut buf1);
-        encoder1.encode(self)?;
-
-        let mut encoder2 = SliceWriter::new(&mut buf2);
-        encoder2.encode(other)?;
+        let buf1 = self.encode_to_slice(&mut buf1)?;
+        let buf2 = other.encode_to_slice(&mut buf2)?;
 
-        Ok(encoder1.finish()?.cmp(encoder2.finish()?))
+        Ok(buf1.cmp(buf2))
     }
 }