Improve performance of String and Vec<u8>

borsh-rs/borsh-derive-internal/src/enum_de.rs

@@ -64,7 +64,7 @@ pub fn enum_de(input: &ItemEnum) -> syn::Result<TokenStream2> {
     if let Some(method_ident) = init_method {
         Ok(quote! {
             impl #generics borsh::de::BorshDeserialize for #name #generics where  #deserializable_field_types {
-                fn deserialize<R: std::io::Read>(reader: &mut R) -> std::result::Result<Self, std::io::Error> {
+                fn deserialize<R: std::io::BufRead>(reader: &mut R) -> std::result::Result<Self, std::io::Error> {
                     #variant_idx
                     let mut return_value = match variant_idx {
                         #variant_arms
@@ -82,7 +82,7 @@ pub fn enum_de(input: &ItemEnum) -> syn::Result<TokenStream2> {
     } else {
         Ok(quote! {
             impl #generics borsh::de::BorshDeserialize for #name #generics where  #deserializable_field_types {
-                fn deserialize<R: std::io::Read>(reader: &mut R) -> std::result::Result<Self, std::io::Error> {
+                fn deserialize<R: std::io::BufRead>(reader: &mut R) -> std::result::Result<Self, std::io::Error> {
                     #variant_idx
                     let return_value = match variant_idx {
                         #variant_arms

borsh-rs/borsh-derive-internal/src/struct_de.rs

@@ -54,7 +54,7 @@ pub fn struct_de(input: &ItemStruct) -> syn::Result<TokenStream2> {
     if let Some(method_ident) = init_method {
         Ok(quote! {
             impl #generics borsh::de::BorshDeserialize for #name #generics where #deserializable_field_types {
-                fn deserialize<R: std::io::Read>(reader: &mut R) -> std::result::Result<Self, std::io::Error> {
+                fn deserialize<R: std::io::BufRead>(reader: &mut R) -> std::result::Result<Self, std::io::Error> {
                     let mut return_value = #return_value;
                     return_value.#method_ident();
                     Ok(return_value)
@@ -64,7 +64,7 @@ pub fn struct_de(input: &ItemStruct) -> syn::Result<TokenStream2> {
     } else {
         Ok(quote! {
             impl #generics borsh::de::BorshDeserialize for #name #generics where #deserializable_field_types {
-                fn deserialize<R: std::io::Read>(reader: &mut R) -> std::result::Result<Self, std::io::Error> {
+                fn deserialize<R: std::io::BufRead>(reader: &mut R) -> std::result::Result<Self, std::io::Error> {
                     Ok(#return_value)
                 }
             }

borsh-rs/borsh/src/de/hint.rs

@@ -3,3 +3,13 @@ pub fn cautious<T>(hint: u32) -> usize {
     let el_size = std::mem::size_of::<T>() as u32;
     std::cmp::max(std::cmp::min(hint, 4096/el_size), 1u32) as _
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    pub fn test_cautious_u8() {
+        assert_eq!(cautious::<u8>(10), 10);
+    }
+}