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Code Issues Releases Wiki Activity

use unchecked reads to group bounds checks where possible

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This commit is contained in:
Robin Appelman 2020-01-07 22:56:34 +01:00
commit 88c9c21d74
1 changed files with 18 additions and 1 deletions
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17
bitstream_reader_derive/src/lib.rs
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@ -209,6 +209,12 @@ fn derive_bitread_trait(
None None
}; };
let extra_param_call = if extra_param.is_some() {
Some(quote!(input_size))
} else {
None
};
let size_method_name = Ident::new( let size_method_name = Ident::new(
if extra_param.is_some() { if extra_param.is_some() {
"bit_size_sized" "bit_size_sized"
@ -221,8 +227,19 @@ fn derive_bitread_trait(
let expanded = quote! { let expanded = quote! {
impl #impl_generics #trait_def for #name #ty_generics #where_clause { impl #impl_generics #trait_def for #name #ty_generics #where_clause {
fn read(stream: &mut ::bitstream_reader::BitStream<#endianness_ident>#extra_param) -> ::bitstream_reader::Result<Self> { fn read(stream: &mut ::bitstream_reader::BitStream<#endianness_ident>#extra_param) -> ::bitstream_reader::Result<Self> {
// if the read has a predicable size, we can do the bounds check in one go
match <Self as #trait_def>::#size_method_name(#extra_param_call) {
Some(size) => {
stream.check_read(size)?;
unsafe {
<Self as #trait_def>::read_unchecked(stream, #extra_param_call)
}
},
None => {
#parsed #parsed
} }
}
}
unsafe fn read_unchecked(stream: &mut ::bitstream_reader::BitStream<#endianness_ident>#extra_param) -> ::bitstream_reader::Result<Self> { unsafe fn read_unchecked(stream: &mut ::bitstream_reader::BitStream<#endianness_ident>#extra_param) -> ::bitstream_reader::Result<Self> {
#parsed_unchecked #parsed_unchecked