remove seperate BitSize traits

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bitstream_reader"
-version = "0.6.9"
+version = "0.7.0"
 authors = ["Robin Appelman <robin@icewind.nl>"]
 edition = "2018"
 description = "Reading bit sequences from a byte slice"
@@ -12,7 +12,7 @@ travis-ci = { repository = "icewind1991/bitstream_reader" }
 
 [dependencies]
 num-traits = "0.2"
-bitstream_reader_derive = { version = "0.6", path = "bitstream_reader_derive" }
+bitstream_reader_derive = { version = "0.7", path = "bitstream_reader_derive" }
 memchr = "2.2"
 
 [dev-dependencies]

bitstream_reader_derive/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bitstream_reader_derive"
-version = "0.6.0"
+version = "0.7.0"
 authors = ["Robin Appelman <robin@icewind.nl>"]
 edition = "2018"
 description = "Reading bit sequences from a byte slice"
@@ -18,4 +18,4 @@ proc-macro2 = "0.4"
 syn_util = "0.3"
 
 [dev-dependencies]
-bitstream_reader = { version = "0.6", path = ".." }
+bitstream_reader = { version = "0.7", path = ".." }

bitstream_reader_derive/src/lib.rs

@@ -185,6 +185,12 @@ fn derive_bitread_trait(
     let (impl_generics, _, _) = trait_generics.split_for_impl();
     let span = input.span();
 
+    let size = size(
+        input.data.clone(),
+        &name,
+        &input.attrs,
+        extra_param.is_some(),
+    );
     let parse = parse(input.data, &name, &input.attrs);
 
     let endianness_placeholder = endianness.unwrap_or("_E".to_owned());
@@ -196,11 +202,30 @@ fn derive_bitread_trait(
 
     let endianness_ident = Ident::new(&endianness_placeholder, span);
 
+    let size_extra_param = if extra_param.is_some() {
+        Some(quote!(input_size: usize))
+    } else {
+        None
+    };
+
+    let size_method_name = Ident::new(
+        if extra_param.is_some() {
+            "bit_size_sized"
+        } else {
+            "bit_size"
+        },
+        Span::call_site(),
+    );
+
     let expanded = quote! {
         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> {
                 #parse
             }
+
+            fn #size_method_name(#size_extra_param) -> Option<usize> {
+                #size
+            }
         }
     };
 
@@ -336,6 +361,91 @@ fn parse(data: Data, struct_name: &Ident, attrs: &Vec<Attribute>) -> TokenStream
     }
 }
 
+fn size(
+    data: Data,
+    struct_name: &Ident,
+    attrs: &Vec<Attribute>,
+    has_input_size: bool,
+) -> TokenStream {
+    let span = struct_name.span();
+
+    match data {
+        Data::Struct(DataStruct { fields, .. }) => {
+            let sizes = fields.iter().map(|f| {
+                // Get attributes `#[..]` on each field
+                if is_const_size(&f.attrs, has_input_size) {
+                    let size = get_field_size(&f.attrs, f.span());
+                    let field_type = &f.ty;
+                    let span = f.span();
+                    match size {
+                        Some(size) => {
+                            quote_spanned! { span =>
+                                <#field_type as ::bitstream_reader::BitReadSized<::bitstream_reader::LittleEndian>>::bit_size_sized(#size)
+                            }
+                        }
+                        None => {
+                            quote_spanned! { span =>
+                                <#field_type as ::bitstream_reader::BitRead<::bitstream_reader::LittleEndian>>::bit_size()
+                            }
+                        }
+                    }
+                } else {
+                    quote_spanned! { span =>
+                        None
+                    }
+                }
+            });
+
+            match &fields {
+                Fields::Named(_) => quote_spanned! { span =>
+                    Some(0usize)#(.and_then(|sum: usize| #sizes.map(|size: usize| sum + size)))*
+                },
+                Fields::Unnamed(_) => quote_spanned! { span =>
+                    Some(0usize)#(.and_then(|sum: usize| #sizes.map(|size: usize| sum + size)))*
+                },
+                Fields::Unit => quote_spanned! {span=>
+                    Some(0usize)
+                },
+            }
+        }
+        Data::Enum(data) => {
+            let discriminant_bits = get_attribute_value::<u64>(attrs, &["discriminant_bits"])
+                .expect(
+                    "'discriminant_bits' attribute is required when deriving `BinRead` for enums",
+                ) as usize;
+
+            let is_unit = data.variants.iter().all(|variant| match &variant.fields {
+                Fields::Unit => true,
+                _ => false,
+            });
+
+            if is_unit {
+                quote_spanned! {span=>
+                    Some(#discriminant_bits)
+                }
+            } else {
+                quote_spanned! {span=>
+                    None
+                }
+            }
+        }
+        _ => unimplemented!(),
+    }
+}
+
+fn is_const_size(attrs: &[Attribute], has_input_size: bool) -> bool {
+    if get_attribute_value::<Lit>(attrs, &["size_bits"]).is_some() {
+        return false;
+    }
+    get_attribute_value(attrs, &["size"])
+        .map(|size_lit| match size_lit {
+            Lit::Int(_) => true,
+            Lit::Str(size_field) => &size_field.value() == "input_size" && has_input_size,
+            _ => panic!("Unsupported value for size attribute"),
+        })
+        .unwrap_or(true)
+}
+
 fn get_field_size(attrs: &[Attribute], span: Span) -> Option<TokenStream> {
     get_attribute_value(attrs, &["size"])
         .map(|size_lit| match size_lit {
@@ -361,76 +471,6 @@ fn get_field_size(attrs: &[Attribute], span: Span) -> Option<TokenStream> {
         })
 }
 
-/// See the [crate documentation](index.html) for details
-#[proc_macro_derive(BitSize, attributes(size))]
-pub fn derive_bitsize(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
-    derive_bitsize_trait(input, "BitSize".to_owned(), None)
-}
-
-/// See the [crate documentation](index.html) for details
-#[proc_macro_derive(BitSizeSized, attributes(size))]
-pub fn derive_bitsize_sized(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
-    let extra_param = parse_str::<TokenStream>("input_size: usize").unwrap();
-    derive_bitsize_trait(input, "BitSizeSized".to_owned(), Some(extra_param))
-}
-
-fn derive_bitsize_trait(
-    input: proc_macro::TokenStream,
-    trait_name: String,
-    extra_param: Option<TokenStream>,
-) -> proc_macro::TokenStream {
-    let input: DeriveInput = parse_macro_input!(input as DeriveInput);
-
-    let name = &input.ident;
-
-    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
-
-    let sum = bit_size_sum(input.data);
-
-    let trait_def_str = format!("::bitstream_reader::{}", trait_name);
-    let trait_def = parse_str::<Path>(&trait_def_str).unwrap();
-
-    let expanded = quote! {
-    impl # impl_generics # trait_def for # name # ty_generics # where_clause {
-    fn bit_size( # extra_param) -> usize {
-    # sum
-    }
-    }
-    };
-
-    // panic!("{}", TokenStream::to_string(&expanded));
-
-    proc_macro::TokenStream::from(expanded)
-}
-
-// Generate an expression to sum up the heap size of each field.
-fn bit_size_sum(data: Data) -> TokenStream {
-    match data {
-        Data::Struct(DataStruct { fields, .. }) => {
-            let recurse = fields.iter().map(|f| {
-                let span = f.span();
-                let field_type = &f.ty;
-                match get_field_size(&f.attrs, span) {
-                    Some(size) => {
-                        quote_spanned! {span =>
-                        ::bitstream_reader::bit_size_of_sized::< # field_type> ( # size)
-                        }
-                    }
-                    None => {
-                        quote_spanned! {span =>
-                        ::bitstream_reader::bit_size_of::< # field_type> ()
-                        }
-                    }
-                }
-            });
-            quote! {
-            0 # ( + # recurse) *
-            }
-        }
-        _ => unimplemented!(),
-    }
-}
-
 enum Discriminant {
     Int(usize),
     Default,

bitstream_reader_derive/tests/test.rs

@@ -4,7 +4,7 @@
 use bitstream_reader::{
     bit_size_of, bit_size_of_sized, BigEndian, BitBuffer, BitStream, Endianness, LittleEndian,
 };
-use bitstream_reader_derive::{BitRead, BitReadSized, BitSize, BitSizeSized};
+use bitstream_reader_derive::{BitRead, BitReadSized};
 
 #[derive(BitRead, PartialEq, Debug)]
 struct TestStruct {
@@ -59,6 +59,7 @@ fn test_read_struct() {
         },
         stream.read().unwrap()
     );
+    assert_eq!(None, bit_size_of::<TestStruct>());
 }
 
 #[derive(BitRead, PartialEq, Debug)]
@@ -87,6 +88,7 @@ fn test_read_bare_enum() {
     assert_eq!(TestBareEnum::Foo, stream.read().unwrap());
     assert_eq!(TestBareEnum::Bar, stream.read().unwrap());
     assert_eq!(true, stream.read::<TestBareEnum>().is_err());
+    assert_eq!(Some(2), bit_size_of::<TestBareEnum>());
 }
 
 #[derive(BitRead, PartialEq, Debug)]
@@ -124,6 +126,7 @@ fn test_read_unnamed_field_enum() {
     stream.set_pos(4).unwrap();
     assert_eq!(TestUnnamedFieldEnum::Bar(true), stream.read().unwrap());
     assert_eq!(7, stream.pos());
+    assert_eq!(None, bit_size_of::<TestUnnamedFieldEnum>());
 }
 
 #[derive(BitReadSized, PartialEq, Debug)]
@@ -150,6 +153,7 @@ fn test_read_struct_sized() {
         },
         stream.read_sized(3).unwrap()
     );
+    assert_eq!(Some(8 + 2 * 8 + 2), bit_size_of_sized::<TestStructSized>(2));
 }
 
 #[derive(BitReadSized, PartialEq, Debug)]
@@ -182,6 +186,7 @@ fn test_read_unnamed_field_enum_sized() {
         stream.read_sized(6).unwrap()
     );
     assert_eq!(8, stream.pos());
+    assert_eq!(None, bit_size_of_sized::<TestUnnamedFieldEnumSized>(6));
 }
 
 #[derive(BitRead, PartialEq, Debug)]
@@ -216,6 +221,7 @@ fn test_read_struct2() {
         },
         stream.read().unwrap()
     );
+    assert_eq!(None, bit_size_of::<TestStruct2>());
 }
 
 #[derive(BitRead)]
@@ -234,6 +240,7 @@ fn test_read_struct3() {
     let result: TestStruct3<BigEndian> = stream.read().unwrap();
     assert_eq!(5, result.size);
     assert_eq!(5, result.stream.bit_len());
+    assert_eq!(None, bit_size_of::<TestStruct3<LittleEndian>>());
 }
 
 #[derive(BitRead, PartialEq, Debug)]
@@ -263,6 +270,7 @@ fn test_read_rest_enum() {
     assert_eq!(TestEnumRest::Foo, stream.read().unwrap());
     assert_eq!(TestEnumRest::Bar, stream.read().unwrap());
     assert_eq!(TestEnumRest::Asd, stream.read().unwrap());
+    assert_eq!(Some(2), bit_size_of::<TestEnumRest>());
 }
 
 #[derive(BitRead, PartialEq, Debug)]
@@ -281,7 +289,7 @@ fn test_unnamed_struct() {
     );
 }
 
-#[derive(BitRead, BitSize, PartialEq, Debug)]
+#[derive(BitRead, PartialEq, Debug)]
 struct EmptyStruct;
 
 fn test_empty_struct() {
@@ -290,10 +298,10 @@ fn test_empty_struct() {
     let mut stream = BitStream::from(buffer);
     assert_eq!(EmptyStruct, stream.read().unwrap());
     assert_eq!(0, stream.pos());
-    assert_eq!(0, bit_size_of::<EmptyStruct>());
+    assert_eq!(Some(0), bit_size_of::<EmptyStruct>());
 }
 
-#[derive(BitSize)]
+#[derive(BitRead)]
 struct SizeStruct {
     foo: u8,
     #[size = 6]
@@ -301,16 +309,16 @@ struct SizeStruct {
     bar: bool,
 }
 
-#[derive(BitSize)]
+#[derive(BitRead)]
 struct UnnamedSizeStruct(u8, #[size = 6] String, bool);
 
 #[test]
 fn test_bit_size() {
-    assert_eq!(bit_size_of::<SizeStruct>(), 8 + 8 * 6 + 1);
+    assert_eq!(bit_size_of::<SizeStruct>(), Some(8 + 8 * 6 + 1));
-    assert_eq!(bit_size_of::<UnnamedSizeStruct>(), 8 + 8 * 6 + 1);
+    assert_eq!(bit_size_of::<UnnamedSizeStruct>(), Some(8 + 8 * 6 + 1));
 }
 
-#[derive(BitSizeSized)]
+#[derive(BitReadSized)]
 struct SizeStructSized {
     foo: u8,
     #[size = "input_size"]
@@ -320,6 +328,9 @@ struct SizeStructSized {
 
 #[test]
 fn test_bit_size_sized() {
-    assert_eq!(bit_size_of_sized::<SizeStructSized>(6), 8 + 8 * 6 + 1);
+    assert_eq!(bit_size_of_sized::<SizeStructSized>(6), Some(8 + 8 * 6 + 1));
-    assert_eq!(bit_size_of_sized::<SizeStructSized>(16), 8 + 8 * 16 + 1);
+    assert_eq!(
+        bit_size_of_sized::<SizeStructSized>(16),
+        Some(8 + 8 * 16 + 1)
+    );
 }

src/buffer.rs

@@ -172,6 +172,8 @@ where
             })
     }
 
+    #[doc(hidden)]
+    #[inline]
     pub unsafe fn read_bool_unchecked(&self, position: usize) -> bool {
         let byte_index = position / 8;
         let bit_offset = position & 7;
@@ -239,6 +241,7 @@ where
         Ok(unsafe { self.read_int_unchecked(position, count) })
     }
 
+    #[doc(hidden)]
     #[inline]
     pub unsafe fn read_int_unchecked<T>(&self, position: usize, count: usize) -> T
     where
@@ -362,6 +365,7 @@ where
         Ok(unsafe { self.read_bytes_unchecked(position, byte_count) })
     }
 
+    #[doc(hidden)]
     #[inline]
     pub unsafe fn read_bytes_unchecked(&self, position: usize, byte_count: usize) -> Vec<u8> {
         let shift = position & 7;
@@ -530,6 +534,8 @@ where
         Ok(unsafe { self.read_float_unchecked(position) })
     }
 
+    #[doc(hidden)]
+    #[inline]
     pub unsafe fn read_float_unchecked<T>(&self, position: usize) -> T
     where
         T: Float + UncheckedPrimitiveFloat,

src/lib.rs

@@ -59,12 +59,10 @@ use std::fmt;
 use std::fmt::Display;
 pub use std::string::FromUtf8Error;
 
-pub use bitstream_reader_derive::{BitRead, BitReadSized, BitSize, BitSizeSized};
+pub use bitstream_reader_derive::{BitRead, BitReadSized};
 pub use buffer::BitBuffer;
 pub use endianness::*;
-pub use read::{
+pub use read::{BitRead, BitReadSized, BitSkip, LazyBitRead, LazyBitReadSized};
-    BitRead, BitReadSized, BitSize, BitSizeSized, BitSkip, LazyBitRead, LazyBitReadSized,
-};
 pub use stream::BitStream;
 
 mod buffer;
@@ -145,12 +143,12 @@ pub type Result<T> = std::result::Result<T, ReadError>;
 
 /// Get the number of bits required to read a type from stream
 #[inline(always)]
-pub fn bit_size_of<T: BitSize>() -> usize {
+pub fn bit_size_of<T: BitRead<LittleEndian>>() -> Option<usize> {
     T::bit_size()
 }
 
 /// Get the number of bits required to read a type from stream
 #[inline(always)]
-pub fn bit_size_of_sized<T: BitSizeSized>(size: usize) -> usize {
+pub fn bit_size_of_sized<T: BitReadSized<LittleEndian>>(size: usize) -> Option<usize> {
-    T::bit_size(size)
+    T::bit_size_sized(size)
 }

src/read.rs

@@ -91,12 +91,13 @@ use std::sync::Arc;
 pub trait BitRead<E: Endianness>: Sized {
     /// Read the type from stream
     fn read(stream: &mut BitStream<E>) -> Result<Self>;
-}
 
-/// Trait to get the number of bits needed to read types that can be read from a stream without requiring the size to be configured.
+    /// The number of bits that will be read or None if the number of bits will change depending
-pub trait BitSize {
+    /// on the bit stream
-    /// How many bits are required to read this type
+    #[inline(always)]
-    fn bit_size() -> usize;
+    fn bit_size() -> Option<usize> {
+        return None;
+    }
 }
 
 /// Trait to allow skipping a type
@@ -105,14 +106,11 @@ pub trait BitSize {
 pub trait BitSkip<E: Endianness>: BitRead<E> {
     /// Skip the type
     fn skip(stream: &mut BitStream<E>) -> Result<()> {
-        Self::read(stream).map(|_| ())
+        match Self::bit_size() {
+            Some(size) => stream.skip_bits(size),
+            None => Self::read(stream).map(|_| ()),
         }
     }
-
-impl<T: BitRead<E> + BitSize, E: Endianness> BitSkip<E> for T {
-    fn skip(stream: &mut BitStream<E>) -> Result<()> {
-        stream.skip_bits(Self::bit_size())
-    }
 }
 
 macro_rules! impl_read_int {
@@ -122,12 +120,10 @@ macro_rules! impl_read_int {
             fn read(stream: &mut BitStream<E>) -> Result<$type> {
                 stream.read_int::<$type>(size_of::<$type>() * 8)
             }
-        }
 
-        impl BitSize for $type {
+            #[inline(always)]
-            #[inline]
+            fn bit_size() -> Option<usize> {
-            fn bit_size() -> usize {
+                Some(size_of::<$type>() * 8)
-                size_of::<$type>() * 8
             }
         }
     };
@@ -140,6 +136,11 @@ macro_rules! impl_read_int_nonzero {
             fn read(stream: &mut BitStream<LittleEndian>) -> Result<Self> {
                 Ok(<$type>::new(stream.read()?))
             }
+
+            #[inline(always)]
+            fn bit_size() -> Option<usize> {
+                Some(size_of::<$type>() * 8)
+            }
         }
 
         impl BitRead<BigEndian> for Option<$type> {
@@ -147,12 +148,10 @@ macro_rules! impl_read_int_nonzero {
             fn read(stream: &mut BitStream<BigEndian>) -> Result<Self> {
                 Ok(<$type>::new(stream.read()?))
             }
-        }
 
-        impl BitSize for $type {
+            #[inline(always)]
-            #[inline]
+            fn bit_size() -> Option<usize> {
-            fn bit_size() -> usize {
+                Some(size_of::<$type>() * 8)
-                size_of::<$type>() * 8
             }
         }
     };
@@ -180,12 +179,10 @@ impl<E: Endianness> BitRead<E> for f32 {
     fn read(stream: &mut BitStream<E>) -> Result<f32> {
         stream.read_float::<f32>()
     }
-}
 
-impl BitSize for f32 {
+    #[inline(always)]
-    #[inline]
+    fn bit_size() -> Option<usize> {
-    fn bit_size() -> usize {
+        Some(32)
-        32
     }
 }
 
@@ -194,12 +191,10 @@ impl<E: Endianness> BitRead<E> for f64 {
     fn read(stream: &mut BitStream<E>) -> Result<f64> {
         stream.read_float::<f64>()
     }
-}
 
-impl BitSize for f64 {
+    #[inline(always)]
-    #[inline]
+    fn bit_size() -> Option<usize> {
-    fn bit_size() -> usize {
+        Some(64)
-        64
     }
 }
 
@@ -208,12 +203,10 @@ impl<E: Endianness> BitRead<E> for bool {
     fn read(stream: &mut BitStream<E>) -> Result<bool> {
         stream.read_bool()
     }
-}
 
-impl BitSize for bool {
+    #[inline(always)]
-    #[inline]
+    fn bit_size() -> Option<usize> {
-    fn bit_size() -> usize {
+        Some(1)
-        1
     }
 }
 
@@ -229,6 +222,11 @@ impl<E: Endianness, T: BitRead<E>> BitRead<E> for Rc<T> {
     fn read(stream: &mut BitStream<E>) -> Result<Self> {
         Ok(Rc::new(T::read(stream)?))
     }
+
+    #[inline(always)]
+    fn bit_size() -> Option<usize> {
+        T::bit_size()
+    }
 }
 
 impl<E: Endianness, T: BitRead<E>> BitRead<E> for Arc<T> {
@@ -236,6 +234,11 @@ impl<E: Endianness, T: BitRead<E>> BitRead<E> for Arc<T> {
     fn read(stream: &mut BitStream<E>) -> Result<Self> {
         Ok(Arc::new(T::read(stream)?))
     }
+
+    #[inline(always)]
+    fn bit_size() -> Option<usize> {
+        T::bit_size()
+    }
 }
 
 impl<E: Endianness, T: BitRead<E>> BitRead<E> for Box<T> {
@@ -243,26 +246,10 @@ impl<E: Endianness, T: BitRead<E>> BitRead<E> for Box<T> {
     fn read(stream: &mut BitStream<E>) -> Result<Self> {
         Ok(Box::new(T::read(stream)?))
     }
-}
 
-impl<T: BitSize> BitSize for Rc<T> {
+    #[inline(always)]
-    #[inline]
+    fn bit_size() -> Option<usize> {
-    fn bit_size() -> usize {
+        T::bit_size().and_then(|sum| T::bit_size().map(|size| sum + size))
-        T::bit_size()
-    }
-}
-
-impl<T: BitSize> BitSize for Arc<T> {
-    #[inline]
-    fn bit_size() -> usize {
-        T::bit_size()
-    }
-}
-
-impl<T: BitSize> BitSize for Box<T> {
-    #[inline]
-    fn bit_size() -> usize {
-        T::bit_size()
     }
 }
 
@@ -273,12 +260,10 @@ macro_rules! impl_read_tuple {
             fn read(stream: &mut BitStream<E>) -> Result<Self> {
                 Ok(($(<$type>::read(stream)?),*))
             }
-        }
 
-        impl<$($type: BitSize),*> BitSize for ($($type),*) {
+            #[inline(always)]
-            #[inline]
+            fn bit_size() -> Option<usize> {
-            fn bit_size() -> usize {
+                Some(0)$(.and_then(|sum| <$type>::bit_size().map(|size| sum + size)))*
-                $(<$type>::bit_size() + )* 0
             }
         }
     };
@@ -355,12 +340,13 @@ impl_read_tuple!(T1, T2, T3, T4);
 pub trait BitReadSized<E: Endianness>: Sized {
     /// Read the type from stream
     fn read(stream: &mut BitStream<E>, size: usize) -> Result<Self>;
-}
 
-/// Trait to get the number of bits needed to read types that can be read from a stream requiring the size to be configured.
+    /// The number of bits that will be read or None if the number of bits will change depending
-pub trait BitSizeSized {
+    /// on the bit stream
-    /// How many bits are required to read this type
+    #[inline(always)]
-    fn bit_size(size: usize) -> usize;
+    fn bit_size_sized(_size: usize) -> Option<usize> {
+        return None;
+    }
 }
 
 macro_rules! impl_read_int_sized {
@@ -370,12 +356,10 @@ macro_rules! impl_read_int_sized {
             fn read(stream: &mut BitStream<E>, size: usize) -> Result<$type> {
                 stream.read_int::<$type>(size)
             }
-        }
 
-        impl BitSizeSized for $type {
+            #[inline(always)]
-            #[inline]
+            fn bit_size_sized(size: usize) -> Option<usize> {
-            fn bit_size(size: usize) -> usize {
+                Some(size)
-                size
             }
         }
     };
@@ -397,12 +381,10 @@ impl<E: Endianness> BitReadSized<E> for String {
     fn read(stream: &mut BitStream<E>, size: usize) -> Result<String> {
         stream.read_string(Some(size))
     }
-}
 
-impl BitSizeSized for String {
+    #[inline(always)]
-    #[inline]
+    fn bit_size_sized(size: usize) -> Option<usize> {
-    fn bit_size(size: usize) -> usize {
+        Some(8 * size)
-        8 * size
     }
 }
 
@@ -417,13 +399,6 @@ impl<E: Endianness, T: BitRead<E>> BitRead<E> for Option<T> {
     }
 }
 
-impl<T: BitSize> BitSize for Option<T> {
-    #[inline]
-    fn bit_size() -> usize {
-        1 + T::bit_size()
-    }
-}
-
 impl<E: Endianness, T: BitReadSized<E>> BitReadSized<E> for Option<T> {
     fn read(stream: &mut BitStream<E>, size: usize) -> Result<Self> {
         if stream.read()? {
@@ -434,24 +409,15 @@ impl<E: Endianness, T: BitReadSized<E>> BitReadSized<E> for Option<T> {
     }
 }
 
-impl<T: BitSizeSized> BitSizeSized for Option<T> {
-    #[inline]
-    fn bit_size(size: usize) -> usize {
-        1 + T::bit_size(size)
-    }
-}
-
 impl<E: Endianness> BitReadSized<E> for BitStream<E> {
     #[inline]
     fn read(stream: &mut BitStream<E>, size: usize) -> Result<Self> {
         stream.read_bits(size)
     }
-}
 
-impl<E: Endianness> BitSizeSized for BitStream<E> {
+    #[inline(always)]
-    #[inline]
+    fn bit_size_sized(size: usize) -> Option<usize> {
-    fn bit_size(size: usize) -> usize {
+        Some(size)
-        size
     }
 }
 
@@ -464,12 +430,10 @@ impl<E: Endianness, T: BitRead<E>> BitReadSized<E> for Vec<T> {
         }
         Ok(vec)
     }
-}
 
-impl<T: BitSize> BitSizeSized for Vec<T> {
+    #[inline(always)]
-    #[inline]
+    fn bit_size_sized(size: usize) -> Option<usize> {
-    fn bit_size(size: usize) -> usize {
+        T::bit_size().map(|element_size| size * element_size)
-        size * T::bit_size()
     }
 }
 
@@ -492,12 +456,14 @@ impl<E: Endianness, K: BitRead<E> + Eq + Hash, T: BitRead<E>> BitReadSized<E> fo
         }
         Ok(map)
     }
-}
 
-impl<K: BitSize, T: BitSize> BitSizeSized for HashMap<K, T> {
+    #[inline(always)]
-    #[inline]
+    fn bit_size_sized(size: usize) -> Option<usize> {
-    fn bit_size(size: usize) -> usize {
+        if let (Some(key_size), Some(value_size)) = (K::bit_size(), T::bit_size()) {
-        size * (K::bit_size() + T::bit_size())
+            Some(size * (key_size + value_size))
+        } else {
+            None
+        }
     }
 }
 
@@ -507,12 +473,12 @@ impl<K: BitSize, T: BitSize> BitSizeSized for HashMap<K, T> {
 /// Requires [`BitSize`] to be implemented for it's contents so it can grab the correct number of bytes
 ///
 /// [`BitSize`]: trait.BitSize.html
-pub struct LazyBitRead<T: BitRead<E> + BitSize, E: Endianness> {
+pub struct LazyBitRead<T: BitRead<E>, E: Endianness> {
     source: BitStream<E>,
     inner_type: PhantomData<T>,
 }
 
-impl<T: BitRead<E> + BitSize, E: Endianness> LazyBitRead<T, E> {
+impl<T: BitRead<E>, E: Endianness> LazyBitRead<T, E> {
     #[inline]
     /// Get the contents of the lazy struct
     pub fn read(mut self) -> Result<T> {
@@ -520,20 +486,20 @@ impl<T: BitRead<E> + BitSize, E: Endianness> LazyBitRead<T, E> {
     }
 }
 
-impl<T: BitRead<E> + BitSize, E: Endianness> BitRead<E> for LazyBitRead<T, E> {
+impl<T: BitRead<E>, E: Endianness> BitRead<E> for LazyBitRead<T, E> {
     #[inline]
     fn read(stream: &mut BitStream<E>) -> Result<Self> {
-        let bit_size = T::bit_size();
+        match T::bit_size() {
-        Ok(LazyBitRead {
+            Some(bit_size) => Ok(LazyBitRead {
                 source: stream.read_bits(bit_size)?,
                 inner_type: PhantomData,
-        })
+            }),
+            None => panic!(),
         }
     }
 
-impl<T: BitRead<E> + BitSize, E: Endianness> BitSize for LazyBitRead<T, E> {
+    #[inline(always)]
-    #[inline]
+    fn bit_size() -> Option<usize> {
-    fn bit_size() -> usize {
         T::bit_size()
     }
 }
@@ -541,16 +507,14 @@ impl<T: BitRead<E> + BitSize, E: Endianness> BitSize for LazyBitRead<T, E> {
 #[derive(Clone, Debug)]
 /// Struct that lazily reads it's contents from the stream
 ///
-/// Requires [`BitSizeSized`] to be implemented for it's contents so it can grab the correct number of bytes
-///
 /// [`BitReadSized`]: trait.BitReadSized.html
-pub struct LazyBitReadSized<T: BitReadSized<E> + BitSizeSized, E: Endianness> {
+pub struct LazyBitReadSized<T: BitReadSized<E>, E: Endianness> {
     source: RefCell<BitStream<E>>,
     size: usize,
     inner_type: PhantomData<T>,
 }
 
-impl<T: BitReadSized<E> + BitSizeSized, E: Endianness> LazyBitReadSized<T, E> {
+impl<T: BitReadSized<E>, E: Endianness> LazyBitReadSized<T, E> {
     #[inline]
     /// Get the contents of the lazy struct
     pub fn value(self) -> Result<T> {
@@ -558,21 +522,21 @@ impl<T: BitReadSized<E> + BitSizeSized, E: Endianness> LazyBitReadSized<T, E> {
     }
 }
 
-impl<T: BitReadSized<E> + BitSizeSized, E: Endianness> BitReadSized<E> for LazyBitReadSized<T, E> {
+impl<T: BitReadSized<E>, E: Endianness> BitReadSized<E> for LazyBitReadSized<T, E> {
     #[inline]
     fn read(stream: &mut BitStream<E>, size: usize) -> Result<Self> {
-        let bit_size = T::bit_size(size);
+        match T::bit_size_sized(size) {
-        Ok(LazyBitReadSized {
+            Some(bit_size) => Ok(LazyBitReadSized {
                 source: RefCell::new(stream.read_bits(bit_size)?),
                 inner_type: PhantomData,
                 size,
-        })
+            }),
+            None => panic!(),
         }
     }
 
-impl<T: BitReadSized<E> + BitSizeSized, E: Endianness> BitSizeSized for LazyBitReadSized<T, E> {
+    #[inline(always)]
-    #[inline]
+    fn bit_size_sized(size: usize) -> Option<usize> {
-    fn bit_size(size: usize) -> usize {
+        T::bit_size_sized(size)
-        T::bit_size(size)
     }
 }

src/stream.rs

@@ -138,6 +138,7 @@ where
         result
     }
 
+    #[doc(hidden)]
     #[inline]
     pub unsafe fn read_int_unchecked<T>(&mut self, count: usize) -> T
     where
@@ -187,6 +188,8 @@ where
         result
     }
 
+    #[doc(hidden)]
+    #[inline]
     pub unsafe fn read_float_unchecked<T>(&mut self) -> T
     where
         T: Float + UncheckedPrimitiveFloat,
@@ -233,6 +236,8 @@ where
         result
     }
 
+    #[doc(hidden)]
+    #[inline]
     pub unsafe fn read_bytes_unchecked(&mut self, byte_count: usize) -> Vec<u8> {
         let count = byte_count * 8;
         self.pos += count;
@@ -585,6 +590,18 @@ where
     pub fn read_sized<T: BitReadSized<E>>(&mut self, size: usize) -> Result<T> {
         T::read(self, size)
     }
+
+    /// Check if we can read a number of bits from the stream
+    pub fn check_read(&self, count: usize) -> Result<()> {
+        if self.bits_left() < count {
+            Err(ReadError::NotEnoughData {
+                requested: count,
+                bits_left: self.bits_left(),
+            })
+        } else {
+            Ok(())
+        }
+    }
 }
 
 impl<E: Endianness> Clone for BitStream<E> {