3 files changed, 33 insertions, 19 deletions

diff --git a/src/types/prefix/count.rs b/src/types/prefix/count.rs
index f8ac68d..5856a72 100644
--- a/src/types/prefix/count.rs
+++ b/src/types/prefix/count.rs
@@ -94,7 +94,7 @@ where
     where
         Self: Sized,
     {
-        let len = L::decode(buf, ctx)?.into_size();
+        let len = L::decode(buf, ctx)?.into_usize();
         let mut data = Vec::with_capacity(len);
         for _ in 0..len {
             let item = I::decode(buf, ctx)?;
diff --git a/src/types/prefix/length.rs b/src/types/prefix/length.rs
index fe839d5..75c4f1b 100644
--- a/src/types/prefix/length.rs
+++ b/src/types/prefix/length.rs
@@ -61,7 +61,7 @@ where
         let mut len = 0;
         let mut inner_buf = Vec::with_capacity(64);
         self.data.encode(&mut inner_buf, ctx)?;
-        let len_val = L::from_size(inner_buf.len());
+        let len_val = L::from_usize(inner_buf.len());
         len += len_val.encode(buffer, ctx)?;
         buffer.extend_from_slice(&inner_buf);
         len += inner_buf.len();
@@ -78,7 +78,7 @@ where
     where
         Self: Sized,
     {
-        let len = L::decode(buf, ctx)?.into_size();
+        let len = L::decode(buf, ctx)?.into_usize();
         if buf.len() < len {
             return Err(crate::codec::error::CodecError::IoError(
                 std::io::Error::new(
diff --git a/src/types/size.rs b/src/types/size.rs
index 788d9af..8295b56 100644
--- a/src/types/size.rs
+++ b/src/types/size.rs
@@ -1,30 +1,44 @@
 macro_rules! impl_size {
-    ($t: ty) => {
+    ($t: ty, $bits: expr) => {
         impl Size for $t {
-            fn from_size(size: usize) -> Self {
+            const BITS: usize = $bits;
+
+            fn from_usize(size: usize) -> Self {
                 size as $t
             }
 
-            fn into_size(self) -> usize {
+            fn into_usize(self) -> usize {
                 self as usize
             }
+
+            fn from_isize(size: isize) -> Self {
+                size as $t
+            }
+
+            fn into_isize(self) -> isize {
+                self as isize
+            }
         }
     };
 }
 
 pub trait Size {
-    fn from_size(size: usize) -> Self;
-    fn into_size(self) -> usize;
+    const BITS: usize;
+
+    fn from_usize(size: usize) -> Self;
+    fn into_usize(self) -> usize;
+    fn from_isize(size: isize) -> Self;
+    fn into_isize(self) -> isize;
 }
 
-impl_size!(u8);
-impl_size!(u16);
-impl_size!(u32);
-impl_size!(u64);
-impl_size!(u128);
-
-impl_size!(i8);
-impl_size!(i16);
-impl_size!(i32);
-impl_size!(i64);
-impl_size!(i128);
+impl_size!(u8, 8);
+impl_size!(u16, 16);
+impl_size!(u32, 32);
+impl_size!(u64, 64);
+impl_size!(u128, 128);
+
+impl_size!(i8, 8);
+impl_size!(i16, 16);
+impl_size!(i32, 32);
+impl_size!(i64, 64);
+impl_size!(i128, 128);