diff --git a/src/lib.rs b/src/lib.rs
index 4a57860..568dee3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -26,6 +26,7 @@ pub mod read {
             })
         }
 
+        #[inline]
         pub fn stream_len(&mut self) -> std::io::Result<u64> {
             let file = match self {
                 Decoder::Raw(file) => file,
@@ -43,6 +44,7 @@ pub mod read {
             Ok(len)
         }
 
+        #[inline]
         pub fn stream_position(&mut self) -> std::io::Result<u64> {
             let file = match self {
                 Decoder::Raw(file) => file,
@@ -94,6 +96,20 @@ pub mod bufread {
             })
         }
 
+        pub fn with_capacity<P>(capacity: usize, path: P) -> Result<BufDecoder, std::io::Error>
+        where
+            P: AsRef<Path>,
+        {
+            let file = File::open(&path).map(|file| BufReader::with_capacity(capacity, file))?;
+
+            Ok(match mime_guess::from_path(path).first_raw() {
+                Some("application/x-gzip") => BufDecoder::Gz(GzDecoder::new(file)),
+                Some("application/x-bzip2") => BufDecoder::Bz(BzDecoder::new(file)),
+                _ => BufDecoder::Raw(file),
+            })
+        }
+
+        #[inline]
         pub fn stream_len(&mut self) -> std::io::Result<u64> {
             let file = match self {
                 BufDecoder::Raw(file) => file,
@@ -111,6 +127,7 @@ pub mod bufread {
             Ok(len)
         }
 
+        #[inline]
         pub fn stream_position(&mut self) -> std::io::Result<u64> {
             let file = match self {
                 BufDecoder::Raw(file) => file,