diff --git a/src/bag.rs b/src/bag.rs
index 2cafb7e..6132351 100644
--- a/src/bag.rs
+++ b/src/bag.rs
@@ -2,8 +2,16 @@ use std::{fs::File, path::Path};
 
 use eyre::Context;
 use log::debug;
+use rayon::iter::ParallelIterator;
 
-use crate::{index::BagIndex, info::BagInfo, message::compute_layout, reader::MmapReader, Result};
+use crate::{
+    chunk::{read_chunks_messages, MessageData},
+    index::BagIndex,
+    info::BagInfo,
+    message::compute_layout,
+    reader::MmapReader,
+    Result,
+};
 
 pub struct Bag {
     reader: MmapReader,
@@ -29,6 +37,12 @@ impl Bag {
     }
 
     pub fn compute_info(&mut self) -> Result<BagInfo> {
-        BagInfo::compute(&mut self.reader, &self.index)
+        let reader = self.reader.clone();
+        BagInfo::compute(|| reader.clone(), &self.index)
+    }
+
+    pub fn read_messages(&mut self) -> impl ParallelIterator<Item = Result<MessageData>> + '_ {
+        let reader = self.reader.clone();
+        read_chunks_messages(move || reader.clone(), &self.index.chunks)
     }
 }
diff --git a/src/chunk.rs b/src/chunk.rs
index e5c2172..170bd7a 100644
--- a/src/chunk.rs
+++ b/src/chunk.rs
@@ -1,13 +1,19 @@
-use std::{io, str::FromStr};
+use std::{
+    io::{self, Read, SeekFrom},
+    mem,
+    str::FromStr,
+};
 
-use eyre::bail;
+use bytes::Bytes;
+use eyre::{bail, eyre, Context};
+use rayon::iter::{IntoParallelIterator, ParallelIterator};
 
 use crate::{
     error,
+    index::ChunkInfo,
     parse::{Header, Op},
-    reader::BagReader,
-    Error, Result,
-    Time
+    reader::{BagReader, BytesReader},
+    Error, Result, Time,
 };
 
 #[derive(Clone, Copy, Debug)]
@@ -31,12 +37,18 @@ impl FromStr for Compression {
 }
 
 impl Compression {
-    pub fn decompress_stream<'a, R: io::Read + 'a>(self, read: R) -> Box<dyn io::Read + 'a> {
+    pub fn decompress<R: io::Read>(self, mut read: R, decompressed_size: usize) -> Result<Vec<u8>> {
+        let mut decompressed = Vec::with_capacity(decompressed_size);
         match self {
-            Compression::None => Box::new(read),
+            Compression::None => {
+                read.read_to_end(&mut decompressed)?;
+            }
             Compression::Bz2 => todo!("bz2 decompression"),
-            Compression::Lz4 => Box::new(lz4_flex::frame::FrameDecoder::new(read)),
+            Compression::Lz4 => {
+                lz4_flex::frame::FrameDecoder::new(read).read_to_end(&mut decompressed)?;
+            }
         }
+        Ok(decompressed)
     }
 }
 
@@ -60,19 +72,41 @@ impl ChunkHeader {
     }
 }
 
-pub fn read_chunk<R: BagReader>(bag_reader: &mut R, pos: u64) -> Result<Vec<u8>> {
-    bag_reader.seek(io::SeekFrom::Start(pos))?;
-
+pub fn read_chunk_data<R: BagReader>(bag_reader: &mut R) -> Result<Vec<u8>> {
     let chunk_header = ChunkHeader::read(bag_reader)?;
 
     let compressed_data = bag_reader.read_data()?;
-    let mut data = Vec::with_capacity(chunk_header.uncompressed_size as usize);
-    let mut decompresor = chunk_header.compression.decompress_stream(compressed_data);
-    io::copy(&mut decompresor, &mut data)?;
+    let data = chunk_header
+        .compression
+        .decompress(compressed_data, chunk_header.uncompressed_size as usize)?;
 
     Ok(data)
 }
 
+pub fn read_chunk_data_at<R: BagReader + io::Seek>(
+    bag_reader: &mut R,
+    pos: u64,
+) -> Result<Vec<u8>> {
+    bag_reader.seek(SeekFrom::Start(pos as u64))?;
+    read_chunk_data(bag_reader).wrap_err_with(|| eyre!("failed to read chunk at offset {}", pos))
+}
+
+pub fn read_chunks_data<'a, R, F, C>(
+    make_reader: F,
+    chunks: C,
+) -> impl ParallelIterator<Item = Result<Vec<u8>>> + 'a
+where
+    R: BagReader + io::Seek,
+    F: Fn() -> R + Send + Sync + 'a,
+    C: IntoParallelIterator<Item = &'a ChunkInfo> + 'a,
+{
+    chunks.into_par_iter().map(move |chunk| {
+        let mut reader = make_reader();
+        read_chunk_data_at(&mut reader, chunk.pos)
+    })
+}
+
+#[derive(Debug)]
 pub struct MessageDataHeader {
     pub conn_id: u32,
     pub time: Time,
@@ -91,3 +125,66 @@ impl MessageDataHeader {
         })
     }
 }
+
+#[derive(Debug)]
+pub struct MessageData {
+    pub header: MessageDataHeader,
+    pub data: Bytes,
+}
+
+pub fn read_chunks_messages<'a, R, F, C>(
+    make_reader: F,
+    chunks: C,
+) -> impl ParallelIterator<Item = Result<MessageData>> + 'a
+where
+    R: BagReader + io::Seek + 'a,
+    F: Fn() -> R + Send + Sync + 'a,
+    C: IntoParallelIterator<Item = &'a ChunkInfo> + 'a,
+{
+    read_chunks_data(make_reader, chunks).flat_map_iter(move |data| ChunkMessageIterator {
+        reader: data.map(|data| BytesReader::from(Bytes::from(data))),
+    })
+}
+
+pub struct ChunkMessageIterator {
+    reader: Result<BytesReader>,
+}
+
+impl ChunkMessageIterator {
+    fn next_impl(&mut self) -> Result<Option<MessageData>> {
+        let reader = match &mut self.reader {
+            Ok(reader) => reader,
+            Err(err) => {
+                // workaround for eyre::Report not being clone
+                let mut new_err = eyre!("original error already consumed");
+                mem::swap(err, &mut new_err);
+                return Err(new_err);
+            }
+        };
+        while reader.remaining() > 0 {
+            let header = reader.read_header()?;
+            let op = header.read_op()?;
+
+            match op {
+                Op::MsgData => {
+                    let header = MessageDataHeader::from_header(header)?;
+                    let data = reader.read_data_bytes()?;
+                    return Ok(Some(MessageData { header, data }));
+                }
+                Op::Connection => {
+                    reader.skip_data()?;
+                }
+                _ => bail!("unexpected op in chunk: {:?}", op),
+            }
+        }
+        Ok(None)
+    }
+}
+
+impl Iterator for ChunkMessageIterator {
+    type Item = Result<MessageData>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.next_impl().transpose()
+    }
+}
diff --git a/src/index.rs b/src/index.rs
index 1af4d88..cae0979 100644
--- a/src/index.rs
+++ b/src/index.rs
@@ -1,4 +1,4 @@
-use std::io::SeekFrom;
+use std::io;
 
 use eyre::bail;
 use log::trace;
@@ -95,7 +95,7 @@ pub struct BagIndex {
 }
 
 impl BagIndex {
-    fn read_v2<R: BagReader>(reader: &mut R) -> Result<Self> {
+    fn read_v2<R: BagReader + io::Seek>(reader: &mut R) -> Result<Self> {
         let file_header = reader.read_header_op(Op::FileHeader)?;
 
         let data_length = reader.read_data_length()?;
@@ -112,7 +112,7 @@ impl BagIndex {
             bail!(error::UnsupportedEncryptor(encryptor));
         }
 
-        reader.seek(SeekFrom::Start(index_pos))?;
+        reader.seek(io::SeekFrom::Start(index_pos))?;
 
         let conn_count = file_header.read_u32(b"conn_count")?;
         trace!("connection count: {}", conn_count);
@@ -141,7 +141,7 @@ impl BagIndex {
         })
     }
 
-    pub fn read<R: BagReader>(reader: &mut R) -> Result<Self> {
+    pub fn read<R: BagReader + io::Seek>(reader: &mut R) -> Result<Self> {
         let version = reader.read_version()?;
         trace!("bag version: {}", version);
         if (version.major, version.minor) == (2, 0) {
diff --git a/src/info.rs b/src/info.rs
index 97f95aa..01f01ec 100644
--- a/src/info.rs
+++ b/src/info.rs
@@ -1,13 +1,11 @@
 use std::{collections::HashMap, io};
 
-use eyre::{bail, Context};
 use rayon::prelude::*;
 
 use crate::{
-    chunk::{read_chunk, ChunkHeader, MessageDataHeader},
+    chunk::{read_chunks_messages, ChunkHeader},
     index::{BagIndex, IndexData},
-    parse::Op,
-    reader::{BagReader, SliceReader},
+    reader::BagReader,
     Result,
 };
 
@@ -26,15 +24,16 @@ impl BagInfo {
         self
     }
 
-    pub fn compute<R: BagReader + Clone + Send + Sync>(
-        reader: &mut R,
-        index: &BagIndex,
-    ) -> Result<BagInfo> {
+    pub fn compute<R, F>(make_reader: F, index: &BagIndex) -> Result<BagInfo>
+    where
+        R: BagReader + io::Seek,
+        F: Fn() -> R + Send + Sync,
+    {
         index
             .chunks
             .par_iter()
-            .try_fold(BagInfo::default, |mut info, chunk| -> Result<_> {
-                let mut reader = reader.clone();
+            .try_fold(BagInfo::default, move |mut info, chunk| -> Result<_> {
+                let mut reader = make_reader();
                 reader.seek(io::SeekFrom::Start(chunk.pos))?;
                 let chunk_header = ChunkHeader::read(&mut reader)?;
                 info.total_uncompressed += chunk_header.uncompressed_size as u64;
@@ -49,33 +48,17 @@ impl BagInfo {
             .try_reduce(BagInfo::default, |a, b| Ok(a.combine(b)))
     }
 
-    pub fn compute_without_index<R: BagReader + Clone + Send + Sync>(
-        reader: &mut R,
-        index: &BagIndex,
-    ) -> Result<BagInfo> {
-        index
-            .chunks
-            .par_iter()
+    pub fn compute_without_index<R, F>(make_reader: F, index: &BagIndex) -> Result<BagInfo>
+    where
+        R: BagReader + io::Seek,
+        F: Fn() -> R + Send + Sync,
+    {
+        read_chunks_messages(make_reader, &index.chunks)
             .try_fold(BagInfo::default, |mut info, chunk| -> Result<_> {
-                let mut reader = reader.clone();
-                let data = read_chunk(&mut reader, chunk.pos)
-                    .wrap_err_with(|| format!("failed to read chunk: {:#?}", chunk))?;
-                info.total_uncompressed += data.len() as u64;
-                let mut chunk_reader = SliceReader::from(data);
-                while chunk_reader.remaining() > 0 {
-                    let header = chunk_reader.read_header()?;
-                    let op = header.read_op()?;
-                    match op {
-                        Op::MsgData => {
-                            let header = MessageDataHeader::from_header(header)?;
-                            let count = info.per_connection.entry(header.conn_id).or_insert(0);
-                            *count += 1;
-                            chunk_reader.skip_data()?;
-                        }
-                        Op::Connection => chunk_reader.skip_data()?,
-                        _ => bail!("unexpected op in chunk: {:?}", op),
-                    }
-                }
+                let data = chunk?;
+                info.total_uncompressed += data.data.len() as u64;
+                let count = info.per_connection.entry(data.header.conn_id).or_insert(0);
+                *count += 1;
                 Ok(info)
             })
             .try_reduce(BagInfo::default, |a, b| Ok(a.combine(b)))
diff --git a/src/reader.rs b/src/reader.rs
index d8a7b45..72eb0f3 100644
--- a/src/reader.rs
+++ b/src/reader.rs
@@ -1,5 +1,4 @@
-use std::io::SeekFrom;
-
+use ::bytes::Bytes;
 use nom::multi::length_data;
 use nom::number::streaming::le_u32;
 
@@ -11,18 +10,19 @@ mod io;
 #[cfg(feature = "mmap")]
 mod mmap;
 mod slice;
+mod bytes;
 
 #[cfg(feature = "mmap")]
 pub use self::mmap::MmapReader;
-pub use self::{io::IoReader, slice::SliceReader};
+pub use self::{io::IoReader, slice::SliceReader, bytes::BytesReader};
 
 pub trait BagReader {
+    fn skip(&mut self, amount: usize) -> Result<()>;
+
     fn read_parser<'a, O: 'a, P>(&'a mut self, parser: P) -> Result<O>
     where
         P: nom::Parser<&'a [u8], O, parse::Error<&'a [u8]>>;
 
-    fn seek(&mut self, pos: SeekFrom) -> Result<()>;
-
     fn read_version(&mut self) -> Result<Version> {
         self.read_parser(Version::parse)
     }
@@ -46,11 +46,15 @@ pub trait BagReader {
 
     fn skip_data(&mut self) -> Result<()> {
         let data_length = self.read_data_length()?;
-        self.seek(SeekFrom::Current(data_length as i64))?;
+        self.skip(data_length as usize)?;
         Ok(())
     }
 
     fn read_data(&mut self) -> Result<&[u8]> {
         self.read_parser(length_data(le_u32))
     }
+
+    fn read_data_bytes(&mut self) -> Result<Bytes> {
+        Ok(Bytes::copy_from_slice(self.read_data()?))
+    }
 }
diff --git a/src/reader/bytes.rs b/src/reader/bytes.rs
new file mode 100644
index 0000000..c0ee702
--- /dev/null
+++ b/src/reader/bytes.rs
@@ -0,0 +1,77 @@
+use bytes::{Buf, Bytes};
+use eyre::bail;
+
+use super::{error::UnexpectedEof, BagReader};
+use crate::{parse, Result};
+
+// This is like a SliceReader, except a byte is reference
+// counted to read_data_bytes can give out unlimited-lifetime references
+// to the same buffer.
+#[derive(Clone)]
+pub struct BytesReader {
+    current: Bytes,
+    last: Option<Bytes>,
+}
+
+impl BytesReader {
+    pub fn into_inner(self) -> Bytes {
+        self.current
+    }
+
+    pub fn remaining(&self) -> usize {
+        self.as_ref().remaining()
+    }
+}
+
+impl AsRef<Bytes> for BytesReader {
+    fn as_ref(&self) -> &Bytes {
+        &self.current
+    }
+}
+
+impl AsMut<Bytes> for BytesReader {
+    fn as_mut(&mut self) -> &mut Bytes {
+        &mut self.current
+    }
+}
+
+impl From<Bytes> for BytesReader {
+    fn from(bytes: Bytes) -> Self {
+        Self {
+            current: bytes,
+            last: None,
+        }
+    }
+}
+
+impl BagReader for BytesReader {
+    fn skip(&mut self, amount: usize) -> Result<()> {
+        self.current.advance(amount);
+        Ok(())
+    }
+
+    fn read_parser<'a, O: 'a, P>(&'a mut self, mut parser: P) -> Result<O>
+    where
+        P: nom::Parser<&'a [u8], O, parse::Error<&'a [u8]>>,
+    {
+        // Store the current buffer to last so we can return a reference
+        // to it.
+        self.last = Some(self.current.clone());
+        let buf = self.last.as_ref().unwrap();
+        match parser.parse(buf.as_ref()) {
+            Ok((rest, output)) => {
+                // Modify current to refer to rest.
+                // This is why parse last, as otherwise current would be borrowed here.
+                self.current = buf.slice_ref(rest);
+                Ok(output)
+            }
+            Err(nom::Err::Incomplete(_)) => bail!(UnexpectedEof),
+            Err(nom::Err::Error(e) | nom::Err::Failure(e)) => Err(e.into_owned().into()),
+        }
+    }
+
+    fn read_data_bytes(&mut self) -> Result<Bytes> {
+        let len = self.read_data_length()?;
+        Ok(self.current.split_to(len as usize))
+    }
+}
diff --git a/src/reader/io.rs b/src/reader/io.rs
index 70a1f5c..c594dbf 100644
--- a/src/reader/io.rs
+++ b/src/reader/io.rs
@@ -1,4 +1,4 @@
-use std::io;
+use std::io::{self, Seek};
 
 use bytes::{Buf, BytesMut};
 
@@ -13,7 +13,7 @@ pub struct IoReader<R> {
     consumed: usize,
 }
 
-impl<R: io::Read + io::Seek> IoReader<R> {
+impl<R: io::Read> IoReader<R> {
     pub fn new(read: R) -> Self {
         Self {
             read,
@@ -38,6 +38,11 @@ impl<R: io::Read + io::Seek> IoReader<R> {
 }
 
 impl<R: io::Read + io::Seek> BagReader for IoReader<R> {
+    fn skip(&mut self, amount: usize) -> Result<()> {
+        self.seek(io::SeekFrom::Current(amount as i64))?;
+        Ok(())
+    }
+
     fn read_parser<'a, O: 'a, P>(&'a mut self, mut parser: P) -> Result<O>
     where
         P: nom::Parser<&'a [u8], O, parse::Error<&'a [u8]>>,
@@ -68,8 +73,10 @@ impl<R: io::Read + io::Seek> BagReader for IoReader<R> {
             }
         }
     }
+}
 
-    fn seek(&mut self, mut pos: io::SeekFrom) -> Result<()> {
+impl<R: io::Seek> io::Seek for IoReader<R> {
+    fn seek(&mut self, mut pos: io::SeekFrom) -> io::Result<u64> {
         if let io::SeekFrom::Current(pos) = &mut pos {
             // If seeking relative to current position, subtract data
             // read from the file but not yet consumed.
@@ -78,14 +85,14 @@ impl<R: io::Read + io::Seek> BagReader for IoReader<R> {
             if *pos >= 0 && new_pos < 0 {
                 // The new position is within the already read data, just consume more data
                 self.consumed += *pos as usize;
-                return Ok(());
+                // TODO: compute this correctly
+                return Ok(0);
             }
             *pos = new_pos;
         }
 
         self.buffer.clear();
         self.consumed = 0;
-        self.read.seek(pos)?;
-        Ok(())
+        self.read.seek(pos)
     }
 }
diff --git a/src/reader/slice.rs b/src/reader/slice.rs
index 26e9af4..08bdf54 100644
--- a/src/reader/slice.rs
+++ b/src/reader/slice.rs
@@ -48,6 +48,12 @@ where
     T: Deref<Target = U>,
     U: AsRef<[u8]> + ?Sized + 'static,
 {
+    fn skip(&mut self, amount: usize) -> Result<()> {
+        // TODO: bounds checking
+        self.pos += amount;
+        Ok(())
+    }
+
     fn read_parser<'a, O: 'a, P>(&'a mut self, mut parser: P) -> Result<O>
     where
         P: nom::Parser<&'a [u8], O, parse::Error<&'a [u8]>>,
@@ -63,8 +69,15 @@ where
             Err(nom::Err::Error(e) | nom::Err::Failure(e)) => Err(e.into_owned().into()),
         }
     }
+}
 
-    fn seek(&mut self, pos: io::SeekFrom) -> Result<()> {
+impl<T, U> io::Seek for SliceReader<T>
+where
+    T: Deref<Target = U>,
+    U: AsRef<[u8]> + ?Sized + 'static,
+{
+    fn seek(&mut self, pos: io::SeekFrom) -> io::Result<u64> {
+        // TODO: bounds checking
         match pos {
             io::SeekFrom::Start(pos) => {
                 self.pos = pos as usize;
@@ -76,6 +89,6 @@ where
                 self.pos = ((self.pos as i64) + pos) as usize;
             }
         }
-        Ok(())
+        Ok(self.pos as u64)
     }
 }