add read_entry benchmark

Cargo.toml

@@ -19,8 +19,14 @@ bzip2 = { version = "0.3", optional = true }
 libflate = { version = "0.1.16", optional = true }
 
 [dev-dependencies]
+bencher = "0.1"
+rand = "0.4"
 walkdir = "1.0"
 
 [features]
 deflate = ["libflate"]
 default = ["bzip2", "deflate"]
+
+[[bench]]
+name = "read_entry"
+harness = false

benches/read_entry.rs

@@ -0,0 +1,46 @@
+#[macro_use]
+extern crate bencher;
+extern crate rand;
+extern crate zip;
+
+use std::io::{Cursor, Read, Write};
+
+use bencher::Bencher;
+use rand::Rng;
+use zip::{ZipArchive, ZipWriter};
+
+fn generate_random_archive(size: usize) -> Vec<u8> {
+    let data = Vec::new();
+    let mut writer = ZipWriter::new(Cursor::new(data));
+    let options = zip::write::FileOptions::default()
+        .compression_method(zip::CompressionMethod::Stored);
+
+    writer.start_file("random.dat", options).unwrap();
+    let mut bytes = vec![0u8; size];
+    rand::thread_rng().fill_bytes(&mut bytes);
+    writer.write_all(&bytes).unwrap();
+
+    writer.finish().unwrap().into_inner()
+}
+
+fn read_entry(bench: &mut Bencher) {
+    let size = 1024 * 1024;
+    let bytes = generate_random_archive(size);
+    let mut archive = ZipArchive::new(Cursor::new(bytes.as_slice())).unwrap();
+
+    bench.iter(|| {
+        let mut file = archive.by_name("random.dat").unwrap();
+        let mut buf = [0u8; 1024];
+        loop {
+            let n = file.read(&mut buf).unwrap();
+            if n == 0 {
+                break;
+            }
+        }
+    });
+
+    bench.bytes = size as u64;
+}
+
+benchmark_group!(benches, read_entry);
+benchmark_main!(benches);