Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

vendor/png/benches/README.md

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+# Getting started with benchmarking
+
+To run the benchmarks you need a nightly rust toolchain.
+Then you launch it with
+
+    rustup run nightly cargo bench --features=benchmarks

vendor/png/benches/decoder.rs

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+use std::fs;
+
+use criterion::{criterion_group, criterion_main, Criterion, Throughput};
+use png::Decoder;
+
+fn load_all(c: &mut Criterion) {
+    for entry in fs::read_dir("tests/benches/").unwrap().flatten() {
+        match entry.path().extension() {
+            Some(st) if st == "png" => {}
+            _ => continue,
+        }
+
+        let data = fs::read(entry.path()).unwrap();
+        bench_file(c, data, entry.file_name().into_string().unwrap());
+    }
+}
+
+criterion_group!(benches, load_all);
+criterion_main!(benches);
+
+fn bench_file(c: &mut Criterion, data: Vec<u8>, name: String) {
+    let mut group = c.benchmark_group("decode");
+    group.sample_size(20);
+
+    let decoder = Decoder::new(&*data);
+    let mut reader = decoder.read_info().unwrap();
+    let mut image = vec![0; reader.output_buffer_size()];
+    let info = reader.next_frame(&mut image).unwrap();
+
+    group.throughput(Throughput::Bytes(info.buffer_size() as u64));
+    group.bench_with_input(name, &data, |b, data| {
+        b.iter(|| {
+            let decoder = Decoder::new(data.as_slice());
+            let mut decoder = decoder.read_info().unwrap();
+            decoder.next_frame(&mut image).unwrap();
+        })
+    });
+}