Add afl fuzz target

Author: dbrgn

fuzz-afl/.gitignore

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+out/

fuzz-afl/Cargo.toml

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+[package]
+name = "fuzz-target-jpeg-decoder"
+version = "0.1.0"
+authors = ["jpeg-decoder developers"]
+edition = "2018"
+
+[[bin]]
+name = "fuzz_decode"
+path = "src/fuzz_decode.rs"
+
+[[bin]]
+name = "reproduce_decode"
+path = "src/reproduce_decode.rs"
+
+[dependencies]
+afl = "0.4"
+jpeg-decoder = { path = "../" }

fuzz-afl/README.md

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+# Fuzzing harnesses
+
+## Using the fuzzer
+
+Install afl:
+
+    $ cargo install afl
+
+Build fuzz target:
+
+    $ cargo afl build --release --bin fuzz_<format>
+
+Run afl:
+
+    $ mkdir out/
+    $ cargo afl fuzz -i in/ -o out/ target/release/fuzz_<target>
+
+To reproduce a crash:
+
+    $ cargo run --bin reproduce_<target>
+
+Note: You should also try fuzzing in debug mode, since things like overflow
+checks don't happen in release mode. (Release mode is much faster though.)

fuzz-afl/in/4x4.jpg

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+use afl::fuzz;
+
+use jpeg_decoder::{Decoder, Error};
+
+#[inline(always)]
+fn decode(data: &[u8]) -> Result<Vec<u8>, Error> {
+    let mut decoder = Decoder::new(data);
+    decoder.decode()
+}
+
+fn main() {
+    fuzz!(|data: &[u8]| {
+        let _ = decode(data);
+    });
+}