Initial fuzzing support, still images only (#23)

fuzz/.gitignore

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+target
+corpus
+artifacts
+coverage

fuzz/Cargo.toml

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+[package]
+name = "webp-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2021"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+
+[dependencies.webp]
+path = ".."
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[profile.release]
+debug = 1
+
+[[bin]]
+name = "decode_still"
+path = "fuzz_targets/decode_still.rs"
+test = false
+doc = false

fuzz/fuzz_targets/decode_still.rs

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+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+use std::io::Cursor;
+
+fuzz_target!(|input: &[u8]| {
+    let decoder = webp::WebPDecoder::new(Cursor::new(input));
+    if let Ok(mut decoder) = decoder {
+        let (width, height) = decoder.dimensions();
+        let bytes_per_pixel = if decoder.has_alpha() { 4 } else { 3 };
+        let mut data = vec![0; width as usize * height as usize * bytes_per_pixel];
+        let _ = decoder.read_image(&mut data);
+    }
+});