gix-config: Add a fuzz harness for File

Author: nathaniel-brough

gix-config/fuzz/Cargo.toml

@@ -32,3 +32,9 @@ name = "fuzz_file_section"
 path = "fuzz_targets/fuzz_file_section.rs"
 test = false
 doc = false
+
+[[bin]]
+name = "fuzz_file"
+path = "fuzz_targets/fuzz_file.rs"
+test = false
+doc = false

gix-config/fuzz/fuzz_targets/fuzz_file.rs

@@ -0,0 +1,42 @@
+#![no_main]
+
+use arbitrary::Arbitrary;
+use gix_config::{
+    file::{init::Options, Metadata},
+    File,
+};
+use libfuzzer_sys::fuzz_target;
+use std::hint::black_box;
+
+#[derive(Arbitrary, Debug)]
+struct Ctx<'a> {
+    input: &'a [u8],
+    sections_by_name: &'a str,
+}
+
+macro_rules! unwrap_or_return {
+    ($e:expr) => {
+        match $e {
+            Ok(val) => val,
+            Err(_) => return,
+        }
+    };
+}
+
+fuzz_target!(|ctx: Ctx| {
+    let meta = Metadata::default();
+    let options = Options::default();
+    let file = unwrap_or_return!(File::from_bytes_no_includes(&ctx.input, meta.clone(), options.clone()));
+    _ = black_box(file.sections().count());
+    _ = black_box(file.sections_and_ids().count());
+    _ = black_box(file.sections_and_postmatter().count());
+    _ = black_box(file.sections_by_name(ctx.sections_by_name).map(|x| x.count()));
+    _ = black_box(file.frontmatter());
+
+    let roundtrip_as_string: Vec<u8> = file.to_bstring().into();
+    _ = unwrap_or_return!(black_box(File::from_bytes_no_includes(
+        &roundtrip_as_string,
+        meta.clone(),
+        options.clone(),
+    )));
+});