Change fuzzing API to mimic upstream's HF_ITER style

The library code is now a lot simpler, does not use macros
and gives users a lot more control.

This solves cargo-fuzz's issue rust-fuzz/cargo-fuzz#101

This syntax is also very similar to the one in AFL.rs.
Maybe we should converge to a compatible API? rust-fuzz/afl.rs#31

example/src/main.rs

@@ -1,18 +1,29 @@
-#![no_main]
-#[macro_use] extern crate honggfuzz;
+extern crate honggfuzz;
+use honggfuzz::fuzz;
 
-fuzz_target!(|data: &[u8]| {
-    if data.len() != 10 {return}
-    if data[0] != 'q' as u8 {return}
-    if data[1] != 'w' as u8 {return}
-    if data[2] != 'e' as u8 {return}
-    if data[3] != 'r' as u8 {return}
-    if data[4] != 't' as u8 {return}
-    if data[5] != 'y' as u8 {return}
-    if data[6] != 'u' as u8 {return}
-    if data[7] != 'i' as u8 {return}
-    if data[8] != 'o' as u8 {return}
-    if data[9] != 'p' as u8 {return}
-    panic!("BOOM")
-});
+fn main() {
+    // Here you can parse `std::env::args and 
+    // setup / initialize your project
 
+    // You have full control over the loop but
+    // you're supposed to call `fuzz` ad vitam aeternam
+    loop {
+        // the fuzz function takes a closure which takes
+        // a reference to a slice of u8.
+        // This slice contains a "random" quantity of "random" data.
+        fuzz(|data|{
+            if data.len() != 10 {return}
+            if data[0] != 'q' as u8 {return}
+            if data[1] != 'w' as u8 {return}
+            if data[2] != 'e' as u8 {return}
+            if data[3] != 'r' as u8 {return}
+            if data[4] != 't' as u8 {return}
+            if data[5] != 'y' as u8 {return}
+            if data[6] != 'u' as u8 {return}
+            if data[7] != 'i' as u8 {return}
+            if data[8] != 'o' as u8 {return}
+            if data[9] != 'p' as u8 {return}
+            panic!("BOOM")
+        });
+    }
+}

src/lib.rs

@@ -82,51 +82,17 @@
 //! 
 //! This crate was inspired by those projects!
 
-// code stolen and adapted from https://github.com/rust-fuzz/libfuzzer-sys/blob/master/src/lib.rs
-#[macro_export]
-macro_rules! fuzz_target {
-    (|$bytes:ident| $body:block) => {
-        #[no_mangle]
-        pub extern fn rust_fuzzer_test_input($bytes: &[u8]) {
-            $body
-        }
+extern "C" {
+    fn HF_ITER(buf_ptr: *mut *const u8, len_ptr: *mut usize );
+}
 
-        #[export_name="LLVMFuzzerTestOneInput"]
-        pub fn test_input_wrap(data: *const u8, size: usize) -> i32 {
-            ::std::panic::catch_unwind(|| unsafe {
-                let data_slice = ::std::slice::from_raw_parts(data, size);
-                rust_fuzzer_test_input(data_slice);
-            }).err().map(|_| ::std::process::abort());
-            0
-        }
-    };
-    (|$data:ident: &[u8]| $body:block) => {
-        fuzz_target!(|$data| $body);
-    };
-    (|$data:ident: $dty: ty| $body:block) => {
-        extern crate arbitrary;
-
-        #[no_mangle]
-        pub extern fn rust_fuzzer_test_input(bytes: &[u8]) {
-            use arbitrary::{Arbitrary, RingBuffer};
-
-            let $data: $dty = if let Ok(d) = RingBuffer::new(bytes, bytes.len()).and_then(|mut b|{
-                Arbitrary::arbitrary(&mut b).map_err(|_| "")
-            }) {
-                d
-            } else {
-                return
-            };
-            $body
-        }
-
-        #[export_name="LLVMFuzzerTestOneInput"]
-        pub fn test_input_wrap(data: *const u8, size: usize) -> i32 {
-            ::std::panic::catch_unwind(|| unsafe {
-                let data_slice = ::std::slice::from_raw_parts(data, size);
-                rust_fuzzer_test_input(data_slice);
-            }).err().map(|_| ::std::process::abort());
-            0
-        }
-    };
+pub fn fuzz<F>(closure: F) where F: Fn(&[u8]) {
+    let buf;
+    unsafe {
+        let mut buf_ptr: *const u8 = std::mem::uninitialized();
+        let mut len_ptr: usize = 0;
+        HF_ITER(&mut buf_ptr, &mut len_ptr);
+        buf = ::std::slice::from_raw_parts(buf_ptr, len_ptr);
+    }
+    closure(buf);
 }