FW-1087: provide wirefilter.h C header file and add ffi/tests/ctests crate

This new crate is here to provide a set of C based tests that will
serve two purposes:
* Provide some examples how to use the FFI bindings
* Test that those bindings are actually working as intended

Internally, it relies on ffi/tests/ctests/src/tests.c file which contains
tests written in C and that is compiled at cargo configuration time
through the use of a build.rs file. This produces a wirefilter_ffi_ctests.a
static library that is later used in the ffi/tests/ctests/src/lib.rs file
to call the different tests functions. All of this is done in order to try
to integrate somehow properly with cargo test.

Author: marmeladema

Cargo.lock

@@ -25,3 +25,4 @@ path = "../engine"
 [dev-dependencies]
 regex = "1.0.1"
 indoc = "0.3.0"
+wirefilter-ffi-ctests = {path = "tests/ctests"}

ffi/Cargo.toml

@@ -0,0 +1,129 @@
+#ifndef _WIREFILTER_H_
+#define _WIREFILTER_H_
+
+#include <stdlib.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct wirefilter_scheme wirefilter_scheme_t;
+typedef struct wirefilter_execution_context wirefilter_execution_context_t;
+typedef struct wirefilter_filter_ast wirefilter_filter_ast_t;
+typedef struct wirefilter_filter wirefilter_filter_t;
+
+typedef struct {
+    const char *data;
+    size_t length;
+} wirefilter_rust_allocated_str_t;
+
+typedef struct {
+    const char *data;
+    size_t length;
+} wirefilter_static_rust_allocated_str_t;
+
+typedef struct {
+    const char *data;
+    size_t length;
+} wirefilter_externally_allocated_str_t;
+
+typedef struct {
+    const unsigned char *data;
+    size_t length;
+} wirefilter_externally_allocated_byte_arr_t;
+
+typedef union {
+    union {
+        uint8_t success;
+        struct {
+            uint8_t _res1;
+            wirefilter_rust_allocated_str_t msg;
+        } err;
+        struct {
+            uint8_t _res2;
+            wirefilter_filter_ast_t *ast;
+        } ok;
+    };
+} wirefilter_parsing_result_t;
+
+typedef enum {
+    WIREFILTER_TYPE_IP,
+    WIREFILTER_TYPE_BYTES,
+    WIREFILTER_TYPE_INT,
+    WIREFILTER_TYPE_BOOL,
+} wirefilter_type_t;
+
+wirefilter_scheme_t *wirefilter_create_scheme();
+void wirefilter_free_scheme(wirefilter_scheme_t *scheme);
+
+void wirefilter_add_type_field_to_scheme(
+    wirefilter_scheme_t *scheme,
+    wirefilter_externally_allocated_str_t name,
+    wirefilter_type_t type
+);
+
+wirefilter_parsing_result_t wirefilter_parse_filter(
+    wirefilter_scheme_t *scheme,
+    wirefilter_externally_allocated_str_t input
+);
+
+void wirefilter_free_parsing_result(wirefilter_parsing_result_t result);
+
+wirefilter_filter_t *wirefilter_compile_filter(wirefilter_filter_ast_t *ast);
+void wirefilter_free_compiled_filter(wirefilter_filter_t *filter);
+
+wirefilter_execution_context_t *wirefilter_create_execution_context(
+    wirefilter_scheme_t *scheme
+);
+void wirefilter_free_execution_context(
+    wirefilter_execution_context_t *exec_ctx
+);
+
+void wirefilter_add_int_value_to_execution_context(
+    wirefilter_execution_context_t *exec_ctx,
+    wirefilter_externally_allocated_str_t name,
+    int32_t value
+);
+
+void wirefilter_add_bytes_value_to_execution_context(
+    wirefilter_execution_context_t *exec_ctx,
+    wirefilter_externally_allocated_str_t name,
+    wirefilter_externally_allocated_byte_arr_t value
+);
+
+void wirefilter_add_ipv6_value_to_execution_context(
+    wirefilter_execution_context_t *exec_ctx,
+    wirefilter_externally_allocated_str_t name,
+    uint8_t value[16]
+);
+
+void wirefilter_add_ipv4_value_to_execution_context(
+    wirefilter_execution_context_t *exec_ctx,
+    wirefilter_externally_allocated_str_t name,
+    uint8_t value[4]
+);
+
+void wirefilter_add_bool_value_to_execution_context(
+    wirefilter_execution_context_t *exec_ctx,
+    wirefilter_externally_allocated_str_t name,
+    bool value
+);
+
+bool wirefilter_match(
+    wirefilter_filter_t *filter,
+    wirefilter_execution_context_t *exec_ctx
+);
+
+bool wirefilter_filter_uses(
+    wirefilter_filter_t *filter,
+    wirefilter_externally_allocated_str_t field_name
+);
+
+wirefilter_static_rust_allocated_str_t wirefilter_get_version();
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // _WIREFILTER_H_

ffi/include/wirefilter.h

@@ -92,6 +92,11 @@ pub extern "C" fn wirefilter_parse_filter<'s, 'i>(
     }
 }
 
+#[no_mangle]
+pub extern "C" fn wirefilter_free_parsing_result(r: ParsingResult<'_>) {
+    drop(r);
+}
+
 /// Wrapper for Hasher that allows using Write API (e.g. with serializer).
 #[derive(Default)]
 struct HasherWrite<H: Hasher>(H);

ffi/src/lib.rs

@@ -0,0 +1,12 @@
+[package]
+authors = ["Elie ROUDNINSKI <[email protected]>"]
+name = "wirefilter-ffi-ctests"
+version = "0.1.0"
+description = "C based tests for FFI bindings of the Wirefilter engine"
+publish = false
+
+[dependencies]
+wirefilter-ffi = {path = "../.."}
+
+[build-dependencies]
+cc = "1.0"

ffi/tests/ctests/Cargo.toml

@@ -0,0 +1,11 @@
+extern crate cc;
+
+fn main() {
+    cc::Build::new()
+        .include("../../include")
+        .file("src/tests.c")
+        .flag("-Wall")
+        .flag("-Wextra")
+        .flag("-Werror")
+        .compile("wirefilter_ffi_ctests");
+}

ffi/tests/ctests/build.rs

@@ -0,0 +1,40 @@
+#[no_mangle]
+unsafe extern "C" fn rust_assert(check: bool, msg: *const std::os::raw::c_char) {
+    assert!(check, "{}", std::ffi::CStr::from_ptr(msg).to_str().unwrap());
+}
+
+macro_rules! ffi_ctest {
+    (@inner $($name:ident => $link_name:expr,)*) => {
+        $(
+            #[test]
+            pub fn $name() {
+                #[link(name = "wirefilter_ffi")]
+                extern "C" {
+                    #[link_name = $link_name]
+                    fn ctest();
+                }
+
+                unsafe { ctest() }
+            }
+        )*
+    };
+
+    ($($name:ident,)*) => {
+        ffi_ctest! { @inner
+            $($name => concat!("wirefilter_ffi_ctest_", stringify!($name)),)*
+        }
+    };
+}
+
+mod ffi_ctest {
+    ffi_ctest!(
+        create_scheme,
+        add_fields_to_scheme,
+        parse_good_filter,
+        parse_bad_filter,
+        compile_filter,
+        create_execution_context,
+        add_values_to_execution_context,
+        match_filter,
+    );
+}