first commit

.gitignore

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+/target
+**/*.rs.bk

Cargo.toml

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+[package]
+name = "rust-ffi-enum-box"
+version = "0.1.0"
+authors = ["marmeladema <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+
+[build-dependencies]
+cc = "1.0"

README.md

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+# rust-ffi-enum-box

build.rs

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+use cc;
+
+fn main() {
+    cc::Build::new()
+        .include("include")
+        .file("src/tests.c")
+        .warnings(true)
+        .extra_warnings(true)
+        .warnings_into_errors(true)
+        .compile("ctests");
+}

include/tests.h

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+#ifndef _TESTS_H_
+#define _TESTS_H_
+
+#include <stdlib.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// https://github.com/rust-lang/rfcs/blob/master/text/2195-really-tagged-unions.md
+typedef enum {
+    SCHEME_TYPE_TAG_IP,
+    SCHEME_TYPE_TAG_BYTES,
+    SCHEME_TYPE_TAG_INT,
+    SCHEME_TYPE_TAG_BOOL,
+    SCHEME_TYPE_TAG_ARRAY,
+    SCHEME_TYPE_TAG_MAP,
+} scheme_type_tag_t;
+
+typedef struct {
+    scheme_type_tag_t tag;
+    void *data[1];
+} scheme_type_t;
+
+static const scheme_type_t SCHEME_TYPE_IP = {.tag = SCHEME_TYPE_TAG_IP, .data = {NULL}};
+static const scheme_type_t SCHEME_TYPE_BYTES = {.tag = SCHEME_TYPE_TAG_BYTES, .data = {NULL}};
+static const scheme_type_t SCHEME_TYPE_INT = {.tag = SCHEME_TYPE_TAG_INT, .data = {NULL}};
+static const scheme_type_t SCHEME_TYPE_BOOL = {.tag = SCHEME_TYPE_TAG_BOOL, .data = {NULL}};
+
+typedef struct scheme scheme_t;
+
+scheme_t *scheme_new();
+void scheme_free(scheme_t *);
+
+void scheme_set_type(scheme_t *scheme, scheme_type_t ty);
+
+void scheme_print(scheme_t *scheme);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // _TESTS_H_

src/main.rs

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+#[derive(Debug)]
+#[repr(C)]
+pub enum SchemeType {
+    Ip,
+    Bytes,
+    Int,
+    Bool,
+    Array(Box<SchemeType>),
+    Map(Box<SchemeType>),
+}
+
+#[derive(Debug)]
+pub struct Scheme {
+    ty: Option<SchemeType>,
+}
+
+#[no_mangle]
+pub extern "C" fn scheme_new() -> *mut Scheme {
+    Box::into_raw(Box::new(Scheme { ty: None }))
+}
+
+#[no_mangle]
+pub extern "C" fn scheme_free(scheme: *mut Scheme) {
+    unsafe {
+        Box::from_raw(scheme);
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn scheme_set_type(scheme: *mut Scheme, ty: SchemeType) {
+    unsafe {
+        (*scheme).ty = Some(ty);
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn scheme_print(scheme: *mut Scheme) {
+    unsafe {
+        println!("{:?}", (*scheme));
+    }
+}
+
+extern "C" {
+    fn scheme_ctest_01();
+    fn scheme_ctest_02();
+}
+
+fn main() {
+    println!("Hello, world!");
+    println!(
+        "sizeof(SchemeType) = {:?}",
+        std::mem::size_of::<SchemeType>()
+    );
+    unsafe { scheme_ctest_01() };
+    unsafe { scheme_ctest_02() };
+}

src/tests.c

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+#include "tests.h"
+
+void scheme_ctest_01() {
+	scheme_t *scheme = scheme_new();
+	scheme_print(scheme);
+	scheme_set_type(scheme, SCHEME_TYPE_INT);
+	scheme_print(scheme);
+	scheme_free(scheme);
+}
+
+void scheme_ctest_02() {
+	scheme_t *scheme = scheme_new();
+	scheme_print(scheme);
+	scheme_type_t *ty = (scheme_type_t *)malloc(sizeof(scheme_type_t));
+	*ty = SCHEME_TYPE_INT;
+	scheme_set_type(scheme, *ty);
+	free(ty);
+	scheme_print(scheme);
+	scheme_free(scheme);
+}