put examples in rust project

Author: hg-anssi

examples/src/counter.c

@@ -0,0 +1,31 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <inttypes.h>
+
+#include "counter.h"
+
+int main(int argc, const char **argv)
+{
+	if (argc < 2)
+	{
+		return -1;
+	}
+	size_t n = (size_t)strtoull(argv[1], NULL, 10);
+
+	Counter *c = counter_create();
+	for (size_t i = 0; i < n; i++)
+	{
+		if (counter_incr(c) != 0)
+		{
+			printf("overflow\n");
+			counter_destroy(c);
+			return -1;
+		}
+	}
+
+	printf("%" PRIu32 "\n", counter_get(c));
+	counter_destroy(c);
+
+	return 0;
+}

examples/src/counter.h

@@ -0,0 +1,14 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+typedef struct Counter Counter;
+
+Counter *counter_create(void);
+
+int counter_destroy(Counter *counter);
+
+uint32_t counter_get(const Counter *counter);
+
+int counter_incr(Counter *counter);

examples/src/counter.rs

@@ -0,0 +1,57 @@
+/// Opaque counter
+pub struct Counter(u32);
+
+impl Counter {
+    /// Create a counter (initially at 0)
+    fn new() -> Self {
+        Self(0)
+    }
+    /// Get the current value of the counter
+    fn get(&self) -> u32 {
+        self.0
+    }
+    /// Increment the value of the counter if there's no overflow
+    fn incr(&mut self) -> bool {
+        if let Some(n) = self.0.checked_add(1) {
+            self.0 = n;
+            true
+        } else {
+            false
+        }
+    }
+}
+
+// C-compatible API
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn counter_create() -> *mut Counter {
+    Box::into_raw(Box::new(Counter::new()))
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn counter_incr(counter: *mut Counter) -> std::os::raw::c_int {
+    if let Some(counter) = unsafe { counter.as_mut() } {
+        if counter.incr() { 0 } else { -1 }
+    } else {
+        -2
+    }
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn counter_get(counter: *const Counter) -> u32 {
+    if let Some(counter) = unsafe { counter.as_ref() } {
+        counter.get()
+    } else {
+        0
+    }
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn counter_destroy(counter: *mut Counter) -> std::os::raw::c_int {
+    if !counter.is_null() {
+        let _ = unsafe { Box::from_raw(counter) }; // get box and drop
+        0
+    } else {
+        -1
+    }
+}

examples/src/ffi.c

@@ -0,0 +1,54 @@
+#include <stdint.h>
+#include <stdio.h>
+
+/////////////////////// ANCHOR: extern_struct
+struct Data
+{
+	uint32_t a;
+	uint16_t b;
+	uint64_t c;
+};
+__attribute__((packed)) struct PackedData
+{
+	uint32_t a;
+	uint16_t b;
+	uint64_t c;
+};
+/////////////////////// ANCHOR_END: extern_struct
+
+/////////////////////// ANCHOR: pointers
+#include <stdint.h>
+#include <inttypes.h>
+
+//! Add in place
+void add_in_place(uint32_t *a, uint32_t b);
+
+int use_add_in_place()
+{
+	uint32_t x = 25;
+	add_in_place(&x, 17);
+	printf("%" PRIu32 " == 42", x);
+	return 0;
+}
+/////////////////////// ANCHOR_END: pointers
+
+/////////////////////// ANCHOR: function_pointers
+uint32_t repeat(uint32_t start, uint32_t n, uint32_t (*f)(uint32_t));
+/////////////////////// ANCHOR_END: function_pointers
+
+/////////////////////// ANCHOR: free_intern
+struct XtraResource;
+void xtra_with(void (*cb)(struct XtraResource *xtra));
+void xtra_sthg(struct XtraResource *xtra);
+
+void cb(struct XtraResource *xtra)
+{
+	// ()...) do anything with the proposed C API for XtraResource
+	xtra_sthg(xtra);
+}
+
+int use_xtra()
+{
+	xtra_with(cb);
+}
+/////////////////////// ANCHOR_END: free_intern