examples/rust: Add a minimal hello world rust example

This is about the smallest it can be.

Its Unit application config would look like

    "applications": {
        "rust-hello-world": {
            "type": "wasm",
            "module": "/path/to/unit-wasm/examples/rust/hello-world/target/wasm32-wasi/debug/rust_hello_world.wasm",
            "request_handler": "uwr_request_handler",
            "malloc_handler": "luw_malloc_handler",
            "free_handler": "luw_free_handler"
        }
    }

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/examples/rust/hello-world/src/lib.rs b/examples/rust/hello-world/src/lib.rs
new file mode 100644
index 0000000..9be1abd
--- /dev/null
+++ b/examples/rust/hello-world/src/lib.rs
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/*
+ * Copyright (C) Andrew Clayton
+ * Copyright (C) Timo Stark
+ * Copyright (C) F5, Inc.
+ */
+
+use unit_wasm::rusty::*;
+
+static mut REQUEST_BUF: *mut u8 = std::ptr::null_mut();
+
+#[no_mangle]
+pub extern "C" fn uwr_request_handler(addr: *mut u8) -> i32 {
+    let ctx = &mut UWR_CTX_INITIALIZER();
+
+    uwr_init_ctx(ctx, addr, 4096);
+    uwr_set_req_buf(ctx, unsafe { &mut REQUEST_BUF }, LUW_SRB_ALLOC);
+
+    uwr_write_str!(
+        ctx,
+        " * Welcome to WebAssembly in Rust on Unit! \
+            [libunit-wasm ({}.{}.{}/{:#010x})] *\n\n",
+        LUW_VERSION_MAJOR,
+        LUW_VERSION_MINOR,
+        LUW_VERSION_PATCH,
+        LUW_VERSION_NUMBER,
+    );
+
+    uwr_http_init_headers(ctx, 2, 0);
+    uwr_http_add_header_content_type(ctx, "text/plain");
+    uwr_http_add_header_content_len(ctx);
+    uwr_http_send_headers(ctx);
+
+    uwr_http_send_response(ctx);
+    uwr_http_response_end();
+
+    uwr_free(unsafe { REQUEST_BUF });
+
+    return 0;
+}