examples: Add C and Rust examples of handling large uploads

The programs demonstrate handling requests with payloads larger than
4GiB which means they need to be written out to disk and so also
demonstrates the use of the file-system access mechanism.

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

3 files changed, 85 insertions, 1 deletions

diff --git a/examples/rust/Makefile b/examples/rust/Makefile
index a000c9c..3d2570d 100644
--- a/examples/rust/Makefile
+++ b/examples/rust/Makefile
@@ -2,7 +2,10 @@ include ../../shared.mk
 
 SDIR = examples/rust
 
-examples: rust-echo-request rust-upload-reflector rust-hello-world
+examples: rust-echo-request \
+	  rust-upload-reflector \
+	  rust-hello-world \
+	  rust-large-upload
 
 rust-echo-request: echo-request/Cargo.toml echo-request/src/lib.rs
 	$(PP_GEN) $(SDIR)/echo-request/target/wasm32-wasi/
@@ -16,6 +19,10 @@ rust-hello-world: hello-world/Cargo.toml hello-world/src/lib.rs
 	$(PP_GEN) $(SDIR)/hello-world/target/wasm32-wasi/
 	$(v)cd hello-world; cargo build --target=wasm32-wasi
 
+rust-large-upload: large-upload/Cargo.toml large-upload/src/lib.rs
+	$(PP_GEN) $(SDIR)/large-upload/target/wasm32-wasi/
+	$(v)cd large-upload; cargo build --target=wasm32-wasi
+
 clean:
 	rm -f */Cargo.lock
 	rm -rf */target
diff --git a/examples/rust/large-upload/Cargo.toml b/examples/rust/large-upload/Cargo.toml
new file mode 100644
index 0000000..b74192e
--- /dev/null
+++ b/examples/rust/large-upload/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "rust-large-upload"
+version = "0.2.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+unit-wasm = { path = "../../../src/rust", version = "0.2.0" }
+
+[lib]
+crate-type = ["cdylib"]
diff --git a/examples/rust/large-upload/src/lib.rs b/examples/rust/large-upload/src/lib.rs
new file mode 100644
index 0000000..a59bdb3
--- /dev/null
+++ b/examples/rust/large-upload/src/lib.rs
@@ -0,0 +1,65 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/*
+ * Copyright (C) Andrew Clayton
+ * Copyright (C) Timo Stark
+ * Copyright (C) F5, Inc.
+ */
+
+use unit_wasm::rusty::*;
+
+use std::fs::File;
+use std::ptr::null_mut;
+
+static mut CTX: luw_ctx_t = UWR_CTX_INITIALIZER();
+static mut REQUEST_BUF: *mut u8 = null_mut();
+static mut TOTAL_BYTES_WROTE: u64 = 0;
+
+#[no_mangle]
+pub extern "C" fn uwr_module_end_handler() {
+    unsafe { uwr_free(REQUEST_BUF); }
+}
+
+#[no_mangle]
+pub extern "C" fn uwr_module_init_handler() {
+    unsafe { REQUEST_BUF = uwr_malloc(uwr_mem_get_init_size()); }
+}
+
+#[no_mangle]
+pub extern "C" fn uwr_response_end_handler() {
+    unsafe { TOTAL_BYTES_WROTE = 0; }
+}
+
+#[no_mangle]
+pub extern "C" fn uwr_request_handler(addr: *mut u8) -> i32 {
+    let ctx: *mut luw_ctx_t = unsafe { &mut CTX };
+    let mut f;
+    let bytes_wrote: isize;
+    let mut total = unsafe { TOTAL_BYTES_WROTE };
+
+    if total == 0 {
+        uwr_init_ctx(ctx, addr, 0);
+        uwr_set_req_buf(ctx, unsafe { &mut REQUEST_BUF }, LUW_SRB_NONE);
+
+        f = File::create("/var/tmp/large-file.dat").unwrap();
+    } else {
+        f = File::options()
+            .append(true)
+            .open("/var/tmp/large-file.dat")
+            .unwrap();
+    }
+
+    bytes_wrote = uwr_mem_splice_file(addr, &mut f);
+    if bytes_wrote == -1 {
+        return -1;
+    }
+
+    total += bytes_wrote as u64;
+    if total == uwr_get_http_content_len(ctx) {
+        uwr_http_response_end();
+    } else {
+        unsafe { TOTAL_BYTES_WROTE = total };
+    }
+
+    return 0;
+}