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>

2 files changed, 74 insertions, 1 deletions

diff --git a/examples/c/Makefile b/examples/c/Makefile
index 1b10269..0b0fc31 100644
--- a/examples/c/Makefile
+++ b/examples/c/Makefile
@@ -12,7 +12,9 @@ luw_deps = $(LUW_SRCDIR)/libunit-wasm.a \
 
 examples: examples-luw
 
-examples-luw: luw-echo-request.wasm luw-upload-reflector.wasm
+examples-luw: luw-echo-request.wasm \
+	      luw-upload-reflector.wasm \
+	      large-upload.wasm
 
 examples-raw: echo-request-raw.wasm upload-reflector-raw.wasm
 
@@ -36,5 +38,9 @@ upload-reflector-raw.wasm: upload-reflector-raw.c unit-wasm-raw.o
 	$(PP_CCLNK) $(SDIR)/$@
 	$(v)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $< unit-wasm-raw.o
 
+large-upload.wasm: large-upload.c $(luw_deps)
+	$(PP_CCLNK) $(SDIR)/$@
+	$(v)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $< $(LIBS)
+
 clean:
 	rm -f *.wasm *.o *.gch
diff --git a/examples/c/large-upload.c b/examples/c/large-upload.c
new file mode 100644
index 0000000..9d89298
--- /dev/null
+++ b/examples/c/large-upload.c
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/* examples/c/large-upload.c - Example of handling request payload larger
+ *			       larger than the shared memory
+ *
+ * Copyright (C) Andrew Clayton
+ * Copyright (C) F5, Inc.
+ */
+
+#define _XOPEN_SOURCE	500
+
+#define _FILE_OFFSET_BITS 64
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "unit/unit-wasm.h"
+
+static luw_ctx_t ctx;
+static u8 *request_buf;
+static unsigned long long total_bytes_wrote;
+static int fd;
+
+__luw_export_name("luw_module_end_handler")
+void luw_module_end_handler(void)
+{
+        free(request_buf);
+}
+
+__luw_export_name("luw_module_init_handler")
+void luw_module_init_handler(void)
+{
+        request_buf = malloc(luw_mem_get_init_size());
+}
+
+__luw_export_name("luw_response_end_handler")
+void luw_response_end_handler(void)
+{
+	close(fd);
+	total_bytes_wrote = 0;
+}
+
+__luw_export_name("luw_request_handler")
+int luw_request_handler(u8 *addr)
+{
+	ssize_t bytes_wrote;
+
+	if (total_bytes_wrote == 0) {
+		luw_init_ctx(&ctx, addr, 0);
+		luw_set_req_buf(&ctx, &request_buf, LUW_SRB_NONE);
+
+		fd = open("/var/tmp/large-file.dat", O_CREAT|O_TRUNC|O_WRONLY,
+			  0666);
+	}
+
+	bytes_wrote = luw_mem_splice_file(addr, fd);
+	if (bytes_wrote == -1)
+		return -1;
+
+	total_bytes_wrote += bytes_wrote;
+	if (total_bytes_wrote == luw_get_http_content_len(&ctx))
+		luw_http_response_end();
+
+	return 0;
+}