1 files changed, 78 insertions, 0 deletions
diff --git a/tests/odirect_write.c b/tests/odirect_write.c
new file mode 100644
index 0000000..1376a51
--- /dev/null
+++ b/tests/odirect_write.c
@@ -0,0 +1,78 @@
+#ifdef __linux__
+
+#include <stdio.h>
+#include <string.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#ifndef O_DIRECT
+#define O_DIRECT 00040000 /* direct disk access hint */
+#endif
+
+int main(int argc, char** argv) {
+    if (argc != 2) {
+        fprintf(stderr, "Expected 1 argument: the file to read.\n");
+        return 1;
+    }
+
+    int fd = open(argv[1], O_WRONLY | O_CREAT | O_DIRECT, 0644);
+    if (fd == -1) {
+        perror("failed to open file");
+        return 1;
+    }
+
+    const size_t buf_size = 4096;
+    unsigned char* buf = mmap(NULL, buf_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+    if (buf == MAP_FAILED) {
+        perror("mmap failed");
+        return 1;
+    }
+
+    size_t total_size = 0;
+    while (1) {
+        if (feof(stdin)) {
+            break;
+        }
+
+        memset(buf, 0, buf_size);
+        size_t amt_read = fread(buf, 1, buf_size, stdin);
+        if (ferror(stdin)) {
+            perror("failed to read stdin");
+            return 1;
+        }
+        if (amt_read == 0) {
+            continue;
+        }
+
+        total_size += amt_read;
+
+        ssize_t res = write(fd, buf, buf_size);
+        if (res == -1) {
+            perror("failed to write");
+            return 1;
+        }
+        if (res != buf_size) {
+            // Too lazy to write a loop here unless it turns out to be necessary.
+            fprintf(stderr, "Failed to write exactly %ld bytes", amt_read);
+        }
+    }
+
+    munmap(buf, buf_size);
+
+    return 0;
+}
+
+#else  // __linux__
+
+#include <stdio.h>
+
+int main() {
+    fprintf(stderr, "Not supported on this platform.\n");
+    return 1;
+}
+
+#endif  // __linux__