From 5db227b05ba316713d6793e728b21366e8337721 Mon Sep 17 00:00:00 2001
From: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>
Date: Sat, 4 Apr 2020 20:23:21 -0400
Subject: Initial commit

---
 nureadahead-preload.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 nureadahead-preload.c

(limited to 'nureadahead-preload.c')

diff --git a/nureadahead-preload.c b/nureadahead-preload.c
new file mode 100644
index 0000000..7d10df8
--- /dev/null
+++ b/nureadahead-preload.c
@@ -0,0 +1,38 @@
+#define _POSIX_C_SOURCE 200112L
+#include <assert.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+void usage() {
+    fputs("usage: nureadahead-preload DEVICE < file\n", stderr);
+}
+
+int main(int argc, char *argv[]) {
+    if (argc != 2 || argv[1][0] == '-' || argv[1][0] == '\0') {
+        usage();
+        exit(1);
+    }
+
+    int fd = open(argv[1], O_RDONLY);
+    if (fd == -1) {
+        perror("nureadahead-preload");
+        exit(1);
+    }
+
+    while (1) {
+        unsigned long long start, end;
+        switch (scanf("%llu %llu\n", &start, &end)) {
+            case 2:
+                if (posix_fadvise(fd, start * 512, (end - start + 1) * 512, POSIX_FADV_WILLNEED) == -1) {
+                    perror("nureadahead-preload: readahead");
+                    exit(1);
+                }
+                break;
+            case EOF:
+                exit(0);
+            default:
+                fputs("nureadahead-preload: invalid input\n", stderr);
+        }
+    }
+}
-- 
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