From a7ab34ebbce60f2af159f9010a2e3629756af3d1 Mon Sep 17 00:00:00 2001
From: human <human@neet.fi>
Date: Thu, 7 Jan 2021 16:31:52 +0200
Subject: fix truncating in defineFile()

- in the C part: enable FUSE_CAP_ATOMIC_O_TRUNC so that open() will get called with O_TRUNC in flags instead of truncate() being called separately
  - this also prevents truncate() from calling setData() with an empty string when a file is opened with O_TRUNC
- in defineFile()->open(): if O_TRUNC is used, don't call getData() but start with an empty file as if it had just been truncated
- in defineFile()->write()/truncate(): correct buffer resizing/copying
---
 fs/tabfs.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

(limited to 'fs')

diff --git a/fs/tabfs.c b/fs/tabfs.c
index 8c28dab..0eab91c 100644
--- a/fs/tabfs.c
+++ b/fs/tabfs.c
@@ -423,6 +423,20 @@ static int tabfs_create(const char *path, mode_t mode, struct fuse_file_info *fi
     return 0;
 }
 
+#define want_capability(conn, flag) \
+    do { \
+        if (conn->capable & flag) { \
+            conn->want |= flag; \
+        } else { \
+            eprintln("warning: " #flag " not supported"); \
+        } \
+    } while (0)
+
+static void *tabfs_init(struct fuse_conn_info *conn) {
+    want_capability(conn, FUSE_CAP_ATOMIC_O_TRUNC);
+    return NULL;
+}
+
 static const struct fuse_operations tabfs_oper = {
     .getattr  = tabfs_getattr,
     .readlink = tabfs_readlink,
@@ -441,6 +455,8 @@ static const struct fuse_operations tabfs_oper = {
 
     .mkdir  = tabfs_mkdir,
     .create = tabfs_create,
+
+    .init = tabfs_init,
 };
 
 int main(int argc, char **argv) {
-- 
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