Port: implement posix_fallocate wrapper

[babeltrace.git] / include / babeltrace / compat / fcntl.h

diff --git a/include/babeltrace/compat/fcntl.h b/include/babeltrace/compat/fcntl.h
new file mode 100644 (file)
index 0000000..59060ff
--- /dev/null
+++ b/include/babeltrace/compat/fcntl.h
@@ -0,0 +1,143 @@
+#ifndef _BABELTRACE_COMPAT_FCNTL_H
+#define _BABELTRACE_COMPAT_FCNTL_H
+
+/*
+ * babeltrace/compat/fcntl.h
+ *
+ * Copyright 2015 (c) - Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ *
+ * fcntl compatibility layer.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <config.h>
+
+#ifdef BABELTRACE_HAVE_POSIX_FALLOCATE
+
+#include <fcntl.h>
+
+static inline
+int bt_posix_fallocate(int fd, off_t offset, off_t len)
+{
+       return posix_fallocate(fd, offset, len);
+}
+
+#else /* #ifdef BABELTRACE_HAVE_POSIX_FALLOCATE */
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <string.h>
+
+#define BABELTRACE_FALLOCATE_BUFLEN    256
+
+#ifndef min_t
+#define min_t(type, a, b)      \
+       ((type) (a) < (type) (b) ? (type) (a) : (type) (b))
+#endif
+
+static inline
+int bt_posix_fallocate(int fd, off_t offset, off_t len)
+{
+       int ret = 0;
+       ssize_t copy_len;
+       char buf[BABELTRACE_FALLOCATE_BUFLEN];
+       off_t i, file_pos, orig_end_offset, range_end;
+
+       if (offset < 0 || len < 0) {
+               ret = EINVAL;
+               goto end;
+       }
+
+       range_end = offset + len;
+       if (range_end < 0) {
+               ret = EFBIG;
+               goto end;
+       }
+
+       file_pos = lseek(fd, 0, SEEK_CUR);
+       if (file_pos < 0) {
+               ret = errno;
+               goto end;
+       }
+
+       orig_end_offset = lseek(fd, 0, SEEK_END);
+       if (orig_end_offset < 0) {
+               ret = errno;
+               goto end;
+       }
+
+       /* Seek back to original position. */
+       ret = lseek(fd, file_pos, SEEK_SET);
+       if (ret) {
+               ret = errno;
+               goto end;
+       }
+
+       /*
+        * The file may not need to grow, but we want to ensure the
+        * space has actually been reserved by the file system. First, copy
+        * the "existing" region of the file, then grow the file if needed.
+        */
+       for (i = file_pos; i < min_t(off_t, range_end, orig_end_offset);
+                       i += copy_len) {
+               ssize_t copy_ret;
+
+               copy_len = min_t(size_t, BABELTRACE_FALLOCATE_BUFLEN,
+                               min_t(off_t, range_end - i,
+                                       orig_end_offset - i));
+               copy_ret = pread(fd, &buf, copy_len, i);
+               if (copy_ret < copy_len) {
+                       /*
+                        * The caller must handle any EINTR.
+                        * POSIX_FALLOCATE(3) does not mention EINTR.
+                        * However, glibc does forward to fallocate()
+                        * directly on Linux, which may be interrupted.
+                        */
+                       ret = errno;
+                       goto end;
+               }
+
+               copy_ret = pwrite(fd, &buf, copy_len, i);
+               if (copy_ret < copy_len) {
+                       /* Same caveat as noted at pread() */
+                       ret = errno;
+                       goto end;
+               }
+       }
+
+       /* Grow file, as necessary. */
+       memset(&buf, 0, BABELTRACE_FALLOCATE_BUFLEN);
+       for (i = orig_end_offset; i < range_end; i += copy_len) {
+               ssize_t write_ret;
+
+               copy_len = min_t(size_t, BABELTRACE_FALLOCATE_BUFLEN,
+                               range_end - i);
+               write_ret = pwrite(fd, &buf, copy_len, i);
+               if (write_ret < copy_len) {
+                       ret = errno;
+                       goto end;
+               }
+       }
+end:
+       return ret;
+}
+#endif /* #else #ifdef BABELTRACE_HAVE_POSIX_FALLOCATE */
+
+#endif /* _BABELTRACE_COMPAT_FCNTL_H */