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-rw-r--r--io/copy_file_range-compat.c160
1 files changed, 160 insertions, 0 deletions
diff --git a/io/copy_file_range-compat.c b/io/copy_file_range-compat.c
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+++ b/io/copy_file_range-compat.c
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+/* Emulation of copy_file_range.
+ Copyright (C) 2017-2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+/* The following macros should be defined before including this
+ file:
+
+ COPY_FILE_RANGE_DECL Declaration specifiers for the function below.
+ COPY_FILE_RANGE Name of the function to define. */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <limits.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+COPY_FILE_RANGE_DECL
+ssize_t
+COPY_FILE_RANGE (int infd, __off64_t *pinoff,
+ int outfd, __off64_t *poutoff,
+ size_t length, unsigned int flags)
+{
+ if (flags != 0)
+ {
+ __set_errno (EINVAL);
+ return -1;
+ }
+
+ {
+ struct stat64 instat;
+ struct stat64 outstat;
+ if (fstat64 (infd, &instat) != 0 || fstat64 (outfd, &outstat) != 0)
+ return -1;
+ if (S_ISDIR (instat.st_mode) || S_ISDIR (outstat.st_mode))
+ {
+ __set_errno (EISDIR);
+ return -1;
+ }
+ if (!S_ISREG (instat.st_mode) || !S_ISREG (outstat.st_mode))
+ {
+ /* We need a regular input file so that the we can seek
+ backwards in case of a write failure. */
+ __set_errno (EINVAL);
+ return -1;
+ }
+ if (instat.st_dev != outstat.st_dev)
+ {
+ /* Cross-device copies are not supported. */
+ __set_errno (EXDEV);
+ return -1;
+ }
+ }
+
+ /* The output descriptor must not have O_APPEND set. */
+ {
+ int flags = __fcntl (outfd, F_GETFL);
+ if (flags & O_APPEND)
+ {
+ __set_errno (EBADF);
+ return -1;
+ }
+ }
+
+ /* Avoid an overflow in the result. */
+ if (length > SSIZE_MAX)
+ length = SSIZE_MAX;
+
+ /* Main copying loop. The buffer size is arbitrary and is a
+ trade-off between stack size consumption, cache usage, and
+ amortization of system call overhead. */
+ size_t copied = 0;
+ char buf[8192];
+ while (length > 0)
+ {
+ size_t to_read = length;
+ if (to_read > sizeof (buf))
+ to_read = sizeof (buf);
+
+ /* Fill the buffer. */
+ ssize_t read_count;
+ if (pinoff == NULL)
+ read_count = read (infd, buf, to_read);
+ else
+ read_count = __libc_pread64 (infd, buf, to_read, *pinoff);
+ if (read_count == 0)
+ /* End of file reached prematurely. */
+ return copied;
+ if (read_count < 0)
+ {
+ if (copied > 0)
+ /* Report the number of bytes copied so far. */
+ return copied;
+ return -1;
+ }
+ if (pinoff != NULL)
+ *pinoff += read_count;
+
+ /* Write the buffer part which was read to the destination. */
+ char *end = buf + read_count;
+ for (char *p = buf; p < end; )
+ {
+ ssize_t write_count;
+ if (poutoff == NULL)
+ write_count = write (outfd, p, end - p);
+ else
+ write_count = __libc_pwrite64 (outfd, p, end - p, *poutoff);
+ if (write_count < 0)
+ {
+ /* Adjust the input read position to match what we have
+ written, so that the caller can pick up after the
+ error. */
+ size_t written = p - buf;
+ /* NB: This needs to be signed so that we can form the
+ negative value below. */
+ ssize_t overread = read_count - written;
+ if (pinoff == NULL)
+ {
+ if (overread > 0)
+ {
+ /* We are on an error recovery path, so we
+ cannot deal with failure here. */
+ int save_errno = errno;
+ (void) __libc_lseek64 (infd, -overread, SEEK_CUR);
+ __set_errno (save_errno);
+ }
+ }
+ else /* pinoff != NULL */
+ *pinoff -= overread;
+
+ if (copied + written > 0)
+ /* Report the number of bytes copied so far. */
+ return copied + written;
+ return -1;
+ }
+ p += write_count;
+ if (poutoff != NULL)
+ *poutoff += write_count;
+ } /* Write loop. */
+
+ copied += read_count;
+ length -= read_count;
+ }
+ return copied;
+}