1 files changed, 163 insertions, 0 deletions
diff --git a/lib/dpkg/fdio.c b/lib/dpkg/fdio.c
new file mode 100644
index 0000000..8e61b5d
--- /dev/null
+++ b/lib/dpkg/fdio.c
@@ -0,0 +1,163 @@
+/*
+ * libdpkg - Debian packaging suite library routines
+ * fdio.c - safe file descriptor based input/output
+ *
+ * Copyright © 2009-2010 Guillem Jover <guillem@debian.org>
+ *
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <compat.h>
+
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <dpkg/fdio.h>
+
+ssize_t
+fd_read(int fd, void *buf, size_t len)
+{
+	ssize_t total = 0;
+	char *ptr = buf;
+
+	while (len > 0) {
+		ssize_t n;
+
+		n = read(fd, ptr + total, len);
+		if (n == -1) {
+			if (errno == EINTR || errno == EAGAIN)
+				continue;
+			return total ? -total : n;
+		}
+		if (n == 0)
+			break;
+
+		total += n;
+		len -= n;
+	}
+
+	return total;
+}
+
+ssize_t
+fd_write(int fd, const void *buf, size_t len)
+{
+	ssize_t total = 0;
+	const char *ptr = buf;
+
+	while (len > 0) {
+		ssize_t n;
+
+		n = write(fd, ptr + total, len);
+		if (n == -1) {
+			if (errno == EINTR || errno == EAGAIN)
+				continue;
+			return total ? -total : n;
+		}
+		if (n == 0)
+			break;
+
+		total += n;
+		len -= n;
+	}
+
+	return total;
+}
+
+#ifdef USE_DISK_PREALLOCATE
+#ifdef HAVE_F_PREALLOCATE
+static void
+fd_preallocate_setup(fstore_t *fs, int flags, off_t offset, off_t len)
+{
+	fs->fst_flags = flags;
+	fs->fst_posmode = F_PEOFPOSMODE;
+	fs->fst_offset = offset;
+	fs->fst_length = len;
+	fs->fst_bytesalloc = 0;
+}
+#endif
+
+/**
+ * Request the kernel to allocate the specified size for a file descriptor.
+ *
+ * We only want to send a hint that we will be using the requested size. But
+ * we do not want to unnecessarily write the file contents. That is why we
+ * are not using posix_fallocate(3) directly if possible, and not at all
+ * on glibc based systems (except on GNU/kFreeBSD).
+ */
+int
+fd_allocate_size(int fd, off_t offset, off_t len)
+{
+	int rc;
+
+	/* Do not preallocate on very small files as that degrades performance
+	 * on some filesystems. */
+	if (len < (4 * 4096) - 1)
+		return 0;
+
+#if defined(HAVE_F_PREALLOCATE)
+	/* On Mac OS X. */
+	fstore_t fs;
+
+	fd_preallocate_setup(&fs, F_ALLOCATECONTIG, offset, len);
+	rc = fcntl(fd, F_PREALLOCATE, &fs);
+	if (rc < 0 && errno == ENOSPC) {
+		/* If we cannot get a contiguous allocation, then try
+		 * non-contiguous. */
+		fd_preallocate_setup(&fs, F_ALLOCATEALL, offset, len);
+		rc = fcntl(fd, F_PREALLOCATE, &fs);
+	}
+#elif defined(HAVE_F_ALLOCSP64)
+	/* On Solaris. */
+	struct flock64 fl;
+
+	fl.l_whence = SEEK_SET;
+	fl.l_start = offset;
+	fl.l_len = len;
+
+	rc = fcntl(fd, F_ALLOCSP64, &fl);
+#elif defined(HAVE_FALLOCATE)
+	/* On Linux. */
+	do {
+		rc = fallocate(fd, 0, offset, len);
+	} while (rc < 0 && errno == EINTR);
+#elif defined(HAVE_POSIX_FALLOCATE) && \
+      ((defined(__GLIBC__) && defined(__FreeBSD_kernel__)) || \
+       !defined(__GLIBC__))
+	/*
+	 * On BSDs, newer GNU/kFreeBSD and other non-glibc based systems
+	 * we can use posix_fallocate(2) which should be a simple syscall
+	 * wrapper. But not on other glibc systems, as there the function
+	 * will try to allocate the size by writing a '\0' to each block
+	 * if the syscall is not implemented or not supported by the
+	 * kernel or the filesystem, which we do not want.
+	 */
+	rc = posix_fallocate(fd, offset, len);
+#else
+	errno = ENOSYS;
+	rc = -1;
+#endif
+
+	return rc;
+}
+#else
+int
+fd_allocate_size(int fd, off_t offset, off_t len)
+{
+	errno = ENOSYS;
+	return -1;
+}
+#endif