1 files changed, 104 insertions, 0 deletions
diff --git a/util-linux/fallocate.c b/util-linux/fallocate.c
new file mode 100644
index 000000000..1cd851bde
--- /dev/null
+++ b/util-linux/fallocate.c
@@ -0,0 +1,104 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Copyright (C) 2017 Denys Vlasenko <vda.linux@googlemail.com>
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+
+//config:config FALLOCATE
+//config:	bool "fallocate"
+//config:	default y
+//config:	help
+//config:	  Preallocate space for files.
+
+//applet:IF_FALLOCATE(APPLET(fallocate, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_FALLOCATE) += fallocate.o
+
+//usage:#define fallocate_trivial_usage
+//usage:       "[-o OFS] -l LEN FILE"
+//		fallocate [-c|-p|-z] [-n] [-o OFS] -l LEN FILE
+//		fallocate -d [-o OFS] [-l LEN] FILE
+//usage:#define fallocate_full_usage "\n\n"
+//usage:	"Preallocate space for FILE\n"
+//           "\n	-c	Remove range"
+//           "\n	-p	Make hole"
+//           "\n	-z	Zero and allocate range"
+//           "\n	-d	Convert zeros to holes"
+//           "\n	-n	Keep size"
+//usage:     "\n	-o OFS	Offset of range"
+//usage:     "\n	-l LEN	Length of range"
+
+//Upstream options:
+//The options --collapse-range, --dig-holes, --punch-hole and --zero-range
+//are mutually exclusive.
+//-c, --collapse-range
+//    Removes a byte range from a file, without leaving a hole. The byte range
+//    to be collapsed starts at offset and continues for length bytes.
+//    At the completion of the operation, the contents of the file starting
+//    at the location offset+length will be appended at the location offset,
+//    and the file will be length bytes smaller. The option --keep-size may
+//    not be specified for the collapse-range operation.
+//-d, --dig-holes
+//    Detect and dig holes. This makes the file sparse in-place, without using
+//    extra disk space. The minimum size of the hole depends on filesystem I/O
+//    block size (usually 4096 bytes). Also,
+//-l, --length length
+//    Specifies the length of the range, in bytes.
+//-n, --keep-size
+//    Do not modify the apparent length of the file. This may effectively
+//    allocate blocks past EOF, which can be removed with a truncate.
+//-o, --offset offset
+//    Specifies the beginning offset of the range, in bytes.
+//-p, --punch-hole
+//    Deallocates space (i.e., creates a hole) in the byte range starting
+//    at offset and continuing for length bytes. Within the specified range,
+//    partial filesystem blocks are zeroed, and whole
+//    filesystem blocks are removed from the file. After a successful call,
+//    subsequent reads from this range will return zeroes. This option may not
+//    be specified at the same time as the
+//    --zero-range option. Also, when using this option, --keep-size is implied.
+//-z, --zero-range
+//    Zeroes space in the byte range starting at offset and continuing for
+//    length bytes. Within the specified range, blocks are preallocated for
+//    the regions that span the holes in the file. After
+//    a successful call, subsequent reads from this range will return zeroes.
+//    Zeroing is done within the filesystem preferably by converting the range
+//    into unwritten extents. This approach means that the specified range
+//    will not be physically zeroed out on the device (except for partial
+//    blocks at the either end of the range), and I/O is (otherwise) required
+//    only to update metadata.
+//    Option --keep-size can be specified to prevent file length modification.
+
+#include "libbb.h"
+
+int fallocate_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int fallocate_main(int argc UNUSED_PARAM, char **argv)
+{
+	const char *str_l;
+	const char *str_o = "0";
+	off_t ofs, len;
+	unsigned opts;
+	int fd;
+
+	/* exactly one non-option arg */
+	opt_complementary = "=1";
+	opts = getopt32(argv, "l:o:", &str_l, &str_o);
+	if (!(opts & 1))
+		bb_show_usage();
+
+	ofs = xatoull_sfx(str_o, kmg_i_suffixes);
+	len = xatoull_sfx(str_l, kmg_i_suffixes);
+
+	argv += optind;
+	fd = xopen3(*argv, O_RDWR | O_CREAT, 0666);
+
+	/* posix_fallocate has unusual method of returning error */
+	/* maybe use Linux-specific fallocate(int fd, int mode, off_t offset, off_t len) instead? */
+	if ((errno = posix_fallocate(fd, ofs, len)) != 0)
+		bb_perror_msg_and_die("fallocate '%s'", *argv);
+
+	/* util-linux also performs fsync(fd); */
+
+	return EXIT_SUCCESS;
+}