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authorAdam Coldrick <adam.coldrick@codethink.co.uk>2015-06-04 15:25:33 +0000
committerAdam Coldrick <adam.coldrick@codethink.co.uk>2015-06-10 09:59:10 +0000
commit840292841f4495a79a037f81a26d6b3f51e7cb8c (patch)
tree2f1e642b71636d920310ffe43178a61ad6c5c1a6 /extensions/xfer-hole
parent07c7f1e46a3113c8fa90ce4b47409db435a86b2f (diff)
downloaddefinitions-840292841f4495a79a037f81a26d6b3f51e7cb8c.tar.gz
Move xfer-hole and recv-hole into extensions/baserock/adamcoldrick/writeexts-in-definitions-v2
Change-Id: I46ed5f3ec85f9662bebac592eff7a6eb6d628f28
Diffstat (limited to 'extensions/xfer-hole')
-rwxr-xr-xextensions/xfer-hole137
1 files changed, 137 insertions, 0 deletions
diff --git a/extensions/xfer-hole b/extensions/xfer-hole
new file mode 100755
index 00000000..91f1be01
--- /dev/null
+++ b/extensions/xfer-hole
@@ -0,0 +1,137 @@
+#!/usr/bin/env python
+#
+# Send a sparse file more space-efficiently.
+# See recv-hole for a description of the protocol.
+#
+# Note that xfer-hole requires a version of Linux with support for
+# SEEK_DATA and SEEK_HOLE.
+#
+#
+# Copyright (C) 2014-2015 Codethink Limited
+#
+# This program 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; version 2 of the License.
+#
+# This program 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 <http://www.gnu.org/licenses/>.
+#
+# =*= License: GPL-2 =*=
+
+
+
+import errno
+import os
+import sys
+
+
+SEEK_DATA = 3
+SEEK_HOLE = 4
+
+
+filename = sys.argv[1]
+fd = os.open(filename, os.O_RDONLY)
+pos = 0
+
+
+DATA = 'data'
+HOLE = 'hole'
+EOF = 'eof'
+
+
+def safe_lseek(fd, pos, whence):
+ try:
+ return os.lseek(fd, pos, whence)
+ except OSError as e:
+ if e.errno == errno.ENXIO:
+ return -1
+ raise
+
+
+def current_data_or_pos(fd, pos):
+ length = safe_lseek(fd, 0, os.SEEK_END)
+ next_data = safe_lseek(fd, pos, SEEK_DATA)
+ next_hole = safe_lseek(fd, pos, SEEK_HOLE)
+
+ if pos == length:
+ return EOF, pos
+ elif pos == next_data:
+ return DATA, pos
+ elif pos == next_hole:
+ return HOLE, pos
+ else:
+ assert False, \
+ ("Do not understand: pos=%d next_data=%d next_hole=%d" %
+ (pos, next_data, next_hole))
+
+
+def next_data_or_hole(fd, pos):
+ length = safe_lseek(fd, 0, os.SEEK_END)
+ next_data = safe_lseek(fd, pos, SEEK_DATA)
+ next_hole = safe_lseek(fd, pos, SEEK_HOLE)
+
+ if pos == length:
+ return EOF, pos
+ elif pos == next_data:
+ # We are at data.
+ if next_hole == -1 or next_hole == length:
+ return EOF, length
+ else:
+ return HOLE, next_hole
+ elif pos == next_hole:
+ # We are at a hole.
+ if next_data == -1 or next_data == length:
+ return EOF, length
+ else:
+ return DATA, next_data
+ else:
+ assert False, \
+ ("Do not understand: pos=%d next_data=%d next_hole=%d" %
+ (pos, next_data, next_hole))
+
+
+def find_data_and_holes(fd):
+ pos = safe_lseek(fd, 0, os.SEEK_CUR)
+
+ kind, pos = current_data_or_pos(fd, pos)
+ while kind != EOF:
+ yield kind, pos
+ kind, pos = next_data_or_hole(fd, pos)
+ yield kind, pos
+
+
+def make_xfer_instructions(fd):
+ prev_kind = None
+ prev_pos = None
+ for kind, pos in find_data_and_holes(fd):
+ if prev_kind == DATA:
+ yield (DATA, prev_pos, pos)
+ elif prev_kind == HOLE:
+ yield (HOLE, prev_pos, pos)
+ prev_kind = kind
+ prev_pos = pos
+
+
+def copy_slice_from_file(to, fd, start, end):
+ safe_lseek(fd, start, os.SEEK_SET)
+ nbytes = end - start
+ max_at_a_time = 1024**2
+ while nbytes > 0:
+ data = os.read(fd, min(nbytes, max_at_a_time))
+ if not data:
+ break
+ to.write(data)
+ nbytes -= len(data)
+
+
+for kind, start, end in make_xfer_instructions(fd):
+ if kind == HOLE:
+ sys.stdout.write('HOLE\n%d\n' % (end - start))
+ elif kind == DATA:
+ sys.stdout.write('DATA\n%d\n' % (end - start))
+ copy_slice_from_file(sys.stdout, fd, start, end)