test.common: new `VirtBlockDevice` class

test/cmdtest_py_d/ct_wallet.py

@@ -25,7 +25,7 @@ import os
 from mmgen.util import msg,capfirst,get_extension
 from mmgen.wallet import get_wallet_cls
 
-from ..include.common import cfg,joinpath,imsg
+from ..include.common import cfg, joinpath, imsg, VirtBlockDevice
 from .common import ref_dir,ref_wallet_brainpass,ref_wallet_incog_offset,hincog_fn,hincog_bytes
 from .ct_base import CmdTestBase
 from .ct_shared import CmdTestShared
@@ -166,26 +166,15 @@ class CmdTestWalletConv(CmdTestBase,CmdTestShared):
 									uopts_chk = ['-H',hi_parms,sl_parm] )
 
 	def ref_hincog_blkdev_conv_out(self):
-		def do_run(cmd):
-			from subprocess import run,PIPE,DEVNULL
-			return run(cmd,stdout=PIPE,stderr=DEVNULL,check=True)
-		if self.skip_for_win():
+
+		if self.skip_for_win('no loop device') or self.skip_for_mac('no loop device'):
 			return 'skip'
-		imsg('Creating block device image file')
-		ic_img = joinpath(self.tmpdir,'hincog_blkdev_img')
-		do_run(['dd','if=/dev/zero','of='+ic_img,'bs=1K','count=1'])
-		ic_dev = do_run(['sudo','/sbin/losetup','-f']).stdout.strip().decode()
-		ic_dev_mode_orig = '{:o}'.format( os.stat(ic_dev).st_mode & 0xfff )
-		ic_dev_mode = '0666'
-		imsg(f'Changing permissions on loop device to {ic_dev_mode!r}')
-		do_run(['sudo','chmod',ic_dev_mode,ic_dev])
-		imsg(f'Attaching loop device {ic_dev!r}')
-		do_run(['sudo','/sbin/losetup',ic_dev,ic_img])
-		self.ref_hincog_conv_out(ic_f=ic_dev)
-		imsg(f'Detaching loop device {ic_dev!r}')
-		do_run(['sudo','/sbin/losetup','-d',ic_dev])
-		imsg(f'Resetting permissions on loop device to {ic_dev_mode_orig!r}')
-		do_run(['sudo','chmod',ic_dev_mode_orig,ic_dev])
+
+		b = VirtBlockDevice(self.tmpdir, '1K', 1)
+		b.setup()
+		self.ref_hincog_conv_out(ic_f=b.dev)
+		b.destroy()
+
 		return 'ok'
 
 	# wallet conversion tests

test/include/common.py

@@ -326,3 +326,32 @@ def get_ethkey():
 			return cmdname
 	else:
 		die(1,f'ethkey executable not found (tried {cmdnames})')
+
+def do_run(cmd):
+	from subprocess import run,PIPE,DEVNULL
+	return run(cmd, stdout=PIPE, stderr=DEVNULL, check=True)
+
+class VirtBlockDevice:
+
+	def __init__(self, tmpdir, blksize, blkcount):
+		self.tmpdir = tmpdir
+		self.blksize = blksize
+		self.blkcount = blkcount
+
+	def setup(self):
+		imsg('Creating block device image file')
+		blkdev_img = joinpath(self.tmpdir, 'hincog_blkdev_img')
+		do_run(['dd', 'if=/dev/zero', f'of={blkdev_img}', f'bs={self.blksize}', f'count={self.blkcount}'])
+		self.dev = do_run(['sudo', '/sbin/losetup', '-f']).stdout.strip().decode()
+		self.dev_mode_orig = '{:o}'.format(os.stat(self.dev).st_mode & 0xfff)
+		dev_mode = '0666'
+		imsg(f'Changing permissions on loop device to {dev_mode!r}')
+		do_run(['sudo', 'chmod', dev_mode, self.dev])
+		imsg(f'Attaching loop device {self.dev!r}')
+		do_run(['sudo', '/sbin/losetup', self.dev, blkdev_img])
+
+	def destroy(self):
+		imsg(f'Detaching loop device {self.dev!r}')
+		do_run(['sudo', '/sbin/losetup', '-d', self.dev])
+		imsg(f'Resetting permissions on loop device to {self.dev_mode_orig!r}')
+		do_run(['sudo', 'chmod', self.dev_mode_orig, self.dev])