circuitpython/tests/extmod/vfs_fat_finaliser.py

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# Test VfsFat class and its finaliser
try:
import uerrno, uos
uos.VfsFat
except (ImportError, AttributeError):
print("SKIP")
raise SystemExit
class RAMBlockDevice:
def __init__(self, blocks, sec_size=512):
self.sec_size = sec_size
self.data = bytearray(blocks * self.sec_size)
def readblocks(self, n, buf):
for i in range(len(buf)):
buf[i] = self.data[n * self.sec_size + i]
def writeblocks(self, n, buf):
for i in range(len(buf)):
self.data[n * self.sec_size + i] = buf[i]
def ioctl(self, op, arg):
if op == 4: # MP_BLOCKDEV_IOCTL_BLOCK_COUNT
return len(self.data) // self.sec_size
if op == 5: # MP_BLOCKDEV_IOCTL_BLOCK_SIZE
return self.sec_size
# Create block device, and skip test if not enough RAM
try:
bdev = RAMBlockDevice(50)
except MemoryError:
print("SKIP")
raise SystemExit
# Format block device and create VFS object
uos.VfsFat.mkfs(bdev)
vfs = uos.VfsFat(bdev)
# Here we test that opening a file with the heap locked fails correctly. This
# is a special case because file objects use a finaliser and allocating with a
# finaliser is a different path to normal allocation. It would be better to
# test this in the core tests but there are no core objects that use finaliser.
import micropython
micropython.heap_lock()
try:
vfs.open("x", "r")
except MemoryError:
print("MemoryError")
micropython.heap_unlock()
# Here we test that the finaliser is actually called during a garbage collection.
import gc
N = 4
for i in range(N):
n = "x%d" % i
f = vfs.open(n, "w")
f.write(n)
f = None # release f without closing
[0, 1, 2, 3] # use up Python stack so f is really gone
gc.collect() # should finalise all N files by closing them
for i in range(N):
with vfs.open("x%d" % i, "r") as f:
print(f.read())