circuitpython/tests/extmod/vfs_fat_fileio1.py

try:
    import uerrno
    import uos
except ImportError:
    print("SKIP")
    raise SystemExit

try:
    uos.VfsFat
except AttributeError:
    print("SKIP")
    raise SystemExit


class RAMFS:

    SEC_SIZE = 512

    def __init__(self, blocks):
        self.data = bytearray(blocks * self.SEC_SIZE)

    # Don't do any allocations in the below functions because they may be called
    # during a gc_sweep from a finalizer.
    def readblocks(self, n, buf):
        for i in range(len(buf)):
            buf[i] = self.data[n * self.SEC_SIZE + i]
        return 0

    def writeblocks(self, n, buf):
        for i in range(len(buf)):
            self.data[n * self.SEC_SIZE + i] = buf[i]
        return 0

    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


try:
    bdev = RAMFS(50)
except MemoryError:
    print("SKIP")
    raise SystemExit

uos.VfsFat.mkfs(bdev)
vfs = uos.VfsFat(bdev)
uos.mount(vfs, "/ramdisk")
uos.chdir("/ramdisk")

# file IO
f = open("foo_file.txt", "w")
print(str(f)[:17], str(f)[-1:])
f.write("hello!")
f.flush()
f.close()
f.close()  # allowed
try:
    f.write("world!")
except OSError as e:
    print(e.args[0] == uerrno.EINVAL)

try:
    f.read()
except OSError as e:
    print(e.args[0] == uerrno.EINVAL)

try:
    f.flush()
except OSError as e:
    print(e.args[0] == uerrno.EINVAL)

try:
    open("foo_file.txt", "x")
except OSError as e:
    print(e.args[0] == uerrno.EEXIST)

with open("foo_file.txt", "a") as f:
    f.write("world!")

with open("foo_file.txt") as f2:
    print(f2.read())
    print(f2.tell())

    f2.seek(0, 0)  # SEEK_SET
    print(f2.read(1))

    f2.seek(0, 1)  # SEEK_CUR
    print(f2.read(1))
    f2.seek(2, 1)  # SEEK_CUR
    print(f2.read(1))

    f2.seek(-2, 2)  # SEEK_END
    print(f2.read(1))

# using constructor of FileIO type to open a file
# no longer working with new VFS sub-system
# FileIO = type(f)
# with FileIO("/ramdisk/foo_file.txt") as f:
#    print(f.read())

# dirs
vfs.mkdir("foo_dir")

try:
    vfs.rmdir("foo_file.txt")
except OSError as e:
    print(e.args[0] == 20)  # uerrno.ENOTDIR

vfs.remove("foo_file.txt")
print(list(vfs.ilistdir()))

# 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, 4, 5]  # 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())