scripts/qcow2-to-stdout.py - people/peter.maydell/qemu-arm.git - Linaro Git Browser

 #!/usr/bin/env python3

 # This tool reads a disk image in any format and converts it to qcow2,
 # writing the result directly to stdout.
 #
 # Copyright (C) 2024 Igalia, S.L.
 #
 # Authors: Alberto Garcia <berto@igalia.com>
 #          Madeeha Javed <javed@igalia.com>
 #
 # SPDX-License-Identifier: GPL-2.0-or-later
 #
 # qcow2 files produced by this script are always arranged like this:
 #
 # - qcow2 header
 # - refcount table
 # - refcount blocks
 # - L1 table
 # - L2 tables
 # - Data clusters
 #
 # A note about variable names: in qcow2 there is one refcount table
 # and one (active) L1 table, although each can occupy several
 # clusters. For the sake of simplicity the code sometimes talks about
 # refcount tables and L1 tables when referring to those clusters.

 import argparse
 import errno
 import math
 import os
 import signal
 import struct
 import subprocess
 import sys
 import tempfile
 import time
 from contextlib import contextmanager

 QCOW2_DEFAULT_CLUSTER_SIZE = 65536
 QCOW2_DEFAULT_REFCOUNT_BITS = 16
 QCOW2_FEATURE_NAME_TABLE = 0x6803F857
 QCOW2_DATA_FILE_NAME_STRING = 0x44415441
 QCOW2_V3_HEADER_LENGTH = 112  # Header length in QEMU 9.0. Must be a multiple of 8
 QCOW2_INCOMPAT_DATA_FILE_BIT = 2
 QCOW2_AUTOCLEAR_DATA_FILE_RAW_BIT = 1
 QCOW_OFLAG_COPIED = 1 << 63
 QEMU_STORAGE_DAEMON = "qemu-storage-daemon"


 def bitmap_set(bitmap, idx):
     bitmap[idx // 8] |= 1 << (idx % 8)


 def bitmap_is_set(bitmap, idx):
     return (bitmap[idx // 8] & (1 << (idx % 8))) != 0


 def bitmap_iterator(bitmap, length):
     for idx in range(length):
         if bitmap_is_set(bitmap, idx):
             yield idx


 def align_up(num, d):
     return d * math.ceil(num / d)


 # Holes in the input file contain only zeroes so we can skip them and
 # save time. This function returns the indexes of the clusters that
 # are known to contain data. Those are the ones that we need to read.
 def clusters_with_data(fd, cluster_size):
     data_to = 0
     while True:
         try:
             data_from = os.lseek(fd, data_to, os.SEEK_DATA)
             data_to = align_up(os.lseek(fd, data_from, os.SEEK_HOLE), cluster_size)
             for idx in range(data_from // cluster_size, data_to // cluster_size):
                 yield idx
         except OSError as err:
             if err.errno == errno.ENXIO:  # End of file reached
                 break
             raise err


 # write_qcow2_content() expects a raw input file. If we have a different
 # format we can use qemu-storage-daemon to make it appear as raw.
 @contextmanager
 def get_input_as_raw_file(input_file, input_format):
     if input_format == "raw":
         yield input_file
         return
     try:
         temp_dir = tempfile.mkdtemp()
         pid_file = os.path.join(temp_dir, "pid")
         raw_file = os.path.join(temp_dir, "raw")
         open(raw_file, "wb").close()
         ret = subprocess.run(
             [
                 QEMU_STORAGE_DAEMON,
                 "--daemonize",
                 "--pidfile", pid_file,
                 "--blockdev", f"driver=file,node-name=file0,driver=file,filename={input_file},read-only=on",
                 "--blockdev", f"driver={input_format},node-name=disk0,file=file0,read-only=on",
                 "--export", f"type=fuse,id=export0,node-name=disk0,mountpoint={raw_file},writable=off",
             ],
             capture_output=True,
         )
         if ret.returncode != 0:
             sys.exit("[Error] Could not start the qemu-storage-daemon:\n" +
                      ret.stderr.decode().rstrip('\n'))
         yield raw_file
     finally:
         # Kill the storage daemon on exit
         # and remove all temporary files
         if os.path.exists(pid_file):
             with open(pid_file, "r") as f:
                 pid = int(f.readline())
             os.kill(pid, signal.SIGTERM)
             while os.path.exists(pid_file):
                 time.sleep(0.1)
         os.unlink(raw_file)
         os.rmdir(temp_dir)


 def write_features(cluster, offset, data_file_name):
     if data_file_name is not None:
         encoded_name = data_file_name.encode("utf-8")
         padded_name_len = align_up(len(encoded_name), 8)
         struct.pack_into(f">II{padded_name_len}s", cluster, offset,
                          QCOW2_DATA_FILE_NAME_STRING,
                          len(encoded_name),
                          encoded_name)
         offset += 8 + padded_name_len

     qcow2_features = [
         # Incompatible
         (0, 0, "dirty bit"),
         (0, 1, "corrupt bit"),
         (0, 2, "external data file"),
         (0, 3, "compression type"),
         (0, 4, "extended L2 entries"),
         # Compatible
         (1, 0, "lazy refcounts"),
         # Autoclear
         (2, 0, "bitmaps"),
         (2, 1, "raw external data"),
     ]
     struct.pack_into(">I", cluster, offset, QCOW2_FEATURE_NAME_TABLE)
     struct.pack_into(">I", cluster, offset + 4, len(qcow2_features) * 48)
     offset += 8
     for feature_type, feature_bit, feature_name in qcow2_features:
         struct.pack_into(">BB46s", cluster, offset,
                          feature_type, feature_bit, feature_name.encode("ascii"))
         offset += 48


 def write_qcow2_content(input_file, cluster_size, refcount_bits, data_file_name, data_file_raw):
     # Some basic values
     l1_entries_per_table = cluster_size // 8
     l2_entries_per_table = cluster_size // 8
     refcounts_per_table  = cluster_size // 8
     refcounts_per_block  = cluster_size * 8 // refcount_bits

     # Virtual disk size, number of data clusters and L1 entries
     disk_size = align_up(os.path.getsize(input_file), 512)
     total_data_clusters = math.ceil(disk_size / cluster_size)
     l1_entries = math.ceil(total_data_clusters / l2_entries_per_table)
     allocated_l1_tables = math.ceil(l1_entries / l1_entries_per_table)

     # Max L1 table size is 32 MB (QCOW_MAX_L1_SIZE in block/qcow2.h)
     if (l1_entries * 8) > (32 * 1024 * 1024):
         sys.exit("[Error] The image size is too large. Try using a larger cluster size.")

     # Two bitmaps indicating which L1 and L2 entries are set
     l1_bitmap = bytearray(allocated_l1_tables * l1_entries_per_table // 8)
     l2_bitmap = bytearray(l1_entries * l2_entries_per_table // 8)
     allocated_l2_tables = 0
     allocated_data_clusters = 0

     if data_file_raw:
         # If data_file_raw is set then all clusters are allocated and
         # we don't need to read the input file at all.
         allocated_l2_tables = l1_entries
         for idx in range(l1_entries):
             bitmap_set(l1_bitmap, idx)
         for idx in range(total_data_clusters):
             bitmap_set(l2_bitmap, idx)
     else:
         # Open the input file for reading
         fd = os.open(input_file, os.O_RDONLY)
         zero_cluster = bytes(cluster_size)
         # Read all the clusters that contain data
         for idx in clusters_with_data(fd, cluster_size):
             cluster = os.pread(fd, cluster_size, cluster_size * idx)
             # If the last cluster is smaller than cluster_size pad it with zeroes
             if len(cluster) < cluster_size:
                 cluster += bytes(cluster_size - len(cluster))
             # If a cluster has non-zero data then it must be allocated
             # in the output file and its L2 entry must be set
             if cluster != zero_cluster:
                 bitmap_set(l2_bitmap, idx)
                 allocated_data_clusters += 1
                 # Allocated data clusters also need their corresponding L1 entry and L2 table
                 l1_idx = math.floor(idx / l2_entries_per_table)
                 if not bitmap_is_set(l1_bitmap, l1_idx):
                     bitmap_set(l1_bitmap, l1_idx)
                     allocated_l2_tables += 1

     # Total amount of allocated clusters excluding the refcount blocks and table
     total_allocated_clusters = 1 + allocated_l1_tables + allocated_l2_tables
     if data_file_name is None:
         total_allocated_clusters += allocated_data_clusters

     # Clusters allocated for the refcount blocks and table
     allocated_refcount_blocks = math.ceil(total_allocated_clusters  / refcounts_per_block)
     allocated_refcount_tables = math.ceil(allocated_refcount_blocks / refcounts_per_table)

     # Now we have a problem because allocated_refcount_blocks and allocated_refcount_tables...
     # (a) increase total_allocated_clusters, and
     # (b) need to be recalculated when total_allocated_clusters is increased
     # So we need to repeat the calculation as long as the numbers change
     while True:
         new_total_allocated_clusters = total_allocated_clusters + allocated_refcount_tables + allocated_refcount_blocks
         new_allocated_refcount_blocks = math.ceil(new_total_allocated_clusters / refcounts_per_block)
         if new_allocated_refcount_blocks > allocated_refcount_blocks:
             allocated_refcount_blocks = new_allocated_refcount_blocks
             allocated_refcount_tables = math.ceil(allocated_refcount_blocks / refcounts_per_table)
         else:
             break

     # Now that we have the final numbers we can update total_allocated_clusters
     total_allocated_clusters += allocated_refcount_tables + allocated_refcount_blocks

     # At this point we have the exact number of clusters that the output
     # image is going to use so we can calculate all the offsets.
     current_cluster_idx = 1

     refcount_table_offset = current_cluster_idx * cluster_size
     current_cluster_idx += allocated_refcount_tables

     refcount_block_offset = current_cluster_idx * cluster_size
     current_cluster_idx += allocated_refcount_blocks

     l1_table_offset = current_cluster_idx * cluster_size
     current_cluster_idx += allocated_l1_tables

     l2_table_offset = current_cluster_idx * cluster_size
     current_cluster_idx += allocated_l2_tables

     data_clusters_offset = current_cluster_idx * cluster_size

     # Calculate some values used in the qcow2 header
     if allocated_l1_tables == 0:
         l1_table_offset = 0

     hdr_cluster_bits = int(math.log2(cluster_size))
     hdr_refcount_bits = int(math.log2(refcount_bits))
     hdr_length = QCOW2_V3_HEADER_LENGTH
     hdr_incompat_features = 0
     if data_file_name is not None:
         hdr_incompat_features |= 1 << QCOW2_INCOMPAT_DATA_FILE_BIT
     hdr_autoclear_features = 0
     if data_file_raw:
         hdr_autoclear_features |= 1 << QCOW2_AUTOCLEAR_DATA_FILE_RAW_BIT

     ### Write qcow2 header
     cluster = bytearray(cluster_size)
     struct.pack_into(">4sIQIIQIIQQIIQQQQII", cluster, 0,
         b"QFI\xfb",            # QCOW magic string
         3,                     # version
         0,                     # backing file offset
         0,                     # backing file sizes
         hdr_cluster_bits,
         disk_size,
         0,                     # encryption method
         l1_entries,
         l1_table_offset,
         refcount_table_offset,
         allocated_refcount_tables,
         0,                     # number of snapshots
         0,                     # snapshot table offset
         hdr_incompat_features,
         0,                     # compatible features
         hdr_autoclear_features,
         hdr_refcount_bits,
         hdr_length,
     )

     write_features(cluster, hdr_length, data_file_name)

     sys.stdout.buffer.write(cluster)

     ### Write refcount table
     cur_offset = refcount_block_offset
     remaining_refcount_table_entries = allocated_refcount_blocks # Each entry is a pointer to a refcount block
     while remaining_refcount_table_entries > 0:
         cluster = bytearray(cluster_size)
         to_write = min(remaining_refcount_table_entries, refcounts_per_table)
         remaining_refcount_table_entries -= to_write
         for idx in range(to_write):
             struct.pack_into(">Q", cluster, idx * 8, cur_offset)
             cur_offset += cluster_size
         sys.stdout.buffer.write(cluster)

     ### Write refcount blocks
     remaining_refcount_block_entries = total_allocated_clusters # One entry for each allocated cluster
     for tbl in range(allocated_refcount_blocks):
         cluster = bytearray(cluster_size)
         to_write = min(remaining_refcount_block_entries, refcounts_per_block)
         remaining_refcount_block_entries -= to_write
         # All refcount entries contain the number 1. The only difference
         # is their bit width, defined when the image is created.
         for idx in range(to_write):
             if refcount_bits == 64:
                 struct.pack_into(">Q", cluster, idx * 8, 1)
             elif refcount_bits == 32:
                 struct.pack_into(">L", cluster, idx * 4, 1)
             elif refcount_bits == 16:
                 struct.pack_into(">H", cluster, idx * 2, 1)
             elif refcount_bits == 8:
                 cluster[idx] = 1
             elif refcount_bits == 4:
                 cluster[idx // 2] |= 1 << ((idx % 2) * 4)
             elif refcount_bits == 2:
                 cluster[idx // 4] |= 1 << ((idx % 4) * 2)
             elif refcount_bits == 1:
                 cluster[idx // 8] |= 1 << (idx % 8)
         sys.stdout.buffer.write(cluster)

     ### Write L1 table
     cur_offset = l2_table_offset
     for tbl in range(allocated_l1_tables):
         cluster = bytearray(cluster_size)
         for idx in range(l1_entries_per_table):
             l1_idx = tbl * l1_entries_per_table + idx
             if bitmap_is_set(l1_bitmap, l1_idx):
                 struct.pack_into(">Q", cluster, idx * 8, cur_offset | QCOW_OFLAG_COPIED)
                 cur_offset += cluster_size
         sys.stdout.buffer.write(cluster)

     ### Write L2 tables
     cur_offset = data_clusters_offset
     for tbl in range(l1_entries):
         # Skip the empty L2 tables. We can identify them because
         # there is no L1 entry pointing at them.
         if bitmap_is_set(l1_bitmap, tbl):
             cluster = bytearray(cluster_size)
             for idx in range(l2_entries_per_table):
                 l2_idx = tbl * l2_entries_per_table + idx
                 if bitmap_is_set(l2_bitmap, l2_idx):
                     if data_file_name is None:
                         struct.pack_into(">Q", cluster, idx * 8, cur_offset | QCOW_OFLAG_COPIED)
                         cur_offset += cluster_size
                     else:
                         struct.pack_into(">Q", cluster, idx * 8, (l2_idx * cluster_size) | QCOW_OFLAG_COPIED)
             sys.stdout.buffer.write(cluster)

     ### Write data clusters
     if data_file_name is None:
         for idx in bitmap_iterator(l2_bitmap, total_data_clusters):
             cluster = os.pread(fd, cluster_size, cluster_size * idx)
             # If the last cluster is smaller than cluster_size pad it with zeroes
             if len(cluster) < cluster_size:
                 cluster += bytes(cluster_size - len(cluster))
             sys.stdout.buffer.write(cluster)

     if not data_file_raw:
         os.close(fd)


 def main():
     # Command-line arguments
     parser = argparse.ArgumentParser(
         description="This program converts a QEMU disk image to qcow2 "
         "and writes it to the standard output"
     )
     parser.add_argument("input_file", help="name of the input file")
     parser.add_argument(
         "-f",
         dest="input_format",
         metavar="input_format",
         help="format of the input file (default: raw)",
         default="raw",
     )
     parser.add_argument(
         "-c",
         dest="cluster_size",
         metavar="cluster_size",
         help=f"qcow2 cluster size (default: {QCOW2_DEFAULT_CLUSTER_SIZE})",
         default=QCOW2_DEFAULT_CLUSTER_SIZE,
         type=int,
         choices=[1 << x for x in range(9, 22)],
     )
     parser.add_argument(
         "-r",
         dest="refcount_bits",
         metavar="refcount_bits",
         help=f"width of the reference count entries (default: {QCOW2_DEFAULT_REFCOUNT_BITS})",
         default=QCOW2_DEFAULT_REFCOUNT_BITS,
         type=int,
         choices=[1 << x for x in range(7)],
     )
     parser.add_argument(
         "-d",
         dest="data_file",
         help="create an image with input_file as an external data file",
         action="store_true",
     )
     parser.add_argument(
         "-R",
         dest="data_file_raw",
         help="enable data_file_raw on the generated image (implies -d)",
         action="store_true",
     )
     args = parser.parse_args()

     if args.data_file_raw:
         args.data_file = True

     if not os.path.isfile(args.input_file):
         sys.exit(f"[Error] {args.input_file} does not exist or is not a regular file.")

     if args.data_file and args.input_format != "raw":
         sys.exit("[Error] External data files can only be used with raw input images")

     # A 512 byte header is too small for the data file name extension
     if args.data_file and args.cluster_size == 512:
         sys.exit("[Error] External data files require a larger cluster size")

     if sys.stdout.isatty():
         sys.exit("[Error] Refusing to write to a tty. Try redirecting stdout.")

     if args.data_file:
         data_file_name = args.input_file
     else:
         data_file_name = None

     with get_input_as_raw_file(args.input_file, args.input_format) as raw_file:
         write_qcow2_content(
             raw_file,
             args.cluster_size,
             args.refcount_bits,
             data_file_name,
             args.data_file_raw,
         )


 if __name__ == "__main__":
     main()
	#!/usr/bin/env python3

	# This tool reads a disk image in any format and converts it to qcow2,
	# writing the result directly to stdout.
	#
	# Copyright (C) 2024 Igalia, S.L.
	#
	# Authors: Alberto Garcia <berto@igalia.com>
	# Madeeha Javed <javed@igalia.com>
	#
	# SPDX-License-Identifier: GPL-2.0-or-later
	#
	# qcow2 files produced by this script are always arranged like this:
	#
	# - qcow2 header
	# - refcount table
	# - refcount blocks
	# - L1 table
	# - L2 tables
	# - Data clusters
	#
	# A note about variable names: in qcow2 there is one refcount table
	# and one (active) L1 table, although each can occupy several
	# clusters. For the sake of simplicity the code sometimes talks about
	# refcount tables and L1 tables when referring to those clusters.

	import argparse
	import errno
	import math
	import os
	import signal
	import struct
	import subprocess
	import sys
	import tempfile
	import time
	from contextlib import contextmanager

	QCOW2_DEFAULT_CLUSTER_SIZE = 65536
	QCOW2_DEFAULT_REFCOUNT_BITS = 16
	QCOW2_FEATURE_NAME_TABLE = 0x6803F857
	QCOW2_DATA_FILE_NAME_STRING = 0x44415441
	QCOW2_V3_HEADER_LENGTH = 112 # Header length in QEMU 9.0. Must be a multiple of 8
	QCOW2_INCOMPAT_DATA_FILE_BIT = 2
	QCOW2_AUTOCLEAR_DATA_FILE_RAW_BIT = 1
	QCOW_OFLAG_COPIED = 1 << 63
	QEMU_STORAGE_DAEMON = "qemu-storage-daemon"


	def bitmap_set(bitmap, idx):
	bitmap[idx // 8] \|= 1 << (idx % 8)


	def bitmap_is_set(bitmap, idx):
	return (bitmap[idx // 8] & (1 << (idx % 8))) != 0


	def bitmap_iterator(bitmap, length):
	for idx in range(length):
	if bitmap_is_set(bitmap, idx):
	yield idx


	def align_up(num, d):
	return d * math.ceil(num / d)


	# Holes in the input file contain only zeroes so we can skip them and
	# save time. This function returns the indexes of the clusters that
	# are known to contain data. Those are the ones that we need to read.
	def clusters_with_data(fd, cluster_size):
	data_to = 0
	while True:
	try:
	data_from = os.lseek(fd, data_to, os.SEEK_DATA)
	data_to = align_up(os.lseek(fd, data_from, os.SEEK_HOLE), cluster_size)
	for idx in range(data_from // cluster_size, data_to // cluster_size):
	yield idx
	except OSError as err:
	if err.errno == errno.ENXIO: # End of file reached
	break
	raise err


	# write_qcow2_content() expects a raw input file. If we have a different
	# format we can use qemu-storage-daemon to make it appear as raw.
	@contextmanager
	def get_input_as_raw_file(input_file, input_format):
	if input_format == "raw":
	yield input_file
	return
	try:
	temp_dir = tempfile.mkdtemp()
	pid_file = os.path.join(temp_dir, "pid")
	raw_file = os.path.join(temp_dir, "raw")
	open(raw_file, "wb").close()
	ret = subprocess.run(
	[
	QEMU_STORAGE_DAEMON,
	"--daemonize",
	"--pidfile", pid_file,
	"--blockdev", f"driver=file,node-name=file0,driver=file,filename={input_file},read-only=on",
	"--blockdev", f"driver={input_format},node-name=disk0,file=file0,read-only=on",
	"--export", f"type=fuse,id=export0,node-name=disk0,mountpoint={raw_file},writable=off",
	],
	capture_output=True,
	)
	if ret.returncode != 0:
	sys.exit("[Error] Could not start the qemu-storage-daemon:\n" +
	ret.stderr.decode().rstrip('\n'))
	yield raw_file
	finally:
	# Kill the storage daemon on exit
	# and remove all temporary files
	if os.path.exists(pid_file):
	with open(pid_file, "r") as f:
	pid = int(f.readline())
	os.kill(pid, signal.SIGTERM)
	while os.path.exists(pid_file):
	time.sleep(0.1)
	os.unlink(raw_file)
	os.rmdir(temp_dir)


	def write_features(cluster, offset, data_file_name):
	if data_file_name is not None:
	encoded_name = data_file_name.encode("utf-8")
	padded_name_len = align_up(len(encoded_name), 8)
	struct.pack_into(f">II{padded_name_len}s", cluster, offset,
	QCOW2_DATA_FILE_NAME_STRING,
	len(encoded_name),
	encoded_name)
	offset += 8 + padded_name_len

	qcow2_features = [
	# Incompatible
	(0, 0, "dirty bit"),
	(0, 1, "corrupt bit"),
	(0, 2, "external data file"),
	(0, 3, "compression type"),
	(0, 4, "extended L2 entries"),
	# Compatible
	(1, 0, "lazy refcounts"),
	# Autoclear
	(2, 0, "bitmaps"),
	(2, 1, "raw external data"),
	]
	struct.pack_into(">I", cluster, offset, QCOW2_FEATURE_NAME_TABLE)
	struct.pack_into(">I", cluster, offset + 4, len(qcow2_features) * 48)
	offset += 8
	for feature_type, feature_bit, feature_name in qcow2_features:
	struct.pack_into(">BB46s", cluster, offset,
	feature_type, feature_bit, feature_name.encode("ascii"))
	offset += 48


	def write_qcow2_content(input_file, cluster_size, refcount_bits, data_file_name, data_file_raw):
	# Some basic values
	l1_entries_per_table = cluster_size // 8
	l2_entries_per_table = cluster_size // 8
	refcounts_per_table = cluster_size // 8
	refcounts_per_block = cluster_size * 8 // refcount_bits

	# Virtual disk size, number of data clusters and L1 entries
	disk_size = align_up(os.path.getsize(input_file), 512)
	total_data_clusters = math.ceil(disk_size / cluster_size)
	l1_entries = math.ceil(total_data_clusters / l2_entries_per_table)
	allocated_l1_tables = math.ceil(l1_entries / l1_entries_per_table)

	# Max L1 table size is 32 MB (QCOW_MAX_L1_SIZE in block/qcow2.h)
	if (l1_entries * 8) > (32 * 1024 * 1024):
	sys.exit("[Error] The image size is too large. Try using a larger cluster size.")

	# Two bitmaps indicating which L1 and L2 entries are set
	l1_bitmap = bytearray(allocated_l1_tables * l1_entries_per_table // 8)
	l2_bitmap = bytearray(l1_entries * l2_entries_per_table // 8)
	allocated_l2_tables = 0
	allocated_data_clusters = 0

	if data_file_raw:
	# If data_file_raw is set then all clusters are allocated and
	# we don't need to read the input file at all.
	allocated_l2_tables = l1_entries
	for idx in range(l1_entries):
	bitmap_set(l1_bitmap, idx)
	for idx in range(total_data_clusters):
	bitmap_set(l2_bitmap, idx)
	else:
	# Open the input file for reading
	fd = os.open(input_file, os.O_RDONLY)
	zero_cluster = bytes(cluster_size)
	# Read all the clusters that contain data
	for idx in clusters_with_data(fd, cluster_size):
	cluster = os.pread(fd, cluster_size, cluster_size * idx)
	# If the last cluster is smaller than cluster_size pad it with zeroes
	if len(cluster) < cluster_size:
	cluster += bytes(cluster_size - len(cluster))
	# If a cluster has non-zero data then it must be allocated
	# in the output file and its L2 entry must be set
	if cluster != zero_cluster:
	bitmap_set(l2_bitmap, idx)
	allocated_data_clusters += 1
	# Allocated data clusters also need their corresponding L1 entry and L2 table
	l1_idx = math.floor(idx / l2_entries_per_table)
	if not bitmap_is_set(l1_bitmap, l1_idx):
	bitmap_set(l1_bitmap, l1_idx)
	allocated_l2_tables += 1

	# Total amount of allocated clusters excluding the refcount blocks and table
	total_allocated_clusters = 1 + allocated_l1_tables + allocated_l2_tables
	if data_file_name is None:
	total_allocated_clusters += allocated_data_clusters

	# Clusters allocated for the refcount blocks and table
	allocated_refcount_blocks = math.ceil(total_allocated_clusters / refcounts_per_block)
	allocated_refcount_tables = math.ceil(allocated_refcount_blocks / refcounts_per_table)

	# Now we have a problem because allocated_refcount_blocks and allocated_refcount_tables...
	# (a) increase total_allocated_clusters, and
	# (b) need to be recalculated when total_allocated_clusters is increased
	# So we need to repeat the calculation as long as the numbers change
	while True:
	new_total_allocated_clusters = total_allocated_clusters + allocated_refcount_tables + allocated_refcount_blocks
	new_allocated_refcount_blocks = math.ceil(new_total_allocated_clusters / refcounts_per_block)
	if new_allocated_refcount_blocks > allocated_refcount_blocks:
	allocated_refcount_blocks = new_allocated_refcount_blocks
	allocated_refcount_tables = math.ceil(allocated_refcount_blocks / refcounts_per_table)
	else:
	break

	# Now that we have the final numbers we can update total_allocated_clusters
	total_allocated_clusters += allocated_refcount_tables + allocated_refcount_blocks

	# At this point we have the exact number of clusters that the output
	# image is going to use so we can calculate all the offsets.
	current_cluster_idx = 1

	refcount_table_offset = current_cluster_idx * cluster_size
	current_cluster_idx += allocated_refcount_tables

	refcount_block_offset = current_cluster_idx * cluster_size
	current_cluster_idx += allocated_refcount_blocks

	l1_table_offset = current_cluster_idx * cluster_size
	current_cluster_idx += allocated_l1_tables

	l2_table_offset = current_cluster_idx * cluster_size
	current_cluster_idx += allocated_l2_tables

	data_clusters_offset = current_cluster_idx * cluster_size

	# Calculate some values used in the qcow2 header
	if allocated_l1_tables == 0:
	l1_table_offset = 0

	hdr_cluster_bits = int(math.log2(cluster_size))
	hdr_refcount_bits = int(math.log2(refcount_bits))
	hdr_length = QCOW2_V3_HEADER_LENGTH
	hdr_incompat_features = 0
	if data_file_name is not None:
	hdr_incompat_features \|= 1 << QCOW2_INCOMPAT_DATA_FILE_BIT
	hdr_autoclear_features = 0
	if data_file_raw:
	hdr_autoclear_features \|= 1 << QCOW2_AUTOCLEAR_DATA_FILE_RAW_BIT

	### Write qcow2 header
	cluster = bytearray(cluster_size)
	struct.pack_into(">4sIQIIQIIQQIIQQQQII", cluster, 0,
	b"QFI\xfb", # QCOW magic string
	3, # version
	0, # backing file offset
	0, # backing file sizes
	hdr_cluster_bits,
	disk_size,
	0, # encryption method
	l1_entries,
	l1_table_offset,
	refcount_table_offset,
	allocated_refcount_tables,
	0, # number of snapshots
	0, # snapshot table offset
	hdr_incompat_features,
	0, # compatible features
	hdr_autoclear_features,
	hdr_refcount_bits,
	hdr_length,
	)

	write_features(cluster, hdr_length, data_file_name)

	sys.stdout.buffer.write(cluster)

	### Write refcount table
	cur_offset = refcount_block_offset
	remaining_refcount_table_entries = allocated_refcount_blocks # Each entry is a pointer to a refcount block
	while remaining_refcount_table_entries > 0:
	cluster = bytearray(cluster_size)
	to_write = min(remaining_refcount_table_entries, refcounts_per_table)
	remaining_refcount_table_entries -= to_write
	for idx in range(to_write):
	struct.pack_into(">Q", cluster, idx * 8, cur_offset)
	cur_offset += cluster_size
	sys.stdout.buffer.write(cluster)

	### Write refcount blocks
	remaining_refcount_block_entries = total_allocated_clusters # One entry for each allocated cluster
	for tbl in range(allocated_refcount_blocks):
	cluster = bytearray(cluster_size)
	to_write = min(remaining_refcount_block_entries, refcounts_per_block)
	remaining_refcount_block_entries -= to_write
	# All refcount entries contain the number 1. The only difference
	# is their bit width, defined when the image is created.
	for idx in range(to_write):
	if refcount_bits == 64:
	struct.pack_into(">Q", cluster, idx * 8, 1)
	elif refcount_bits == 32:
	struct.pack_into(">L", cluster, idx * 4, 1)
	elif refcount_bits == 16:
	struct.pack_into(">H", cluster, idx * 2, 1)
	elif refcount_bits == 8:
	cluster[idx] = 1
	elif refcount_bits == 4:
	cluster[idx // 2] \|= 1 << ((idx % 2) * 4)
	elif refcount_bits == 2:
	cluster[idx // 4] \|= 1 << ((idx % 4) * 2)
	elif refcount_bits == 1:
	cluster[idx // 8] \|= 1 << (idx % 8)
	sys.stdout.buffer.write(cluster)

	### Write L1 table
	cur_offset = l2_table_offset
	for tbl in range(allocated_l1_tables):
	cluster = bytearray(cluster_size)
	for idx in range(l1_entries_per_table):
	l1_idx = tbl * l1_entries_per_table + idx
	if bitmap_is_set(l1_bitmap, l1_idx):
	struct.pack_into(">Q", cluster, idx * 8, cur_offset \| QCOW_OFLAG_COPIED)
	cur_offset += cluster_size
	sys.stdout.buffer.write(cluster)

	### Write L2 tables
	cur_offset = data_clusters_offset
	for tbl in range(l1_entries):
	# Skip the empty L2 tables. We can identify them because
	# there is no L1 entry pointing at them.
	if bitmap_is_set(l1_bitmap, tbl):
	cluster = bytearray(cluster_size)
	for idx in range(l2_entries_per_table):
	l2_idx = tbl * l2_entries_per_table + idx
	if bitmap_is_set(l2_bitmap, l2_idx):
	if data_file_name is None:
	struct.pack_into(">Q", cluster, idx * 8, cur_offset \| QCOW_OFLAG_COPIED)
	cur_offset += cluster_size
	else:
	struct.pack_into(">Q", cluster, idx * 8, (l2_idx * cluster_size) \| QCOW_OFLAG_COPIED)
	sys.stdout.buffer.write(cluster)

	### Write data clusters
	if data_file_name is None:
	for idx in bitmap_iterator(l2_bitmap, total_data_clusters):
	cluster = os.pread(fd, cluster_size, cluster_size * idx)
	# If the last cluster is smaller than cluster_size pad it with zeroes
	if len(cluster) < cluster_size:
	cluster += bytes(cluster_size - len(cluster))
	sys.stdout.buffer.write(cluster)

	if not data_file_raw:
	os.close(fd)


	def main():
	# Command-line arguments
	parser = argparse.ArgumentParser(
	description="This program converts a QEMU disk image to qcow2 "
	"and writes it to the standard output"
	)
	parser.add_argument("input_file", help="name of the input file")
	parser.add_argument(
	"-f",
	dest="input_format",
	metavar="input_format",
	help="format of the input file (default: raw)",
	default="raw",
	)
	parser.add_argument(
	"-c",
	dest="cluster_size",
	metavar="cluster_size",
	help=f"qcow2 cluster size (default: {QCOW2_DEFAULT_CLUSTER_SIZE})",
	default=QCOW2_DEFAULT_CLUSTER_SIZE,
	type=int,
	choices=[1 << x for x in range(9, 22)],
	)
	parser.add_argument(
	"-r",
	dest="refcount_bits",
	metavar="refcount_bits",
	help=f"width of the reference count entries (default: {QCOW2_DEFAULT_REFCOUNT_BITS})",
	default=QCOW2_DEFAULT_REFCOUNT_BITS,
	type=int,
	choices=[1 << x for x in range(7)],
	)
	parser.add_argument(
	"-d",
	dest="data_file",
	help="create an image with input_file as an external data file",
	action="store_true",
	)
	parser.add_argument(
	"-R",
	dest="data_file_raw",
	help="enable data_file_raw on the generated image (implies -d)",
	action="store_true",
	)
	args = parser.parse_args()

	if args.data_file_raw:
	args.data_file = True

	if not os.path.isfile(args.input_file):
	sys.exit(f"[Error] {args.input_file} does not exist or is not a regular file.")

	if args.data_file and args.input_format != "raw":
	sys.exit("[Error] External data files can only be used with raw input images")

	# A 512 byte header is too small for the data file name extension
	if args.data_file and args.cluster_size == 512:
	sys.exit("[Error] External data files require a larger cluster size")

	if sys.stdout.isatty():
	sys.exit("[Error] Refusing to write to a tty. Try redirecting stdout.")

	if args.data_file:
	data_file_name = args.input_file
	else:
	data_file_name = None

	with get_input_as_raw_file(args.input_file, args.input_format) as raw_file:
	write_qcow2_content(
	raw_file,
	args.cluster_size,
	args.refcount_bits,
	data_file_name,
	args.data_file_raw,
	)


	if __name__ == "__main__":
	main()