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dump-file.py: allow skipping part of a file

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Reading a file (or partition like /dev/block/mmcblk0p1) from an offset
was requested in #26.
This commit is contained in:
Peter Wu 2017-12-01 03:57:11 +00:00
parent 39c9872ca0
commit 05564d5ffe
1 changed files with 10 additions and 3 deletions
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13
dump-file.py
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@ -60,9 +60,8 @@ def laf_read(comm, fd_num, offset, size):
MAX_BLOCK_SIZE = (16 * 1024 - 512) // 512 MAX_BLOCK_SIZE = (16 * 1024 - 512) // 512
BLOCK_SIZE = 512 BLOCK_SIZE = 512
def dump_file(comm, file_fd, output_file, size): def dump_file(comm, file_fd, output_file, size, offset=0):
with open_local_writable(output_file) as f: with open_local_writable(output_file) as f:
offset = 0
while offset < size: while offset < size:
chunksize = min(size - offset, BLOCK_SIZE * MAX_BLOCK_SIZE) chunksize = min(size - offset, BLOCK_SIZE * MAX_BLOCK_SIZE)
data = laf_read(comm, file_fd, offset // BLOCK_SIZE, chunksize) data = laf_read(comm, file_fd, offset // BLOCK_SIZE, chunksize)
@ -79,6 +78,8 @@ def open_local_writable(path):
parser = argparse.ArgumentParser() parser = argparse.ArgumentParser()
parser.add_argument("--debug", action='store_true', help="Enable debug messages") parser.add_argument("--debug", action='store_true', help="Enable debug messages")
parser.add_argument("--offset", type=int, default=0,
help="Start reading the file from an offset")
parser.add_argument("--size", type=int, parser.add_argument("--size", type=int,
help="Override file size (useful for files in /proc)") help="Override file size (useful for files in /proc)")
parser.add_argument("file", help="File path on the device") parser.add_argument("file", help="File path on the device")
@ -97,14 +98,20 @@ def main():
# Be careful: a too large read size will result in a hang while LAF # Be careful: a too large read size will result in a hang while LAF
# tries to read more data, requiring a reset. # tries to read more data, requiring a reset.
if args.size: if args.size:
offset = args.offset
size = args.size size = args.size
else: else:
offset = args.offset
size = get_file_size(comm, args.file) size = get_file_size(comm, args.file)
if offset > size:
_logger.warning("Offset %d is larger than the detected size %d",
offset, size)
size -= offset
if size > 0: if size > 0:
_logger.debug("File size is %d", size) _logger.debug("File size is %d", size)
with laf_open_ro(comm, args.file) as file_fd: with laf_open_ro(comm, args.file) as file_fd:
_logger.debug("Opened fd %d for file %s", file_fd, args.file) _logger.debug("Opened fd %d for file %s", file_fd, args.file)
dump_file(comm, file_fd, args.output_file, size) dump_file(comm, file_fd, args.output_file, size, offset)
else: else:
_logger.warning("Not a file or zero size, not writing file") _logger.warning("Not a file or zero size, not writing file")