hexdumper non blocking io

This commit is contained in:
Christoph J. Scherr 2023-09-14 17:10:34 +02:00
parent 61dbf7a500
commit bf9a01d7ba
2 changed files with 34 additions and 2 deletions

View File

@ -7,7 +7,9 @@ This is a list of tasks that would be cool to add.
- (x) Dump basic files with format
- (x) Dump basic files with chars
- (x) Be able to dump larger files or put out an error
- ( ) Stop reading when read gets blocked /somehow/
- (x) Stop reading when read gets blocked /somehow/
Simple syscall
- ( ) Wait for new input when the file is lazy
- ( ) Install script to system
*** Networking
- ( ) Mini curl

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@ -2,6 +2,7 @@
import argparse
import os
import sys
import fcntl # only for non blocking IO, if you dont know what it is, you can ignore it or study up
# 2**30 bytes aka 1 Mebibyte
MAX_SIZE: int = 0x100000
@ -40,7 +41,35 @@ def main():
# open file
try:
file = open(args.file, "rb")
# Tl;Dr, use this unless you want to do some lower level stuff
# vvvvvvvvvvvvvvvvvvvvvvvvvvvvv
#file = open(args.file, "rb")
# the above is sufficient for most regular uses
#
# some "files" are "lazy" and block the reading process until they have
# content, like network connections, fifos, sockets, and so on.
# the following is a lower level approach to handling these. We
# basically call a part of the libc, telling it to open the file
# nonblocking. If something blocks, it will simply refuse.
#
# as far as i know, this only works on UNIX (like) systems. Windows
# is the only major exception.
# make a syscall that will open our file in readonly mode, nonblocking.
# if it did not exist and we write to it, it would be created with the
# perms: 644 (like `chmod 644 myfile`)
fd = os.open(args.file, os.O_RDONLY | os.O_NONBLOCK, mode=0o644)
# now we make the fd into the high level python class `file`
file = os.fdopen(fd, "rb")
# i read somewhere that file.readline() does not work like this, but as
# we are reading binary data anyways, I don't care.
# check if the file is readable
if not file.peek(1):
print("File is blocked, trying to wait...")
file = open(args.file, "rb")
except Exception as e:
print(f"Could not open file '{args.file}': {e}")
sys.exit(1)
@ -99,6 +128,7 @@ def main():
print(line)
index += 16
file.close()
if __name__ == "__main__":
main()