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Shrlok/shrlok/shrlok.py

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Python
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#!/usr/bin/env python3
"""shrlok server: receive text/files from a socket, put them on a Web server.
The server expects messages with the following format to come through the
socket:
1. a length, as ASCII digits,
2. a null byte,
3. a JSON object containing at least the "type" key with a known value,
4. another null byte,
5. the text or file itself.
The length is of the JSON object + the null char + the content itself.
Example, with \\0 representing a null byte:
28\\0{"type":"txt"}\\0hello shrlok!
The content is 13 bytes (assuming no LF at the end), the header is 14 bytes,
plus the null byte it is 13 + 14 + 1 = 28 bytes, thus the prefixed length.
After the content is succesfully retrieved and put on an appropriate location,
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the server will reply the file path through the socket and close the
connection.
"""
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import argparse
import json
import os
import socketserver
import tempfile
from pathlib import Path
ARGS = None
HTML_TEMPLATE = """\
<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>{title}</title>
<style>
body {{ max-width: 40em; }}
</style>
</head>
<body>
{content}
</body>
</html>
"""
class Handler(socketserver.StreamRequestHandler):
def handle(self):
data = self.receive_input()
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# Extract header.
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try:
first_zero = data.index(b"\0")
header_data, data = data[:first_zero], data[first_zero + 1:]
header = json.loads(header_data.decode())
except (ValueError, IndexError):
print("Bad header.")
return
file_name = None
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if header.get("type") == "txt":
file_name = write_text(data, title=header.get("title"))
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elif header.get("type") == "html":
file_name = write_content(data)
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else:
print("Unknown type.")
if file_name is None:
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return
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print(f"{len(data)} bytes — {header}'{file_name}'.")
try:
self.request.sendall(file_name.encode())
except BrokenPipeError:
print("Broken pipe.")
def receive_input(self):
length = None
data = b""
while True:
chunk = self.request.recv(4096)
if not chunk:
break
data += chunk
if length is None:
try:
first_zero = data.index(b"\0")
except ValueError:
return b""
length_data, data = data[:first_zero], data[first_zero + 1:]
length = int(length_data.decode())
if len(data) >= length: # retrieval completed
break
return data
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def write_text(data: bytes, title=None):
content = "<pre>{}</pre>".format(data.decode(errors="replace"))
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html = HTML_TEMPLATE.format(title=title or "?", content=content).encode()
write_content(html)
def write_content(data: bytes):
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path = str(Path(ARGS.root) / "txt")
if not os.path.isdir(path):
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print(f"Missing '{path}' folder.")
return None
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with tempfile.NamedTemporaryFile(
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mode="wb",
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dir=path,
suffix=".html",
delete=False
) as output_file:
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output_file.write(data)
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os.chmod(output_file.name, 0o644)
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return output_file.name
def main():
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argp = argparse.ArgumentParser(description="Share stuff through a socket.")
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argp.add_argument("root", help="root path where to put files")
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argp.add_argument("-s", "--socket", help="socket path")
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global ARGS
ARGS = argp.parse_args()
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socket_path = ARGS.socket
if not socket_path:
runtime_dir = os.environ.get("RUNTIME_DIRECTORY")
if not runtime_dir:
exit("No socket path nor runtime directory specified.")
socket_path = os.path.join(runtime_dir, "shr.sock")
print("Socket path:", socket_path)
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if os.path.exists(socket_path):
os.unlink(socket_path)
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try:
with socketserver.UnixStreamServer(socket_path, Handler) as server:
os.chmod(socket_path, 0o664)
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server.serve_forever()
except KeyboardInterrupt:
print("Stopping server.")
finally:
os.unlink(socket_path)
if __name__ == "__main__":
main()