meerschaum.utils.daemon.StdinFile

  1#! /usr/bin/env python3
  2# -*- coding: utf-8 -*-
  3# vim:fenc=utf-8
  4
  5"""
  6Create a file manager to pass STDIN to the Daemon.
  7"""
  8
  9import io
 10import pathlib
 11import time
 12import os
 13import selectors
 14import traceback
 15
 16from meerschaum.utils.typing import Optional, Union
 17from meerschaum.utils.warnings import warn
 18
 19
 20class StdinFile(io.TextIOBase):
 21    """
 22    Redirect user input into a Daemon's context.
 23    """
 24    def __init__(
 25        self,
 26        file_path: Union[pathlib.Path, str],
 27        lock_file_path: Optional[pathlib.Path] = None,
 28    ):
 29        if isinstance(file_path, str):
 30            file_path = pathlib.Path(file_path)
 31
 32        self.file_path = file_path
 33        self.blocking_file_path = (
 34            lock_file_path
 35            if lock_file_path is not None
 36            else (file_path.parent / (file_path.name + '.block'))
 37        )
 38        self._file_handler = None
 39        self._fd = None
 40        self.sel = selectors.DefaultSelector()
 41
 42    @property
 43    def file_handler(self):
 44        """
 45        Return the read file handler to the provided file path.
 46        """
 47        if self._file_handler is not None:
 48            return self._file_handler
 49
 50        if self.file_path.exists():
 51            self.file_path.unlink()
 52
 53        self.file_path.parent.mkdir(parents=True, exist_ok=True)
 54        os.mkfifo(self.file_path.as_posix(), mode=0o600)
 55
 56        self._fd = os.open(self.file_path, os.O_RDONLY | os.O_NONBLOCK)
 57        self._file_handler = os.fdopen(self._fd, 'rb', buffering=0)
 58        self.sel.register(self._file_handler, selectors.EVENT_READ)
 59        return self._file_handler
 60
 61    def write(self, data):
 62        if isinstance(data, str):
 63            data = data.encode('utf-8')
 64
 65        with open(self.file_path, 'wb') as f:
 66            f.write(data)
 67
 68    def fileno(self):
 69        fileno = self.file_handler.fileno()
 70        return fileno
 71
 72    def read(self, size=-1):
 73        """
 74        Read from the FIFO pipe, blocking on EOFError.
 75        """
 76        _ = self.file_handler
 77        while True:
 78            try:
 79                data = self._file_handler.read(size)
 80                if data:
 81                    try:
 82                        if self.blocking_file_path.exists():
 83                            self.blocking_file_path.unlink()
 84                    except Exception:
 85                        warn(traceback.format_exc())
 86                    return data.decode('utf-8')
 87            except (OSError, EOFError):
 88                pass
 89
 90            self.blocking_file_path.touch()
 91            time.sleep(0.1)
 92
 93    def readline(self, size=-1):
 94        line = ''
 95        while True:
 96            data = self.read(1)
 97            if not data or data == '\n':
 98                break
 99            line += data
100
101        return line
102
103    def close(self):
104        if self._file_handler is not None:
105            self.sel.unregister(self._file_handler)
106            self._file_handler.close()
107            os.close(self._fd)
108            self._file_handler = None
109            self._fd = None
110
111        super().close()
112
113    def is_open(self):
114        return self._file_handler is not None
115
116
117    def __str__(self) -> str:
118        return f"StdinFile('{self.file_path}')"
119
120    def __repr__(self) -> str:
121        return str(self)