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95 lines
3.7 KiB
Python
95 lines
3.7 KiB
Python
import io
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import sys
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# The maximum length of a log message in bytes, including the level marker and
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# tag, is defined as LOGGER_ENTRY_MAX_PAYLOAD in
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# platform/system/logging/liblog/include/log/log.h. As of API level 30, messages
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# longer than this will be be truncated by logcat. This limit has already been
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# reduced at least once in the history of Android (from 4076 to 4068 between API
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# level 23 and 26), so leave some headroom.
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MAX_BYTES_PER_WRITE = 4000
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# UTF-8 uses a maximum of 4 bytes per character, so limiting text writes to this
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# size ensures that TextIOWrapper can always avoid exceeding MAX_BYTES_PER_WRITE.
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# However, if the actual number of bytes per character is smaller than that,
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# then TextIOWrapper may still join multiple consecutive text writes into binary
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# writes containing a larger number of characters.
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MAX_CHARS_PER_WRITE = MAX_BYTES_PER_WRITE // 4
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# When embedded in an app on current versions of Android, there's no easy way to
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# monitor the C-level stdout and stderr. The testbed comes with a .c file to
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# redirect them to the system log using a pipe, but that wouldn't be convenient
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# or appropriate for all apps. So we redirect at the Python level instead.
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def init_streams(android_log_write, stdout_prio, stderr_prio):
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if sys.executable:
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return # Not embedded in an app.
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sys.stdout = TextLogStream(
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android_log_write, stdout_prio, "python.stdout", errors=sys.stdout.errors)
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sys.stderr = TextLogStream(
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android_log_write, stderr_prio, "python.stderr", errors=sys.stderr.errors)
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class TextLogStream(io.TextIOWrapper):
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def __init__(self, android_log_write, prio, tag, **kwargs):
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kwargs.setdefault("encoding", "UTF-8")
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kwargs.setdefault("line_buffering", True)
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super().__init__(BinaryLogStream(android_log_write, prio, tag), **kwargs)
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self._CHUNK_SIZE = MAX_BYTES_PER_WRITE
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def __repr__(self):
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return f"<TextLogStream {self.buffer.tag!r}>"
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def write(self, s):
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if not isinstance(s, str):
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raise TypeError(
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f"write() argument must be str, not {type(s).__name__}")
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# In case `s` is a str subclass that writes itself to stdout or stderr
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# when we call its methods, convert it to an actual str.
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s = str.__str__(s)
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# We want to emit one log message per line wherever possible, so split
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# the string before sending it to the superclass. Note that
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# "".splitlines() == [], so nothing will be logged for an empty string.
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for line in s.splitlines(keepends=True):
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while line:
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super().write(line[:MAX_CHARS_PER_WRITE])
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line = line[MAX_CHARS_PER_WRITE:]
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return len(s)
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class BinaryLogStream(io.RawIOBase):
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def __init__(self, android_log_write, prio, tag):
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self.android_log_write = android_log_write
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self.prio = prio
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self.tag = tag
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def __repr__(self):
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return f"<BinaryLogStream {self.tag!r}>"
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def writable(self):
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return True
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def write(self, b):
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if type(b) is not bytes:
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try:
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b = bytes(memoryview(b))
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except TypeError:
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raise TypeError(
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f"write() argument must be bytes-like, not {type(b).__name__}"
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) from None
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# Writing an empty string to the stream should have no effect.
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if b:
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# Encode null bytes using "modified UTF-8" to avoid truncating the
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# message. This should not affect the return value, as the caller
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# may be expecting it to match the length of the input.
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self.android_log_write(self.prio, self.tag,
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b.replace(b"\x00", b"\xc0\x80"))
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return len(b)
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