STINNER Victor <[email protected]> added the comment:
os.write(data) can write less than len(data) bytes. It's by contract, as
socket.send(data) can send less than len(data).
It is used to truncated the length argument to INT_MAX, to be able to cast it
to an int on Windows. Extract of _Py_write():
#ifdef MS_WINDOWS
if (count > 32767 && isatty(fd)) {
/* Issue #11395: the Windows console returns an error (12: not
enough space error) on writing into stdout if stdout mode is
binary and the length is greater than 66,000 bytes (or less,
depending on heap usage). */
count = 32767;
}
#endif
if (count > _PY_WRITE_MAX) {
count = _PY_WRITE_MAX;
}
with:
#if defined(MS_WINDOWS) || defined(__APPLE__)
/* On Windows, the count parameter of read() is an int (bpo-9015, bpo-9611).
On macOS 10.13, read() and write() with more than INT_MAX bytes
fail with EINVAL (bpo-24658). */
# define _PY_READ_MAX INT_MAX
# define _PY_WRITE_MAX INT_MAX
#else
/* write() should truncate the input to PY_SSIZE_T_MAX bytes,
but it's safer to do it ourself to have a portable behaviour */
# define _PY_READ_MAX PY_SSIZE_T_MAX
# define _PY_WRITE_MAX PY_SSIZE_T_MAX
#endif
Can we do something similar for sendfile()?
----------
nosy: +vstinner
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Python tracker <[email protected]>
<https://bugs.python.org/issue35179>
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