hgext/fsmonitor/pywatchman/load.py

util: remove datapath and swith users over to resourceutil

The util module no longer needs the datapath for injecting it into the
i18n module, so we can remove it from there and update other users.

Differential Revision: https://phab.mercurial-scm.org/D7436

# Copyright 2016 Facebook, Inc.
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# no unicode literals
from __future__ import absolute_import, division, print_function

import ctypes


try:
    from . import bser
except ImportError:
    from . import pybser as bser


EMPTY_HEADER = b"\x00\x01\x05\x00\x00\x00\x00"


def _read_bytes(fp, buf):
    """Read bytes from a file-like object

    @param fp: File-like object that implements read(int)
    @type fp: file

    @param buf: Buffer to read into
    @type buf: bytes

    @return: buf
    """

    # Do the first read without resizing the input buffer
    offset = 0
    remaining = len(buf)
    while remaining > 0:
        l = fp.readinto((ctypes.c_char * remaining).from_buffer(buf, offset))
        if l is None or l == 0:
            return offset
        offset += l
        remaining -= l
    return offset


def load(fp, mutable=True, value_encoding=None, value_errors=None):
    """Deserialize a BSER-encoded blob.

    @param fp: The file-object to deserialize.
    @type file:

    @param mutable: Whether to return mutable results.
    @type mutable: bool

    @param value_encoding: Optional codec to use to decode values. If
                           unspecified or None, return values as bytestrings.
    @type value_encoding: str

    @param value_errors: Optional error handler for codec. 'strict' by default.
                         The other most common argument is 'surrogateescape' on
                         Python 3. If value_encoding is None, this is ignored.
    @type value_errors: str
    """
    buf = ctypes.create_string_buffer(8192)
    SNIFF_BUFFER_SIZE = len(EMPTY_HEADER)
    header = (ctypes.c_char * SNIFF_BUFFER_SIZE).from_buffer(buf)
    read_len = _read_bytes(fp, header)
    if read_len < len(header):
        return None

    total_len = bser.pdu_len(buf)
    if total_len > len(buf):
        ctypes.resize(buf, total_len)

    body = (ctypes.c_char * (total_len - len(header))).from_buffer(
        buf, len(header)
    )
    read_len = _read_bytes(fp, body)
    if read_len < len(body):
        raise RuntimeError("bser data ended early")

    return bser.loads(
        (ctypes.c_char * total_len).from_buffer(buf, 0),
        mutable,
        value_encoding,
        value_errors,
    )