view hgext/fsmonitor/pywatchman/load.py @ 33554:2943141f5e07

revset: pass repo when passing ui

The repo instance is currently only used to provide a changeset
lookup function as part of parsing revsets. I /think/ this allows
node fragments to resolve. I'm not sure why we wouldn't want this
to always "just work" if parsing a revset string.

Plus, an upcoming commit will introduce a new consumer that needs a
handle on the repo. So passing it more often will make that code
work more.

Passing a repo instance in all callers of revset.match* results in
a bunch of test changes. Notably, branch and tags caches get
populated as part of evaluating revsets. I'm not sure if this is
desirable. So this patch takes the conservative approach and only
passes the repo if we're passing a ui instance.

Differential Revision: https://phab.mercurial-scm.org/D97

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from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
# no unicode literals

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

import ctypes

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)