--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgext/fsmonitor/pywatchman/load.py	Thu Dec 22 11:22:32 2016 -0800
@@ -0,0 +1,107 @@
+# Copyright 2016 Facebook, Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#  * Redistributions of source code must retain the above copyright notice,
+#    this list of conditions and the following disclaimer.
+#
+#  * Redistributions in binary form must reproduce the above copyright notice,
+#    this list of conditions and the following disclaimer in the documentation
+#    and/or other materials provided with the distribution.
+#
+#  * Neither the name Facebook nor the names of its contributors may be used to
+#    endorse or promote products derived from this software without specific
+#    prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+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)