2026-1-6

venv/Lib/site-packages/whoosh/util/varints.py

@@ -0,0 +1,110 @@
+# Copyright 2007 Matt Chaput. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+#    1. Redistributions of source code must retain the above copyright notice,
+#       this list of conditions and the following disclaimer.
+#
+#    2. 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.
+#
+# THIS SOFTWARE IS PROVIDED BY MATT CHAPUT ``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 MATT CHAPUT 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.
+#
+# The views and conclusions contained in the software and documentation are
+# those of the authors and should not be interpreted as representing official
+# policies, either expressed or implied, of Matt Chaput.
+
+from array import array
+
+from whoosh.compat import array_tobytes, xrange
+
+
+# Varint cache
+
+# Build a cache of the varint byte sequences for the first N integers, so we
+# don't have to constantly recalculate them on the fly. This makes a small but
+# noticeable difference.
+
+def _varint(i):
+    a = array("B")
+    while (i & ~0x7F) != 0:
+        a.append((i & 0x7F) | 0x80)
+        i = i >> 7
+    a.append(i)
+    return array_tobytes(a)
+
+
+_varint_cache_size = 512
+_varint_cache = []
+for i in xrange(0, _varint_cache_size):
+    _varint_cache.append(_varint(i))
+_varint_cache = tuple(_varint_cache)
+
+
+def varint(i):
+    """Encodes the given integer into a string of the minimum number  of bytes.
+    """
+    if i < len(_varint_cache):
+        return _varint_cache[i]
+    return _varint(i)
+
+
+def varint_to_int(vi):
+    b = ord(vi[0])
+    p = 1
+    i = b & 0x7f
+    shift = 7
+    while b & 0x80 != 0:
+        b = ord(vi[p])
+        p += 1
+        i |= (b & 0x7F) << shift
+        shift += 7
+    return i
+
+
+def signed_varint(i):
+    """Zig-zag encodes a signed integer into a varint.
+    """
+
+    if i >= 0:
+        return varint(i << 1)
+    return varint((i << 1) ^ (~0))
+
+
+def decode_signed_varint(i):
+    """Zig-zag decodes an integer value.
+    """
+
+    if not i & 1:
+        return i >> 1
+    return (i >> 1) ^ (~0)
+
+
+def read_varint(readfn):
+    """
+    Reads a variable-length encoded integer.
+
+    :param readfn: a callable that reads a given number of bytes,
+        like file.read().
+    """
+
+    b = ord(readfn(1))
+    i = b & 0x7F
+
+    shift = 7
+    while b & 0x80 != 0:
+        b = ord(readfn(1))
+        i |= (b & 0x7F) << shift
+        shift += 7
+    return i