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use a constant instead of 12 ; some better comments ; remove prefix_len weirdness

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This commit is contained in:
Alec Grieser 2017-10-24 16:40:58 -07:00
parent 584b56ecaf
commit deb48641e3
1 changed files with 14 additions and 12 deletions
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26
bindings/python/fdb/tuple.py
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@ -117,6 +117,7 @@ class SingleFloat(object):
return bool(self.value) return bool(self.value)
class Versionstamp(object): class Versionstamp(object):
LENGTH = 12
_TR_VERSION_LEN = 10 _TR_VERSION_LEN = 10
_MAX_USER_VERSION = (1 << 16) - 1 _MAX_USER_VERSION = (1 << 16) - 1
_UNSET_TR_VERSION = 10 * six.int2byte(0xff) _UNSET_TR_VERSION = 10 * six.int2byte(0xff)
@ -148,7 +149,7 @@ class Versionstamp(object):
def from_bytes(cls, v, start=0): def from_bytes(cls, v, start=0):
if not isinstance(v, bytes): if not isinstance(v, bytes):
raise TypeError("Cannot parse versionstamp from non-byte string") raise TypeError("Cannot parse versionstamp from non-byte string")
elif len(v) - start < cls._TR_VERSION_LEN + 2: elif len(v) - start < cls.LENGTH:
raise ValueError("Versionstamp byte string is too short (only " + str(len(v) - start) + " bytes to read from") raise ValueError("Versionstamp byte string is too short (only " + str(len(v) - start) + " bytes to read from")
else: else:
tr_version = v[start:start + cls._TR_VERSION_LEN] tr_version = v[start:start + cls._TR_VERSION_LEN]
@ -173,7 +174,7 @@ class Versionstamp(object):
def completed(self, new_tr_version): def completed(self, new_tr_version):
if self.is_complete(): if self.is_complete():
raise RuntimeError("Cannot complete Versionstamp twice") raise RuntimeError("Versionstamp already completed")
else: else:
return Versionstamp(new_tr_version, self.user_version) return Versionstamp(new_tr_version, self.user_version)
@ -260,7 +261,7 @@ def _decode(v, pos):
raise ValueError("Invalid API version " + str(fdb._version) + " for boolean types") raise ValueError("Invalid API version " + str(fdb._version) + " for boolean types")
return True, pos+1 return True, pos+1
elif code == VERSIONSTAMP_CODE: elif code == VERSIONSTAMP_CODE:
return Versionstamp.from_bytes(v, pos+1), pos + 13 return Versionstamp.from_bytes(v, pos+1), pos + 1 + Versionstamp.LENGTH
elif code == NESTED_CODE: elif code == NESTED_CODE:
ret = [] ret = []
end_pos = pos+1 end_pos = pos+1
@ -352,12 +353,13 @@ def _encode(value, nested=False):
else: else:
raise ValueError("Unsupported data type: " + str(type(value))) raise ValueError("Unsupported data type: " + str(type(value)))
# packs the specified tuple into that may be used for versionstamp operations but may be used for regular ops # packs the tuple possibly for versionstamp operations and returns the position of the
def _pack_maybe_with_versionstamp(t, prefix=None, prefix_len=0): # incomplete versionstamp
if prefix is not None and prefix_len > 0 and len(prefix) != prefix_len: # * if there are no incomplete versionstamp members, this returns the packed tuple and -1
raise ValueError("Inconsistent values specified for prefix and prefix_len") # * if there is exactly one incomplete versionstamp member, it returns the tuple with the
if prefix_len < 0: # two extra version bytes and the position of the version start
raise ValueError("Illegal prefix_len " + str(prefix_len) + " specified") # * if there is more than one incomplete versionstamp member, it throws an error
def _pack_maybe_with_versionstamp(t, prefix=None):
if not isinstance(t, tuple): if not isinstance(t, tuple):
raise Exception("fdbtuple pack() expects a tuple, got a " + str(type(t))) raise Exception("fdbtuple pack() expects a tuple, got a " + str(type(t)))
@ -365,7 +367,7 @@ def _pack_maybe_with_versionstamp(t, prefix=None, prefix_len=0):
child_bytes, version_pos = _reduce_children(map(_encode, t)) child_bytes, version_pos = _reduce_children(map(_encode, t))
if version_pos >= 0: if version_pos >= 0:
version_pos += len(prefix) if prefix is not None else prefix_len version_pos += len(prefix) if prefix is not None else 0
bytes_list.extend(child_bytes) bytes_list.extend(child_bytes)
bytes_list.append(struct.pack('<H', version_pos)) bytes_list.append(struct.pack('<H', version_pos))
else: else:
@ -381,8 +383,8 @@ def pack(t, prefix=None):
return res return res
# packs the specified tuple into a key for versionstamp operations # packs the specified tuple into a key for versionstamp operations
def pack_with_versionstamp(t, prefix=None, prefix_len=0): def pack_with_versionstamp(t, prefix=None):
res, version_pos = _pack_maybe_with_versionstamp(t, prefix, prefix_len) res, version_pos = _pack_maybe_with_versionstamp(t, prefix)
if version_pos < 0: if version_pos < 0:
raise ValueError("No incomplete versionstamp included in tuple pack with versionstamp") raise ValueError("No incomplete versionstamp included in tuple pack with versionstamp")
return res return res