small optimizations and code reduction

supyr_struct/blocks/array_block.py

@@ -2,7 +2,7 @@
 from sys import getsizeof
 
 from supyr_struct.blocks.block import Block
-from supyr_struct.blocks.list_block import ListBlock
+from supyr_struct.blocks.list_block import ListBlock, repeat
 from supyr_struct.defs.constants import NAME, UNNAMED, NAME_MAP
 from supyr_struct.exceptions import DescEditError, DescKeyError
 from supyr_struct.buffer import get_rawdata_context
@@ -37,7 +37,7 @@ def __init__(self, desc, parent=None, init_attrs=None, **kwargs):
             self.parse(init_attrs=init_attrs, **kwargs)
         else:
             # populate the listblock with the right number of fields
-            list.__init__(self, [None]*self.get_size())
+            list.__init__(self, repeat(None, self.get_size()))
 
     def __sizeof__(self, seenset=None):
         '''
@@ -150,10 +150,9 @@ def __delitem__(self, index):
             # the descriptor since its list indexes
             # aren't attributes, but instanced objects
             start, stop, step = index.indices(len(self))
+            step = -step if step < 0 else step
             if start < stop:
                 start, stop = stop, start
-            if step > 0:
-                step = -step
 
             list.__delitem__(self, index)
             self.set_size()
@@ -239,7 +238,7 @@ def extend(self, new_attrs, **kwargs):
             index = len(self)
 
             # create new, empty indices
-            list.extend(self, [None]*new_attrs)
+            list.extend(self, repeat(None, new_attrs))
             # read new sub_structs into the empty indices
             for i in range(index, index + new_attrs):
                 attr_f_type.parser(attr_desc, parent=self,
@@ -705,10 +704,10 @@ def parse(self, **kwargs):
             # parsing/initializing all array elements, so clear and resize
             list.__delitem__(self, slice(None, None, None))
             if initdata is not None:
-                list.extend(self, [None]*len(initdata))
+                list.extend(self, repeat(None, len(initdata)))
                 self.set_size()  # update the size to the initdata length
             else:
-                list.extend(self, [None]*self.get_size())
+                list.extend(self, repeat(None, self.get_size()))
 
             if rawdata is not None:
                 # parse the ArrayBlock from raw data
@@ -798,7 +797,7 @@ def __init__(self, desc, parent=None, steptree=None,
             self.parse(init_attrs=init_attrs, **kwargs)
         else:
             # populate the listblock with the right number of fields
-            list.__init__(self, [None]*self.get_size())
+            list.__init__(self, repeat(None, self.get_size()))
 
     def __sizeof__(self, seenset=None):
         '''

supyr_struct/blocks/list_block.py

@@ -1,7 +1,7 @@
 '''
 '''
 from copy import deepcopy
-from itertools import takewhile
+from itertools import repeat, takewhile
 from sys import getsizeof
 
 from supyr_struct.blocks.block import Block
@@ -47,7 +47,7 @@ def __init__(self, desc, parent=None, init_attrs=None, **kwargs):
             self.parse(init_attrs=init_attrs, **kwargs)
         else:
             # populate the listblock with the right number of fields
-            list.__init__(self, [None]*desc['ENTRIES'])
+            list.__init__(self, repeat(None, desc['ENTRIES']))
 
     def __str__(self, **kwargs):
         '''
@@ -215,7 +215,7 @@ def __deepcopy__(self, memo):
 
         # clear the Block so it can be populated
         list.__delitem__(dup_block, slice(None, None, None))
-        list.extend(dup_block, [None]*len(self))
+        list.extend(dup_block, repeat(None, len(self)))
 
         # populate the duplicate
         for i in range(len(self)):
@@ -269,9 +269,9 @@ def __getitem__(self, index):
 
         If index is a string, returns self.__getattr__(index)
         '''
-        if isinstance(index, str):
-            return self.__getattr__(index)
-        return list.__getitem__(self, index)
+        return (self.__getattr__(index) if isinstance(index, str) else
+                list.__getitem__(self, index)
+                )
 
     def __setitem__(self, index, new_value):
         '''
@@ -300,8 +300,7 @@ def __setitem__(self, index, new_value):
         '''
         if isinstance(index, int):
             # handle accessing negative indexes
-            if index < 0:
-                index += len(self)
+            index = index + len(self) if index < 0 else index
 
             assert not self.assert_is_valid_field_value(index, new_value)
             list.__setitem__(self, index, new_value)
@@ -332,10 +331,9 @@ def __setitem__(self, index, new_value):
 
         elif isinstance(index, slice):
             start, stop, step = index.indices(len(self))
+            step = -step if step < 0 else step
             if start > stop:
                 start, stop = stop, start
-            if step < 0:
-                step = -step
 
             assert hasattr(new_value, '__iter__'), (
                 "must assign iterable to extended slice")
@@ -810,7 +808,7 @@ def parse(self, **kwargs):
             if kwargs.get("clear", True):
                 # parsing/initializing all attributes, so clear the block
                 # and create as many elements as it needs to hold
-                list.__init__(self, [None]*desc['ENTRIES'])
+                list.__init__(self, repeat(None, desc['ENTRIES']))
 
             if rawdata is not None:
                 # parse the ListBlock from raw data
@@ -899,7 +897,7 @@ def __init__(self, desc, parent=None, steptree=None,
             self.parse(init_attrs=init_attrs, **kwargs)
         else:
             # populate the listblock with the right number of fields
-            list.__init__(self, [None]*desc['ENTRIES'])
+            list.__init__(self, repeat(None, desc['ENTRIES']))
 
     def __sizeof__(self, seenset=None):
         '''

supyr_struct/blocks/while_block.py

@@ -4,7 +4,7 @@
 stored anywhere and must be parsed until some function says to stop.
 '''
 from supyr_struct.blocks.block import Block
-from supyr_struct.blocks.list_block import ListBlock
+from supyr_struct.blocks.list_block import ListBlock, repeat
 from supyr_struct.blocks.array_block import ArrayBlock, PArrayBlock
 from supyr_struct.defs.constants import SUB_STRUCT, NAME, UNNAMED
 from supyr_struct.exceptions import DescEditError, DescKeyError
@@ -36,8 +36,7 @@ def __setitem__(self, index, new_value):
         '''
         if isinstance(index, int):
             # handle accessing negative indexes
-            if index < 0:
-                index += len(self)
+            index = index + len(self) if index < 0 else index
 
             assert not self.assert_is_valid_field_value(index, new_value)
             list.__setitem__(self, index, new_value)
@@ -48,10 +47,9 @@ def __setitem__(self, index, new_value):
 
         elif isinstance(index, slice):
             start, stop, step = index.indices(len(self))
+            step = -step if step < 0 else step
             if start > stop:
                 start, stop = stop, start
-            if step < 0:
-                step = -step
 
             assert hasattr(new_value, '__iter__'), (
                 "must assign iterable to extended slice")
@@ -428,7 +426,7 @@ def parse(self, **kwargs):
             raise TypeError("Could not locate the sub-struct descriptor." +
                             "\nCould not initialize array")
 
-        list.extend(self, [None]*init_len)
+        list.extend(self, repeat(None, init_len))
 
         if kwargs.get('init_attrs', True) or issubclass(attr_f_type.node_cls, Block):
             # loop through each element in the array and initialize it

supyr_struct/field_type_methods/decoders.py

@@ -67,12 +67,9 @@ def decode_decimal(self, rawdata, desc=None, parent=None, attr_index=None):
 
     Returns a Decimal represention of the "rawdata" argument.
     '''
-    if self.endian == '<':
-        endian = 'little'
-    else:
-        endian = 'big'
-    d_exp = parent.get_meta('DECIMAL_EXP', attr_index)
-    bigint = str(int.from_bytes(
+    endian  = 'little' if self.endian == '<' else 'big'
+    d_exp   = parent.get_meta('DECIMAL_EXP', attr_index)
+    bigint  = str(int.from_bytes(
         rawdata, endian, signed=self.enc.endswith('S')))
 
     return Decimal(bigint[:len(bigint)-d_exp] + '.' +
@@ -87,11 +84,10 @@ def decode_24bit_numeric(self, rawdata, desc=None,
 
     Returns an int decoded represention of the "rawdata" argument.
     '''
-    if self.endian == '<':
-        rawint = unpack('<I', rawdata + b'\x00')[0]
-    else:
-        rawint = unpack('>I', b'\x00' + rawdata)[0]
-
+    rawint  = (
+        unpack('<I', rawdata + b'\x00') if self.endian == '<' else
+        unpack('>I', b'\x00' + rawdata)
+        )[0]
     # if the int can be signed and IS signed then take care of that
     if rawint & 0x800000 and self.enc[1] == 't':
         return rawint - 0x1000000  # 0x1000000 == 0x800000 * 2
@@ -148,20 +144,14 @@ def decode_big_int(self, rawdata, desc=None, parent=None, attr_index=None):
     if not len(rawdata):
         return 0
 
-    if self.endian == '<':
-        endian = 'little'
-    else:
-        endian = 'big'
-
-    if self.enc[-1] == 's':
-        # ones compliment
-        bigint = int.from_bytes(rawdata, endian, signed=True)
-        if bigint < 0:
-            return bigint + 1
-        return bigint
-    elif self.enc[-1] == 'S':
+    endian  = 'little' if self.endian == '<' else 'big'
+    if self.enc[-1] == 'S':
         # twos compliment
         return int.from_bytes(rawdata, endian, signed=True)
+    elif self.enc[-1] == 's':
+        # ones compliment
+        bigint = int.from_bytes(rawdata, endian, signed=True)
+        return bigint + (bigint < 0)
 
     return int.from_bytes(rawdata, endian)
 

supyr_struct/field_type_methods/encoders.py

@@ -78,17 +78,17 @@ def encode_24bit_numeric(self, node, parent=None, attr_index=None):
         # int can be signed
         assert node >= -0x800000 and node <= 0x7fffff, (
             '%s is too large to pack as a 24bit signed int.' % node)
-        if node < 0:
-            # int IS signed
-            node += 0x1000000
+        # int IS signed
+        node += 0x1000000 if node < 0 else 0
     else:
         assert node >= 0 and node <= 0xffffff, (
             '%s is too large to pack as a 24bit unsigned int.' % node)
 
     # pack and return the int
-    if self.endian == '<':
-        return pack('<I', node)[0:3]
-    return pack('>I', node)[1:4]
+    return (
+        pack('<I', node)[0:3] if self.endian == '<' else
+        pack('>I', node)[1:4]
+        )
 
 
 def encode_int_timestamp(self, node, parent=None, attr_index=None):
@@ -148,19 +148,13 @@ def encode_big_int(self, node, parent=None, attr_index=None):
     if not bytecount:
         return b''
 
-    if self.endian == '<':
-        endian = 'little'
-    else:
-        endian = 'big'
-
+    endian  = 'little' if self.endian == '<' else 'big'
     if self.enc[-1] == 'S':
         # twos compliment
         return node.to_bytes(bytecount, endian, signed=True)
     elif self.enc[-1] == 's':
         # ones compliment
-        if node < 0:
-            return (node-1).to_bytes(bytecount, endian, signed=True)
-        return node.to_bytes(bytecount, endian, signed=False)
+        return (node - (node < 0)).to_bytes(bytecount, endian, signed=True)
 
     return node.to_bytes(bytecount, endian)