io: add align= to Terminated Stream, fix UCS-2 cstr, fix small errors

sx/types/control.py

@@ -54,7 +54,7 @@ class Switch(G[T, V], Type[T]):
     def default(self, context: Context) -> T:
         child = self.get_value(context, peek=True)
         with context.enter(None, child):
-            return context.default(ChildProcessError)
+            return context.default(child)
 
     def __str__(self) -> str:
         return f'{format_value(self.options, str)}[{self.selector}]'
@@ -106,7 +106,7 @@ class If(G[T,V], Type[U[T, V]]):
         else:
             child = to_type(self.false)
         with context.enter(None, child):
-            return context.default(self.child)
+            return context.default(child)
 
     def __str__(self) -> str:
         return f'({self.cond} ? {self.true} : {self.false})'

sx/types/io.py

@@ -95,11 +95,12 @@ class Sized(G[T], Wrapper[T]):
 
 
 class TerminatedStream:
-    def __init__(self, stream: Stream, terminator: bytes, included: bool, blocksize: int = 8192) -> None:
+    def __init__(self, stream: Stream, terminator: bytes, included: bool, align: int = 1, blocksize: int = 8192) -> None:
         self._stream = stream
         self._terminator = terminator
         self._included = included
         self._end_pos = None
+        self._align = align
         self._blocksize = blocksize
 
     def read(self, n: int = -1, *, bits: bool = False) -> U[bytes, int]:
@@ -115,6 +116,7 @@ class TerminatedStream:
                 n = min(n, remaining)
 
         value = b''
+        off = 0
         while n < 0 or len(value) < n:
             try:
                 p = self._stream.tell()
@@ -131,7 +133,14 @@ class TerminatedStream:
 
             # find full terminator or start of terminator at the end
             if self._end_pos is None:
-                termpos = find_overlap(value, self._terminator, len(value) - len(v))
+                while True:
+                    termpos = find_overlap(value[off:], self._terminator, 0)
+                    if termpos is None:
+                        break
+                    termpos += off
+                    if termpos % self._align == 0:
+                        break
+                    off = termpos + 1
                 if termpos is not None:
                     # need to read more data?
                     termrem = len(self._terminator) - (len(value) - termpos)
@@ -183,18 +192,19 @@ class TerminatedStream:
         return getattr(self._stream, attr)
 
 class Terminated(G[T], Wrapper[T]):
-    def __init__(self, child: Type[T], terminator: U[bytes, PossibleDynamic], required: U[bool, PossibleDynamic] = True, included: U[bool, PossibleDynamic] = False, blocksize: int = 8192) -> None:
+    def __init__(self, child: Type[T], terminator: U[bytes, PossibleDynamic], align=1, required: U[bool, PossibleDynamic] = True, included: U[bool, PossibleDynamic] = False, blocksize: int = 8192) -> None:
         super().__init__(child)
         self.terminator = terminator
         self.required = required
         self.included = included
         self.blocksize = blocksize
+        self.align = align
 
     def parse(self, context: Context, stream: Stream) -> T:
         terminator = context.get(self.terminator)
         required = context.get(self.required)
         included = context.get(self.included)
-        tstream = TerminatedStream(stream, terminator, included, blocksize=self.blocksize)
+        tstream = TerminatedStream(stream, terminator, included, align=self.align, blocksize=self.blocksize)
         value = super().parse(context, tstream)
         if required and tstream._end_pos is None:
             raise EOFError(f'terminator {terminator} not found in stream')
@@ -204,7 +214,7 @@ class Terminated(G[T], Wrapper[T]):
         terminator = context.get(self.terminator)
         required = context.get(self.required)
         included = context.get(self.included)
-        tstream = TerminatedStream(stream, terminator, included, blocksize=self.blocksize)
+        tstream = TerminatedStream(stream, terminator, included, align=self.align, blocksize=self.blocksize)
         super().dump(context, tstream, value)
         if required and not included:
             stream.write(terminator)
@@ -374,8 +384,9 @@ class AlignTo(G[T], Wrapper[T]):
 
         align = context.get(self.alignment)
         adjustment = stream.tell() % align
-        padding = stretch(context.get(self.value), align - adjustment)
-        stream.write(padding)
+        if adjustment:
+            padding = stretch(context.get(self.value), align - adjustment)
+            stream.write(padding)
 
     def sizeof(self, context: Context, value: O[T]) -> O[Pos]:
         # TODO
@@ -406,9 +417,9 @@ class AlignedTo(G[T], Wrapper[T]):
     def dump(self, context: Context, stream: Stream, value: T) -> None:
         align = context.get(self.alignment)
         adjustment = stream.tell() % align
-        padding = stretch(context.get(self.value), align - adjustment)
-        stream.write(padding)
-
+        if adjustment:
+            padding = stretch(context.get(self.value), align - adjustment)
+            stream.write(padding)
         super().dump(context, stream, value)
 
     def sizeof(self, context: Context, value: O[T]) -> O[Pos]:

sx/types/str.py

@@ -59,7 +59,7 @@ class Str(Type[str]):
 class CStr(Terminated[str]):
     def __init__(self, *args, terminator_required=True, **kwargs) -> None:
         terminator = '\x00'.encode(kwargs.get('encoding', 'utf-8'))
-        super().__init__(Str(*args, **kwargs), terminator, required=terminator_required, blocksize=16)
+        super().__init__(Str(*args, **kwargs), terminator, required=terminator_required, align=len(terminator), blocksize=16)
 
     def __str__(self) -> str:
         if self.child.encoding == 'utf-8':