Fix LasAppender

By not rewritting the vlrs when the appender is closed,
as it might break things if the vlrs we would rewrite don't have the
exact same byter len (which can happen if we remove extra null bytes)

pylas/header.py

@@ -494,11 +494,12 @@ def read_from(cls, stream: BinaryIO, seekable=True) -> "LasHeader":
 
         return header
 
-    def write_to(self, stream: BinaryIO) -> None:
+    def write_to(self, stream: BinaryIO, write_vlrs: bool = True) -> None:
         little_endian = "little"
-        with io.BytesIO() as tmp:
-            self.vlrs.write_to(tmp)
-            vlr_bytes = tmp.getvalue()
+        if write_vlrs is True:
+            with io.BytesIO() as tmp:
+                self.vlrs.write_to(tmp)
+                vlr_bytes = tmp.getvalue()
 
         stream.write(LAS_FILE_SIGNATURE)
         stream.write(self.file_source_id.to_bytes(2, little_endian, signed=False))
@@ -538,7 +539,8 @@ def write_to(self, stream: BinaryIO) -> None:
         )
 
         header_size = LAS_HEADERS_SIZE[str(self.version)]
-        self.offset_to_point_data = header_size + len(vlr_bytes)
+        if write_vlrs is True:
+            self.offset_to_point_data = header_size + len(vlr_bytes)
 
         stream.write(header_size.to_bytes(2, little_endian, signed=False))
         stream.write(self.offset_to_point_data.to_bytes(4, little_endian, signed=False))
@@ -598,7 +600,8 @@ def write_to(self, stream: BinaryIO) -> None:
                     )
                 )
 
-        stream.write(vlr_bytes)
+        if write_vlrs is True:
+            stream.write(vlr_bytes)
 
     def _sync_extra_bytes_vlr(self) -> None:
         try:

pylas/lasappender.py

@@ -99,7 +99,11 @@ def _write_evlrs(self) -> None:
     def _write_updated_header(self) -> None:
         pos = self.dest.tell()
         self.dest.seek(0, io.SEEK_SET)
-        self.header.write_to(self.dest)
+        # we don't want to rewrite the vlrs
+        # as written vlrs may not have to exact
+        # same number of bytes (e.g. if we remove
+        # extra spurious null bytes)
+        self.header.write_to(self.dest, write_vlrs=False)
         self.dest.seek(pos, io.SEEK_SET)
 
     def _create_laz_backend(

pylas/utils.py

@@ -9,6 +9,6 @@ def encode_to_len(string: str, wanted_len: int, codec="ascii") -> bytes:
 
 def encode_to_null_terminated(string: str, codec: str = "utf-8") -> bytes:
     b = string.encode(codec)
-    if b[-1] != b"\0":
+    if b[-1] != 0:
         b += b"\0"
     return b