Release 260111

common/file_helpers.py

@@ -0,0 +1,58 @@
+import io
+import os
+import tempfile
+import contextlib
+import zstandard as zstd
+
+LOG_COMPRESSION_LEVEL = 10 # little benefit up to level 15. level ~17 is a small step change
+
+
+class CallbackReader:
+  """Wraps a file, but overrides the read method to also
+  call a callback function with the number of bytes read so far."""
+  def __init__(self, f, callback, *args):
+    self.f = f
+    self.callback = callback
+    self.cb_args = args
+    self.total_read = 0
+
+  def __getattr__(self, attr):
+    return getattr(self.f, attr)
+
+  def read(self, *args, **kwargs):
+    chunk = self.f.read(*args, **kwargs)
+    self.total_read += len(chunk)
+    self.callback(*self.cb_args, self.total_read)
+    return chunk
+
+
+@contextlib.contextmanager
+def atomic_write_in_dir(path: str, mode: str = 'w', buffering: int = -1, encoding: str = None, newline: str = None,
+                        overwrite: bool = False):
+  """Write to a file atomically using a temporary file in the same directory as the destination file."""
+  dir_name = os.path.dirname(path)
+
+  if not overwrite and os.path.exists(path):
+    raise FileExistsError(f"File '{path}' already exists. To overwrite it, set 'overwrite' to True.")
+
+  with tempfile.NamedTemporaryFile(mode=mode, buffering=buffering, encoding=encoding, newline=newline, dir=dir_name, delete=False) as tmp_file:
+    yield tmp_file
+    tmp_file_name = tmp_file.name
+  os.replace(tmp_file_name, path)
+
+
+def get_upload_stream(filepath: str, should_compress: bool) -> tuple[io.BufferedIOBase, int]:
+  if not should_compress:
+    file_size = os.path.getsize(filepath)
+    file_stream = open(filepath, "rb")
+    return file_stream, file_size
+
+  # Compress the file on the fly
+  compressed_stream = io.BytesIO()
+  compressor = zstd.ZstdCompressor(level=LOG_COMPRESSION_LEVEL)
+
+  with open(filepath, "rb") as f:
+    compressor.copy_stream(f, compressed_stream)
+    compressed_size = compressed_stream.tell()
+    compressed_stream.seek(0)
+    return compressed_stream, compressed_size