Thread pool is no longer used for files in memory (#933)

* Tinche/aiofiles#47
Thread pool is no longer used for files in memory

* fix tests

* fix import sorted

* little change

requirements.txt

@@ -16,6 +16,7 @@ isort
 mypy
 pytest
 pytest-cov
+pytest-asyncio
 
 # Documentation
 mkdocs

starlette/datastructures.py

@@ -433,17 +433,33 @@ def __init__(
             file = tempfile.SpooledTemporaryFile(max_size=self.spool_max_size)
         self.file = file
 
+    @property
+    def _in_memory(self) -> bool:
+        rolled_to_disk = getattr(self.file, "_rolled", True)
+        return not rolled_to_disk
+
     async def write(self, data: typing.Union[bytes, str]) -> None:
-        await run_in_threadpool(self.file.write, data)
+        if self._in_memory:
+            self.file.write(data)  # type: ignore
+        else:
+            await run_in_threadpool(self.file.write, data)
 
-    async def read(self, size: int = None) -> typing.Union[bytes, str]:
+    async def read(self, size: int = -1) -> typing.Union[bytes, str]:
+        if self._in_memory:
+            return self.file.read(size)
         return await run_in_threadpool(self.file.read, size)
 
     async def seek(self, offset: int) -> None:
-        await run_in_threadpool(self.file.seek, offset)
+        if self._in_memory:
+            self.file.seek(offset)
+        else:
+            await run_in_threadpool(self.file.seek, offset)
 
     async def close(self) -> None:
-        await run_in_threadpool(self.file.close)
+        if self._in_memory:
+            self.file.close()
+        else:
+            await run_in_threadpool(self.file.close)
 
 
 class FormData(ImmutableMultiDict):

tests/test_datastructures.py

@@ -1,5 +1,7 @@
 import io
 
+import pytest
+
 from starlette.datastructures import (
     URL,
     CommaSeparatedStrings,
@@ -8,6 +10,7 @@
     MultiDict,
     MutableHeaders,
     QueryParams,
+    UploadFile,
 )
 
 
@@ -210,6 +213,20 @@ def test_queryparams():
     assert QueryParams(q) == q
 
 
+class TestUploadFile(UploadFile):
+    spool_max_size = 1024
+
+
+@pytest.mark.asyncio
+async def test_upload_file():
+    big_file = TestUploadFile("big-file")
+    await big_file.write(b"big-data" * 512)
+    await big_file.write(b"big-data")
+    await big_file.seek(0)
+    assert await big_file.read(1024) == b"big-data" * 128
+    await big_file.close()
+
+
 def test_formdata():
     upload = io.BytesIO(b"test")
     form = FormData([("a", "123"), ("a", "456"), ("b", upload)])