sendfile support

When a sendfile library is available, expose it via wsgi.file_wrapper.
This support spans both asynchronous and forkpool.

1 files changed, 57 insertions, 0 deletions

diff --git a/wsgitools/scgi/__init__.py b/wsgitools/scgi/__init__.py
index 20f6625..cbe7a80 100644
--- a/wsgitools/scgi/__init__.py
+++ b/wsgitools/scgi/__init__.py
@@ -1,3 +1,58 @@
+__all__ = []
+
+try:
+    import sendfile
+except ImportError:
+    have_sendfile = False
+else:
+    have_sendfile = True
+
+class FileWrapper:
+    """
+    @ivar offset: Initially 0. Becomes -1 when reading using next and 
+        becomes positive when reading using next. In the latter case it
+        counts the number of bytes sent. It also ensures that next and
+        transfer are never mixed.
+    """
+    def __init__(self, filelike, blksize=8192):
+        self.filelike = filelike
+        self.blksize = blksize
+        self.offset = 0
+        if hasattr(filelike, "close"):
+            self.close = filelike.close
+
+    def can_transfer(self):
+        return have_sendfile and hasattr(self.filelike, "fileno") and \
+                self.offset >= 0
+
+    def transfer(self, sock, blksize=None):
+        assert self.offset >= 0
+        if blksize is None:
+            blksize = self.blksize
+        else:
+            blksize = min(self.blksize, blksize)
+        try:
+            sent = sendfile.sendfile(sock.fileno(), self.filelike.fileno(),
+                    self.offset, blksize)
+        except OSError:
+            return -1
+        # There are two different sendfile libraries. Yeah!
+        if isinstance(sent, tuple):
+            sent = sent[1]
+        self.offset += sent
+        return sent
+
+    def __iter__(self):
+        return self
+
+    def next(self):
+        assert self.offset <= 0
+        self.offset = -1
+        data = self.filelike.read(self.blksize)
+        if data:
+            return data
+        raise StopIteration
+
 def _convert_environ(environ, multithread=False, multiprocess=False,
         run_once=False):
     environ.update({
@@ -13,3 +68,5 @@ def _convert_environ(environ, multithread=False, multiprocess=False,
     except KeyError:
         pass
     environ.pop("HTTP_CONTENT_LENGTH", None) # TODO: better way?
+    if have_sendfile:
+        environ["wsgi.file_wrapper"] = FileWrapper