Add a toy HTTP backend.

tftp/httpbackend.py

@@ -0,0 +1,100 @@
+from tftp.backend import IReader, IWriter, IBackend
+from tftp.errors import Unsupported, FileNotFound
+from tftp.util import deferred
+from zope import interface
+from cStringIO import StringIO
+import requests
+
+class HTTPReader(object):
+    interface.implements(IReader)
+
+    def __init__(self, url):
+        self.url = url
+
+        self.r = requests.get(url)
+
+        if self.r.status_code >= 300:
+            raise FileNotFound(self.url)
+
+        self.offset = 0
+        self.content_size = len(self.r.content)
+        self.state = 'active'
+
+    @property
+    def size(self):
+        return self.content_size
+
+    def read(self, size):
+        if self.state in ('eof', 'finished'):
+            return ''
+
+        old_offset = self.offset
+
+        self.offset  = min(old_offset + size, self.content_size)
+        if self.offset == self.content_size:
+            self.state = 'eof'
+
+        return self.r.content[old_offset:self.offset]
+
+    def finish(self):
+        self.r = None
+        self.state = 'finished'
+
+
+class HTTPWriter(object):
+    interface.implements(IWriter)
+
+    def __init__(self, url):
+        self.url = url
+        self.data = StringIO()
+        self.state = 'active'
+
+    def write(self, data):
+        self.data.write(data)
+
+    def finish(self):
+        if self.state not in ('finished', 'cancelled'):
+            requests.put(self.url, data=self.data.getvalue())
+            self.data.close()
+            self.data = None
+            self.state = 'finished'
+
+    def cancel(self):
+        if self.state not in ('finished', 'cancelled'):
+            self.data.close()
+            self.data = None
+            self.state = 'cancelled'
+
+
+class HTTPSynchronousBackend(object):
+    """
+    Synchronous HTTP backend using the Requests library.
+
+    The basic concept of this backend is to forward TFTP queries "as is" to an
+    HTTP server, as a simple way to allow dynamic files generated on the fly for
+    each TFTP request.
+
+    RRQ are forwarded as GET requests.
+    WRQ are forwarded as PUT requests.
+    """
+
+    interface.implements(IBackend)
+
+    def __init__(self, base_url, can_read=True, can_write=True):
+        self.base = base_url
+        if not self.base.endswith('/'):
+            self.base = self.base + '/'
+
+        self.can_read, self.can_write = can_read, can_write
+
+    @deferred
+    def get_reader(self, file_name):
+        if not self.can_read:
+            raise Unsupported("Reading not supported")
+        return HTTPReader(self.base + file_name)
+
+    @deferred
+    def get_writer(self, file_name):
+        if not self.can_write:
+            raise Unsupported("Writing not supported")
+        return HTTPWriter(self.base + file_name)