From c0c1da323237f5e807e9b052d7d052905854bb05 Mon Sep 17 00:00:00 2001
From: Joseph Schorr <josephschorr@users.noreply.github.com>
Date: Fri, 28 Aug 2015 14:08:13 -0400
Subject: [PATCH] Change build logs load to using streaming Gzip

---
 data/archivedlogs.py             |   9 +--
 util/registry/gzipinputstream.py | 113 +++++++++++++++++++++++++++++++
 2 files changed, 116 insertions(+), 6 deletions(-)
 create mode 100644 util/registry/gzipinputstream.py

diff --git a/data/archivedlogs.py b/data/archivedlogs.py
index e190b9782..fd532c3ca 100644
--- a/data/archivedlogs.py
+++ b/data/archivedlogs.py
@@ -1,8 +1,7 @@
 import logging
 
-from gzip import GzipFile
+from util.registry.gzipinputstream import GzipInputStream
 from flask import send_file, abort
-from cStringIO import StringIO
 
 from data.userfiles import DelegateUserfiles, UserfilesHandlers
 
@@ -17,10 +16,8 @@ class LogArchiveHandlers(UserfilesHandlers):
   def get(self, file_id):
     path = self._files.get_file_id_path(file_id)
     try:
-      with self._storage.stream_read_file(self._locations, path) as gzip_stream:
-        with GzipFile(fileobj=gzip_stream) as unzipped:
-          unzipped_buffer = StringIO(unzipped.read())
-          return send_file(unzipped_buffer, mimetype=JSON_MIMETYPE)
+      data_stream = self._storage.stream_read_file(self._locations, path)
+      return send_file(GzipInputStream(data_stream), mimetype=JSON_MIMETYPE)
     except IOError:
       abort(404)
 
diff --git a/util/registry/gzipinputstream.py b/util/registry/gzipinputstream.py
new file mode 100644
index 000000000..10dc060f1
--- /dev/null
+++ b/util/registry/gzipinputstream.py
@@ -0,0 +1,113 @@
+import zlib
+import string
+
+BLOCK_SIZE = 16384
+"""Read block size"""
+
+WINDOW_BUFFER_SIZE = 16 + zlib.MAX_WBITS
+"""zlib window buffer size, set to gzip's format"""
+
+
+class GzipInputStream(object):
+  """
+  Simple class that allow streaming reads from GZip files.
+
+  Python 2.x gzip.GZipFile relies on .seek() and .tell(), so it
+  doesn't support this (@see: http://bo4.me/YKWSsL).
+
+  Adapted from: https://gist.github.com/beaufour/4205533
+  """
+
+  def __init__(self, fileobj):
+    """
+    Initialize with the given file-like object.
+
+    @param fileobj: file-like object,
+    """
+    self._file = fileobj
+    self._zip = zlib.decompressobj(WINDOW_BUFFER_SIZE)
+    self._offset = 0  # position in unzipped stream
+    self._data = ""
+
+  def __fill(self, num_bytes):
+    """
+    Fill the internal buffer with 'num_bytes' of data.
+
+    @param num_bytes: int, number of bytes to read in (0 = everything)
+    """
+
+    if not self._zip:
+      return
+
+    while not num_bytes or len(self._data) < num_bytes:
+      data = self._file.read(BLOCK_SIZE)
+      if not data:
+        self._data = self._data + self._zip.flush()
+        self._zip = None  # no more data
+        break
+
+      self._data = self._data + self._zip.decompress(data)
+
+  def __iter__(self):
+    return self
+
+  def seek(self, offset, whence=0):
+    if whence == 0:
+      position = offset
+    elif whence == 1:
+      position = self._offset + offset
+    else:
+      raise IOError("Illegal argument")
+
+    if position < self._offset:
+      raise IOError("Cannot seek backwards")
+
+    # skip forward, in blocks
+    while position > self._offset:
+      if not self.read(min(position - self._offset, BLOCK_SIZE)):
+        break
+
+  def tell(self):
+    return self._offset
+
+  def read(self, size=0):
+    self.__fill(size)
+    if size:
+      data = self._data[:size]
+      self._data = self._data[size:]
+    else:
+      data = self._data
+      self._data = ""
+
+    self._offset = self._offset + len(data)
+    return data
+
+  def next(self):
+    line = self.readline()
+    if not line:
+      raise StopIteration()
+    return line
+
+  def readline(self):
+    # make sure we have an entire line
+    while self._zip and "\n" not in self._data:
+      self.__fill(len(self._data) + 512)
+
+    pos = string.find(self._data, "\n") + 1
+    if pos <= 0:
+      return self.read()
+
+    return self.read(pos)
+
+  def readlines(self):
+    lines = []
+    while True:
+      line = self.readline()
+      if not line:
+        break
+
+      lines.append(line)
+    return lines
+
+  def close(self):
+    self._file.close()