Add readinto() API

readinto()
This method is useful when you have to read a large file over multiple
read calls. While read() allocates a buffer every time it's invoked,
readinto() copies data to an already allocated buffer passed to it.

Change-Id: Ic8a3aa0e544e09e05101c983b329c91864832e4a
Signed-off-by: Prashanth Pai <ppai@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/test/functional/libgfapi-python-tests.py b/test/functional/libgfapi-python-tests.py
index 6840d18..3a0b89e 100644
--- a/test/functional/libgfapi-python-tests.py
+++ b/test/functional/libgfapi-python-tests.py
@@ -502,6 +502,24 @@ class FileOpsTest(unittest.TestCase):
         self.vol.symlink(file_name, link_name)
         self.assertEqual(self.vol.readlink(link_name), file_name)
 
+    def test_readinto(self):
+        file_name = uuid4().hex
+        with File(self.vol.open(file_name, os.O_WRONLY | os.O_CREAT)) as f:
+            s = ''.join([str(i) for i in xrange(10)])
+            f.write(s)
+            f.fsync()
+
+        buf = bytearray(1)
+        with File(self.vol.open(file_name, os.O_RDONLY)) as f:
+            for i in xrange(10):
+                # Read one character at a time into buf
+                f.readinto(buf)
+                self.assertEqual(len(buf), 1)
+                self.assertEqual(buf, bytearray(str(i)))
+
+        with File(self.vol.open(file_name, os.O_RDONLY)) as f:
+            self.assertRaises(TypeError, f.readinto, str("buf"))
+
 
 class DirOpsTest(unittest.TestCase):