[Libguestfs] [PATCH 2/6] v2v: rhv-upload-plugin: Use API_VERSION 2

[Nir Soffer]

Update the callbacks to use new API, avoiding copies in pread(). Since
pread() is not used during import, this is not very useful, but it allow
using parallel threading model.

Signed-off-by: Nir Soffer <nsoffer at redhat.com>
---
 v2v/rhv-upload-plugin.py | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/v2v/rhv-upload-plugin.py b/v2v/rhv-upload-plugin.py
index e261dfdb..0f8101dd 100644
--- a/v2v/rhv-upload-plugin.py
+++ b/v2v/rhv-upload-plugin.py
@@ -32,6 +32,9 @@ from urllib.parse import urlparse
 import ovirtsdk4 as sdk
 import ovirtsdk4.types as types
 
+# Using version 2 supporting the buffer protocol for better performance.
+API_VERSION = 2
+
 # Timeout to wait for oVirt disks to change status, or the transfer
 # object to finish initializing [seconds].
 timeout = 5 * 60
@@ -190,7 +193,8 @@ def request_failed(r, msg):
 
 
 @failing
-def pread(h, count, offset):
+def pread(h, buf, offset, flags):
+    count = len(buf)
     http = h['http']
 
     headers = {"Range": "bytes=%d-%d" % (offset, offset + count - 1)}
@@ -203,11 +207,26 @@ def pread(h, count, offset):
                        "could not read sector offset %d size %d" %
                        (offset, count))
 
-    return r.read()
+    content_length = int(r.getheader("content-length"))
+    if content_length != count:
+        # Should never happen.
+        request_failed(r,
+                       "unexpected Content-Length offset %d size %d got %d" %
+                       (offset, count, content_length))
+
+    with memoryview(buf) as view:
+        got = 0
+        while got < count:
+            n = r.readinto(view[got:])
+            if n == 0:
+                request_failed(r,
+                               "short read offset %d size %d got %d" %
+                               (offset, count, got))
+            got += n
 
 
 @failing
-def pwrite(h, buf, offset):
+def pwrite(h, buf, offset, flags):
     http = h['http']
 
     count = len(buf)
@@ -234,7 +253,7 @@ def pwrite(h, buf, offset):
 
 
 @failing
-def zero(h, count, offset, may_trim):
+def zero(h, count, offset, flags):
     http = h['http']
 
     # Unlike the trim and flush calls, there is no 'can_zero' method
@@ -292,7 +311,7 @@ def emulate_zero(h, count, offset):
 
 
 @failing
-def flush(h):
+def flush(h, flags):
     http = h['http']
 
     # Construct the JSON request for flushing.
-- 
2.26.2