[oe-commits] [bitbake] 09/10: utils/md5_file: don't iterate line-by-line

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rpurdie pushed a commit to branch master-next
in repository bitbake.

commit d2dcb4cbe83680f41c7076341298d4f2f58417ea
Author: Ross Burton <ross.burton at intel.com>
AuthorDate: Mon Aug 13 19:02:25 2018 +0100

    utils/md5_file: don't iterate line-by-line
    
    Opening a file in binary mode and iterating it seems like the simple solution
    but will still break on newlines, which for binary files isn't really useful as
    the size of the chunks could be huge or tiny.
    
    Instead, let's be a bit more clever: we'll be MD5ing lots of files, but we don't
    want to fill up memory: use mmap() to open the file and read the file in 8k
    blocks.
    
    Signed-off-by: Ross Burton <ross.burton at intel.com>
    Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
 lib/bb/utils.py | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/lib/bb/utils.py b/lib/bb/utils.py
index 9903183..b20cdab 100644
--- a/lib/bb/utils.py
+++ b/lib/bb/utils.py
@@ -524,12 +524,17 @@ def md5_file(filename):
     """
     Return the hex string representation of the MD5 checksum of filename.
     """
-    import hashlib
-    m = hashlib.md5()
+    import hashlib, mmap
 
     with open(filename, "rb") as f:
-        for line in f:
-            m.update(line)
+        m = hashlib.md5()
+        try:
+            with mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ) as mm:
+                for chunk in iter(lambda: mm.read(8192), b''):
+                    m.update(chunk)
+        except ValueError:
+            # You can't mmap() an empty file so silence this exception
+            pass
     return m.hexdigest()
 
 def sha256_file(filename):

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