From 490b293ba1aa4f65b81b0f4cc7582d85167ecbec Mon Sep 17 00:00:00 2001
From: Edwin Eefting <edwin@datux.nl>
Date: Mon, 21 Feb 2022 14:27:22 +0100
Subject: [PATCH] block compare

---
 tests/test_check.py           | 21 +++++++++++++++++++++
 zfs_autobackup/BlockHasher.py | 22 +++++++++++++++++-----
 2 files changed, 38 insertions(+), 5 deletions(-)

diff --git a/tests/test_check.py b/tests/test_check.py
index 84a7036..ead0f05 100644
--- a/tests/test_check.py
+++ b/tests/test_check.py
@@ -68,6 +68,27 @@ class TestZfsCheck(unittest2.TestCase):
                 (0, "309ffffba2e1977d12f3b7469971f30d28b94bd8"), #whole_whole2_partial
             ])
 
+    def test_blockhash_compare(self):
+
+
+        block_hasher=BlockHasher(count=1)
+        generator=block_hasher.generate("tests/data/whole_whole2_partial")
+        self.assertEqual(3,block_hasher.compare("tests/data/whole_whole2_partial", generator))
+
+        block_hasher=BlockHasher(count=1)
+        with self.assertRaisesRegexp(Exception, "^Block 1 mismatched!"):
+            generator=block_hasher.generate("tests/data/whole_whole2_partial")
+            self.assertEqual(3,block_hasher.compare("tests/data/whole", generator))
+
+        block_hasher=BlockHasher(count=10)
+        generator=block_hasher.generate("tests/data/whole_whole2_partial")
+        self.assertEqual(1,block_hasher.compare("tests/data/whole_whole2_partial", generator))
+
+        #different order to make sure seek functions
+        block_hasher=BlockHasher(count=1)
+        checksums=list(block_hasher.generate("tests/data/whole_whole2_partial"))
+        checksums.reverse()
+        self.assertEqual(3,block_hasher.compare("tests/data/whole_whole2_partial", checksums))
 
     def test_volume(self):
         prepare_zpools()
diff --git a/zfs_autobackup/BlockHasher.py b/zfs_autobackup/BlockHasher.py
index c0db08f..487cd86 100644
--- a/zfs_autobackup/BlockHasher.py
+++ b/zfs_autobackup/BlockHasher.py
@@ -38,8 +38,20 @@ class BlockHasher():
             if block_nr % self.count != 0:
                 yield (chunk_nr, hash.hexdigest())
 
-        # def compare(fname, generator):
-        #     """reads from generatos and compares blocks"""
-        #
-        #     with open(fname, "rb") as f:
-        #         for ( count, bs , chunk_nr, hexdigest) in input_generator:
\ No newline at end of file
+    def compare(self, fname, generator):
+        """reads from generator and compares blocks, raises exception on error"""
+
+        checked=0
+        with open(fname, "rb") as f:
+            for ( chunk_nr, hexdigest ) in generator:
+                checked=checked+1
+                hash = self.hash_class()
+                f.seek(chunk_nr * self.bs * self.count)
+                for block_nr in range(0,self.count):
+                    hash.update(f.read(self.bs))
+
+                if (hash.hexdigest()!=hexdigest):
+                    raise Exception("Block {} mismatched! Hash is {}, but should be {}".format(chunk_nr, hash.hexdigest(), hexdigest))
+
+        return checked
+