def test_ReviseStashSize(self):
        """ReviseStashSize should convert transfers to 'new' commands as needed.

    t1: diff <20-29> => <11-15>
    t2: diff <11-15> => <20-29>
    """

        src = EmptyImage()
        tgt = EmptyImage()
        block_image_diff = BlockImageDiff(tgt, src, version=3)

        transfers = block_image_diff.transfers
        Transfer("t1", "t1", RangeSet("11-15"), RangeSet("20-29"), "t1hash",
                 "t1hash", "diff", transfers)
        Transfer("t2", "t2", RangeSet("20-29"), RangeSet("11-15"), "t2hash",
                 "t2hash", "diff", transfers)

        block_image_diff.GenerateDigraph()
        block_image_diff.FindVertexSequence()
        block_image_diff.ReverseBackwardEdges()

        # Sufficient cache to stash 5 blocks (size * 0.8 >= 5).
        common.OPTIONS.cache_size = 7 * 4096
        self.assertEqual((0, 5), block_image_diff.ReviseStashSize())

        # Insufficient cache to stash 5 blocks (size * 0.8 < 5).
        common.OPTIONS.cache_size = 6 * 4096
        self.assertEqual((10, 0), block_image_diff.ReviseStashSize())
    def test_ReviseStashSize_bug_33687949(self):
        """ReviseStashSize() should "free" the used stash _after_ the command.

    t1: diff <1-5> => <11-15>
    t2: diff <11-15> => <21-25>
    t3: diff <11-15 30-39> => <1-5 30-39>

    For transfer t3, the used stash "11-15" should not be freed until the
    command finishes. Assume the allowed cache size is 12-block, it should
    convert the command to 'new' due to insufficient cache (12 < 5 + 10).
    """

        src = EmptyImage()
        tgt = EmptyImage()
        block_image_diff = BlockImageDiff(tgt, src, version=3)

        transfers = block_image_diff.transfers
        t1 = Transfer("t1", "t1", RangeSet("11-15"), RangeSet("1-5"), "t1hash",
                      "t1hash", "diff", transfers)
        t2 = Transfer("t2", "t2", RangeSet("21-25"), RangeSet("11-15"),
                      "t2hash", "t2hash", "diff", transfers)
        t3 = Transfer("t3", "t3", RangeSet("1-5 30-39"),
                      RangeSet("11-15 30-39"), "t3hash", "t3hash", "diff",
                      transfers)

        block_image_diff.GenerateDigraph()

        # Instead of calling FindVertexSequence() and ReverseBackwardEdges(), we
        # just set up the stash_before and use_stash manually. Otherwise it will
        # reorder the transfer, which makes testing ReviseStashSize() harder.
        t1.stash_before.append((0, RangeSet("11-15")))
        t2.use_stash.append((0, RangeSet("11-15")))
        t1.stash_before.append((1, RangeSet("11-15")))
        t3.use_stash.append((1, RangeSet("11-15")))

        # Insufficient cache to stash 15 blocks (size * 0.8 < 15).
        common.OPTIONS.cache_size = 15 * 4096
        self.assertEqual((15, 5), block_image_diff.ReviseStashSize())