1 files changed, 56 insertions, 0 deletions
diff --git a/python/mozbuild/mozbuild/chunkify.py b/python/mozbuild/mozbuild/chunkify.py
new file mode 100644
index 0000000000..b2c1057450
--- /dev/null
+++ b/python/mozbuild/mozbuild/chunkify.py
@@ -0,0 +1,56 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is a direct clone of
+# https://github.com/bhearsum/chunkify/blob/master/chunkify/__init__.py
+# of version 1.2. Its license (MPL2) is contained in repo root LICENSE file.
+# Please make modifications there where possible.
+
+from itertools import islice
+
+
+class ChunkingError(Exception):
+    pass
+
+
+def split_evenly(n, chunks):
+    """Split an integer into evenly distributed list
+
+    >>> split_evenly(7, 3)
+    [3, 2, 2]
+
+    >>> split_evenly(12, 3)
+    [4, 4, 4]
+
+    >>> split_evenly(35, 10)
+    [4, 4, 4, 4, 4, 3, 3, 3, 3, 3]
+
+    >>> split_evenly(1, 2)
+    Traceback (most recent call last):
+        ...
+    ChunkingError: Number of chunks is greater than number
+
+    """
+    if n < chunks:
+        raise ChunkingError("Number of chunks is greater than number")
+    if n % chunks == 0:
+        # Either we can evenly split or only 1 chunk left
+        return [n // chunks] * chunks
+    # otherwise the current chunk should be a bit larger
+    max_size = n // chunks + 1
+    return [max_size] + split_evenly(n - max_size, chunks - 1)
+
+
+def chunkify(things, this_chunk, chunks):
+    if this_chunk > chunks:
+        raise ChunkingError("this_chunk is greater than total chunks")
+
+    dist = split_evenly(len(things), chunks)
+    start = sum(dist[: this_chunk - 1])
+    end = start + dist[this_chunk - 1]
+
+    try:
+        return things[start:end]
+    except TypeError:
+        return islice(things, start, end)