[catapult] - Copy Telemetry's gsutilz over to third_party.

third_party/gsutil/third_party/apitools/apitools/base/py/list_pager.py

Index: third_party/gsutil/third_party/apitools/apitools/base/py/list_pager.py
diff --git a/third_party/gsutil/third_party/apitools/apitools/base/py/list_pager.py b/third_party/gsutil/third_party/apitools/apitools/base/py/list_pager.py
new file mode 100755
index 0000000000000000000000000000000000000000..cf90389f8819ca44e6b121d0b838b7f163849553
--- /dev/null
+++ b/third_party/gsutil/third_party/apitools/apitools/base/py/list_pager.py
@@ -0,0 +1,62 @@
+#!/usr/bin/env python
+"""A helper function that executes a series of List queries for many APIs."""
+
+import copy
+
+__all__ = [
+    'YieldFromList',
+]
+
+
+def YieldFromList(
+        service, request, limit=None, batch_size=100,
+        method='List', field='items', predicate=None,
+        current_token_attribute='pageToken',
+        next_token_attribute='nextPageToken',
+        batch_size_attribute='maxResults'):
+    """Make a series of List requests, keeping track of page tokens.
+
+    Args:
+      service: apitools_base.BaseApiService, A service with a .List() method.
+      request: protorpc.messages.Message, The request message
+          corresponding to the service's .List() method, with all the
+          attributes populated except the .maxResults and .pageToken
+          attributes.
+      limit: int, The maximum number of records to yield. None if all available
+          records should be yielded.
+      batch_size: int, The number of items to retrieve per request.
+      method: str, The name of the method used to fetch resources.
+      field: str, The field in the response that will be a list of items.
+      predicate: lambda, A function that returns true for items to be yielded.
+      current_token_attribute: str, The name of the attribute in a
+          request message holding the page token for the page being
+          requested.
+      next_token_attribute: str, The name of the attribute in a
+          response message holding the page token for the next page.
+      batch_size_attribute: str, The name of the attribute in a
+          response message holding the maximum number of results to be
+          returned.
+
+    Yields:
+      protorpc.message.Message, The resources listed by the service.
+
+    """
+    request = copy.deepcopy(request)
+    setattr(request, batch_size_attribute, batch_size)
+    setattr(request, current_token_attribute, None)
+    while limit is None or limit:
+        response = getattr(service, method)(request)
+        items = getattr(response, field)
+        if predicate:
+            items = list(filter(predicate, items))
+        for item in items:
+            yield item
+            if limit is None:
+                continue
+            limit -= 1
+            if not limit:
+                return
+        token = getattr(response, next_token_attribute)
+        if not token:
+            return
+        setattr(request, current_token_attribute, token)