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From w...@apache.org
Subject arrow git commit: ARROW-1416: Clarify memory layout documentation
Date Mon, 28 Aug 2017 13:36:45 GMT
Repository: arrow
Updated Branches:
  refs/heads/master 6cd2a1716 -> f250d4657


ARROW-1416: Clarify memory layout documentation

This PR slightly reduces ambiguity in the array example for null bitmaps. The original example
was left/right symmetric; this PR changes the example to break that symmetry. Asymmetry is
important since readers who skip the byte endianness section could have interpreted the bitmap
buffer in two distinct ways: left-to-right with an offset of 3 (wrong), or right-to-left with
zero offset (correct).

Author: Fritz Obermeyer <fritz.obermeyer@gmail.com>

Closes #998 from fritzo/patch-1 and squashes the following commits:

af3dcbd0 [Fritz Obermeyer] Clarify memory layout documentation


Project: http://git-wip-us.apache.org/repos/asf/arrow/repo
Commit: http://git-wip-us.apache.org/repos/asf/arrow/commit/f250d465
Tree: http://git-wip-us.apache.org/repos/asf/arrow/tree/f250d465
Diff: http://git-wip-us.apache.org/repos/asf/arrow/diff/f250d465

Branch: refs/heads/master
Commit: f250d46578fa02fbfe432f5a4e44b66eed3b4b2b
Parents: 6cd2a17
Author: Fritz Obermeyer <fritz.obermeyer@gmail.com>
Authored: Mon Aug 28 09:36:40 2017 -0400
Committer: Wes McKinney <wes.mckinney@twosigma.com>
Committed: Mon Aug 28 09:36:40 2017 -0400

----------------------------------------------------------------------
 format/Layout.md | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/arrow/blob/f250d465/format/Layout.md
----------------------------------------------------------------------
diff --git a/format/Layout.md b/format/Layout.md
index 3342511..3c21dbc 100644
--- a/format/Layout.md
+++ b/format/Layout.md
@@ -206,7 +206,7 @@ does not need to be adjacent in memory to the values buffer.
 ### Example Layout: Int32 Array
 For example a primitive array of int32s:
 
-[1, 2, null, 4, 8]
+[1, null, 2, 4, 8]
 
 Would look like:
 
@@ -216,13 +216,13 @@ Would look like:
 
   |Byte 0 (validity bitmap) | Bytes 1-63            |
   |-------------------------|-----------------------|
-  | 00011011                | 0 (padding)           |
+  | 00011101                | 0 (padding)           |
 
 * Value Buffer:
 
   |Bytes 0-3   | Bytes 4-7   | Bytes 8-11  | Bytes 12-15 | Bytes 16-19 | Bytes 20-63 |
   |------------|-------------|-------------|-------------|-------------|-------------|
-  | 1          | 2           | unspecified | 4           | 8           | unspecified |
+  | 1          | unspecified | 2           | 4           | 8           | unspecified |
 ```
 
 ### Example Layout: Non-null int32 Array


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