DOC: update npy-format NEP and lib/format.py with version 2.0 description.

As discussed on gh-5413.  Version 2.0 was added in gh-4765.

1 files changed, 20 insertions, 3 deletions

diff --git a/doc/neps/npy-format.rst b/doc/neps/npy-format.rst
index f7bb799f2..bf88c3fee 100644
--- a/doc/neps/npy-format.rst
+++ b/doc/neps/npy-format.rst
@@ -199,6 +199,21 @@ bytes of the array.  Consumers can figure out the number of bytes
 by multiplying the number of elements given by the shape (noting
 that shape=() means there is 1 element) by dtype.itemsize.
 
+Format Specification: Version 1.0
+---------------------------------
+
+The version 1.0 format only allowed the array header to have a
+total size of 65535 bytes.  This can be exceeded by structured
+arrays with a large number of columns.  The version 2.0 format
+extends the header size to 4 GiB.  `numpy.save` will automatically
+save in 2.0 format if the data requires it, else it will always use
+the more compatible 1.0 format.
+
+The description of the fourth element of the header therefore has
+become:
+
+    The next 4 bytes form a little-endian unsigned int: the length
+    of the header data HEADER_LEN.
 
 Conventions
 -----------
@@ -269,13 +284,15 @@ the file format.
 Implementation
 --------------
 
-The current implementation is included in the 1.0.5 release of numpy.
-
-    http://github.com/numpy/numpy/blob/v1.5.0/numpy/lib/format.py
+The version 1.0 implementation was first included in the 1.0.5 release of
+numpy, and remains available.  The version 2.0 implementation was first
+included in the 1.9.0 release of numpy.
 
 Specifically, the file format.py in this directory implements the
 format as described here.
 
+    http://github.com/numpy/numpy/blob/master/numpy/lib/format.py
+
 
 References
 ----------