SF 964876 mapping a 0 length file
Document that it can't be done on Windows.
diff --git a/Doc/lib/libmmap.tex b/Doc/lib/libmmap.tex
index 426f658..0334147 100644
--- a/Doc/lib/libmmap.tex
+++ b/Doc/lib/libmmap.tex
@@ -42,10 +42,12 @@
\begin{funcdesc}{mmap}{fileno, length\optional{, tagname\optional{, access}}}
\strong{(Windows version)} Maps \var{length} bytes from the file
specified by the file handle \var{fileno}, and returns a mmap
- object. If \var{length} is \code{0}, the maximum length of the map
- will be the current size of the file when \function{mmap()} is
- called.
-
+ object. If \var{length} is larger than the current size of the file,
+ the file is extended to contain \var{length} bytes. If \var{length}
+ is \code{0}, the maximum length of the map is the current size
+ of the file, except that if the file is empty Windows raises an
+ exception (you cannot create an empty mapping on Windows).
+
\var{tagname}, if specified and not \code{None}, is a string giving
a tag name for the mapping. Windows allows you to have many
different mappings against the same file. If you specify the name
@@ -61,19 +63,19 @@
\strong{(\UNIX{} version)} Maps \var{length} bytes from the file
specified by the file descriptor \var{fileno}, and returns a mmap
object.
-
+
\var{flags} specifies the nature of the mapping.
\constant{MAP_PRIVATE} creates a private copy-on-write mapping, so
changes to the contents of the mmap object will be private to this
process, and \constant{MAP_SHARED} creates a mapping that's shared
with all other processes mapping the same areas of the file. The
default value is \constant{MAP_SHARED}.
-
+
\var{prot}, if specified, gives the desired memory protection; the
two most useful values are \constant{PROT_READ} and
\constant{PROT_WRITE}, to specify that the pages may be read or
written. \var{prot} defaults to \constant{PROT_READ | PROT_WRITE}.
-
+
\var{access} may be specified in lieu of \var{flags} and \var{prot}
as an optional keyword parameter. It is an error to specify both
\var{flags}, \var{prot} and \var{access}. See the description of
@@ -123,7 +125,7 @@
\end{methoddesc}
\begin{methoddesc}{readline}{}
- Returns a single line, starting at the current file position and up to
+ Returns a single line, starting at the current file position and up to
the next newline.
\end{methoddesc}