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Clarified some points about the interface to the mmap() function. 

This closes SF bug #448918.
This commit is contained in:
Fred Drake 2001-09-25 19:00:08 +00:00
parent c0765c2381
commit 5055545fc0
1 changed files with 11 additions and 10 deletions
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21
Doc/lib/libmmap.tex
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@ -14,17 +14,20 @@ change a substring by assigning to a slice:
data starting at the current file position, and \method{seek()}
through the file to different positions.
A memory-mapped file is created by the following function, which is
different on Unix and on Windows.
A memory-mapped file is created by the \function{mmap()} function,
which is different on \UNIX{} and on Windows. In either case you must
provide a file descriptor for a file opened for update.
If you wish to map an existing Python file object, use its
\method{fileno()} method to obtain the correct value for the
\var{fileno} parameter. Otherwise, you can open the file using the
\function{os.open()} function, which returns a file descriptor
directly (the file still needs to be closed when done).
\begin{funcdesc}{mmap}{fileno, length\optional{, tagname}}
\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.
If you wish to map an existing Python file object, use its
\method{fileno()} method to obtain the correct value for the
\var{fileno} parameter. The file must be opened for update.
\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
@ -35,12 +38,9 @@ created without a name. Avoiding the use of the tag parameter will
assist in keeping your code portable between \UNIX{} and Windows.
\end{funcdesc}
\begin{funcdesc}{mmap}{fileno, size\optional{, flags, prot}}
\begin{funcdesc}{mmap}{fileno, length\optional{, flags\optional{, prot}}}
\strong{(\UNIX{} version)} Maps \var{length} bytes from the file
specified by the file handle \var{fileno}, and returns a mmap object.
If you wish to map an existing Python file object, use its
\method{fileno()} method to obtain the correct value for the
\var{fileno} parameter. The file must be opened for update.
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
@ -55,6 +55,7 @@ to specify that the pages may be read or written.
\var{prot} defaults to \constant{PROT_READ | PROT_WRITE}.
\end{funcdesc}
Memory-mapped file objects support the following methods: