Beman Dawes wrote:
"Jonathan Turkanis" <technews@kangaroologic.com> wrote in message news:d1v087$6r0$1@sea.gmane.org...
Hi All,
Is there a reason to avoid providing a uniform interface to implementation-defined standard library features?
One of the most often heard complaints about the standard iostreams library is that there is no portable way to seek within a file stream using large (64-bit) offsets.
I really want to see this fixed in the standard library. Any interest in getting a proposal together?
Yes, definitely.
It seems to me the first step is to fix the <cstdio> stuff inherited from the C library. An easy way to do that is to propose the addition of fseeko and ftello functions. They are already provided on Solaris, FreeBSD, HP-UX, NetBSD, OpenBSD, and HP/Compaq/DEC Alpha OSF/1. SGI IRIX offers the same functionality, but named fseek64() and ftell64(). Apparently Linux is the only weak spot in the POSIX world. The functionality is trivial to provide under modern flavors of Windows. (Thanks to Nelson Beebe for survey of POSIX practice.)
Good survey.
I haven't given much thought to changes that would be required for iostreams yet.
Two possibilities I can think of are as follows (I'm writing this off the top of my head -- I'll need to give it more thought): 1. require streamoff (and the various member types, such as char_traits<>::off_type which have the same requirements as streamoff) to satisfying whatever requirements you would impose on the second parameter of fseeko. 2. Change the legend to Table 88 (27.4.3.2/1) so that - instead of referring to type streamoff, "O" refers to an integral type satisfying whatever requirements you would impose on the second parameter of fseeko. - "o" refers to a value of type "O" Option 1 is more straightforward, but could require some standard libraries (notably Dinkumware) to change the size of their streamoff type even though their streampos already provides adequate large-file support. Standard libraries which already provide a large streamoff would need no change. Option 2 would allow standard libraries which provide a small streamoff but a streampos capable of storing large values to conform by providing a streampos constructor callable with a single parameter of type "O" and by replacing the conversion to streamoff with a conversion to "O". How do these strike you? Jonathan