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author | Ludovic Courtès <ludo@gnu.org> | 2024-04-15 19:48:10 +0200 |
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committer | Ludovic Courtès <ludo@gnu.org> | 2024-04-15 19:58:25 +0200 |
commit | 696acfc9e590ecff70ff369460304e96b269efe5 (patch) | |
tree | 8681a47921281310b9d34f4c0214412c49a4d922 /doc/ref/api-io.texi | |
parent | 4a0c2433d97be9d995b3be74d90bc074d8efb5a7 (diff) | |
download | guile-696acfc9e590ecff70ff369460304e96b269efe5.tar.gz |
‘seek’ now accepts ‘SEEK_DATA’ and ‘SEEK_HOLE’ where supported.
* libguile/ports.c (scm_seek): Let SEEK_DATA and SEEK_HOLE through.
(scm_init_ice_9_ports): Define ‘SEEK_DATA’ and ‘SEEK_HOLE’.
* module/ice-9/ports.scm: Export ‘SEEK_DATA’ and ‘SEEK_HOLE’ when
defined.
* test-suite/tests/ports.test ("size of sparse file")
("SEEK_DATA while on data", "SEEK_DATA while in hole")
("SEEK_HOLE while in hole"): New tests.
* NEWS: Update.
Diffstat (limited to 'doc/ref/api-io.texi')
-rw-r--r-- | doc/ref/api-io.texi | 22 |
1 files changed, 20 insertions, 2 deletions
diff --git a/doc/ref/api-io.texi b/doc/ref/api-io.texi index e263e2985..3dd2b6fa0 100644 --- a/doc/ref/api-io.texi +++ b/doc/ref/api-io.texi @@ -823,8 +823,26 @@ Seek from the current position. @defvar SEEK_END Seek from the end of the file. @end defvar -If @var{fd_port} is a file descriptor, the underlying system -call is @code{lseek}. @var{port} may be a string port. + +On systems that support it, such as GNU/Linux, the following +constants can be used for @var{whence} to navigate ``holes'' in +sparse files: +@defvar SEEK_DATA +Seek to the next location in the file greater than or equal to +@var{offset} containing data. If @var{offset} points to data, +then the file offset is set to @var{offset}. +@end defvar +@defvar SEEK_HOLE +Seek to the next hole in the file greater than or equal to the +@var{offset}. If @var{offset} points into the middle of a hole, +then the file offset is set to @var{offset}. If there is no hole +past @var{offset}, then the file offset is adjusted to the end of +the file---i.e., there is an implicit hole at the end of any file. +@end defvar + +If @var{fd_port} is a file descriptor, the underlying system call +is @code{lseek} (@pxref{File Position Primitive,,, libc, The GNU C +Library Reference Manual}). @var{port} may be a string port. The value returned is the new position in @var{fd_port}. This means that the current position of a port can be obtained using: |