From 8ffec2a3aba6f114784e11f89ef1d57a096ae540 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 27 Apr 2024 19:39:29 +0200 Subject: Adding upstream version 8.32. Signed-off-by: Daniel Baumann --- lib/fadvise.h | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) create mode 100644 lib/fadvise.h (limited to 'lib/fadvise.h') diff --git a/lib/fadvise.h b/lib/fadvise.h new file mode 100644 index 0000000..5413908 --- /dev/null +++ b/lib/fadvise.h @@ -0,0 +1,72 @@ +/* Declare an access pattern hint for files. + Copyright (C) 2010-2020 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . */ + +#include +#include +#include +#include + +/* There are a few hints one can provide, which have the + following characteristics on Linux 2.6.31 at least. + + POSIX_FADV_SEQUENTIAL + Doubles the size of read ahead done for file + POSIX_FADV_WILLNEED + _synchronously_ prepopulate the buffer cache with the file + POSIX_FADV_NOREUSE + Could lower priority of data in buffer caches, + but currently does nothing. + POSIX_FADV_DONTNEED + Drop the file from cache. + Note this is automatically done when files are unlinked. + + We use this enum "type" both to make it explicit that + these options are mutually exclusive, and to discourage + the passing of the possibly undefined POSIX_FADV_... values. + Note we could #undef the POSIX_FADV_ values, but that would + preclude using the posix_fadvise() function with its standard + constants. Using posix_fadvise() might be required if the return + value is needed, but it must be guarded by appropriate #ifdefs. */ + +#if HAVE_POSIX_FADVISE +typedef enum { + FADVISE_NORMAL = POSIX_FADV_NORMAL, + FADVISE_SEQUENTIAL = POSIX_FADV_SEQUENTIAL, + FADVISE_NOREUSE = POSIX_FADV_NOREUSE, + FADVISE_DONTNEED = POSIX_FADV_DONTNEED, + FADVISE_WILLNEED = POSIX_FADV_WILLNEED, + FADVISE_RANDOM = POSIX_FADV_RANDOM +} fadvice_t; +#else +typedef enum { + FADVISE_NORMAL, + FADVISE_SEQUENTIAL, + FADVISE_NOREUSE, + FADVISE_DONTNEED, + FADVISE_WILLNEED, + FADVISE_RANDOM +} fadvice_t; +#endif + +/* We ignore any errors as these hints are only advisory. + There is the chance one can pass invalid ADVICE, which will + not be indicated, but given the simplicity of the interface + this is unlikely. Also not returning errors allows the + unconditional passing of descriptors to non standard files, + which will just be ignored if unsupported. */ + +void fdadvise (int fd, off_t offset, off_t len, fadvice_t advice); +void fadvise (FILE *fp, fadvice_t advice); -- cgit v1.2.3