diff options
| -rw-r--r-- | include/stdio.h | 6 | ||||
| -rw-r--r-- | lib/libc/sys/lseek.2 | 54 | ||||
| -rw-r--r-- | lib/libc/sys/pathconf.2 | 12 | ||||
| -rw-r--r-- | sys/kern/vfs_syscalls.c | 7 | ||||
| -rw-r--r-- | sys/sys/filio.h | 3 | ||||
| -rw-r--r-- | sys/sys/unistd.h | 5 |
6 files changed, 86 insertions, 1 deletions
diff --git a/include/stdio.h b/include/stdio.h index 348db22..bf01429 100644 --- a/include/stdio.h +++ b/include/stdio.h @@ -200,6 +200,12 @@ __END_DECLS #ifndef SEEK_END #define SEEK_END 2 /* set file offset to EOF plus offset */ #endif +#ifndef SEEK_DATA +#define SEEK_DATA 3 /* set file offset to next data past offset */ +#endif +#ifndef SEEK_HOLE +#define SEEK_HOLE 4 /* set file offset to next hole past offset */ +#endif #define stdin __stdinp #define stdout __stdoutp diff --git a/lib/libc/sys/lseek.2 b/lib/libc/sys/lseek.2 index df225f3..6fdf79b 100644 --- a/lib/libc/sys/lseek.2 +++ b/lib/libc/sys/lseek.2 @@ -87,6 +87,23 @@ the offset is set to the size of the file plus .Fa offset bytes. +.It +If +.Fa whence +is +.Dv SEEK_HOLE , +the offset of the start of the next hole greater than or equal to the supplied +.Fa offset +is returned. +The definition of a hole is provided below. +.It +If +.Fa whence +is +.Dv SEEK_DATA , +the offset is set to the start of the next non-hole file region greater +than or equal to the supplied +.Fa offset . .El .Pp The @@ -100,6 +117,33 @@ bytes of zeros (until data is actually written into the gap). Some devices are incapable of seeking. The value of the pointer associated with such a device is undefined. +.Pp +A +.Qq hole +is defined as a contiguous range of bytes in a file, all having the value of +zero, but not all zeros in a file are guaranteed to be represented as holes +returned with +.Dv SEEK_HOLE . +File systems are allowed to expose ranges of zeros with +.Dv SEEK_HOLE , +but not required to. +Applications can use +.Dv SEEK_HOLE +to optimise their behavior for ranges of zeros, but must not depend on it to +find all such ranges in a file. +The existence of a hole at the end of every data region allows for easy +programming and implies that a virtual hole exists at the end of the file. +Applications should use +.Fn fpathconf _PC_MIN_HOLE_SIZE +or +.Fn pathconf _PC_MIN_HOLE_SIZE +to determine if a file system supports +.Dv SEEK_HOLE . +See +.Xr pathconf 2 . +.Pp +For file systems that do not supply information about holes, the file will be +represented as one entire data region. .Sh RETURN VALUES Upon successful completion, .Fn lseek @@ -128,6 +172,13 @@ argument is not a proper value or the resulting file offset would be negative for a non-character special file. +.It Bq Er ENXIO +For +.Dv SEEK_DATA , +there are no more data regions past the supplied offset. +For +.Dv SEEK_HOLE , +there are no more holes past the supplied offset. .It Bq Er EOVERFLOW The resulting file offset would be a value which cannot be represented correctly in an object of type @@ -140,7 +191,8 @@ is associated with a pipe, socket, or FIFO. .El .Sh SEE ALSO .Xr dup 2 , -.Xr open 2 +.Xr open 2 , +.Xr pathconf 2 .Sh STANDARDS The .Fn lseek diff --git a/lib/libc/sys/pathconf.2 b/lib/libc/sys/pathconf.2 index e3c17d6..968f307 100644 --- a/lib/libc/sys/pathconf.2 +++ b/lib/libc/sys/pathconf.2 @@ -144,6 +144,17 @@ otherwise 0. .It Li _PC_MAC_PRESENT Returns 1 if a Mandatory Access Control (MAC) label can be set on the specified file, otherwise 0. +.It Li _PC_MIN_HOLE_SIZE +If a file system supports the reporting of holes (see +.Xr lseek 2 , +.Fn pathconf +and +.Fn fpathconf +return a positive number that represents the minimum hole size returned in +bytes. +The offsets of holes returned will be aligned to this same value. +A special value of 1 is returned if the file system does not specify the minimum +hole size but still reports holes. .El .Sh RETURN VALUES If the call to @@ -216,6 +227,7 @@ is not a valid open file descriptor. An I/O error occurred while reading from or writing to the file system. .El .Sh SEE ALSO +.Xr lseek 2 , .Xr sysctl 3 .Sh HISTORY The diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c index c7b278e..72a3f4e 100644 --- a/sys/kern/vfs_syscalls.c +++ b/sys/kern/vfs_syscalls.c @@ -54,6 +54,7 @@ __FBSDID("$FreeBSD$"); #include <sys/kernel.h> #include <sys/fcntl.h> #include <sys/file.h> +#include <sys/filio.h> #include <sys/limits.h> #include <sys/linker.h> #include <sys/stat.h> @@ -1740,6 +1741,12 @@ lseek(td, uap) break; case L_SET: break; + case SEEK_DATA: + error = fo_ioctl(fp, FIOSEEKDATA, &offset, cred, td); + break; + case SEEK_HOLE: + error = fo_ioctl(fp, FIOSEEKHOLE, &offset, cred, td); + break; default: error = EINVAL; } diff --git a/sys/sys/filio.h b/sys/sys/filio.h index 8f2731a..5f13288 100644 --- a/sys/sys/filio.h +++ b/sys/sys/filio.h @@ -55,5 +55,8 @@ struct fiodgname_arg { void *buf; }; #define FIODGNAME _IOW('f', 120, struct fiodgname_arg) /* get dev. name */ +/* Handle lseek SEEK_DATA and SEEK_HOLE for holey file knowledge. */ +#define FIOSEEKDATA _IOWR('f', 97, off_t) /* SEEK_DATA */ +#define FIOSEEKHOLE _IOWR('f', 98, off_t) /* SEEK_HOLE */ #endif /* !_SYS_FILIO_H_ */ diff --git a/sys/sys/unistd.h b/sys/sys/unistd.h index 1fcd384..9f3eac9 100644 --- a/sys/sys/unistd.h +++ b/sys/sys/unistd.h @@ -107,6 +107,8 @@ #define SEEK_SET 0 /* set file offset to offset */ #define SEEK_CUR 1 /* set file offset to current plus offset */ #define SEEK_END 2 /* set file offset to EOF plus offset */ +#define SEEK_DATA 3 /* set file offset to next data past offset */ +#define SEEK_HOLE 4 /* set file offset to next hole past offset */ #endif #ifndef _POSIX_SOURCE @@ -151,6 +153,9 @@ #define _PC_MAC_PRESENT 63 #endif +/* From OpenSolaris, used by SEEK_DATA/SEEK_HOLE. */ +#define _PC_MIN_HOLE_SIZE 21 + #if __BSD_VISIBLE /* * rfork() options. |
