193 lines
5.1 KiB
Groff
193 lines
5.1 KiB
Groff
.TH INT64 3
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.SH NAME
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int64, add64, add64u, add64ul, sub64, sub64u, sub64ul, diff64, cvu64, cvul64, cv64u, cv64ul, div64u, rem64u, mul64u, cmp64, cmp64u, cmp64ul, ex64lo, ex64hi, make64 \- 64 bit disk offset computations
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.SH SYNOPSIS
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.ft B
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.nf
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#include <minix/u64.h>
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u64_t add64(u64_t \fIi\fP, u64_t \fIj\fP)
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u64_t add64u(u64_t \fIi\fP, unsigned \fIj\fP)
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u64_t add64ul(u64_t \fIi\fP, unsigned long \fIj\fP)
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u64_t sub64(u64_t \fIi\fP, u64_t \fIj\fP)
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u64_t sub64u(u64_t \fIi\fP, unsigned \fIj\fP)
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u64_t sub64ul(u64_t \fIi\fP, unsigned long \fIj\fP)
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unsigned diff64(u64_t \fIi\fP, u64_t \fIj\fP)
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u64_t cvu64(unsigned \fIi\fP)
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u64_t cvul64(unsigned long \fIi\fP)
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unsigned cv64u(u64_t \fIi\fP)
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unsigned long cv64ul(u64_t \fIi\fP)
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unsigned long div64u(u64_t \fIi\fP, unsigned \fIj\fP)
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unsigned rem64u(u64_t \fIi\fP, unsigned \fIj\fP)
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u64_t mul64u(unsigned long \fIi\fP, unsigned \fIj\fP)
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int cmp64(u64_t \fIi\fP, u64_t \fIj\fP)
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int cmp64u(u64_t \fIi\fP, unsigned \fIj\fP)
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int cmp64ul(u64_t \fIi\fP, unsigned long \fIj\fP)
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unsigned long ex64lo(u64_t \fIi\fP)
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unsigned long ex64hi(u64_t \fIi\fP)
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u64_t make64(unsigned long \fIlo\fP, unsigned long \fIhi\fP)
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.fi
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.ft P
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.SH DESCRIPTION
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.de SP
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.if t .sp 0.4
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.if n .sp
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..
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The
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.B int64
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family of functions allow Minix to handle disks of up to 4 terabytes using
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32 bit sector numbers and 64 bit byte offsets on a machine where the C type
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.B long
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is 32 bits. The <minix/u64.h> include file defines a 64 bit data
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type,
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.BR u64_t ,
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and a number of functions to operate on them. Note that these functions are
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geared towards common disk offset and block computations, and do not provide
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a full set of 64 bit operations. They are:
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.PP
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.TP
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.B "u64_t add64(u64_t \fIi\fP, u64_t \fIj\fP)"
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Add the 64 bit numbers
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.I i
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and
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.I j
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forming a 64 bit result.
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.TP
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.B "u64_t add64u(u64_t \fIi\fP, unsigned \fIj\fP)"
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Add an unsigned
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.I j
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to a 64 bit number
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.I i
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forming a 64 bit result.
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.TP
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.B "u64_t add64ul(u64_t \fIi\fP, unsigned long \fIj\fP)"
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Add an unsigned long
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.I j
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to a 64 bit number
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.I i
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forming a 64 bit result.
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.TP
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.B "u64_t sub64(u64_t \fIi\fP, u64_t \fIj\fP)"
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Subtract the 64 bit number
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.I j
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from the 64 bit number
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.I i
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forming a 64 bit result.
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.TP
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.B "u64_t sub64u(u64_t \fIi\fP, unsigned \fIj\fP)"
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Subtract the unsigned
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.I j
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from the 64 bit number
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.I i
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forming a 64 bit result.
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.TP
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.B "u64_t sub64ul(u64_t \fIi\fP, unsigned long \fIj\fP)"
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Subtract the unsigned long
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.I j
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from the 64 bit number
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.I i
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forming a 64 bit result.
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.TP
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.B "unsigned diff64(u64_t \fIi\fP, u64_t \fIj\fP)"
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Subtract the 64 bit number
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.I j
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from the 64 bit number
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.I i
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forming an unsigned. Overflow is not checked.
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.TP
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.B "u64_t cvu64(unsigned \fIi\fP)"
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Convert an unsigned to a 64 bit number.
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.TP
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.B "u64_t cvul64(unsigned long \fIi\fP)"
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Convert an unsigned long to a 64 bit number.
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.TP
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.B "unsigned cv64u(u64_t \fIi\fP)"
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Convert a 64 bit number to an unsigned if it fits, otherwise return
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.BR UINT_MAX .
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.TP
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.B "unsigned long cv64ul(u64_t \fIi\fP)"
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Convert a 64 bit number to an unsigned long if it fits, otherwise return
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.BR ULONG_MAX .
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.TP
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.B "unsigned long div64u(u64_t \fIi\fP, unsigned \fIj\fP)"
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Divide the 64 bit number
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.I i
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by the unsigned
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.I j
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giving an unsigned long. Overflow is not checked. (Typical "byte offset to
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block number" conversion.)
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.TP
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.B "unsigned rem64u(u64_t \fIi\fP, unsigned \fIj\fP)"
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Compute the remainder of the division of the 64 bit number
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.I i
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by the unsigned
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.I j
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as an unsigned. (Typical "byte offset within a block" computation.)
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.TP
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.B "u64_t mul64u(unsigned long \fIi\fP, unsigned \fIj\fP)"
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Multiply the unsigned long
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.I i
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by the unsigned
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.I j
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giving a 64 bit number. (Typical "block number to byte offset" conversion.)
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.TP
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.B "int cmp64(u64_t \fIi\fP, u64_t \fIj\fP)"
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Compare two 64 bit numbers.
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Returns
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.B -1
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if
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.I i
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<
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.IR j ,
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.B 0
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if
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.I i
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==
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.IR j ,
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and
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.B 1
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if
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.I i
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>
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.IR j .
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.TP
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.B "int cmp64u(u64_t \fIi\fP, unsigned \fIj\fP)"
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Likewise compare a 64 bit number with an unsigned.
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.TP
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.B "int cmp64ul(u64_t \fIi\fP, unsigned long \fIj\fP)"
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Likewise compare a 64 bit number with an unsigned long.
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.TP
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.B "unsigned long ex64lo(u64_t \fIi\fP)"
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Extract the low 32 bits of a 64 bit number.
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.TP
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.B "unsigned long ex64hi(u64_t \fIi\fP)"
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Extract the high 32 bits of a 64 bit number.
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.TP
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.B "u64_t make64(unsigned long \fIlo\fP, unsigned long \fIhi\fP)"
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Combine the low and high parts of a 64 bit number to a 64 bit number. (The
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last three functions are used to pass 64 bit numbers in messages within the
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kernel. They should not be used for anything else.)
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.SH "SEE ALSO"
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.BR fcntl (2),
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.BR controller (4).
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.SH NOTES
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With the usual disk block size of 512 bytes the maximum disk size is 512
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\(** 4 gigabytes = 2 terabytes.
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.PP
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Standard Minix only uses 64 bit computations within the disk drivers, so
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individual partitions are still limited to 4 gigabytes. Minix-vmd has 64
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bit computations also in the file system code.
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.PP
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Special care must be taken when accessing disk devices. For Minix one may
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have to temporarily change the start of the partition to go beyond 4 G.
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Minix-vmd can go beyond 4 G, but the
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.B lseek
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system call is still limited to a 32 bit offset. One needs to use
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.PP
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.RS
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.BI "fcntl(" fd ", F_SEEK, u64_t " offset ")"
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.RE
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.PP
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to seek to a 64 bit position.
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.SH AUTHOR
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Kees J. Bot <kjb@cs.vu.nl>
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