65 lines
1.4 KiB
C
65 lines
1.4 KiB
C
/*
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FUNCTION
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<<pwrite64>>---write a large file from specified position
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INDEX
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pwrite64
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ANSI_SYNOPSIS
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#include <unistd.h>
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ssize_t pwrite64(int <[fd]>, void *<[buf]>, size_t <[n]>, loff_t <[off]>);
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TRAD_SYNOPSIS
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#include <unistd.h>
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ssize_t pwrite64(<[fd]>, <[buf]>, <[n]>, <[off]>)
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int <[fd]>;
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void *<[buf]>;
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size_t <[n]>;
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loff_t <[off]>;
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DESCRIPTION
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The <<pwrite64>> function is similar to <<pwrite>>. The only difference is
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that it operates on large files and so takes a 64-bit offset. Like <<pwrite>>>,
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the file position is unchanged by the function (i.e. the file position
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is the same before and after a call to <<pwrite>>).
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RETURNS
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<<pwrite64>> returns the number of bytes written or <<-1>> if failure occurred.
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PORTABILITY
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<<pwrite64>> is an EL/IX extension.
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Supporting OS subroutine required: <<write>>, <<lseek64>>.
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*/
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#include <_ansi.h>
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#include <unistd.h>
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#include <reent.h>
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#include <machine/weakalias.h>
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ssize_t
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_DEFUN (__libc_pwrite64, (fd, buf, n, off),
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int fd _AND
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_PTR buf _AND
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size_t n _AND
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loff_t off)
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{
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loff_t cur_pos;
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_READ_WRITE_RETURN_TYPE num_written;
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if ((cur_pos = lseek64 (fd, 0, SEEK_CUR)) == (loff_t)-1)
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return -1;
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if (lseek64 (fd, off, SEEK_SET) == (loff_t)-1)
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return -1;
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num_written = write (fd, buf, n);
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if (lseek64 (fd, cur_pos, SEEK_SET) == (loff_t)-1)
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return -1;
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return (ssize_t)num_written;
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}
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weak_alias(__libc_pwrite64,pwrite64)
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