| 1 | /* |
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| 2 | FUNCTION |
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| 3 | <<pread64>>---read a large file from specified position |
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| 4 | |
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| 5 | INDEX |
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| 6 | pread64 |
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| 7 | |
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| 8 | SYNOPSIS |
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| 9 | #include <unistd.h> |
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| 10 | ssize_t pread64(int <[fd]>, void *<[buf]>, size_t <[n]>, loff_t <[off]>); |
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| 11 | |
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| 12 | DESCRIPTION |
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| 13 | The <<pread64>> function is similar to <<pread>>. The only difference is |
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| 14 | that it operates on large files and so takes a 64-bit offset. Like <<pread>>>, |
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| 15 | the file position is unchanged by the function (i.e. the file position |
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| 16 | is the same before and after a call to <<pread>>). |
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| 17 | |
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| 18 | RETURNS |
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| 19 | <<pread64>> returns the number of bytes read or <<-1>> if failure occurred. |
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| 20 | |
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| 21 | PORTABILITY |
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| 22 | <<pread64>> is an EL/IX extension. |
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| 23 | |
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| 24 | Supporting OS subroutine required: <<read>>, <<lseek64>>. |
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| 25 | */ |
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| 26 | |
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| 27 | #include <_ansi.h> |
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| 28 | #include <unistd.h> |
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| 29 | #include <reent.h> |
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| 30 | #include <machine/weakalias.h> |
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| 31 | |
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| 32 | ssize_t |
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| 33 | __libc_pread64 (int fd, |
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| 34 | void *buf, |
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| 35 | size_t n, |
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| 36 | loff_t off) |
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| 37 | { |
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| 38 | loff_t cur_pos; |
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| 39 | _READ_WRITE_RETURN_TYPE num_read; |
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| 40 | |
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| 41 | if ((cur_pos = lseek64 (fd, 0, SEEK_CUR)) == (loff_t)-1) |
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| 42 | return -1; |
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| 43 | |
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| 44 | if (lseek64 (fd, off, SEEK_SET) == (loff_t)-1) |
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| 45 | return -1; |
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| 46 | |
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| 47 | num_read = read (fd, buf, n); |
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| 48 | |
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| 49 | if (lseek64 (fd, cur_pos, SEEK_SET) == (loff_t)-1) |
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| 50 | return -1; |
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| 51 | |
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| 52 | return (ssize_t)num_read; |
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| 53 | } |
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| 54 | weak_alias(__libc_pread64,pread64); |
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| 55 | weak_alias(__libc_pread64,__pread64); |
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| 56 | |
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