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.TH io_canread 3
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.SH NAME
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io_canread \- return a file descriptor that can be read from
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.SH SYNTAX
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.B #include <libowfat/io.h>
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int64 \fBio_canread\fP();
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.SH DESCRIPTION
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io_canread returns the next file descriptor that can be read from.
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You have to have used io_wantread() on the file descriptor earlier, and
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you have to have called io_wait() or io_waituntil().
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These functions then keep an internal data structure on which
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descriptors were reported readable by the operating system.
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Please note that there is no guarantee that there still is data that can
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be read from the descriptor, just that there was data when io_wait() or
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io_waituntil() were called. Another process could have read the data
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before you. Look at the result from io_tryread().
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If there are no more descriptors that you can write to without blocking,
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io_canwrite will return -1. In this case you should call io_wait() or
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io_waituntil() again.
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You should use io_tryread(3) to read from the descriptor, not plain
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read(2). If you use read(2) and you get EAGAIN, call io_eagain(3).
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.SH "SEE ALSO"
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io_wait(3), io_canwrite(3), io_eagain(3)
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