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.TH iob_write 3
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.SH NAME
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iob_write \- send I/O batch through callback
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.SH SYNTAX
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.B #include <iob.h>
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typedef int64 (*io_write_callback)(int64 s,const void* buf,uint64 n);
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int64 \fBiob_write\fR(int64 s,io_batch* b,io_write_callback cb);
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.SH DESCRIPTION
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iob_write sends the (rest of) \fIb\fR through the callback \fIcb\fR,
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passing \fIs\fR as first argument. \fIcb\fR is expected to behave like
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io_trywrite(2).
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This interface is intended to send an I/O batch through a filter, for
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example to encrypt or compress it. If you just want to send an I/O
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batch to a socket, use iob_send instead.
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iob_write returns the number of bytes written, 0 if there were no more
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bytes to be written in the batch, -1 for EAGAIN, or -3 for a permanent
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error (for example "connection reset by peer").
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The normal usage pattern is using io_wait to know when a descriptor is
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writable, and then calling iob_write until it returns 0, -1 or -3.
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If it returns 0, terminate the loop (everything was written OK). If it
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returns -1, call io_wait again. If it returned -3, signal an error.
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.SH NOTE
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iob_write will continue to call your callback until it returns an error.
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So if you are in a state machine, for example a web server using this
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for SSL support, make sure to write at most n bytes at a time (e.g. 64k)
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and the next time you are called return -1. Otherwise iob_write might
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not return until the whole file is served.
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.SH "SEE ALSO"
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iob_send(3)
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