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Diffstat (limited to 'man/io_uring_prep_recv.3')
| -rw-r--r-- | man/io_uring_prep_recv.3 | 83 |
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diff --git a/man/io_uring_prep_recv.3 b/man/io_uring_prep_recv.3 new file mode 100644 index 0000000..993e331 --- /dev/null +++ b/man/io_uring_prep_recv.3 @@ -0,0 +1,83 @@ +.\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk> +.\" +.\" SPDX-License-Identifier: LGPL-2.0-or-later +.\" +.TH io_uring_prep_recv 3 "March 12, 2022" "liburing-2.2" "liburing Manual" +.SH NAME +io_uring_prep_recv \- prepare a recv request +.SH SYNOPSIS +.nf +.B #include <liburing.h> +.PP +.BI "void io_uring_prep_recv(struct io_uring_sqe *" sqe "," +.BI " int " sockfd "," +.BI " void *" buf "," +.BI " size_t " len "," +.BI " int " flags ");" +.fi +.SH DESCRIPTION +.PP +The +.BR io_uring_prep_recv (3) +function prepares a recv request. The submission +queue entry +.I sqe +is setup to use the file descriptor +.I sockfd +to start receiving the data into the buffer destination +.I buf +of size +.I size +and with modifier flags +.IR flags . + +This function prepares an async +.BR recv (2) +request. See that man page for details on the arguments specified to this +prep helper. + +After calling this function, additional io_uring internal modifier flags +may be set in the SQE +.I off +field. The following flags are supported: +.TP +.B IORING_RECVSEND_POLL_FIRST +If set, io_uring will assume the socket is currently empty and attempting to +receive data will be unsuccessful. For this case, io_uring will arm internal +poll and trigger a receive of the data when the socket has data to be read. +This initial receive attempt can be wasteful for the case where the socket +is expected to be empty, setting this flag will bypass the initial receive +attempt and go straight to arming poll. If poll does indicate that data is +ready to be received, the operation will proceed. + +Can be used with the CQE +.B IORING_CQE_F_SOCK_NONEMPTY +flag, which io_uring will set on CQEs after a +.BR recv (2) +or +.BR recvmsg (2) +operation. If set, the socket still had data to be read after the operation +completed. Both these flags are available since 5.19. +.P + +.SH RETURN VALUE +None +.SH ERRORS +The CQE +.I res +field will contain the result of the operation. See the related man page for +details on possible values. Note that where synchronous system calls will return +.B -1 +on failure and set +.I errno +to the actual error value, io_uring never uses +.IR errno . +Instead it returns the negated +.I errno +directly in the CQE +.I res +field. +.SH SEE ALSO +.BR io_uring_get_sqe (3), +.BR io_uring_submit (3), +.BR recv (2) |