.\" -*- mode: troff; coding: utf-8 -*- .\" Automatically generated by Podwrapper::Man 1.20.1 (Pod::Simple 3.43) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" \*(C` and \*(C' are quotes in nroff, nothing in troff, for use with C<>. .ie n \{\ . ds C` "" . ds C' "" 'br\} .el\{\ . ds C` . ds C' 'br\} .\" .\" Escape single quotes in literal strings from groff's Unicode transform. .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" .\" If the F register is >0, we'll generate index entries on stderr for .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index .\" entries marked with X<> in POD. Of course, you'll have to process the .\" output yourself in some meaningful fashion. .\" .\" Avoid warning from groff about undefined register 'F'. .de IX .. .nr rF 0 .if \n(.g .if rF .nr rF 1 .if (\n(rF:(\n(.g==0)) \{\ . if \nF \{\ . de IX . tm Index:\\$1\t\\n%\t"\\$2" .. . if !\nF==2 \{\ . nr % 0 . nr F 2 . \} . \} .\} .rr rF .\" ======================================================================== .\" .IX Title "nbd_aio_pread_structured 3" .TH nbd_aio_pread_structured 3 2024-05-08 libnbd-1.20.1 LIBNBD .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH NAME nbd_aio_pread_structured \- read from the NBD server .SH SYNOPSIS .IX Header "SYNOPSIS" .Vb 1 \& #include \& \& typedef struct { \& int (*callback) (void *user_data, const void *subbuf, \& size_t count, uint64_t offset, \& unsigned status, int *error); \& void *user_data; \& void (*free) (void *user_data); \& } nbd_chunk_callback; \& \& typedef struct { \& int (*callback) (void *user_data, int *error); \& void *user_data; \& void (*free) (void *user_data); \& } nbd_completion_callback; \& \& int64_t nbd_aio_pread_structured ( \& struct nbd_handle *h, void *buf, size_t count, \& uint64_t offset, \& nbd_chunk_callback chunk_callback, \& nbd_completion_callback completion_callback, \& uint32_t flags \& ); .Ve .SH DESCRIPTION .IX Header "DESCRIPTION" Issue a read command to the NBD server. .PP To check if the command completed, call \fBnbd_aio_command_completed\fR\|(3). Or supply the optional \f(CW\*(C`completion_callback\*(C'\fR which will be invoked as described in "Completion callbacks" in \fBlibnbd\fR\|(3). .PP Note that you must ensure \f(CW\*(C`buf\*(C'\fR is valid until the command has completed. Furthermore, if the \f(CW\*(C`error\*(C'\fR parameter to \&\f(CW\*(C`completion_callback\*(C'\fR is set or if \fBnbd_aio_command_completed\fR\|(3) reports failure, and if \fBnbd_get_pread_initialize\fR\|(3) returns true, then libnbd sanitized \f(CW\*(C`buf\*(C'\fR, but it is unspecified whether the contents of \f(CW\*(C`buf\*(C'\fR will read as zero or as partial results from the server. If \fBnbd_get_pread_initialize\fR\|(3) returns false, then libnbd did not sanitize \f(CW\*(C`buf\*(C'\fR, and the contents are undefined on failure. .PP Other parameters behave as documented in \fBnbd_pread_structured\fR\|(3). .PP By default, libnbd will reject attempts to use this function with parameters that are likely to result in server failure, such as requesting an unknown command flag. The \fBnbd_set_strict_mode\fR\|(3) function can be used to alter which scenarios should await a server reply rather than failing fast. .SH "RETURN VALUE" .IX Header "RETURN VALUE" This call returns the 64 bit cookie of the command. The cookie is ≥ \f(CW1\fR. Cookies are unique (per libnbd handle, not globally). .SH ERRORS .IX Header "ERRORS" On error \f(CW\-1\fR is returned. .PP Refer to "ERROR HANDLING" in \fBlibnbd\fR\|(3) for how to get further details of the error. .PP The following parameters must not be NULL: \f(CW\*(C`h\*(C'\fR, \f(CW\*(C`buf\*(C'\fR. For more information see "Non-NULL parameters" in \fBlibnbd\fR\|(3). .SH "HANDLE STATE" .IX Header "HANDLE STATE" nbd_aio_pread_structured can be called when the handle is in the following state: .PP .Vb 8 \& ┌─────────────────────────────────────┬─────────────────────────┐ \& │ Handle created, before connecting │ ❌ error │ \& │ Connecting │ ❌ error │ \& │ Connecting & handshaking (opt_mode) │ ❌ error │ \& │ Connected to the server │ ✅ allowed │ \& │ Connection shut down │ ❌ error │ \& │ Handle dead │ ❌ error │ \& └─────────────────────────────────────┴─────────────────────────┘ .Ve .SH VERSION .IX Header "VERSION" This function first appeared in libnbd 1.0. .PP If you need to test if this function is available at compile time check if the following macro is defined: .PP .Vb 1 \& #define LIBNBD_HAVE_NBD_AIO_PREAD_STRUCTURED 1 .Ve .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBnbd_aio_command_completed\fR\|(3), \&\fBnbd_aio_pread\fR\|(3), \&\fBnbd_create\fR\|(3), \&\fBnbd_get_pread_initialize\fR\|(3), \&\fBnbd_pread_structured\fR\|(3), \&\fBnbd_set_pread_initialize\fR\|(3), \&\fBnbd_set_strict_mode\fR\|(3), "Issuing asynchronous commands" in \fBlibnbd\fR\|(3), \&\fBlibnbd\fR\|(3). .SH AUTHORS .IX Header "AUTHORS" Eric Blake .PP Richard W.M. Jones .SH COPYRIGHT .IX Header "COPYRIGHT" Copyright Red Hat .SH LICENSE .IX Header "LICENSE" This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. .PP This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. .PP You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110\-1301 USA