1nbd_aio_pread_structured(3)         LIBNBD         nbd_aio_pread_structured(3)
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NAME

6       nbd_aio_pread_structured - read from the NBD server
7

SYNOPSIS

9        #include <libnbd.h>
10
11        typedef struct {
12          int (*callback) (void *user_data, const void *subbuf,
13                           size_t count, uint64_t offset,
14                           unsigned status, int *error);
15          void *user_data;
16          void (*free) (void *user_data);
17        } nbd_chunk_callback;
18
19        typedef struct {
20          int (*callback) (void *user_data, int *error);
21          void *user_data;
22          void (*free) (void *user_data);
23        } nbd_completion_callback;
24
25        int64_t nbd_aio_pread_structured (struct nbd_handle *h,
26                                          void *buf, size_t count,
27                                          uint64_t offset,
28                                          nbd_chunk_callback chunk_callback,
29                                          nbd_completion_callback completion_callback,
30                                          uint32_t flags);
31

DESCRIPTION

33       Issue a read command to the NBD server.
34
35       To check if the command completed, call nbd_aio_command_completed(3).
36       Or supply the optional "completion_callback" which will be invoked as
37       described in "Completion callbacks" in libnbd(3).
38
39       Other parameters behave as documented in nbd_pread_structured(3).
40
41       By default, libnbd will reject attempts to use this function with
42       parameters that are likely to result in server failure, such as
43       requesting an unknown command flag.  The nbd_set_strict_mode(3)
44       function can be used to alter which scenarios should await a server
45       reply rather than failing fast.
46

RETURN VALUE

48       This call returns the 64 bit cookie of the command.  The cookie is ≥ 1.
49       Cookies are unique (per libnbd handle, not globally).
50

ERRORS

52       On error "-1" is returned.
53
54       Refer to "ERROR HANDLING" in libnbd(3) for how to get further details
55       of the error.
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HANDLE STATE

58       The handle must be connected with the server, otherwise this call will
59       return an error.
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VERSION

62       This function first appeared in libnbd 1.0.
63
64       If you need to test if this function is available at compile time check
65       if the following macro is defined:
66
67        #define LIBNBD_HAVE_NBD_AIO_PREAD_STRUCTURED 1
68

SEE ALSO

70       nbd_aio_command_completed(3), nbd_aio_pread(3), nbd_create(3),
71       nbd_pread_structured(3), nbd_set_strict_mode(3), "Issuing asynchronous
72       commands" in libnbd(3), libnbd(3).
73

AUTHORS

75       Eric Blake
76
77       Richard W.M. Jones
78

80       Copyright (C) 2019-2021 Red Hat Inc.
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LICENSE

83       This library is free software; you can redistribute it and/or modify it
84       under the terms of the GNU Lesser General Public License as published
85       by the Free Software Foundation; either version 2 of the License, or
86       (at your option) any later version.
87
88       This library is distributed in the hope that it will be useful, but
89       WITHOUT ANY WARRANTY; without even the implied warranty of
90       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
91       Lesser General Public License for more details.
92
93       You should have received a copy of the GNU Lesser General Public
94       License along with this library; if not, write to the Free Software
95       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
96       02110-1301 USA
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100libnbd-1.7.12                     2021-05-29       nbd_aio_pread_structured(3)
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