NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | HISTORY | SEE ALSO | NOTES | COLOPHON |
|
|
SD_BUS_M...EAD_BASIC(3) sd_bus_message_read_basicSD_BUS_M...EAD_BASIC(3)
sd_bus_message_read_basic - Read a basic type from a message
#include <systemd/sd-bus.h> int sd_bus_message_read_basic(sd_bus_message *m, char type, void *p);
sd_bus_message_read_basic() reads a basic type from a message and advances the read position in the message. The set of basic types and their ascii codes passed in type are described in the D-Bus Specification[1]. If p is not NULL, it should contain a pointer to an appropriate object. For example, if type is 'y', the object passed in p should have type uint8_t *. If type is 's', the object passed in p should have type const char **. Note that, if the basic type is a pointer (e.g., const char * in the case of a string), the pointer is only borrowed and the contents must be copied if they are to be used after the end of the message's lifetime. Similarly, during the lifetime of such a pointer, the message must not be modified. If type is 'h' (UNIX file descriptor), the descriptor is not duplicated by this call and the returned descriptor remains in possession of the message object, and needs to be duplicated by the caller in order to keep an open reference to it after the message object is freed (for example by calling "fcntl(fd, FD_DUPFD_CLOEXEC, 3)"). See the table below for a complete list of allowed types. Table 1. Item type specifiers ┌───────────┬─────────────────────────┬────────────────┬────────────────┐ │ Specifier │ Constant │ Description │ Expected C │ │ │ │ │ Type │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "y" │ SD_BUS_TYPE_BYTE │ 8-bit unsigned │ uint8_t * │ │ │ │ integer │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "b" │ SD_BUS_TYPE_BOOLEAN │ boolean │ int * (NB: not │ │ │ │ │ bool *) │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "n" │ SD_BUS_TYPE_INT16 │ 16-bit signed │ int16_t * │ │ │ │ integer │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "q" │ SD_BUS_TYPE_UINT16 │ 16-bit │ uint16_t * │ │ │ │ unsigned │ │ │ │ │ integer │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "i" │ SD_BUS_TYPE_INT32 │ 32-bit signed │ int32_t * │ │ │ │ integer │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "u" │ SD_BUS_TYPE_UINT32 │ 32-bit │ uint32_t * │ │ │ │ unsigned │ │ │ │ │ integer │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "x" │ SD_BUS_TYPE_INT64 │ 64-bit signed │ int64_t * │ │ │ │ integer │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "t" │ SD_BUS_TYPE_UINT64 │ 64-bit │ uint64_t * │ │ │ │ unsigned │ │ │ │ │ integer │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "d" │ SD_BUS_TYPE_DOUBLE │ IEEE 754 │ double * │ │ │ │ double │ │ │ │ │ precision │ │ │ │ │ floating-point │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "s" │ SD_BUS_TYPE_STRING │ UTF-8 string │ const char ** │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "o" │ SD_BUS_TYPE_OBJECT_PATH │ D-Bus object │ const char ** │ │ │ │ path string │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "g" │ SD_BUS_TYPE_SIGNATURE │ D-Bus │ const char ** │ │ │ │ signature │ │ │ │ │ string │ │ ├───────────┼─────────────────────────┼────────────────┼────────────────┤ │ "h" │ SD_BUS_TYPE_UNIX_FD │ UNIX file │ int * │ │ │ │ descriptor │ │ └───────────┴─────────────────────────┴────────────────┴────────────────┘ If there is no object of the specified type at the current position in the message, an error is returned.
On success, sd_bus_message_read_basic() returns a positive integer. If the end of the currently opened array has been reached, it returns 0. On failure, it returns a negative errno-style error code. Errors Returned errors may indicate the following problems: -EINVAL Specified type string is invalid or the message parameter is NULL. -ENXIO The message does not contain the specified type at current position. -EBADMSG The message cannot be parsed.
sd_bus_message_read_basic() was added in version 221.
systemd(1), sd-bus(3), sd_bus_message_append_basic(3), sd_bus_message_skip(3), sd_bus_message_read(3)
1. D-Bus Specification https://dbus.freedesktop.org/doc/dbus-specification.html
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel SD_BUS_M...EAD_BASIC(3)
Pages that refer to this page: sd-bus(3), sd_bus_message_append_basic(3), sd_bus_message_read(3), sd_bus_message_skip(3), systemd.directives(7), systemd.index(7)