sd_bus_message_append_string

Name

sd_bus_message_append_string_memfd, sd_bus_message_append_string_iovec, sd_bus_message_append_string_space — Attach a string to a message

Synopsis

#include <systemd/sd-bus.h>

`int sd_bus_message_append_string_memfd(`	sd_bus_message *`m`,
	int `memfd`,
	uint64_t `offset`,
	uint64_t `size)`;

`int sd_bus_message_append_string_iovec(`	sd_bus_message *`m`,
	const struct iovec *`iov`,
	unsigned `n)`;

`int sd_bus_message_append_string_space(`	sd_bus_message *`m`,
	size_t `size`,
	char **`ret)`;

Description¶

The functions sd_bus_message_append_string_memfd() and sd_bus_message_append_string_iovec() can be used to append a single string (item of type "s") to message m.

In case of sd_bus_message_append_string_memfd(), the contents of memfd starting at the specified offset and of the specified size are used as the string. size must include the terminating NUL byte, i.e. the resulting string has length size - 1. If offset is zero and size is UINT64_MAX, the full contents of the memory file descriptor are used, and hence must themselves end in a NUL byte. If offset plus size exceeds the actual size of the memory file descriptor, this call fails with -EMSGSIZE. The memory file descriptor is sealed by this call if it has not been sealed yet, and cannot be modified after this call. The appended contents must satisfy the same constraints as described for the "s" type in sd_bus_message_append_basic(3).

In case of sd_bus_message_append_string_iovec(), the payload of iov is the string. It must satisfy the same constraints as described for the "s" type in sd_bus_message_append_basic(3).

The iov argument must point to n struct iovec structures. Each structure may have the iov_base field set, in which case the memory pointed to will be copied into the message, or unset, in which case a block of spaces (ASCII 32) of length iov_len will be inserted. The memory pointed at by iov may be changed after this call.

The sd_bus_message_append_string_space() function appends space for a string to message m. It behaves similar to sd_bus_message_append_basic() with type "s", but instead of copying a string into the message, it returns a pointer to the destination area to the caller in pointer ret. Space for the string of length size plus the terminating NUL is allocated.

Return Value¶

On success, those calls return 0 or a positive integer. On failure, they return a negative errno-style error code.

Errors¶

Returned errors may indicate the following problems:

-EINVAL¶: Specified parameter is invalid.
-EPERM¶: Message has been sealed.
-ESTALE¶: Message is in invalid state.
-ENXIO¶: Message cannot be appended to.
-ENOMEM¶: Memory allocation failed.

Notes¶

Functions described here are available as a shared library, which can be compiled against and linked to with the libsystemd pkg-config(1) file.

All functions listed here are thread-agnostic and only a single thread may operate on a given object at any given time. Different threads may access the same object at different times. Multiple independent objects may be used from different threads in parallel.

The code described here uses getenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not call setenv(3) from a parallel thread. It is recommended to only do calls to setenv() from an early phase of the program when no other threads have been started.