обработка ошибок SD-шины (sd-bus error handling)
Имя (Name)
sd_bus_error, SD_BUS_ERROR_MAKE_CONST, SD_BUS_ERROR_NULL,
sd_bus_error_free, sd_bus_error_set, sd_bus_error_setf,
sd_bus_error_set_const, sd_bus_error_set_errno,
sd_bus_error_set_errnof, sd_bus_error_set_errnofv,
sd_bus_error_get_errno, sd_bus_error_copy, sd_bus_error_move,
sd_bus_error_is_set, sd_bus_error_has_name,
sd_bus_error_has_names_sentinel, sd_bus_error_has_names - sd-bus
error handling
Синопсис (Synopsis)
#include <systemd/sd-bus.h>
typedef struct {
const char *name;
const char *message;
...
} sd_bus_error;
SD_BUS_ERROR_MAKE_CONST(name, message)
SD_BUS_ERROR_NULL
void sd_bus_error_free(sd_bus_error *e);
int sd_bus_error_set(sd_bus_error *e, const char *name,
const char *message);
int sd_bus_error_setf(sd_bus_error *e, const char *name,
const char *format, ...);
int sd_bus_error_set_const(sd_bus_error *e, const char *name,
const char *message);
int sd_bus_error_set_errno(sd_bus_error *e, int error);
int sd_bus_error_set_errnof(sd_bus_error *e, int error,
const char *format, ...);
int sd_bus_error_set_errnofv(sd_bus_error *e, int error,
const char *format, va_list ap);
int sd_bus_error_get_errno(const sd_bus_error *e);
int sd_bus_error_copy(sd_bus_error *dst, const sd_bus_error *e);
int sd_bus_error_move(sd_bus_error *dst, sd_bus_error *e);
int sd_bus_error_is_set(const sd_bus_error *e);
int sd_bus_error_has_name(const sd_bus_error *e,
const char *name);
int sd_bus_error_has_names_sentinel(const sd_bus_error *e, ...);
#define sd_bus_error_has_names(e, ...)
sd_bus_error_has_names_sentinel(e, ..., NULL)
Описание (Description)
The sd_bus_error structure carries information about a D-Bus
error condition, or lack thereof. The functions described below
may be used to set and query fields in this structure.
• The name field contains a short identifier of an error. It
should follow the rules for error names described in the
D-Bus specification, subsection Valid Names
• The message field usually contains a human-readable string
describing the details, but might be NULL.
An unset sd_bus_error structure should have both fields
initialized to NULL, and signifies lack of an error, i.e.
success. Assign SD_BUS_ERROR_NULL to the structure in order to
initialize both fields to NULL. When no longer necessary,
resources held by the sd_bus_error structure should be destroyed
with sd_bus_error_free().
sd_bus_error_set() sets an error structure to the specified name
and message strings. The strings will be copied into internal,
newly allocated memory. It is essential to free the contents
again when they are not required anymore (see above). Do not use
this call on error structures that have already been set. If you
intend to reuse an error structure, free the old data stored in
it with sd_bus_error_free() first.
sd_bus_error_set() will return an errno-like value (see errno(3))
determined from the specified error name name. If name is NULL,
it is assumed that no error occurred, and 0 is returned. If name
is nonnull, a negative value is always returned. If e is NULL, no
error structure is initialized, but name is still converted into
an errno-style value.
Various well-known D-Bus errors are converted to well-known errno
counterparts, and the other ones to -EIO. See sd-bus-errors(3)
for a list of well-known error names. Additional error mappings
may be defined with sd_bus_error_add_map(3).
sd_bus_error_set() is designed to be conveniently used in a
return statement. If message is NULL, no message is set. This
call can fail if no memory may be allocated for the name and
message strings, in which case an SD_BUS_ERROR_NO_MEMORY error
will be set instead and -ENOMEM returned.
sd_bus_error_setf() is similar to sd_bus_error_set(), but takes a
printf(3) format string and corresponding arguments to generate
the message field.
sd_bus_error_set_const() is similar to sd_bus_error_set(), but
the string parameters are not copied internally, and must hence
remain constant and valid for the lifetime of e. Use this call to
avoid memory allocations when setting error structures. Since
this call does not allocate memory, it will not fail with an
out-of-memory condition as sd_bus_error_set() may, as described
above. Alternatively, the SD_BUS_ERROR_MAKE_CONST() macro may be
used to generate a literal, constant bus error structure
on-the-fly.
sd_bus_error_set_errno() will immediately return 0 if the
specified error parameter error is 0. Otherwise, it will set name
from an errno-like value that is converted to a D-Bus error.
strerror_r(3) will be used to set message. Well-known D-Bus error
names will be used for name if applicable, otherwise a name in
the "System.Error." namespace will be generated. The sign of the
specified error number is ignored and the absolute value is used
implicitly. If the specified error error is non-zero, the call
always returns a negative value, for convenient usage in return
statements. This call might fail due to lack of memory, in which
case an SD_BUS_ERROR_NO_MEMORY error is set instead, and -ENOMEM
is returned.
sd_bus_error_set_errnof() is similar to sd_bus_error_set_errno(),
but in addition to error, takes a printf(3) format string and
corresponding arguments. The message field will be generated from
format and the arguments.
sd_bus_error_set_errnofv() is similar to
sd_bus_error_set_errnof(), but takes the format string parameters
as va_arg(3) parameter list.
sd_bus_error_get_errno() converts the name field of an error
structure to an errno-like (positive) value using the same rules
as sd_bus_error_set(). If e is NULL, 0 will be returned.
sd_bus_error_copy() will initialize dst using the values in e, if
e has been set with an error value before. Otherwise, it will
return immediately. If the strings in e were set using
sd_bus_error_set_const(), they will be shared. Otherwise, they
will be copied. Returns a converted errno-like, negative error
code or 0. Before this call, dst must be unset, i.e. either
freshly initialized with NULL or reset using sd_bus_error_free().
sd_bus_error_move() is similar to sd_bus_error_copy(), but will
move any error information from e into dst, resetting the former.
This function cannot fail, as no new memory is allocated. Note
that if e is not set, dst is initialized to SD_BUS_ERROR_NULL.
Moreover, if dst is NULL no operation is executed on it and
resources held by e are freed and reset. Returns a converted
errno-like, non-positive error value.
sd_bus_error_is_set() will return a non-zero value if e is
non-NULL and an error has been set, false otherwise.
sd_bus_error_has_name() will return a non-zero value if e is
non-NULL and an error with the same name has been set, false
otherwise.
sd_bus_error_has_names_sentinel() is similar to
sd_bus_error_has_name(), but takes multiple names to check
against. The list must be terminated with NULL.
sd_bus_error_has_names() is a macro wrapper around
sd_bus_error_has_names_sentinel() that adds the NULL sentinel
automatically.
sd_bus_error_free() will destroy resources held by e. The
parameter itself will not be deallocated, and must be free(3)d by
the caller if necessary. The function may also be called safely
on unset errors (error structures with both fields set to NULL),
in which case it performs no operation. This call will reset the
error structure after freeing the data, so that all fields are
set to NULL. The structure may be reused afterwards.
Возвращаемое значение (Return value)
The functions sd_bus_error_set(), sd_bus_error_setf(), and
sd_bus_error_set_const() always return 0 when the specified error
value is NULL, and a negative errno-like value corresponding to
the name parameter otherwise. The functions
sd_bus_error_set_errno(), sd_bus_error_set_errnof() and
sd_bus_error_set_errnofv(), return 0 when the specified error
value is 0, and a negative errno-like value corresponding to the
error parameter otherwise. If an error occurs internally, one of
the negative error values listed below will be returned.
sd_bus_error_get_errno() returns false when e is NULL, and a
positive errno value mapped from e->name otherwise.
sd_bus_error_copy() and sd_bus_error_move() return a negative
error value converted from the source error, and zero if the
error has not been set.
sd_bus_error_is_set() returns a non-zero value when e and the
name field are non-NULL, zero otherwise.
sd_bus_error_has_name(), sd_bus_error_has_names(), and
sd_bus_error_has_names_sentinel() return a non-zero value when e
is non-NULL and the name field is equal to one of the given
names, zero otherwise.
sd_bus_error is not reference counted. Users should destroy
resources held by it by calling sd_bus_error_free(). Usually,
error structures are allocated on the stack or passed in as
function parameters, but they may also be allocated dynamically,
in which case it is the duty of the caller to free(3) the memory
held by the structure itself after freeing its contents with
sd_bus_error_free().
Errors
Returned errors may indicate the following problems:
-EINVAL
Error was already set in sd_bus_error structure when one the
error-setting functions was called.
-ENOMEM
Memory allocation failed.
Примечание (Note)
These APIs are implemented as a shared library, which can be
compiled and linked to with the libsystemd pkg-config(1) file.
Смотри также (See also)
systemd(1), sd-bus(3), sd-bus-errors(3), sd_bus_error_add_map(3),
errno(3), strerror_r(3)
Примечание (Note)
1. Valid Names
http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names
