Intel Extensible Firmware Interface, Specification

Page: 98 / 494

Extensible Firmware Interface Specification
80 12/12/00 Version 1.02
3.5.2 GetNextVariableName()
Summary
Enumerates the current variable names.
Prototype
EFI_STATUS
GetNextVariableName (
IN OUT UINTN *VariableNameSize,
IN OUT CHAR16 *VariableName,
IN OUT EFI_GUID *VendorGuid
);
Parameters
VariableNameSize
The size of the
VariableName
buffer.
VariableName
On input, supplies the last
VariableName
that was returned
by
GetNextVariableName()
. On output, returns the Null-
terminated Unicode string of the current variable.
VendorGuid
On input, supplies the last
VendorGuid
that was returned by
GetNextVariableName()
. On output, returns the
VendorGuid
of the current variable. Type
EFI_GUID
is
defined in Section 3.3.1.
Description
GetNextVariableName()
is called multiple times to retrieve the
VariableName
and
VendorGuid
of all variables currently available in the system. On each call to
GetNextVariableName()
the previous results are passed into the interface, and on output the
interface returns the next variable name data. When the entire variable list has been returned, the
error
EFI_NOT_FOUND
is returned.
Note that if
EFI_BUFFER_TOO_SMALL
is returned, the
VariableName
buffer was too small
for the next variable. When such an error occurs, the
VariableNameSize
is updated to reflect
the size of buffer needed. In all cases when calling
GetNextVariableName()
the
VariableNameSize
must not exceed the actual buffer size that was allocated for
VariableName
.
To start the search, a Null-terminated string is passed in
VariableName
; that is,
VariableName
is a pointer to a Null Unicode character. This is always done on the initial call to
GetNextVariableName()
. When
VariableName
is a pointer to a Null Unicode character,
VendorGuid
is ignored.
GetNextVariableName()
cannot be used as a filter to return
variable names with a specific GUID. Instead, the entire list of variables must be retrieved, and the
caller may act as a filter if it chooses. Calls to
SetVariable()
between calls to
GetNextVariableName()
may produce unpredictable results.