Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
19.6.60 Index (Indexed Reference To Member Object)
Syntax
Index (Source, Index, Destination) => ObjectReference
Destination = Source [Index] => ObjectReference
Arguments
Source is evaluated to a buffer, string, or package data type. Index is evaluated to an integer. The
reference to the nth object (where n = Index) within Source is optionally stored as a reference into
Destination.
Description
When Source evaluates to a Buffer, Index returns a reference to a Buffer Field containing the nth
byte in the buffer. When Source evaluates to a String, Index returns a reference to a Buffer Field
containing the nth character in the string. When Source evaluates to a Package, Index returns a
reference to the nth object in the package.
19.6.60.1 Index with Packages
The following example ASL code shows a way to use the Index term to store into a local variable
the sixth element of the first package of a set of nested packages:
Name (IO0D, Package () {
Package () {
0x01, 0x03F8, 0x03F8, 0x01, 0x08, 0x01, 0x25, 0xFF, 0xFE, 0x00, 0x00
},
Package () {
0x01, 0x02F8, 0x02F8, 0x01, 0x08, 0x01, 0x25, 0xFF, 0xBE, 0x00, 0x00
},
Package () {
0x01, 0x03E8, 0x03E8, 0x01, 0x08, 0x01, 0x25, 0xFF, 0xFA, 0x00, 0x00
},
Package () {
x01, 0x02E8, 0x02E8, 0x01, 0x08, 0x01, 0x25, 0xFF, 0xBA, 0x00, 0x00
},
Package() {
0x01, 0x0100, 0x03F8, 0x08, 0x08, 0x02, 0x25, 0x20, 0x7F, 0x00, 0x00
}
})
// Get the 6th element of the first package
Store (DeRefOf (Index (DeRefOf (Index (IO0D, 0)), 5)), Local0)
Note: DeRefOf is necessary in the first operand of the Store operator in order to get the actual object,
rather than just a reference to the object. If DeRefOf were not used, then Local0 would contain an
object reference to the sixth element in the first package rather than the number 1.
19.6.60.2 Index with Buffers
The following example ASL code shows a way to store into the third byte of a buffer:
848 April, 2015 Version 6.0