/*
|
* FILE bitfield.h
|
*
|
* Version 1.1
|
* Author Copyright (c) Marc A. Viredaz, 1998
|
* DEC Western Research Laboratory, Palo Alto, CA
|
* Date April 1998 (April 1997)
|
* System Advanced RISC Machine (ARM)
|
* Language C or ARM Assembly
|
* Purpose Definition of macros to operate on bit fields.
|
*/
|
|
|
#ifndef __BITFIELD_H
|
#define __BITFIELD_H
|
|
#ifndef __ASSEMBLY__
|
#define UData(Data) ((unsigned long) (Data))
|
#else
|
#define UData(Data) (Data)
|
#endif
|
|
|
/*
|
* MACRO: Fld
|
*
|
* Purpose
|
* The macro "Fld" encodes a bit field, given its size and its shift value
|
* with respect to bit 0.
|
*
|
* Note
|
* A more intuitive way to encode bit fields would have been to use their
|
* mask. However, extracting size and shift value information from a bit
|
* field's mask is cumbersome and might break the assembler (255-character
|
* line-size limit).
|
*
|
* Input
|
* Size Size of the bit field, in number of bits.
|
* Shft Shift value of the bit field with respect to bit 0.
|
*
|
* Output
|
* Fld Encoded bit field.
|
*/
|
|
#define Fld(Size, Shft) (((Size) << 16) + (Shft))
|
|
|
/*
|
* MACROS: FSize, FShft, FMsk, FAlnMsk, F1stBit
|
*
|
* Purpose
|
* The macros "FSize", "FShft", "FMsk", "FAlnMsk", and "F1stBit" return
|
* the size, shift value, mask, aligned mask, and first bit of a
|
* bit field.
|
*
|
* Input
|
* Field Encoded bit field (using the macro "Fld").
|
*
|
* Output
|
* FSize Size of the bit field, in number of bits.
|
* FShft Shift value of the bit field with respect to bit 0.
|
* FMsk Mask for the bit field.
|
* FAlnMsk Mask for the bit field, aligned on bit 0.
|
* F1stBit First bit of the bit field.
|
*/
|
|
#define FSize(Field) ((Field) >> 16)
|
#define FShft(Field) ((Field) & 0x0000FFFF)
|
#define FMsk(Field) (((UData (1) << FSize (Field)) - 1) << FShft (Field))
|
#define FAlnMsk(Field) ((UData (1) << FSize (Field)) - 1)
|
#define F1stBit(Field) (UData (1) << FShft (Field))
|
|
|
/*
|
* MACRO: FInsrt
|
*
|
* Purpose
|
* The macro "FInsrt" inserts a value into a bit field by shifting the
|
* former appropriately.
|
*
|
* Input
|
* Value Bit-field value.
|
* Field Encoded bit field (using the macro "Fld").
|
*
|
* Output
|
* FInsrt Bit-field value positioned appropriately.
|
*/
|
|
#define FInsrt(Value, Field) \
|
(UData (Value) << FShft (Field))
|
|
|
/*
|
* MACRO: FExtr
|
*
|
* Purpose
|
* The macro "FExtr" extracts the value of a bit field by masking and
|
* shifting it appropriately.
|
*
|
* Input
|
* Data Data containing the bit-field to be extracted.
|
* Field Encoded bit field (using the macro "Fld").
|
*
|
* Output
|
* FExtr Bit-field value.
|
*/
|
|
#define FExtr(Data, Field) \
|
((UData (Data) >> FShft (Field)) & FAlnMsk (Field))
|
|
|
#endif /* __BITFIELD_H */
|
