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/*
* 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 */
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