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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 */