| /* | |
| * 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 */ |