1 /* 2 * FILE bitfield.h 3 * 4 * Version 1.1 5 * Author Copyright (c) Marc A. Viredaz, 1998 6 * DEC Western Research Laboratory, Palo Alto, CA 7 * Date April 1998 (April 1997) 8 * System Advanced RISC Machine (ARM) 9 * Language C or ARM Assembly 10 * Purpose Definition of macros to operate on bit fields. 11 */ 12 13 14 #ifndef __BITFIELD_H 15 #define __BITFIELD_H 16 17 #ifndef __ASSEMBLY__ 18 #define UData(Data) ((unsigned long) (Data)) 19 #else 20 #define UData(Data) (Data) 21 #endif 22 23 24 /* 25 * MACRO: Fld 26 * 27 * Purpose 28 * The macro "Fld" encodes a bit field, given its size and its shift value 29 * with respect to bit 0. 30 * 31 * Note 32 * A more intuitive way to encode bit fields would have been to use their 33 * mask. However, extracting size and shift value information from a bit 34 * field's mask is cumbersome and might break the assembler (255-character 35 * line-size limit). 36 * 37 * Input 38 * Size Size of the bit field, in number of bits. 39 * Shft Shift value of the bit field with respect to bit 0. 40 * 41 * Output 42 * Fld Encoded bit field. 43 */ 44 45 #define Fld(Size, Shft) (((Size) << 16) + (Shft)) 46 47 48 /* 49 * MACROS: FSize, FShft, FMsk, FAlnMsk, F1stBit 50 * 51 * Purpose 52 * The macros "FSize", "FShft", "FMsk", "FAlnMsk", and "F1stBit" return 53 * the size, shift value, mask, aligned mask, and first bit of a 54 * bit field. 55 * 56 * Input 57 * Field Encoded bit field (using the macro "Fld"). 58 * 59 * Output 60 * FSize Size of the bit field, in number of bits. 61 * FShft Shift value of the bit field with respect to bit 0. 62 * FMsk Mask for the bit field. 63 * FAlnMsk Mask for the bit field, aligned on bit 0. 64 * F1stBit First bit of the bit field. 65 */ 66 67 #define FSize(Field) ((Field) >> 16) 68 #define FShft(Field) ((Field) & 0x0000FFFF) 69 #define FMsk(Field) (((UData (1) << FSize (Field)) - 1) << FShft (Field)) 70 #define FAlnMsk(Field) ((UData (1) << FSize (Field)) - 1) 71 #define F1stBit(Field) (UData (1) << FShft (Field)) 72 73 74 /* 75 * MACRO: FInsrt 76 * 77 * Purpose 78 * The macro "FInsrt" inserts a value into a bit field by shifting the 79 * former appropriately. 80 * 81 * Input 82 * Value Bit-field value. 83 * Field Encoded bit field (using the macro "Fld"). 84 * 85 * Output 86 * FInsrt Bit-field value positioned appropriately. 87 */ 88 89 #define FInsrt(Value, Field) \ 90 (UData (Value) << FShft (Field)) 91 92 93 /* 94 * MACRO: FExtr 95 * 96 * Purpose 97 * The macro "FExtr" extracts the value of a bit field by masking and 98 * shifting it appropriately. 99 * 100 * Input 101 * Data Data containing the bit-field to be extracted. 102 * Field Encoded bit field (using the macro "Fld"). 103 * 104 * Output 105 * FExtr Bit-field value. 106 */ 107 108 #define FExtr(Data, Field) \ 109 ((UData (Data) >> FShft (Field)) & FAlnMsk (Field)) 110 111 112 #endif /* __BITFIELD_H */ 113