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