114 lines
2.8 KiB
C
114 lines
2.8 KiB
C
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/*
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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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