Source file src/pkg/cmd/vendor/golang.org/x/arch/ppc64/ppc64asm/field.go

     1	// Copyright 2014 The Go Authors.  All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	package ppc64asm
     6	
     7	import (
     8		"fmt"
     9		"strings"
    10	)
    11	
    12	// A BitField is a bit-field in a 32-bit word.
    13	// Bits are counted from 0 from the MSB to 31 as the LSB.
    14	type BitField struct {
    15		Offs uint8 // the offset of the left-most bit.
    16		Bits uint8 // length in bits.
    17	}
    18	
    19	func (b BitField) String() string {
    20		if b.Bits > 1 {
    21			return fmt.Sprintf("[%d:%d]", b.Offs, int(b.Offs+b.Bits)-1)
    22		} else if b.Bits == 1 {
    23			return fmt.Sprintf("[%d]", b.Offs)
    24		} else {
    25			return fmt.Sprintf("[%d, len=0]", b.Offs)
    26		}
    27	}
    28	
    29	// Parse extracts the bitfield b from i, and return it as an unsigned integer.
    30	// Parse will panic if b is invalid.
    31	func (b BitField) Parse(i uint32) uint32 {
    32		if b.Bits > 32 || b.Bits == 0 || b.Offs > 31 || b.Offs+b.Bits > 32 {
    33			panic(fmt.Sprintf("invalid bitfiled %v", b))
    34		}
    35		return (i >> (32 - b.Offs - b.Bits)) & ((1 << b.Bits) - 1)
    36	}
    37	
    38	// ParseSigned extracts the bitfield b from i, and return it as a signed integer.
    39	// ParseSigned will panic if b is invalid.
    40	func (b BitField) ParseSigned(i uint32) int32 {
    41		u := int32(b.Parse(i))
    42		return u << (32 - b.Bits) >> (32 - b.Bits)
    43	}
    44	
    45	// BitFields is a series of BitFields representing a single number.
    46	type BitFields []BitField
    47	
    48	func (bs BitFields) String() string {
    49		ss := make([]string, len(bs))
    50		for i, bf := range bs {
    51			ss[i] = bf.String()
    52		}
    53		return fmt.Sprintf("<%s>", strings.Join(ss, "|"))
    54	}
    55	
    56	func (bs *BitFields) Append(b BitField) {
    57		*bs = append(*bs, b)
    58	}
    59	
    60	// parse extracts the bitfields from i, concatenate them and return the result
    61	// as an unsigned integer and the total length of all the bitfields.
    62	// parse will panic if any bitfield in b is invalid, but it doesn't check if
    63	// the sequence of bitfields is reasonable.
    64	func (bs BitFields) parse(i uint32) (u uint32, Bits uint8) {
    65		for _, b := range bs {
    66			u = (u << b.Bits) | b.Parse(i)
    67			Bits += b.Bits
    68		}
    69		return u, Bits
    70	}
    71	
    72	// Parse extracts the bitfields from i, concatenate them and return the result
    73	// as an unsigned integer. Parse will panic if any bitfield in b is invalid.
    74	func (bs BitFields) Parse(i uint32) uint32 {
    75		u, _ := bs.parse(i)
    76		return u
    77	}
    78	
    79	// Parse extracts the bitfields from i, concatenate them and return the result
    80	// as a signed integer. Parse will panic if any bitfield in b is invalid.
    81	func (bs BitFields) ParseSigned(i uint32) int32 {
    82		u, l := bs.parse(i)
    83		return int32(u) << (32 - l) >> (32 - l)
    84	}
    85	

View as plain text