85 lines
2.4 KiB
Go
85 lines
2.4 KiB
Go
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// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ppc64asm
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import (
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"fmt"
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"strings"
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)
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// A BitField is a bit-field in a 32-bit word.
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// Bits are counted from 0 from the MSB to 31 as the LSB.
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type BitField struct {
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Offs uint8 // the offset of the left-most bit.
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Bits uint8 // length in bits.
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}
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func (b BitField) String() string {
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if b.Bits > 1 {
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return fmt.Sprintf("[%d:%d]", b.Offs, int(b.Offs+b.Bits)-1)
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} else if b.Bits == 1 {
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return fmt.Sprintf("[%d]", b.Offs)
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} else {
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return fmt.Sprintf("[%d, len=0]", b.Offs)
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}
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}
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// Parse extracts the bitfield b from i, and return it as an unsigned integer.
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// Parse will panic if b is invalid.
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func (b BitField) Parse(i uint32) uint32 {
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if b.Bits > 32 || b.Bits == 0 || b.Offs > 31 || b.Offs+b.Bits > 32 {
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panic(fmt.Sprintf("invalid bitfiled %v", b))
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}
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return (i >> (32 - b.Offs - b.Bits)) & ((1 << b.Bits) - 1)
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}
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// ParseSigned extracts the bitfield b from i, and return it as a signed integer.
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// ParseSigned will panic if b is invalid.
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func (b BitField) ParseSigned(i uint32) int32 {
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u := int32(b.Parse(i))
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return u << (32 - b.Bits) >> (32 - b.Bits)
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}
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// BitFields is a series of BitFields representing a single number.
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type BitFields []BitField
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func (bs BitFields) String() string {
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ss := make([]string, len(bs))
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for i, bf := range bs {
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ss[i] = bf.String()
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}
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return fmt.Sprintf("<%s>", strings.Join(ss, "|"))
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}
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func (bs *BitFields) Append(b BitField) {
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*bs = append(*bs, b)
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}
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// parse extracts the bitfields from i, concatenate them and return the result
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// as an unsigned integer and the total length of all the bitfields.
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// parse will panic if any bitfield in b is invalid, but it doesn't check if
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// the sequence of bitfields is reasonable.
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func (bs BitFields) parse(i uint32) (u uint32, Bits uint8) {
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for _, b := range bs {
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u = (u << b.Bits) | b.Parse(i)
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Bits += b.Bits
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}
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return u, Bits
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}
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// Parse extracts the bitfields from i, concatenate them and return the result
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// as an unsigned integer. Parse will panic if any bitfield in b is invalid.
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func (bs BitFields) Parse(i uint32) uint32 {
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u, _ := bs.parse(i)
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return u
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}
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// Parse extracts the bitfields from i, concatenate them and return the result
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// as a signed integer. Parse will panic if any bitfield in b is invalid.
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func (bs BitFields) ParseSigned(i uint32) int32 {
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u, l := bs.parse(i)
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return int32(u) << (32 - l) >> (32 - l)
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}
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