libct/cg: replace bitset with std math/big library

Cut down third party dependency.

Signed-off-by: Shengjing Zhu <zhsj@debian.org>

go.mod

@@ -3,7 +3,6 @@ module github.com/opencontainers/runc
 go 1.15
 
 require (
-	github.com/bits-and-blooms/bitset v1.2.1
 	github.com/checkpoint-restore/go-criu/v5 v5.0.0
 	github.com/cilium/ebpf v0.6.2
 	github.com/containerd/console v1.0.3

go.sum

@@ -1,7 +1,6 @@
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
+github.com/bits-and-blooms/bitset v1.2.0 h1:Kn4yilvwNtMACtf1eYDlG8H77R07mZSPbMjLyS07ChA=
 github.com/bits-and-blooms/bitset v1.2.0/go.mod h1:gIdJ4wp64HaoK2YrL1Q5/N7Y16edYb8uY+O0FJTyyDA=
-github.com/bits-and-blooms/bitset v1.2.1 h1:M+/hrU9xlMp7t4TyTDQW97d3tRPVuKFC6zBEK16QnXY=
-github.com/bits-and-blooms/bitset v1.2.1/go.mod h1:gIdJ4wp64HaoK2YrL1Q5/N7Y16edYb8uY+O0FJTyyDA=
 github.com/checkpoint-restore/go-criu/v5 v5.0.0 h1:TW8f/UvntYoVDMN1K2HlT82qH1rb0sOjpGw3m6Ym+i4=
 github.com/checkpoint-restore/go-criu/v5 v5.0.0/go.mod h1:cfwC0EG7HMUenopBsUf9d89JlCLQIfgVcNsNN0t6T2M=
 github.com/cilium/ebpf v0.6.2 h1:iHsfF/t4aW4heW2YKfeHrVPGdtYTL4C4KocpM8KTSnI=

libcontainer/cgroups/systemd/cpuset.go

@@ -1,12 +1,10 @@
 package systemd
 
 import (
-	"encoding/binary"
 	"errors"
+	"math/big"
 	"strconv"
 	"strings"
-
-	"github.com/bits-and-blooms/bitset"
 )
 
 // RangeToBits converts a text representation of a CPU mask (as written to
@@ -14,7 +12,7 @@ import (
 // with the corresponding bits set (as consumed by systemd over dbus as
 // AllowedCPUs/AllowedMemoryNodes unit property value).
 func RangeToBits(str string) ([]byte, error) {
-	bits := &bitset.BitSet{}
+	bits := new(big.Int)
 
 	for _, r := range strings.Split(str, ",") {
 		// allow extra spaces around
@@ -36,32 +34,22 @@ func RangeToBits(str string) ([]byte, error) {
 			if start > end {
 				return nil, errors.New("invalid range: " + r)
 			}
-			for i := uint(start); i <= uint(end); i++ {
-				bits.Set(i)
+			for i := start; i <= end; i++ {
+				bits.SetBit(bits, int(i), 1)
 			}
 		} else {
 			val, err := strconv.ParseUint(ranges[0], 10, 32)
 			if err != nil {
 				return nil, err
 			}
-			bits.Set(uint(val))
+			bits.SetBit(bits, int(val), 1)
 		}
 	}
 
-	val := bits.Bytes()
-	if len(val) == 0 {
+	ret := bits.Bytes()
+	if len(ret) == 0 {
 		// do not allow empty values
 		return nil, errors.New("empty value")
 	}
-	ret := make([]byte, len(val)*8)
-	for i := range val {
-		// bitset uses BigEndian internally
-		binary.BigEndian.PutUint64(ret[i*8:], val[len(val)-1-i])
-	}
-	// remove upper all-zero bytes
-	for ret[0] == 0 {
-		ret = ret[1:]
-	}
-
 	return ret, nil
 }

vendor/github.com/bits-and-blooms/bitset/bitset.go

@@ -254,9 +254,7 @@ func (b *BitSet) Shrink(lastbitindex uint) *BitSet {
 	copy(shrunk, b.set[:idx])
 	b.set = shrunk
 	b.length = length
-	if length < 64 {
-	  b.set[idx-1] &= (allBits >> (uint64(64) - uint64(length&(wordSize-1))))
-    }
+	b.set[idx-1] &= (allBits >> (uint64(64) - uint64(length&(wordSize-1))))
 	return b
 }
 

vendor/modules.txt

@@ -1,5 +1,4 @@
-# github.com/bits-and-blooms/bitset v1.2.1
-## explicit
+# github.com/bits-and-blooms/bitset v1.2.0
 github.com/bits-and-blooms/bitset
 # github.com/checkpoint-restore/go-criu/v5 v5.0.0
 ## explicit