7 files changed, 192 insertions, 0 deletions
diff --git a/pkg/bits/bits.go b/pkg/bits/bits.go
new file mode 100644
index 000000000..a26433ad6
--- /dev/null
+++ b/pkg/bits/bits.go
@@ -0,0 +1,16 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package bits includes all bit related types and operations.
+package bits
diff --git a/pkg/bits/bits32.go b/pkg/bits/bits32.go
new file mode 100755
index 000000000..4e9e45dce
--- /dev/null
+++ b/pkg/bits/bits32.go
@@ -0,0 +1,25 @@
+package bits
+
+// IsOn returns true if *all* bits set in 'bits' are set in 'mask'.
+func IsOn32(mask, bits uint32) bool {
+	return mask&bits == bits
+}
+
+// IsAnyOn returns true if *any* bit set in 'bits' is set in 'mask'.
+func IsAnyOn32(mask, bits uint32) bool {
+	return mask&bits != 0
+}
+
+// Mask returns a T with all of the given bits set.
+func Mask32(is ...int) uint32 {
+	ret := uint32(0)
+	for _, i := range is {
+		ret |= MaskOf32(i)
+	}
+	return ret
+}
+
+// MaskOf is like Mask, but sets only a single bit (more efficiently).
+func MaskOf32(i int) uint32 {
+	return uint32(1) << uint32(i)
+}
diff --git a/pkg/bits/bits64.go b/pkg/bits/bits64.go
new file mode 100755
index 000000000..f49158792
--- /dev/null
+++ b/pkg/bits/bits64.go
@@ -0,0 +1,25 @@
+package bits
+
+// IsOn returns true if *all* bits set in 'bits' are set in 'mask'.
+func IsOn64(mask, bits uint64) bool {
+	return mask&bits == bits
+}
+
+// IsAnyOn returns true if *any* bit set in 'bits' is set in 'mask'.
+func IsAnyOn64(mask, bits uint64) bool {
+	return mask&bits != 0
+}
+
+// Mask returns a T with all of the given bits set.
+func Mask64(is ...int) uint64 {
+	ret := uint64(0)
+	for _, i := range is {
+		ret |= MaskOf64(i)
+	}
+	return ret
+}
+
+// MaskOf is like Mask, but sets only a single bit (more efficiently).
+func MaskOf64(i int) uint64 {
+	return uint64(1) << uint64(i)
+}
diff --git a/pkg/bits/bits_state_autogen.go b/pkg/bits/bits_state_autogen.go
new file mode 100755
index 000000000..2abb1291b
--- /dev/null
+++ b/pkg/bits/bits_state_autogen.go
@@ -0,0 +1,4 @@
+// automatically generated by stateify.
+
+package bits
+
diff --git a/pkg/bits/uint64_arch_amd64.go b/pkg/bits/uint64_arch_amd64.go
new file mode 100644
index 000000000..faccaa61a
--- /dev/null
+++ b/pkg/bits/uint64_arch_amd64.go
@@ -0,0 +1,36 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build amd64
+
+package bits
+
+// TrailingZeros64 returns the number of bits before the least significant 1
+// bit in x; in other words, it returns the index of the least significant 1
+// bit in x. If x is 0, TrailingZeros64 returns 64.
+func TrailingZeros64(x uint64) int
+
+// MostSignificantOne64 returns the index of the most significant 1 bit in
+// x. If x is 0, MostSignificantOne64 returns 64.
+func MostSignificantOne64(x uint64) int
+
+// ForEachSetBit64 calls f once for each set bit in x, with argument i equal to
+// the set bit's index.
+func ForEachSetBit64(x uint64, f func(i int)) {
+	for x != 0 {
+		i := TrailingZeros64(x)
+		f(i)
+		x &^= MaskOf64(i)
+	}
+}
diff --git a/pkg/bits/uint64_arch_amd64_asm.s b/pkg/bits/uint64_arch_amd64_asm.s
new file mode 100644
index 000000000..8ff364181
--- /dev/null
+++ b/pkg/bits/uint64_arch_amd64_asm.s
@@ -0,0 +1,31 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build amd64
+
+TEXT ·TrailingZeros64(SB),$0-16
+  BSFQ  x+0(FP), AX
+  JNZ   end
+  MOVQ  $64, AX
+end:
+  MOVQ  AX, ret+8(FP)
+  RET
+
+TEXT ·MostSignificantOne64(SB),$0-16
+  BSRQ  x+0(FP), AX
+  JNZ   end
+  MOVQ  $64, AX
+end:
+  MOVQ  AX, ret+8(FP)
+  RET
diff --git a/pkg/bits/uint64_arch_generic.go b/pkg/bits/uint64_arch_generic.go
new file mode 100644
index 000000000..7dd2d1480
--- /dev/null
+++ b/pkg/bits/uint64_arch_generic.go
@@ -0,0 +1,55 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build !amd64
+
+package bits
+
+// TrailingZeros64 returns the number of bits before the least significant 1
+// bit in x; in other words, it returns the index of the least significant 1
+// bit in x. If x is 0, TrailingZeros64 returns 64.
+func TrailingZeros64(x uint64) int {
+	if x == 0 {
+		return 64
+	}
+	i := 0
+	for ; x&1 == 0; i++ {
+		x >>= 1
+	}
+	return i
+}
+
+// MostSignificantOne64 returns the index of the most significant 1 bit in
+// x. If x is 0, MostSignificantOne64 returns 64.
+func MostSignificantOne64(x uint64) int {
+	if x == 0 {
+		return 64
+	}
+	i := 63
+	for ; x&(1<<63) == 0; i-- {
+		x <<= 1
+	}
+	return i
+}
+
+// ForEachSetBit64 calls f once for each set bit in x, with argument i equal to
+// the set bit's index.
+func ForEachSetBit64(x uint64, f func(i int)) {
+	for i := 0; x != 0; i++ {
+		if x&1 != 0 {
+			f(i)
+		}
+		x >>= 1
+	}
+}