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Diffstat (limited to 'pkg/sentry/fsimpl/cgroupfs/bitmap.go')
-rw-r--r-- | pkg/sentry/fsimpl/cgroupfs/bitmap.go | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/cgroupfs/bitmap.go b/pkg/sentry/fsimpl/cgroupfs/bitmap.go new file mode 100644 index 000000000..8074641db --- /dev/null +++ b/pkg/sentry/fsimpl/cgroupfs/bitmap.go @@ -0,0 +1,139 @@ +// Copyright 2021 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 cgroupfs + +import ( + "fmt" + "strconv" + "strings" + + "gvisor.dev/gvisor/pkg/bitmap" +) + +// formatBitmap produces a string representation of b, which lists the indicies +// of set bits in the bitmap. Indicies are separated by commas and ranges of +// set bits are abbreviated. Example outputs: "0,2,4", "0,3-7,10", "0-10". +// +// Inverse of parseBitmap. +func formatBitmap(b *bitmap.Bitmap) string { + ones := b.ToSlice() + if len(ones) == 0 { + return "" + } + + elems := make([]string, 0, len(ones)) + runStart := ones[0] + lastVal := ones[0] + inRun := false + + for _, v := range ones[1:] { + last := lastVal + lastVal = v + + if last+1 == v { + // In a contiguous block of ones. + if !inRun { + runStart = last + inRun = true + } + + continue + } + + // Non-contiguous bit. + if inRun { + // Render a run + elems = append(elems, fmt.Sprintf("%d-%d", runStart, last)) + inRun = false + continue + } + + // Lone non-contiguous bit. + elems = append(elems, fmt.Sprintf("%d", last)) + + } + + // Process potential final run + if inRun { + elems = append(elems, fmt.Sprintf("%d-%d", runStart, lastVal)) + } else { + elems = append(elems, fmt.Sprintf("%d", lastVal)) + } + + return strings.Join(elems, ",") +} + +func parseToken(token string) (start, end uint32, err error) { + ts := strings.SplitN(token, "-", 2) + switch len(ts) { + case 0: + return 0, 0, fmt.Errorf("invalid token %q", token) + case 1: + val, err := strconv.ParseUint(ts[0], 10, 32) + if err != nil { + return 0, 0, err + } + return uint32(val), uint32(val), nil + case 2: + val1, err := strconv.ParseUint(ts[0], 10, 32) + if err != nil { + return 0, 0, err + } + val2, err := strconv.ParseUint(ts[1], 10, 32) + if err != nil { + return 0, 0, err + } + if val1 >= val2 { + return 0, 0, fmt.Errorf("start (%v) must be less than end (%v)", val1, val2) + } + return uint32(val1), uint32(val2), nil + default: + panic(fmt.Sprintf("Unreachable: got %d substrs", len(ts))) + } +} + +// parseBitmap parses input as a bitmap. input should be a comma separated list +// of indices, and ranges of set bits may be abbreviated. Examples: "0,2,4", +// "0,3-7,10", "0-10". Input after the first newline or null byte is discarded. +// +// sizeHint sets the initial size of the bitmap, which may prevent reallocation +// when growing the bitmap during parsing. Ideally sizeHint should be at least +// as large as the bitmap represented by input, but this is not required. +// +// Inverse of formatBitmap. +func parseBitmap(input string, sizeHint uint32) (*bitmap.Bitmap, error) { + b := bitmap.New(sizeHint) + + if termIdx := strings.IndexAny(input, "\n\000"); termIdx != -1 { + input = input[:termIdx] + } + input = strings.TrimSpace(input) + + if len(input) == 0 { + return &b, nil + } + tokens := strings.Split(input, ",") + + for _, t := range tokens { + start, end, err := parseToken(strings.TrimSpace(t)) + if err != nil { + return nil, err + } + for i := start; i <= end; i++ { + b.Add(i) + } + } + return &b, nil +} |