|
| 1 | +package fold |
| 2 | + |
| 3 | +import ( |
| 4 | + "bufio" |
| 5 | + "bytes" |
| 6 | + "container/heap" |
| 7 | + "context" |
| 8 | + "encoding/hex" |
| 9 | + "errors" |
| 10 | + "fmt" |
| 11 | + "io" |
| 12 | + "os" |
| 13 | + "path/filepath" |
| 14 | + "sort" |
| 15 | +) |
| 16 | + |
| 17 | +const ( |
| 18 | + digestBytes = 32 |
| 19 | + digestChunkCount = 1 << 20 |
| 20 | + maxMergeRunInputs = 64 |
| 21 | +) |
| 22 | + |
| 23 | +type diskDigestSet struct { |
| 24 | + directory string |
| 25 | + input *os.File |
| 26 | + closed bool |
| 27 | +} |
| 28 | + |
| 29 | +func newDiskDigestSet() (*diskDigestSet, error) { |
| 30 | + directory, err := os.MkdirTemp("", "codexfold-digests-") |
| 31 | + if err != nil { |
| 32 | + return nil, err |
| 33 | + } |
| 34 | + input, err := os.OpenFile(filepath.Join(directory, "input.bin"), os.O_CREATE|os.O_EXCL|os.O_RDWR, 0o600) |
| 35 | + if err != nil { |
| 36 | + _ = os.RemoveAll(directory) |
| 37 | + return nil, err |
| 38 | + } |
| 39 | + return &diskDigestSet{directory: directory, input: input}, nil |
| 40 | +} |
| 41 | + |
| 42 | +func (s *diskDigestSet) Add(value string) error { |
| 43 | + if s.closed { |
| 44 | + return errors.New("digest set is closed") |
| 45 | + } |
| 46 | + digest, err := hex.DecodeString(value) |
| 47 | + if err != nil || len(digest) != digestBytes { |
| 48 | + return fmt.Errorf("invalid SHA-256 %q", value) |
| 49 | + } |
| 50 | + _, err = s.input.Write(digest) |
| 51 | + return err |
| 52 | +} |
| 53 | + |
| 54 | +func (s *diskDigestSet) Count(ctx context.Context) (int, error) { |
| 55 | + if s.closed { |
| 56 | + return 0, errors.New("digest set is closed") |
| 57 | + } |
| 58 | + if err := s.input.Sync(); err != nil { |
| 59 | + return 0, err |
| 60 | + } |
| 61 | + if _, err := s.input.Seek(0, io.SeekStart); err != nil { |
| 62 | + return 0, err |
| 63 | + } |
| 64 | + runs, err := s.createRuns(ctx) |
| 65 | + if err != nil { |
| 66 | + return 0, err |
| 67 | + } |
| 68 | + for len(runs) > maxMergeRunInputs { |
| 69 | + next := make([]string, 0, (len(runs)+maxMergeRunInputs-1)/maxMergeRunInputs) |
| 70 | + for start := 0; start < len(runs); start += maxMergeRunInputs { |
| 71 | + end := min(start+maxMergeRunInputs, len(runs)) |
| 72 | + path := filepath.Join(s.directory, fmt.Sprintf("merged-%06d.bin", len(next))) |
| 73 | + if _, err := mergeDigestRuns(ctx, runs[start:end], path); err != nil { |
| 74 | + return 0, err |
| 75 | + } |
| 76 | + next = append(next, path) |
| 77 | + for _, old := range runs[start:end] { |
| 78 | + _ = os.Remove(old) |
| 79 | + } |
| 80 | + } |
| 81 | + runs = next |
| 82 | + } |
| 83 | + if len(runs) == 0 { |
| 84 | + return 0, nil |
| 85 | + } |
| 86 | + return mergeDigestRuns(ctx, runs, "") |
| 87 | +} |
| 88 | + |
| 89 | +func (s *diskDigestSet) createRuns(ctx context.Context) ([]string, error) { |
| 90 | + reader := bufio.NewReaderSize(s.input, 1<<20) |
| 91 | + runs := make([]string, 0) |
| 92 | + for { |
| 93 | + if err := ctx.Err(); err != nil { |
| 94 | + return nil, err |
| 95 | + } |
| 96 | + values := make([][digestBytes]byte, 0, digestChunkCount) |
| 97 | + for len(values) < digestChunkCount { |
| 98 | + var digest [digestBytes]byte |
| 99 | + _, err := io.ReadFull(reader, digest[:]) |
| 100 | + if errors.Is(err, io.EOF) { |
| 101 | + break |
| 102 | + } |
| 103 | + if err != nil { |
| 104 | + return nil, err |
| 105 | + } |
| 106 | + values = append(values, digest) |
| 107 | + } |
| 108 | + if len(values) == 0 { |
| 109 | + break |
| 110 | + } |
| 111 | + sort.Slice(values, func(left, right int) bool { return bytes.Compare(values[left][:], values[right][:]) < 0 }) |
| 112 | + path := filepath.Join(s.directory, fmt.Sprintf("run-%06d.bin", len(runs))) |
| 113 | + file, err := os.OpenFile(path, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600) |
| 114 | + if err != nil { |
| 115 | + return nil, err |
| 116 | + } |
| 117 | + writer := bufio.NewWriterSize(file, 1<<20) |
| 118 | + var previous [digestBytes]byte |
| 119 | + for index, digest := range values { |
| 120 | + if index > 0 && digest == previous { |
| 121 | + continue |
| 122 | + } |
| 123 | + if _, err := writer.Write(digest[:]); err != nil { |
| 124 | + _ = file.Close() |
| 125 | + return nil, err |
| 126 | + } |
| 127 | + previous = digest |
| 128 | + } |
| 129 | + if err := writer.Flush(); err != nil { |
| 130 | + _ = file.Close() |
| 131 | + return nil, err |
| 132 | + } |
| 133 | + if err := file.Close(); err != nil { |
| 134 | + return nil, err |
| 135 | + } |
| 136 | + runs = append(runs, path) |
| 137 | + } |
| 138 | + return runs, nil |
| 139 | +} |
| 140 | + |
| 141 | +type digestRun struct { |
| 142 | + file *os.File |
| 143 | + reader *bufio.Reader |
| 144 | + digest [digestBytes]byte |
| 145 | + ordinal int |
| 146 | +} |
| 147 | + |
| 148 | +type digestHeap []*digestRun |
| 149 | + |
| 150 | +func (h digestHeap) Len() int { return len(h) } |
| 151 | +func (h digestHeap) Less(left, right int) bool { |
| 152 | + comparison := bytes.Compare(h[left].digest[:], h[right].digest[:]) |
| 153 | + return comparison < 0 || (comparison == 0 && h[left].ordinal < h[right].ordinal) |
| 154 | +} |
| 155 | +func (h digestHeap) Swap(left, right int) { h[left], h[right] = h[right], h[left] } |
| 156 | +func (h *digestHeap) Push(value any) { *h = append(*h, value.(*digestRun)) } |
| 157 | +func (h *digestHeap) Pop() any { |
| 158 | + old := *h |
| 159 | + value := old[len(old)-1] |
| 160 | + *h = old[:len(old)-1] |
| 161 | + return value |
| 162 | +} |
| 163 | + |
| 164 | +func mergeDigestRuns(ctx context.Context, paths []string, outputPath string) (int, error) { |
| 165 | + var output *os.File |
| 166 | + var writer *bufio.Writer |
| 167 | + if outputPath != "" { |
| 168 | + file, err := os.OpenFile(outputPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600) |
| 169 | + if err != nil { |
| 170 | + return 0, err |
| 171 | + } |
| 172 | + output = file |
| 173 | + writer = bufio.NewWriterSize(file, 1<<20) |
| 174 | + defer output.Close() |
| 175 | + } |
| 176 | + runs := make([]*digestRun, 0, len(paths)) |
| 177 | + defer func() { |
| 178 | + for _, run := range runs { |
| 179 | + _ = run.file.Close() |
| 180 | + } |
| 181 | + }() |
| 182 | + queue := digestHeap{} |
| 183 | + for ordinal, path := range paths { |
| 184 | + file, err := os.Open(path) |
| 185 | + if err != nil { |
| 186 | + return 0, err |
| 187 | + } |
| 188 | + run := &digestRun{file: file, reader: bufio.NewReaderSize(file, 64<<10), ordinal: ordinal} |
| 189 | + runs = append(runs, run) |
| 190 | + if _, err := io.ReadFull(run.reader, run.digest[:]); err == nil { |
| 191 | + heap.Push(&queue, run) |
| 192 | + } else if !errors.Is(err, io.EOF) { |
| 193 | + return 0, err |
| 194 | + } |
| 195 | + } |
| 196 | + count := 0 |
| 197 | + var previous [digestBytes]byte |
| 198 | + havePrevious := false |
| 199 | + for queue.Len() > 0 { |
| 200 | + if err := ctx.Err(); err != nil { |
| 201 | + return 0, err |
| 202 | + } |
| 203 | + run := heap.Pop(&queue).(*digestRun) |
| 204 | + if !havePrevious || run.digest != previous { |
| 205 | + count++ |
| 206 | + previous = run.digest |
| 207 | + havePrevious = true |
| 208 | + if writer != nil { |
| 209 | + if _, err := writer.Write(run.digest[:]); err != nil { |
| 210 | + return 0, err |
| 211 | + } |
| 212 | + } |
| 213 | + } |
| 214 | + if _, err := io.ReadFull(run.reader, run.digest[:]); err == nil { |
| 215 | + heap.Push(&queue, run) |
| 216 | + } else if !errors.Is(err, io.EOF) { |
| 217 | + return 0, err |
| 218 | + } |
| 219 | + } |
| 220 | + if writer != nil { |
| 221 | + if err := writer.Flush(); err != nil { |
| 222 | + return 0, err |
| 223 | + } |
| 224 | + } |
| 225 | + return count, nil |
| 226 | +} |
| 227 | + |
| 228 | +func (s *diskDigestSet) Close() error { |
| 229 | + if s.closed { |
| 230 | + return nil |
| 231 | + } |
| 232 | + s.closed = true |
| 233 | + err := s.input.Close() |
| 234 | + return errors.Join(err, os.RemoveAll(s.directory)) |
| 235 | +} |
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