146 lines
3.1 KiB
Go
146 lines
3.1 KiB
Go
package flatfs
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import (
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"fmt"
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"io/ioutil"
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"os"
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"path/filepath"
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"strconv"
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"strings"
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)
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var IPFS_DEF_SHARD = NextToLast(2)
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var IPFS_DEF_SHARD_STR = IPFS_DEF_SHARD.String()
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const PREFIX = "/repo/flatfs/shard/"
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const SHARDING_FN = "SHARDING"
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const README_FN = "_README"
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type ShardIdV1 struct {
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funName string
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param int
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fun ShardFunc
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}
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func (f *ShardIdV1) String() string {
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return fmt.Sprintf("%sv1/%s/%d", PREFIX, f.funName, f.param)
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}
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func (f *ShardIdV1) Func() ShardFunc {
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return f.fun
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}
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func Prefix(prefixLen int) *ShardIdV1 {
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padding := strings.Repeat("_", prefixLen)
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return &ShardIdV1{
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funName: "prefix",
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param: prefixLen,
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fun: func(noslash string) string {
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return (noslash + padding)[:prefixLen]
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},
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}
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}
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func Suffix(suffixLen int) *ShardIdV1 {
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padding := strings.Repeat("_", suffixLen)
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return &ShardIdV1{
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funName: "suffix",
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param: suffixLen,
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fun: func(noslash string) string {
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str := padding + noslash
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return str[len(str)-suffixLen:]
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},
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}
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}
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func NextToLast(suffixLen int) *ShardIdV1 {
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padding := strings.Repeat("_", suffixLen+1)
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return &ShardIdV1{
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funName: "next-to-last",
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param: suffixLen,
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fun: func(noslash string) string {
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str := padding + noslash
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offset := len(str) - suffixLen - 1
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return str[offset : offset+suffixLen]
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},
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}
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}
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func ParseShardFunc(str string) (*ShardIdV1, error) {
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str = strings.TrimSpace(str)
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if len(str) == 0 {
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return nil, fmt.Errorf("empty shard identifier")
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}
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trimmed := strings.TrimPrefix(str, PREFIX)
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if str == trimmed { // nothing trimmed
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return nil, fmt.Errorf("invalid or no prefix in shard identifier: %s", str)
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}
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str = trimmed
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parts := strings.Split(str, "/")
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if len(parts) != 3 {
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return nil, fmt.Errorf("invalid shard identifier: %s", str)
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}
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version := parts[0]
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if version != "v1" {
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return nil, fmt.Errorf("expected 'v1' for version string got: %s\n", version)
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}
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funName := parts[1]
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param, err := strconv.Atoi(parts[2])
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if err != nil {
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return nil, fmt.Errorf("invalid parameter: %v", err)
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}
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switch funName {
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case "prefix":
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return Prefix(param), nil
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case "suffix":
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return Suffix(param), nil
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case "next-to-last":
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return NextToLast(param), nil
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default:
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return nil, fmt.Errorf("expected 'prefix', 'suffix' or 'next-to-last' got: %s", funName)
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}
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}
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func ReadShardFunc(dir string) (*ShardIdV1, error) {
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buf, err := ioutil.ReadFile(filepath.Join(dir, SHARDING_FN))
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if os.IsNotExist(err) {
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return nil, ErrShardingFileMissing
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} else if err != nil {
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return nil, err
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}
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return ParseShardFunc(string(buf))
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}
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func WriteShardFunc(dir string, id *ShardIdV1) error {
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file, err := os.OpenFile(filepath.Join(dir, SHARDING_FN), os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0666)
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if err != nil {
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return err
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}
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defer file.Close()
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_, err = file.WriteString(id.String())
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if err != nil {
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return err
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}
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_, err = file.WriteString("\n")
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return err
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}
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func WriteReadme(dir string, id *ShardIdV1) error {
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if id.String() == IPFS_DEF_SHARD.String() {
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err := ioutil.WriteFile(filepath.Join(dir, README_FN), []byte(README_IPFS_DEF_SHARD), 0444)
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if err != nil {
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return err
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}
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}
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return nil
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}
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