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Merge pull request #64 from jstarks/tar_ea
Add support for EAs to Windows tars
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,137 @@ | ||
| package winio | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "encoding/binary" | ||
| "errors" | ||
| ) | ||
|
|
||
| type fileFullEaInformation struct { | ||
| NextEntryOffset uint32 | ||
| Flags uint8 | ||
| NameLength uint8 | ||
| ValueLength uint16 | ||
| } | ||
|
|
||
| var ( | ||
| fileFullEaInformationSize = binary.Size(&fileFullEaInformation{}) | ||
|
|
||
| errInvalidEaBuffer = errors.New("invalid extended attribute buffer") | ||
| errEaNameTooLarge = errors.New("extended attribute name too large") | ||
| errEaValueTooLarge = errors.New("extended attribute value too large") | ||
| ) | ||
|
|
||
| // ExtendedAttribute represents a single Windows EA. | ||
| type ExtendedAttribute struct { | ||
| Name string | ||
| Value []byte | ||
| Flags uint8 | ||
| } | ||
|
|
||
| func parseEa(b []byte) (ea ExtendedAttribute, nb []byte, err error) { | ||
| var info fileFullEaInformation | ||
| err = binary.Read(bytes.NewReader(b), binary.LittleEndian, &info) | ||
| if err != nil { | ||
| err = errInvalidEaBuffer | ||
| return | ||
| } | ||
|
|
||
| nameOffset := fileFullEaInformationSize | ||
| nameLen := int(info.NameLength) | ||
| valueOffset := nameOffset + int(info.NameLength) + 1 | ||
| valueLen := int(info.ValueLength) | ||
| nextOffset := int(info.NextEntryOffset) | ||
| if valueLen+valueOffset > len(b) || nextOffset < 0 || nextOffset > len(b) { | ||
| err = errInvalidEaBuffer | ||
| return | ||
| } | ||
|
|
||
| ea.Name = string(b[nameOffset : nameOffset+nameLen]) | ||
| ea.Value = b[valueOffset : valueOffset+valueLen] | ||
| ea.Flags = info.Flags | ||
| if info.NextEntryOffset != 0 { | ||
| nb = b[info.NextEntryOffset:] | ||
| } | ||
| return | ||
| } | ||
|
|
||
| // DecodeExtendedAttributes decodes a list of EAs from a FILE_FULL_EA_INFORMATION | ||
| // buffer retrieved from BackupRead, ZwQueryEaFile, etc. | ||
| func DecodeExtendedAttributes(b []byte) (eas []ExtendedAttribute, err error) { | ||
| for len(b) != 0 { | ||
| ea, nb, err := parseEa(b) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| eas = append(eas, ea) | ||
| b = nb | ||
| } | ||
| return | ||
| } | ||
|
|
||
| func writeEa(buf *bytes.Buffer, ea *ExtendedAttribute, last bool) error { | ||
| if int(uint8(len(ea.Name))) != len(ea.Name) { | ||
| return errEaNameTooLarge | ||
| } | ||
| if int(uint16(len(ea.Value))) != len(ea.Value) { | ||
| return errEaValueTooLarge | ||
| } | ||
| entrySize := uint32(fileFullEaInformationSize + len(ea.Name) + 1 + len(ea.Value)) | ||
| withPadding := (entrySize + 3) &^ 3 | ||
| nextOffset := uint32(0) | ||
| if !last { | ||
| nextOffset = withPadding | ||
| } | ||
| info := fileFullEaInformation{ | ||
| NextEntryOffset: nextOffset, | ||
| Flags: ea.Flags, | ||
| NameLength: uint8(len(ea.Name)), | ||
| ValueLength: uint16(len(ea.Value)), | ||
| } | ||
|
|
||
| err := binary.Write(buf, binary.LittleEndian, &info) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| _, err = buf.Write([]byte(ea.Name)) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| err = buf.WriteByte(0) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| _, err = buf.Write(ea.Value) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| _, err = buf.Write([]byte{0, 0, 0}[0 : withPadding-entrySize]) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| return nil | ||
| } | ||
|
|
||
| // EncodeExtendedAttributes encodes a list of EAs into a FILE_FULL_EA_INFORMATION | ||
| // buffer for use with BackupWrite, ZwSetEaFile, etc. | ||
| func EncodeExtendedAttributes(eas []ExtendedAttribute) ([]byte, error) { | ||
| var buf bytes.Buffer | ||
| for i := range eas { | ||
| last := false | ||
| if i == len(eas)-1 { | ||
| last = true | ||
| } | ||
|
|
||
| err := writeEa(&buf, &eas[i], last) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| } | ||
| return buf.Bytes(), nil | ||
| } |
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