Packmatic v1.0.0 Packmatic.Field.Local.FileHeader View Source

Represents the Local File Header, which is emitted before the content of each file is incorporated into the Zip stream.

Structure

Size	Content
4 bytes	Signature
2 bytes	Version needed to extract
2 bytes	General Purpose Flag
2 bytes	Compression Method (0 = No Compression; 8 = Deflated)
2 bytes	Modification Time (DOS Format)
2 bytes	Modification Date (DOS Format)
4 bytes	Checksum (CRC-32; 0 since Data Descriptor is used)
4 bytes	Compressed Size (Bytes; 0 since Data Descriptor is used)
4 bytes	Original Size (Bytes; 0 since Data Descriptor is used)
2 bytes	File Path Length (Bytes)
2 bytes	Extra Fields Length (Bytes)
Variable	File Path
Variable	Extra Fields

The General Purpose Flag has the following bits set.
- Bit 3: Indicating a Streaming Archive; Data Descriptor is used, and the Local File Header has no Size or CRC information.
- Bit 11: Language encoding flag, indicating that the Filename and Comment are both already in UTF-8. As per APPNOTE, the presence of this flag obviates the need to emit a separate Info-ZIP Unicode Path Extra Field.
The Checksum, Compressed Size and Original Size fields are set to 0, since when the Local File Header is written, no further data has been read and so this information is not available. When the file has been read fully, a Data Descriptor will be written, which contains relevant information.
The following Extra Field is emitted:
- Extended Timestamp, see Packmatic.Field.Shared.ExtendedTimestamp

t()

t() :: %Packmatic.Field.Local.FileHeader{
  path: Path.t(),
  timestamp: DateTime.t()
}