Data Compression


Criteria

Survey Formats

Basics

Compression Methods

Data Formats

Files

BZIP2

GZIP

ZIP

Specification

Characteristics

Compression

File Structure

Security Features

Platforms

Applications

Audio Data

Image Data

Video Data


Glossary

Index


Download


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File Structure


General layout of a ZIP file:

FieldContents
File 1 for each single file:
Local file header:
Information required for decoding and verification of the file's contents.
File data:
Data compressed according to the method defined by the local file header.
Data descriptor:
Optional information: Repetition of CRC-32 checksum, original and compressed file size.
Usage is provided for applications that are not able to access the local file header afterwards, e.g. for online compression during data transfers.
...  
File N     "  "
Archive decryption header Optional information for decryption of the central directory structure.
Archive extra data record     "  "
central directory List of file headers (containing file name, size, attributes, CRC-32 checksum, start addresses, etc.). A subset of information is redundantly provided by the local file headers.
zip64 end of central directory record Termination of the "central directory" in ZIP64™ format (intended for files larger than 232 byte.)
zip64 end of central directory locator     "  "
end of central directory record Termination of the "central directory", e.g. providing information about the location of the central directory (offset address, identification of file or disk containing the directory, size of the directory, number of files, etc.)

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