Feng is a command line app for querying, presenting and extracting structured binary data, using a yaml-based template format that allows for specifying the file structure.

Usage

Usage: feng <filename>

A binary template reader and data presenter.

Arguments:
  <filename>

Flags:
  -h, --help                  Show context-sensitive help.
      --template=STRING       Parse file using this template.
  -x, --extract               Extract data streams from input file.
  -p, --pack-dir=STRING       Packs directory of data streams according to filename layout.
  -d, --out-dir=STRING        Write files to this directory. Requires --extract
  -o, --out-file=STRING       Output filename. Requires --pack-dir
      --offset=INT-64         Starting offset (default is 0).
      --raw                   Show raw values
      --local-time            Show timestamps in local timezone (default is UTC).
      --brief                 Show brief file information.
      --tree                  Show parsed file structure tree.
      --decimal               Show offsets in decimal (default is hex).
      --unmapped              [Dev] Print a report on unmapped bytes.
      --overlapping           [Dev] Print a report on overlapping bytes.
      --debug                 [Dev] Enable debug logging
      --time                  [Dev] Measure where processing time is spent.
      --cpu-profile=STRING    [Dev] Create CPU profile.
      --mem-profile=STRING    [Dev] Create memory profile.

Extracting data streams

If feng recognizes the input file, you can extract the data streams from it.

feng file.ext -x --out-dir extracted-streams

Hint: A data stream is of a type like "compressed:zlib", "raw:u8" or "encrypted:u8".

Packing the extracted data streams

TODO, #3

After making changes to the files in extracted-streams, you can reconstruct a file based on the original file layout.

feng file.ext -p extracted-streams -o file-modded.ext

Installation

Binary releases can be downloaded from the Releases page.

Installation from git

You need golang installed on your system. Install the feng command:

go install github.com/martinlindhe/feng/cmd/feng@latest

Template example

Binary formats are specified in a template file. See TEMPLATE.md for the template format documentation.

Here's the OpenType Font table parsing:

endian: big

magic:
  - offset: 0000
    match: c'OTTO'

structs:
  header:
    ascii[4] Magic: c'OTTO'
    u16 TableCount: ??
    u16 SearchRange: ??
    u16 EntrySelector: ??
    u16 RangeShift: ??

  table:
    ascii[4] Tag: ??
    label: self.Tag

    u32 Checksum: ??
    u32 Offset: ??
    u32 Length: ??

    offset: self.Offset
    u8[self.Length] Data: ??
    u8[alignment(self.Length, 4)] Padding: ??
    offset: restore

layout:
  - header Header
  - table[Header.TableCount] Table

Mapping a file with the above structure would result in something like smoketest/reference/fonts/otf.

Template is from templates/fonts/otf.yml.

User templates

feng reads user templates from ~/.config/feng, or from a custom path with the --template argument.