fasthex

fasthex — a very fast hex dumper (written in Rust), with all features that other hex dumpers have too.

Table of Contents

• Quick Start
• Benchmarks
• Uninstall
• Usage
• Features
• Example Output
• How It Works
• Testing Conditions

Quick Start

• On Arch

paru -S fasthex 
# or fasthex-bin for a prebuilt release

• Non-arch

cargo install fasthex

Note: Make sure ~/.cargo/bin is in your PATH. It's added automatically by rustup, but if fasthex isn't found, add this to your shell config file:

# If you use Bash:
export PATH="$HOME/.cargo/bin:$PATH"

# If you use Fish:
fish_add_path $HOME/.cargo/bin

# If you use Zsh:
export PATH="$PATH:$HOME/.cargo/bin"

# Use it!
fasthex /path/to/file

Benchmarks

Benchmark 1: 1.5 GiB file (output to /dev/null)

¹ --color=never was used to avoid colors.

Benchmark 2: 69 GiB file (output to /dev/null)

Uninstall

cargo uninstall fasthex

Usage

Basic usage

# Display a file
fasthex /path/to/file

# Pipe it (faster with zero-copy output)
fasthex /path/to/file > output.txt

# Skip first 1 KiB and read only 512 bytes
fasthex -s 1KiB -n 512 /path/to/file

# Display with colors
fasthex --color=always /path/to/file

# Binary display
fasthex -b /path/to/file

Common use cases

# Test on RAM disk (avoids SSD/HDD bottleneck)
sudo mkdir -p /mnt/ramdisk
sudo mount -t tmpfs -o size=2G tmpfs /mnt/ramdisk
cp /path/to/file /mnt/ramdisk
time fasthex /mnt/ramdisk/file > /dev/null

# Measure time with `time`
time fasthex /path/to/file

# Interactive viewing
fasthex /path/to/file | less

Features

Supported Output Formats

• Octal (-o)
• Decimal (-d)
• Binary (-b)
• Colored output (--color=always)
• ... and more!

Display Options

• ASCII representation (default, disable with -A)
• Line squeezing for identical lines (-w)
• Arbitrary skip/length with size suffixes (KiB, MiB, GiB, TiB, PiB, EiB, ZiB, YiB)

Example Output

❯ fasthex3 /bin/ls | head
00000000: 7f 45 4c 46 02 01 01 00  00 00 00 00 00 00 00 00  |.ELF............|
00000010: 03 00 3e 00 01 00 00 00  f0 54 00 00 00 00 00 00  |..>......T......|
00000020: 40 00 00 00 00 00 00 00  a8 73 02 00 00 00 00 00  |@........s......|
00000030: 00 00 00 00 40 00 38 00  0e 00 40 00 1c 00 1b 00  |....@.8...@.....|
00000040: 06 00 00 00 04 00 00 00  40 00 00 00 00 00 00 00  |........@.......|
00000050: 40 00 00 00 00 00 00 00  40 00 00 00 00 00 00 00  |@.......@.......|
00000060: 10 03 00 00 00 00 00 00  10 03 00 00 00 00 00 00  |................|
00000070: 08 00 00 00 00 00 00 00  03 00 00 00 04 00 00 00  |................|
00000080: 74 03 00 00 00 00 00 00  74 03 00 00 00 00 00 00  |t.......t.......|
00000090: 74 03 00 00 00 00 00 00  1c 00 00 00 00 00 00 00  |t...............|

How It Works:

1. mmap path: output formatted in parallel with rayon in 64 MiB chunks.
2. AVX2 path: processes 32 bytes (2 rows) per SIMD call; falls back to SSE4.1/SSSE3 (16 bytes / 1 row) or scalar.
3. Double-buffered I/O: a dedicated writer thread drains completed chunks while rayon formats the next one.
4. MADV_SEQUENTIAL on open + MADV_WILLNEED two chunks ahead to hide mmap page-fault latency.
5. Zero-copy output via an internal pipe pair: formatted buffer → vmsplice (userspace pages → kernel pipe, zero-copy) → splice (kernel pipe → stdout fd, zero-copy) This path works regardless of what stdout is (/dev/null, file, pipe, socket) because we own the intermediate pipe. Falls back to write_all if splice rejects the stdout fd (e.g. a tty).
6. Streaming (stdin) path uses a 4 MiB write buffer.

Full Help

fasthex 0.3.0 - a very fast hex dumper

Usage:
  fasthex [options] [file]...
  fasthex -r [options] [file] [-j <offset>]
  fasthex [options] -          read from stdin explicitly

Multiple files are concatenated and treated as one stream.
If no file is given, reads from stdin.

OUTPUT FORMAT
  Rule: lowercase = one-byte mode, UPPERCASE = two-byte mode.

      (default)               canonical hex + ASCII display
  -x, --hex                   one-byte hexadecimal display
  -X, --hex-wide              two-byte hexadecimal display
  -o, --octal                 one-byte octal display
  -O, --octal-wide            two-byte octal display
  -d, --decimal               one-byte decimal display
  -D, --decimal-wide          two-byte decimal display
  -c, --chars                 one-byte character display
  -b, --binary                binary display (8 bits per byte)
  -p, --plain                 plain hex string, no offset or ASCII
  -i, --include               C include file style output
  -r, --reverse               convert hex dump back to binary

LAYOUT
  -W, --width <N>             bytes per row (default: 16)
  -g, --group <N>             bytes per group: 1, 2, 4, 8
  -E, --endian <MODE>         big | little  (default: big)
  -B, --border <STYLE>        none | ascii | unicode  (default: none)
  -A, --no-ascii              hide the ASCII panel
  -P, --no-position           hide the offset/position column

OFFSET & NAVIGATION
  -s, --skip <N>              skip first N bytes (negative = from end)
  -n, --length <N>            read only N bytes
  -j, --jump <N>              bias added to every displayed offset
  -u, --uppercase             uppercase hex digits (A-F)
      --offset-dec            show offsets in decimal

COLOR
  -L, --color <WHEN>          auto | always | never  (default: auto)
  -S, --scheme <NAME>         default | type | gradient
  -T, --table <MODE>          ascii | default | braille | cp437 | ebcdic

FILTERING & FLOW
  -w, --squeeze               replace identical rows with '*'
  -m, --max-lines <N>         stop after N output lines
  -q, --quiet                 suppress warnings

CUSTOM FORMAT
  -F, --format <FMT>          hexdump -e style format string
  -f, --format-file <FILE>    read format strings from file

MISC
  -h, --help                  show this help
  -v, --version               show version

SIZE SUFFIXES: KiB/K/MiB/M/GiB/G/TiB/T/PiB/P/EiB/E  kB/MB/GB/TB/PB/EB  0x…

Testing Conditions

https://gist.github.com/CallMeAlphabet/4b7022c4b1a8849e6943526de6a23582