cmprs 🗜️#

Self-extracting executable compression

Why does this exist? 🤔#

🍎 macOS Reality Check: UPX is fantastic for executable compression, but it doesn't work with bun build --compile artifacts on MacOS, so I guess it is pretty widespread.

What does it do? ✨#

🗜️ Compress: cmprs takes any executable and creates a compressed self-extracting version using zstd compression

🎭 Self-Extract: The compressed executable automatically decompresses itself when run, replacing the compressed version with the original

⚡ Process Replacement: Uses exec() to completely replace the decompressor process with the actual program - no wrapper processes or performance overhead

🧹 One-Time Cost: After the first run, the executable is permanently decompressed, so subsequent runs have zero decompression overhead

How it works 🔧#

# Compress an executable
./cmprs my_program -o my_program.cmprs

# Run the compressed version (decompresses automatically)
./my_program.cmprs args...

# Subsequent runs are instant (already decompressed)
./my_program.cmprs more_args...

Architecture 🏗️#

🔗 Format: [dcmprs binary][MAGIC_HEADER][SHA256][zstd compressed data]

🎯 Smart Execution:

Finds the magic boundary in the self-extracting executable
Decompresses the original program to a temporary file
Simultaneously replaces the compressed file with decompressed content
Uses exec() to become the original program (no wrapper process)

🛡️ Secure: Uses proper temporary file handling with automatic cleanup

Building 🔨#

# Build both tools
cargo build --release

# The magic happens in target/release/
ls target/release/{cmprs,dcmprs}

Technical Details 🤓#

🎛️ Compression: zstd for excellent compression ratios and fast decompression

🧵 Parallel: File replacement happens in parallel with program execution

📦 Minimal Overhead: dcmprs is aggressively optimized for size (opt-level="z", LTO, stripped)

🔄 Process Hygiene: Complete process replacement means proper signal handling and exit codes

Status 📊#

🧪 Experimental: This is a proof of concept exploring alternatives to UPX on macOS

🎯 Works: Successfully compresses and self-extracts executables

🚧 Evolving: Open to improvements and real-world testing

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