bitcoin-script

Bitcoin scripts inline in Rust.

Usage

This crate exports a bitcoin_script! macro which can be used to build Bitcoin scripts. The macro returns the Script type from the bitcoin crate.

Example:

#![feature(proc_macro_hygiene)]

use bitcoin_script::bitcoin_script;

let htlc_script = bitcoin_script! {
    OP_IF
        OP_SHA256 <digest> OP_EQUALVERIFY OP_DUP OP_SHA256 <seller_pubkey_hash>
    OP_ELSE
        100 OP_CSV OP_DROP OP_DUP OP_HASH160 <buyer_pubkey_hash>
    OP_ENDIF
    OP_EQUALVERIFY
    OP_CHECKSIG
};

NOTE: As of rustc 1.41, the Rust compiler prevents using procedural macros as expressions. To use this macro you'll need to be on nightly and add #![feature(proc_macro_hygiene)] to the root of your crate. This will be stablized in the near future, the PR can be found here: https://github.com/rust-lang/rust/pull/68717

Syntax

Scripts are based on the standard syntax made up of opcodes, base-10 integers, or hex string literals. Additionally, Rust expressions can be interpolated in order to support dynamically capturing Rust variables or computing values (delimited by <angle brackets>).

Whitespace is ignored - scripts can be formatted in the author's preferred style.

Opcodes

All normal opcodes are available, in the form OP_X.

let script = bitcoin_script!(OP_CHECKSIG OP_VERIFY);

Integer Literals

Positive and negative 64-bit integer literals can be used, and will resolve to their most efficient encoding.

For example:

2 will resolve to OP_PUSHNUM_2 (0x52)
255 will resolve to a length-delimited varint: 0x02ff00 (note the extra zero byte, due to the way Bitcoin scripts use the most-significant bit to represent the sign)`

let script = bitcoin_script!(123 -456 999999);

Hex Literals

Hex strings can be specified, prefixed with 0x.

let script = bitcoin_script!(
    0x0102030405060708090a0b0c0d0e0f OP_HASH160
);

Escape Sequences

Dynamic Rust expressions are supported inside the script, surrounded by angle brackets. In many cases, this will just be a variable identifier, but this can also be a function call or arithmetic.

Rust expressions of the following types are supported:

i64
Vec<u8>
bitcoin::PublicKey

let bytes = vec![1, 2, 3];

let script = bitcoin_script! {
    <bytes> OP_CHECKSIGVERIFY

    <2016 * 5> OP_CSV
};