Decode Bitcoin raw transactions to bitcoinjs-lib's Transaction object with CoffeeScript

bitcoin-decoderawtransaction.coffee

decode_raw_tx = do ->
  { Transaction, TransactionIn, TransactionOut } = Bitcoin
  { bytesToBase64 } = Crypto.util


  # Parse an bytearray of length `size` as an integer
  # Works for numbers up to 32-bit only
  parse_int = (size) -> (bytes) ->
    n = 0
    n += (bytes.shift() & 0xff) << (8 * i) for i in [0...size]
    n
  u8  = (bytes) -> bytes.shift()
  u16 = parse_int 2
  u32 = parse_int 4
  # 64 bit numbers are kept as bytes
  # (bitcoinjs-lib expects them that way)
  u64 = (bytes) -> bytes.splice 0, 8

  # https://en.bitcoin.it/wiki/Protocol_specification#Variable_length_integer
  varint = (bytes) ->
    switch n = u8 bytes
      when 0xfd then u16 bytes
      when 0xfe then u32 bytes
      when 0xff then u64 bytes
      else n

  # https://en.bitcoin.it/wiki/Protocol_specification#Variable_length_string
  varchar = (bytes) -> bytes.splice 0, varint bytes

  (bytes) ->
    bytes = bytes.slice() # clone
    ver = u32 bytes
    throw new Error 'Unsupported version' unless ver is 0x01

    tx = new Transaction

    # Parse inputs
    in_count = varint bytes
    for [0...in_count]
      tx.addInput new TransactionIn
        outpoint:
          hash: bytesToBase64 bytes.splice 0, 32
          index: u32 bytes
        script: varchar bytes
        seq: u32 bytes

    # Parse outputs
    out_count = varint bytes
    for [0...out_count]
      tx.addOutput new TransactionOut
        value: u64 bytes
        script: varchar bytes

    tx.lock_time = u32 bytes

    tx

This is great! I'm using bitcoind to create raw transactions, and I need to decode them so I can check to make sure they are correct.

I need to sign a bitcoin raw transaction on the client-side and be able to send it via sendrawtransaction next. I have no idea how I'm going to do it yet. It's possible that bitcoinjs-lib supports this format, but I haven't figured it out yet.

@kyledrake Did you find a way to sign raw transactions on the client without using bitcoind? Need to do the same if possible. Thanks!