Encode a commitment transaction (SegWit format with witness).

SegWit format:

• version (4 bytes LE)
• marker (0x00)
• flag (0x01)
• input count (varint)
• inputs
• output count (varint)
• outputs
• witness data
• locktime (4 bytes LE)

Note: The witness is empty (just count=0) since the commitment tx spending the funding output requires external signatures.

Encode an HTLC transaction (SegWit format with witness).

HTLC transactions have a single input (the commitment tx HTLC output) and a single output (the to_local-style delayed output).

Encode a closing transaction (SegWit format with witness).

Closing transactions have a single input (the funding output) and one or two outputs (to_local and/or to_remote).

Encode a commitment transaction for signing (stripped format).

The stripped format omits the SegWit marker, flag, and witness data. This is the format used to compute the sighash for signing.

Format:

• version (4 bytes LE)
• input count (varint)
• inputs
• output count (varint)
• outputs
• locktime (4 bytes LE)

Encode a witness stack.

Format: varint item count + (varint length + data) for each item

>>> encode_witness (Witness [sig, pubkey])
<varint 2><varint sigLen><sig><varint pkLen><pubkey>

Encode a funding witness (2-of-2 multisig).

The witness stack is: 0 sig1 sig2 witnessScript

Signatures must be ordered to match pubkey order in the funding script.

>>> encode_funding_witness sig1 sig2 fundingScript
<witness with 4 items: empty, sig1, sig2, script>

Encode a value as a Bitcoin varint (CompactSize).

Encoding scheme:

• 0-252: 1 byte
• 253-65535: 0xFD followed by 2 bytes LE
• 65536-4294967295: 0xFE followed by 4 bytes LE
• larger: 0xFF followed by 8 bytes LE

>>> encode_varint 100
"\x64"
>>> encode_varint 1000
"\xFD\xE8\x03"

Encode a 32-bit value in little-endian format.

>>> encode_le32 0x12345678
"\x78\x56\x34\x12"

Encode a 64-bit value in little-endian format.

>>> encode_le64 0x123456789ABCDEF0
"\xF0\xDE\xBC\x9A\x78\x56\x34\x12"

Encode an outpoint (txid + output index).

Format: 32 bytes txid (already LE in TxId) + 4 bytes output index LE

>>> encode_outpoint (Outpoint txid 0)
<32-byte txid><4-byte index>

Encode a transaction output.

Format: 8 bytes value LE + varint scriptPubKey length + scriptPubKey

>>> encode_output (TxOutput (Satoshi 100000) script OutputToLocal)
<8-byte value><varint length><scriptPubKey>