Method addData

txscript/scriptbuilder.go:159–200

addData is the internal function that actually pushes the passed data to the end of the script. It automatically chooses canonical opcodes depending on the length of the data. A zero length buffer will lead to a push of empty data onto the stack (OP_0). No data limits are enforced with this funct

(data []byte)

// the length of the data.  A zero length buffer will lead to a push of empty
// data onto the stack (OP_0).  No data limits are enforced with this function.
func (b *ScriptBuilder) addData(data []byte) *ScriptBuilder {
	dataLen := len(data)

	// When the data consists of a single number that can be represented
	// by one of the "small integer" opcodes, use that opcode instead of
	// a data push opcode followed by the number.
	if dataLen == 0 || dataLen == 1 && data[0] == 0 {
		b.script = append(b.script, OP_0)
		return b
	} else if dataLen == 1 && data[0] <= 16 {
		b.script = append(b.script, (OP_1-1)+data[0])
		return b
	} else if dataLen == 1 && data[0] == 0x81 {
		b.script = append(b.script, byte(OP_1NEGATE))
		return b
	}

	// Use one of the OP_DATA_# opcodes if the length of the data is small
	// enough so the data push instruction is only a single byte.
	// Otherwise, choose the smallest possible OP_PUSHDATA# opcode that
	// can represent the length of the data.
	if dataLen < OP_PUSHDATA1 {
		b.script = append(b.script, byte((OP_DATA_1-1)+dataLen))
	} else if dataLen <= 0xff {
		b.script = append(b.script, OP_PUSHDATA1, byte(dataLen))
	} else if dataLen <= 0xffff {
		buf := make([]byte, 2)
		binary.LittleEndian.PutUint16(buf, uint16(dataLen))
		b.script = append(b.script, OP_PUSHDATA2)
		b.script = append(b.script, buf...)
	} else {
		buf := make([]byte, 4)
		binary.LittleEndian.PutUint32(buf, uint32(dataLen))
		b.script = append(b.script, OP_PUSHDATA4)
		b.script = append(b.script, buf...)
	}

	// Append the actual data.
	b.script = append(b.script, data...)

	return b
}

// AddFullData should not typically be used by ordinary users as it does not
// include the checks which prevent data pushes larger than the maximum allowed