# Class BSV::Wallet::Wire::Writer <a id="class-BSV-Wallet-Wire-Writer"></a>

**Inherits:** `Object`

Writer accumulates bytes into a binary string buffer.

## Attributes
### `buf` [R] <a id="attribute-i-buf"></a> <a id="buf-instance_method"></a>
Returns the value of attribute buf.

## Public Instance Methods
### `initialize()` <a id="method-i-initialize"></a> <a id="initialize-instance_method"></a>
- **@return** [Writer] a new instance of Writer

### `write_byte(byte)` <a id="method-i-write_byte"></a> <a id="write_byte-instance_method"></a>
Write a raw byte.

### `write_bytes(bytes)` <a id="method-i-write_bytes"></a> <a id="write_bytes-instance_method"></a>
Write raw bytes (binary string).

### `write_int_bytes(bytes)` <a id="method-i-write_int_bytes"></a> <a id="write_int_bytes-instance_method"></a>
Write a varint length-prefixed byte array (WriteIntBytes in Go).
- **@param** `bytes` [String, nil] binary string; nil or empty → write varint 0

### `write_int_from_base64(base64_str)` <a id="method-i-write_int_from_base64"></a> <a id="write_int_from_base64-instance_method"></a>
Write a binary value encoded as a Base64 string on the wire. Decodes the
Base64 string and writes the raw bytes prefixed by varint length.
- **@param** `base64_str` [String] standard Base64-encoded string

### `write_negative_one()` <a id="method-i-write_negative_one"></a> <a id="write_negative_one-instance_method"></a>
Write the NegativeOne sentinel (MaxUint64 as a 9-byte varint: 9 × 0xFF). Used
as a nil sentinel for optional fields in Go-compatible encoding.

### `write_optional_bool(value)` <a id="method-i-write_optional_bool"></a> <a id="write_optional_bool-instance_method"></a>
Write an optional boolean as a single byte (Go/BRC-103 convention). nil →
0xFF, false → 0x00, true → 0x01

### `write_optional_bytes_with_flag(bytes, fixed_size: = nil)` <a id="method-i-write_optional_bytes_with_flag"></a> <a id="write_optional_bytes_with_flag-instance_method"></a>
Write optional bytes with a 1-byte flag prefix (Go BytesOptionWithFlag).
nil/empty → 0x00; else → 0x01 + varint_len + bytes (or fixed_size bytes).
- **@param** `bytes` [String, nil] binary data
- **@param** `fixed_size` [Integer, nil] if set, omit the varint length prefix

### `write_optional_string(str)` <a id="method-i-write_optional_string"></a> <a id="write_optional_string-instance_method"></a>
Write an optional string: nil or empty → NegativeOne; else varint len + bytes.
Matches Go WriteOptionalString.
- **@param** `str` [String, nil]

### `write_optional_uint32(n)` <a id="method-i-write_optional_uint32"></a> <a id="write_optional_uint32-instance_method"></a>
Write an optional uint32: nil → NegativeOne; else varint.
- **@param** `n` [Integer, nil]

### `write_outpoint(txid_hex, vout)` <a id="method-i-write_outpoint"></a> <a id="write_outpoint-instance_method"></a>
Write an outpoint: 32-byte display-order txid followed by varint vout.

Go encodeOutpoint calls WriteBytesReverse(`Txid`) which writes the
wire-order (chainhash) bytes reversed — i.e. display order on the wire. The
vout is a varint, not a fixed 4-byte LE integer.
- **@param** `txid_hex` [String] 64-char display-order hex txid
- **@param** `vout` [Integer] output index

### `write_privileged_params(privileged, reason)` <a id="method-i-write_privileged_params"></a> <a id="write_privileged_params-instance_method"></a>
Write the privileged flag and reason (Go encodePrivilegedParams). privileged:
nil → NegativeOneByte (0xFF), false → 0x00, true → 0x01. reason: nil or empty
→ NegativeOneByte; else varint len + bytes.

### `write_satoshis(n)` <a id="method-i-write_satoshis"></a> <a id="write_satoshis-instance_method"></a>
Write a satoshi amount as 8-byte little-endian uint64.

### `write_str_with_varint_len(str)` <a id="method-i-write_str_with_varint_len"></a> <a id="write_str_with_varint_len-instance_method"></a>
Write a UTF-8 string prefixed by its byte length as a varint.

### `write_string(str)` <a id="method-i-write_string"></a> <a id="write_string-instance_method"></a>
Write a varint-len string (always present, 0-length for nil/empty). Matches Go
WriteString which always writes the length prefix.
- **@param** `str` [String, nil]

### `write_string_map(map)` <a id="method-i-write_string_map"></a> <a id="write_string_map-instance_method"></a>
Write a string map (Hash<String,String>) sorted by key. Matches Go
WriteStringMap.
- **@param** `map` [Hash, nil]

### `write_string_slice(arr)` <a id="method-i-write_string_slice"></a> <a id="write_string_slice-instance_method"></a>
Write an array of strings: nil → NegativeOne; else varint count + each as
optional string. Matches Go WriteStringSlice.
- **@param** `arr` [Array<String>, nil]

### `write_txid_slice(txids)` <a id="method-i-write_txid_slice"></a> <a id="write_txid_slice-instance_method"></a>
Write a txid slice (array of 32-byte txids in wire order). nil → NegativeOne;
else varint count + 32 raw bytes per txid. Txids are passed as 64-char
display-order hex; written as-is (no byte reversal) to match Go WriteTxidSlice
which writes `txID` (wire-order bytes directly).
- **@param** `txids` [Array<String>, nil] 64-char display-order hex strings

### `write_varint(n)` <a id="method-i-write_varint"></a> <a id="write_varint-instance_method"></a>
Write a Bitcoin varint.