Buffer

class cometa.buffer.Buffer(ptr)[source]

Bases: object

A dynamic, reference-counted byte buffer with configurable exponential growth.

This class wraps the C cardano_buffer_t type. It behaves similarly to a mutable Python bytearray, offering automatic resizing, slicing, and binary data manipulation.

classmethod new(capacity)[source]

Creates a new dynamic buffer with the specified initial capacity.

Parameters:: capacity (int) – The initial allocation size in bytes.
Returns:: An empty buffer with the reserved capacity.
Return type:: Buffer

classmethod from_bytes(data)[source]

Creates a new buffer initialized with a copy of the given data.

Parameters:: data (bytes) – The raw bytes to copy into the buffer.
Returns:: A new buffer containing the data.
Return type:: Buffer

classmethod from_hex(hex_string)[source]

Creates a new buffer by decoding a given hex string.

Parameters:: hex_string (str) – A hexadecimal string (e.g., “deadbeef”).
Returns:: A new buffer containing the decoded bytes.
Return type:: Buffer

property size: int: Returns the current number of used bytes in the buffer.

property capacity: int: Returns the total allocated memory capacity of the buffer.

compare(other)[source]

Compares two buffer objects lexicographically.

Returns:: < 0 if self < other, 0 if equal, > 0 if self > other.
Return type:: int
Parameters:: other (Buffer)

clone()[source]

Creates a deep copy of the buffer.

Return type:: Buffer

copy_bytes()[source]

Returns a copy of the raw bytes (alias for to_bytes).

Return type:: bytes

to_bytes()[source]

Converts the internal data to a Python bytes object.

Return type:: bytes

to_hex()[source]

Returns the hexadecimal string representation (e.g., ‘deadbeef’).

Return type:: str

to_str()[source]

Converts the buffer content to a UTF-8 string. Assumes the buffer contains valid UTF-8 encoded text.

Return type:: str

set_size(size)[source]

Sets the logical size of the buffer.

Warning: This does not allocate new memory; it only updates the internal usage marker. The new size must not exceed the current capacity.

Parameters:: size (int) – The new size.
Return type:: None

memzero()[source]

Securely wipes the contents of the buffer from memory. Useful for clearing sensitive data like private keys.

Return type:: None

write(data)[source]

Appends raw bytes to the end of the buffer. The buffer will automatically resize if necessary.

Parameters:: data (bytes)
Return type:: None

read(length)[source]

Reads a specified amount of data from the current cursor position.

Parameters:: length (int) – Number of bytes to read.
Returns:: The data read.
Return type:: bytes

seek(position)[source]

Repositions the internal cursor within the buffer.

Parameters:: position (int) – The offset to seek to.
Return type:: None

write_uint16(value, order=ByteOrder.LITTLE_ENDIAN)[source]

Writes a 16-bit unsigned integer to the buffer.

Parameters:

value (int)
order (ByteOrder)

Return type:

None

write_uint32(value, order=ByteOrder.LITTLE_ENDIAN)[source]

Writes a 32-bit unsigned integer to the buffer.

Parameters:

value (int)
order (ByteOrder)

Return type:

None

write_uint64(value, order=ByteOrder.LITTLE_ENDIAN)[source]

Writes a 64-bit unsigned integer to the buffer.

Parameters:

value (int)
order (ByteOrder)

Return type:

None

write_int16(value, order=ByteOrder.LITTLE_ENDIAN)[source]

Writes a 16-bit signed integer to the buffer.

Parameters:

value (int)
order (ByteOrder)

Return type:

None

write_int32(value, order=ByteOrder.LITTLE_ENDIAN)[source]

Writes a 32-bit signed integer to the buffer.

Parameters:

value (int)
order (ByteOrder)

Return type:

None

write_int64(value, order=ByteOrder.LITTLE_ENDIAN)[source]

Writes a 64-bit signed integer to the buffer.

Parameters:

value (int)
order (ByteOrder)

Return type:

None

write_float(value, order=ByteOrder.LITTLE_ENDIAN)[source]

Writes a 32-bit floating point number to the buffer.

Parameters:

value (float)
order (ByteOrder)

Return type:

None

write_double(value, order=ByteOrder.LITTLE_ENDIAN)[source]

Writes a 64-bit floating point number (double) to the buffer.

Parameters:

value (float)
order (ByteOrder)

Return type:

None

read_uint16(order=ByteOrder.LITTLE_ENDIAN)[source]

Reads a 16-bit unsigned integer from the current position.

Parameters:: order (ByteOrder)
Return type:: int

read_uint32(order=ByteOrder.LITTLE_ENDIAN)[source]

Reads a 32-bit unsigned integer from the current position.

Parameters:: order (ByteOrder)
Return type:: int

read_uint64(order=ByteOrder.LITTLE_ENDIAN)[source]

Reads a 64-bit unsigned integer from the current position.

Parameters:: order (ByteOrder)
Return type:: int

read_int16(order=ByteOrder.LITTLE_ENDIAN)[source]

Reads a 16-bit signed integer from the current position.

Parameters:: order (ByteOrder)
Return type:: int

read_int32(order=ByteOrder.LITTLE_ENDIAN)[source]

Reads a 32-bit signed integer from the current position.

Parameters:: order (ByteOrder)
Return type:: int

read_int64(order=ByteOrder.LITTLE_ENDIAN)[source]

Reads a 64-bit signed integer from the current position.

Parameters:: order (ByteOrder)
Return type:: int

read_float(order=ByteOrder.LITTLE_ENDIAN)[source]

Reads a 32-bit floating point number from the current position.

Parameters:: order (ByteOrder)
Return type:: float

read_double(order=ByteOrder.LITTLE_ENDIAN)[source]

Reads a 64-bit floating point number from the current position.

Parameters:: order (ByteOrder)
Return type:: float

set_last_error(message)[source]

Records an error message in the buffer’s error register.

Parameters:: message (str)
Return type:: None

get_last_error()[source]

Retrieves the last error message recorded for this buffer.

Return type:: str

__init__(ptr)[source]

Internal constructor.

Use factories like Buffer.new(), Buffer.from_bytes(), etc. instead.

Return type:: None

__enter__()[source]

Context manager entry (no-op).

Return type:: Buffer

__exit__(exc_type, exc_val, exc_tb)[source]

Context manager exit (no-op).

Return type:: None

__len__()[source]

Returns the number of bytes in the buffer.

Return type:: int

__bool__()[source]

Returns True if the buffer is not empty, False otherwise.

Return type:: bool

__bytes__()[source]

Converts the buffer content to a Python immutable bytes object.

Return type:: bytes

__getitem__(key: int) → int[source]

__getitem__(key: slice) → Buffer

Retrieve a byte or a slice of the buffer.

Parameters:: key (int | slice) – The index or slice range.
Returns:: If key is an int, returns the byte value (0-255). Buffer: If key is a slice, returns a new Buffer containing the slice.
Return type:: int

__setitem__(key, value)[source]

Modifies a byte at the specified index.

Parameters:

key (int) – The index to modify.
value (int) – The new byte value (0-255).

Return type:

None

__iter__()[source]

Iterates over the bytes in the buffer.

Return type:: Iterator[int]

__eq__(other)[source]

Checks if two buffers contain identical data.

Parameters:: other (object)
Return type:: bool

__add__(other)[source]

Concatenates two buffers (lhs + rhs) into a new Buffer.

Parameters:: other (Buffer)
Return type:: Buffer

__repr__()[source]

Returns a string representation of the buffer.

Return type:: str

__lt__(other)[source]

Returns True if this buffer is lexicographically less than the other.

Parameters:: other (Buffer)
Return type:: bool

__le__(other)[source]

Returns True if this buffer is lexicographically less than or equal to the other.

Parameters:: other (Buffer)
Return type:: bool

__gt__(other)[source]

Returns True if this buffer is lexicographically greater than the other.

Parameters:: other (Buffer)
Return type:: bool

__hash__ = None

__ge__(other)[source]

Returns True if this buffer is lexicographically greater than or equal to the other.

Parameters:: other (Buffer)
Return type:: bool