tokenization_binaryllm.py

from __future__ import annotations

import json
import os
import re
from typing import Dict, List, Optional, Tuple

from transformers import PreTrainedTokenizer


class BinaryLLMTokenizer(PreTrainedTokenizer):
    model_input_names = ["input_ids", "attention_mask"]

    TOKEN_RE = re.compile(r"^<U([0-9A-Fa-f]{4})>$")

    def __init__(
        self,
        bos_token: str = "<BOS>",
        eos_token: str = "<EOS>",
        unk_token: str = "<UNK>",
        pad_token: Optional[str] = None,
        **kwargs,
    ):
        # base ids 0..65535 reserved for radix tokens (strict)
        self._base_vocab_size = 65536

        # reserve ids
        self._bos_id = 65536
        self._eos_id = 65537

        # UNK is an alias to EOS to preserve radix purity (no new base id)
        self._unk_id = self._eos_id

        # special token strings
        self._bos_str = bos_token
        self._eos_str = eos_token
        self._unk_str = unk_token
        self._pad_str = pad_token

        super().__init__(
            bos_token=bos_token,
            eos_token=eos_token,
            unk_token=unk_token,
            pad_token=pad_token,
            **kwargs,
        )

    @property
    def vocab_size(self) -> int:
        return 65538

    def get_vocab(self) -> Dict[str, int]:
        # IMPORTANT: never call self.unk_token_id here (it triggers recursion)
        v = {
            self._bos_str: self._bos_id,
            self._eos_str: self._eos_id,
            self._unk_str: self._unk_id,
        }
        if self.pad_token is not None:
            # if pad_token == "<EOS>", it will map to eos id via _convert_token_to_id()
            v[self.pad_token] = self._convert_token_to_id(self.pad_token)
        return v

    def _tokenize(self, text: str) -> List[str]:
        ids = self._encode_to_uint16(text)
        return [self._id_to_token_base(i) for i in ids]

    def _convert_token_to_id(self, token: str) -> int:
        if token == self._bos_str:
            return self._bos_id
        if token == self._eos_str:
            return self._eos_id
        if token == self._unk_str:
            return self._unk_id

        if self.pad_token is not None and token == self.pad_token:
            # common case: pad_token is "<EOS>"
            if self.pad_token == self._eos_str:
                return self._eos_id
            # otherwise: no dedicated PAD id in this vocab, alias to EOS
            return self._eos_id

        m = self.TOKEN_RE.match(token)
        if m:
            return int(m.group(1), 16)

        return self._unk_id

    def _convert_id_to_token(self, index: int) -> str:
        if index == self._bos_id:
            return self._bos_str
        if index == self._eos_id:
            return self._eos_str
        if index == self._unk_id:
            return self._unk_str
        if self.pad_token is not None and index == self.pad_token_id:
            return self.pad_token

        if 0 <= index < self._base_vocab_size:
            return self._id_to_token_base(index)

        return self._unk_str

    def convert_tokens_to_string(self, tokens: List[str]) -> str:
        ids: List[int] = []
        for t in tokens:
            if t in (self._bos_str, self._eos_str, self._unk_str):
                continue
            if self.pad_token is not None and t == self.pad_token:
                continue
            m = self.TOKEN_RE.match(t)
            if m:
                ids.append(int(m.group(1), 16))
        return self._decode_from_uint16(ids)

    def build_inputs_with_special_tokens(
        self,
        token_ids_0: List[int],
        token_ids_1: Optional[List[int]] = None,
    ) -> List[int]:
        if token_ids_1 is None:
            return [self._bos_id] + token_ids_0 + [self._eos_id]
        return [self._bos_id] + token_ids_0 + [self._eos_id] + token_ids_1 + [self._eos_id]

    def get_special_tokens_mask(
        self,
        token_ids_0: List[int],
        token_ids_1: Optional[List[int]] = None,
        already_has_special_tokens: bool = False,
    ) -> List[int]:
        pad_id = self.pad_token_id if self.pad_token is not None else -1

        if already_has_special_tokens:
            return [
                1 if t in (self._bos_id, self._eos_id, self._unk_id, pad_id) else 0
                for t in token_ids_0
            ]

        if token_ids_1 is None:
            return [1] + [0] * len(token_ids_0) + [1]
        return [1] + [0] * len(token_ids_0) + [1] + [0] * len(token_ids_1) + [1]

    def create_token_type_ids_from_sequences(
        self,
        token_ids_0: List[int],
        token_ids_1: Optional[List[int]] = None,
    ) -> List[int]:
        if token_ids_1 is None:
            return [0] * (len(token_ids_0) + 2)
        return [0] * (len(token_ids_0) + len(token_ids_1) + 3)

    def save_vocabulary(self, save_directory: str, filename_prefix: Optional[str] = None) -> Tuple[str]:
        if not os.path.isdir(save_directory):
            os.makedirs(save_directory, exist_ok=True)

        name = (filename_prefix + "-" if filename_prefix else "") + "binaryllm_vocab.json"
        path = os.path.join(save_directory, name)

        data = {
            "base_vocab_size": 65536,
            "vocab_size": 65538,
            "bos_token": self._bos_str,
            "bos_token_id": self._bos_id,
            "eos_token": self._eos_str,
            "eos_token_id": self._eos_id,
            "unk_token": self._unk_str,
            "unk_token_id": self._unk_id,
            "pad_token": self.pad_token,
            "pad_token_id": self.pad_token_id,
        }
        with open(path, "w", encoding="utf-8") as f:
            json.dump(data, f, ensure_ascii=False, indent=2)

        return (path,)

    def _id_to_token_base(self, i: int) -> str:
        return f"<U{i:04X}>"

    def _encode_to_uint16(self, text: str) -> List[int]:
        b = text.encode("utf-8", errors="strict")
        if len(b) % 2 == 1:
            b += b"\x00"
        out: List[int] = []
        for k in range(0, len(b), 2):
            out.append(b[k] | (b[k + 1] << 8))
        return out

    def _decode_from_uint16(self, ids: List[int]) -> str:
        bb = bytearray()
        for x in ids:
            x &= 0xFFFF
            bb.append(x & 0xFF)
            bb.append((x >> 8) & 0xFF)
        if len(bb) and bb[-1] == 0:
            bb = bb[:-1]
        return bb.decode("utf-8", errors="replace")