Allow hash algorithm selection

Closes #9

README.md

@@ -43,13 +43,13 @@ example of the format. Any exceptions will be printed to stderr.
 
 ## Library
 
-### `Model.serialize()`
+### `Model.serialize(file)`
 
-Returns a `bytes` representing the model.
+Write binary data representing the model to `file`.
 
 ### `gptc.deserialize(encoded_model)`
 
-Deserialize a `Model` from a `bytes` returned by `Model.serialize()`.
+Deserialize a `Model` from a file containing data from `Model.serialize()`.
 
 ### `Model.confidence(text, max_ngram_length)`
 
@@ -69,7 +69,7 @@ Return a confidence dict for the given token or ngram. This function is very
 similar to `Model.confidence()`, except it treats the input as a single token
 or ngram.
 
-### `gptc.compile(raw_model, max_ngram_length=1, min_count=1)`
+### `gptc.compile(raw_model, max_ngram_length=1, min_count=1, hash_algorithm="sha256")`
 
 Compile a raw model (as a list, not JSON) and return the compiled model (as a
 `gptc.Model` object).
@@ -79,6 +79,26 @@ For information about `max_ngram_length`, see section "Ngrams."
 Words or ngrams used less than `min_count` times throughout the input text are
 excluded from the model.
 
+The hash algorithm should be left as the default, which may change with a minor
+version update, but it can be changed by the application if needed. It is
+stored in the model, so changing the algorithm does not affect compatibility.
+The following algorithms are supported:
+
+* `md5`
+* `sha1`
+* `sha224`
+* `sha256`
+* `sha384`
+* `sha512`
+* `sha3_224`
+* `sha3_384`
+* `sha3_256`
+* `sha3_512`
+* `shake_128`
+* `shake_256`
+* `blake2b`
+* `blake2s`
+
 ### `gptc.pack(directory, print_exceptions=False)`
 
 Pack the model in `directory` and return a tuple of the format:

gptc/__main__.py

@@ -66,12 +66,10 @@ def main() -> None:
         with open(args.model, "r") as f:
             model = json.load(f)
 
-        sys.stdout.buffer.write(
-            gptc.compile(model, args.max_ngram_length, args.min_count).serialize()
-        )
+        gptc.compile(model, args.max_ngram_length, args.min_count).serialize(sys.stdout.buffer)
     elif args.subparser_name == "classify":
         with open(args.model, "rb") as f:
-            model = gptc.deserialize(f.read())
+            model = gptc.deserialize(f)
 
         if sys.stdin.isatty():
             text = input("Text to analyse: ")
@@ -87,7 +85,7 @@ def main() -> None:
             print(json.dumps(probabilities))
     elif args.subparser_name == "check":
         with open(args.model, "rb") as f:
-            model = gptc.deserialize(f.read())
+            model = gptc.deserialize(f)
         print(json.dumps(model.get(args.token)))
     else:
         print(json.dumps(gptc.pack(args.model, True)[0]))

gptc/compiler.py

@@ -9,6 +9,7 @@ def compile(
     raw_model: Iterable[Mapping[str, str]],
     max_ngram_length: int = 1,
     min_count: int = 1,
+    hash_algorithm: str = "sha256",
 ) -> gptc.model.Model:
     """Compile a raw model.
 
@@ -27,23 +28,24 @@ def compile(
 
     """
 
-    categories: Dict[str, List[int]] = {}
+    word_counts: Dict[int, Dict[str, int]] = {}
+    category_lengths: Dict[str, int] = {}
+    names: List[str] = []
 
     for portion in raw_model:
         text = gptc.tokenizer.hash(
-            gptc.tokenizer.tokenize(portion["text"], max_ngram_length)
+            gptc.tokenizer.tokenize(portion["text"], max_ngram_length),
+            hash_algorithm,
         )
         category = portion["category"]
-        try:
-            categories[category] += text
-        except KeyError:
-            categories[category] = text
 
-    word_counts: Dict[int, Dict[str, int]] = {}
+        if not category in names:
+            names.append(category)
 
-    names = list(categories.keys())
+        category_lengths[category] = category_lengths.get(category, 0) + len(
+            text
+        )
 
-    for category, text in categories.items():
         for word in text:
             if word in word_counts:
                 try:
@@ -53,21 +55,13 @@ def compile(
             else:
                 word_counts[word] = {category: 1}
 
-    category_lengths = {
-        category: len(text) for category, text in categories.items()
-    }
-
-    word_weights: Dict[int, Dict[str, float]] = {
-        word: {
-            category: value / category_lengths[category]
-            for category, value in values.items()
-        }
-        for word, values in word_counts.items()
-        if sum(values.values()) >= min_count
-    }
-
     model: Dict[int, List[int]] = {}
-    for word, weights in word_weights.items():
+    for word, counts in word_counts.items():
+        if sum(counts.values()) >= min_count:
+            weights = {
+                category: value / category_lengths[category]
+                for category, value in counts.items()
+            }
             total = sum(weights.values())
             new_weights: List[int] = []
             for category in names:
@@ -76,4 +70,4 @@ def compile(
                 )
             model[word] = new_weights
 
-    return gptc.model.Model(model, names, max_ngram_length)
+    return gptc.model.Model(model, names, max_ngram_length, hash_algorithm)

gptc/model.py

@@ -3,7 +3,7 @@
 import gptc.tokenizer
 from gptc.exceptions import InvalidModelError
 import gptc.weighting
-from typing import Iterable, Mapping, List, Dict, Union, cast
+from typing import Iterable, Mapping, List, Dict, Union, cast, BinaryIO
 import json
 
 
@@ -13,10 +13,12 @@ class Model:
         weights: Dict[int, List[int]],
         names: List[str],
         max_ngram_length: int,
+        hash_algorithm: str,
     ):
         self.weights = weights
         self.names = names
         self.max_ngram_length = max_ngram_length
+        self.hash_algorithm = hash_algorithm
 
     def confidence(self, text: str, max_ngram_length: int) -> Dict[str, float]:
         """Classify text with confidence.
@@ -40,7 +42,10 @@ class Model:
         model = self.weights
 
         tokens = gptc.tokenizer.hash(
-            gptc.tokenizer.tokenize(text, min(max_ngram_length, self.max_ngram_length))
+            gptc.tokenizer.tokenize(
+                text, min(max_ngram_length, self.max_ngram_length)
+            ),
+            self.hash_algorithm,
         )
         numbered_probs: Dict[int, float] = {}
         for word in tokens:
@@ -74,42 +79,39 @@ class Model:
             for index, category in enumerate(self.names)
         }
 
-    def serialize(self) -> bytes:
-        out = b"GPTC model v4\n"
-        out += (
+    def serialize(self, file: BinaryIO):
+        file.write(b"GPTC model v5\n")
+        file.write(
             json.dumps(
                 {
                     "names": self.names,
                     "max_ngram_length": self.max_ngram_length,
-                    "has_emoji": True,
-                    # Due to an oversight in development, version 3.0.0 still
-                    # had the code used to make emoji support optional, even
-                    # though the `emoji` library was made a hard dependency.
-                    # Part of this code checked whether or not the model
-                    # supports emoji; deserialization would not work in 3.0.0
-                    # if the model was compiled without this field. Emoji are
-                    # always supported with 3.0.0 and newer when GPTC has been
-                    # installed correctly, so this value should always be True.
-                    # Related: #11
+                    "hash_algorithm": self.hash_algorithm,
                 }
             ).encode("utf-8")
             + b"\n"
         )
         for word, weights in self.weights.items():
-            out += word.to_bytes(6, "big") + b"".join(
-                [weight.to_bytes(2, "big") for weight in weights]
+            file.write(
+                word.to_bytes(6, "big")
+                + b"".join([weight.to_bytes(2, "big") for weight in weights])
             )
-        return out
 
 
-def deserialize(encoded_model: bytes) -> Model:
-    try:
-        prefix, config_json, encoded_weights = encoded_model.split(b"\n", 2)
-    except ValueError:
+def deserialize(encoded_model: BinaryIO) -> Model:
+    prefix = encoded_model.read(14)
+    if prefix != b"GPTC model v5\n":
         raise InvalidModelError()
 
-    if prefix != b"GPTC model v4":
+    config_json = b""
+    while True:
+        byte = encoded_model.read(1)
+        if byte == b"\n":
+            break
+        elif byte == b"":
             raise InvalidModelError()
+        else:
+            config_json += byte
 
     try:
         config = json.loads(config_json.decode("utf-8"))
@@ -119,30 +121,29 @@ def deserialize(encoded_model: bytes) -> Model:
     try:
         names = config["names"]
         max_ngram_length = config["max_ngram_length"]
+        hash_algorithm = config["hash_algorithm"]
     except KeyError:
         raise InvalidModelError()
 
-    if not (isinstance(names, list) and isinstance(max_ngram_length, int)) or not all(
-        [isinstance(name, str) for name in names]
-    ):
+    if not (
+        isinstance(names, list) and isinstance(max_ngram_length, int)
+    ) or not all([isinstance(name, str) for name in names]):
         raise InvalidModelError()
 
     weight_code_length = 6 + 2 * len(names)
 
-    if len(encoded_weights) % weight_code_length != 0:
+    weights: Dict[int : List[int]] = {}
+
+    while True:
+        code = encoded_model.read(weight_code_length)
+        if not code:
+            break
+        elif len(code) != weight_code_length:
             raise InvalidModelError()
 
-    weight_codes = [
-        encoded_weights[x : x + weight_code_length]
-        for x in range(0, len(encoded_weights), weight_code_length)
-    ]
-
-    weights = {
-        int.from_bytes(code[:6], "big"): [
+        weights[int.from_bytes(code[:6], "big")] = [
             int.from_bytes(value, "big")
             for value in [code[x : x + 2] for x in range(6, len(code), 2)]
         ]
-        for code in weight_codes
-    }
 
-    return Model(weights, names, max_ngram_length)
+    return Model(weights, names, max_ngram_length, hash_algorithm)

gptc/tokenizer.py

@@ -1,12 +1,13 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-from typing import List, Union
+from typing import List, Union, Callable
 import hashlib
 import emoji
+import unicodedata
 
 
 def tokenize(text: str, max_ngram_length: int = 1) -> List[str]:
-    text = text.lower()
+    text = unicodedata.normalize("NFKD", text).lower()
     parts = []
     highest_end = 0
     for emoji_part in emoji.emoji_list(text):
@@ -19,7 +20,12 @@ def tokenize(text: str, max_ngram_length: int = 1) -> List[str]:
     tokens = [""]
 
     for char in converted_text:
-        if char.isalpha() or char == "'":
+        if (
+            char.isalpha()
+            or char.isnumeric()
+            or char == "'"
+            or (char in ",." and (" " + tokens[-1])[-1].isnumeric())
+        ):
             tokens[-1] += char
         elif emoji.is_emoji(char):
             tokens.append(char)
@@ -39,14 +45,33 @@ def tokenize(text: str, max_ngram_length: int = 1) -> List[str]:
         return ngrams
 
 
-def hash_single(token: str) -> int:
+def hash_single(token: str, hash_function: Callable) -> int:
     return int.from_bytes(
-        hashlib.sha256(token.encode("utf-8")).digest()[:6], "big"
+        hash_function(token.encode("utf-8")).digest()[:6], "big"
     )
 
 
-def hash(tokens: List[str]) -> List[int]:
-    return [hash_single(token) for token in tokens]
+def hash(tokens: List[str], hash_algorithm: str) -> List[int]:
+    if hash_algorithm in {
+        "sha224",
+        "md5",
+        "sha512",
+        "sha3_256",
+        "blake2s",
+        "sha3_224",
+        "sha1",
+        "sha256",
+        "sha384",
+        "shake_256",
+        "blake2b",
+        "sha3_512",
+        "shake_128",
+        "sha3_384",
+    }:
+        hash_function = getattr(hashlib, hash_algorithm)
+        return [hash_single(token, hash_function) for token in tokens]
+    else:
+        raise ValueError("not a valid hash function: " + hash_algorithm)
 
 
 def normalize(text: str) -> str: