encode part done

reimplement/set.py

@@ -11,34 +11,137 @@ class Set:
     """just a bag of strings and their hash values.
 
     Attributes:
-        count (int): The number of elements in the set.
+        cnt (int): The number of elements in the set.
         labels (List[Tuple[str, int]]): A list of tuples, where each tuple contains a string and its corresponding hash value.
     """
 
-    count: int
+    cnt: int
     labels: List[Tuple[str, int]]  # List of tuples (string, hash value)
 
 
+def check_bpp(bpp: int) -> bool:
+    """Check if the bits per pixel (bpp) value is within the valid range."""
+    return 2 <= bpp <= 64
+
+
+def check_Mshift(Mshift: int) -> bool:
+    """Check if the Mshift value is within the valid range."""
+    return 1 <= Mshift <= 63
+
+
+def int_to_char(value: int) -> str:
+    """Convert an integer value to a base64 character."""
+    if 0 <= value <= 9:
+        return chr(value + ord("0"))
+    elif 10 <= value <= 35:
+        return chr(value - 10 + ord("a"))
+    elif 36 <= value <= 61:
+        return chr(value - 36 + ord("A"))
+    elif value == 62:
+        return "+"
+    elif value == 63:
+        return "/"
+    else:
+        raise ValueError("Value must be in the range [0, 63] for base64 encoding.")
+
+
+def encode_golomb_Mshift(cnt: int, bpp: int) -> int:
+    """Calculate Mshift paramter for encoding."""
+    Mshift = bpp - (cnt.bit_length() - 1) - 1
+
+    Mshift = max(Mshift, 1)
+    Mshift = min(Mshift, 63)
+    assert Mshift < bpp, "Mshift must be less than bpp"
+
+    return Mshift
+
+
+def encode_delta(hash_values: List[int]) -> List[int]:
+    """Encode the hash values into delta values."""
+    if not hash_values:
+        return []
+
+    delta_values = [hash_values[0]]
+    for i in range(1, len(hash_values)):
+        delta = hash_values[i] - hash_values[i - 1]
+        delta_values.append(delta)
+
+    return delta_values
+
+
+def encode_golomb(delta_values: List[int], Mshift: int) -> List[int]:
+    """Main golomb encoding routine: package integers into bits."""
+    mask = (1 << Mshift) - 1
+    golomb_encoded = []
+
+    for val in delta_values:
+        q = val >> Mshift  # quotient
+        r = val & mask  # remainder
+
+        for _ in range(q):
+            golomb_encoded.append(0)  # "unary" part
+        golomb_encoded.append(1)  # separator
+
+        for i in range(Mshift):
+            golomb_encoded.append((r >> i) & 1)  # binary part
+
+    return golomb_encoded
+
+
+def encode_base64(bits: List[int]) -> str:
+    """Encode a list of bits into a base64 string."""
+    base64_chars = []
+
+    for i in range(0, len(bits), 6):
+        chunk = bits[i : i + 6]
+
+        while len(chunk) < 6:
+            chunk.append(0)  # pad with zeros if necessary
+
+        value = sum(bit << (5 - j) for j, bit in enumerate(chunk))
+        base64_chars.append(int_to_char(value))
+
+    return "".join(base64_chars)
+
+
+def encode_set(hash_values: List[int], bpp: int) -> str:
+    """Encode the set of hash values into a set-string representation using base64 and Golomb coding."""
+
+    cnt = len(hash_values)
+    Mshift = encode_golomb_Mshift(cnt, bpp)
+
+    assert check_bpp(bpp), "bpp must be between 2 and 64"
+    assert check_Mshift(Mshift), "Mshift must be between 1 and 63"
+
+    delta_values = encode_delta(hash_values)
+
+    bits = encode_golomb(delta_values, Mshift)
+
+    base64_chars = encode_base64(bits)
+
+    return int_to_char(bpp) + int_to_char(Mshift) + base64_chars
+
+
 def rpmsetcmp():
     pass
 
 
 def set_new() -> Set:
-    """Create a new Set instance with count initialized to 0 and an empty list of labels."""
+    """Create a new Set instance with cnt initialized to 0 and an empty list of labels."""
-    return Set(count=0, labels=[])
+    return Set(cnt=0, labels=[])
 
 
 def set_add(set: Set, label: str) -> None:
     """Add a label to the set."""
-    hash_value = hash(label)
+    hash_value = 0
     set.labels.append((label, hash_value))
-    set.count += 1
+    set.cnt += 1
 
 
 def set_free(set: Set) -> None:
     """Free the resources associated with the set."""
     set.labels.clear()
-    set.count = 0
+    set.cnt = 0
 
 
 def hash(label: str) -> int:
@@ -50,15 +153,40 @@ def hash(label: str) -> int:
 def set_fini(set: Set, bpp: int) -> str | None:
     """Finalize the set and return a set-string representation."""
 
-    if set.count < 1:
+    if set.cnt < 1:
         return None
 
-    # bpp < 10 in original code
+    assert check_bpp(bpp), "bpp must be between 2 and 64"
-    if bpp < 2:
-        return None
 
-    if bpp > 64:
+    mask = (1 << bpp) - 1
-        return None
 
-    # Placeholder implementation - replace with actual finalization logic
+    # calculate hash values for each label and store them in the set
-    return f"Set with {set.count} elements"
+    for i in range(set.cnt):
+        label, _ = set.labels[i]
+        computed_hash = hash(label) & mask
+        set.labels[i] = (label, computed_hash)
+
+    set.labels.sort(key=lambda x: x[1])  # Sort by hash value
+
+    # warn on hash collisions
+    for i in range(1, set.cnt):
+        if set.labels[i][1] == set.labels[i - 1][1]:
+            print(
+                f"Warning: Hash collision detected for labels '{set.labels[i][0]}' and '{set.labels[i - 1][0]}'"
+            )
+
+    hash_values = [label_hash for _, label_hash in set.labels]
+
+    encoded_string = encode_set(hash_values, bpp)
+
+    return encoded_string
+
+
+if __name__ == "__main__":
+    # Example usage
+    my_set = set_new()
+    set_add(my_set, "example_label_1")
+    set_add(my_set, "example_label_2")
+    result = set_fini(my_set, 8)
+    print(result)
+    set_free(my_set)