Rename the 'cretonne' crate to 'cretonne-codegen'.

This fixes the next part of #287.

lib/codegen/meta/unique_table.py

@@ -0,0 +1,80 @@
+"""
+Generate a table of unique items.
+
+The `UniqueTable` class collects items into an array, removing duplicates. Each
+item is mapped to its offset in the final array.
+
+This is a compression technique for compile-time generated tables.
+"""
+
+try:
+    from typing import Any, List, Dict, Tuple, Sequence  # noqa
+except ImportError:
+    pass
+
+
+class UniqueTable:
+    """
+    Collect items into the `table` list, removing duplicates.
+    """
+    def __init__(self):
+        # type: () -> None
+        # List of items added in order.
+        self.table = list()  # type: List[Any]
+        # Map item -> index.
+        self.index = dict()  # type: Dict[Any, int]
+
+    def add(self, item):
+        # type: (Any) -> int
+        """
+        Add a single item to the table if it isn't already there.
+
+        Return the offset into `self.table` of the item.
+        """
+        if item in self.index:
+            return self.index[item]
+
+        idx = len(self.table)
+        self.index[item] = idx
+        self.table.append(item)
+        return idx
+
+
+class UniqueSeqTable:
+    """
+    Collect sequences into the `table` list, removing duplicates.
+
+    Sequences don't have to be of the same length.
+    """
+    def __init__(self):
+        # type: () -> None
+        self.table = list()  # type: List[Any]
+        # Map seq -> index.
+        self.index = dict()  # type: Dict[Tuple[Any, ...], int]
+
+    def add(self, seq):
+        # type: (Sequence[Any]) -> int
+        """
+        Add a sequence of items to the table. If the table already contains the
+        items in `seq` in the same order, use those instead.
+
+        Return the offset into `self.table` of the beginning of `seq`.
+        """
+        if len(seq) == 0:
+            return 0
+        tseq = tuple(seq)
+        if tseq in self.index:
+            return self.index[tseq]
+
+        idx = len(self.table)
+        self.table.extend(tseq)
+
+        # Add seq and all sub-sequences to `index`.
+        index = self.index  # type: Dict[Tuple[Any, ...], int]
+        assert index is not None
+        for length in range(1, len(tseq) + 1):
+            for offset in range(len(tseq) - length + 1):
+                key = tseq[offset:offset+length]
+                index[key] = idx + offset
+
+        return idx