1 files changed, 162 insertions, 0 deletions
diff --git a/intl/unicharutil/util/base_chars.py b/intl/unicharutil/util/base_chars.py
new file mode 100644
index 0000000000..91d3ba3352
--- /dev/null
+++ b/intl/unicharutil/util/base_chars.py
@@ -0,0 +1,162 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import re
+from collections import namedtuple
+from unicodedata import category, combining, normalize
+
+UNICODE_LIMIT = 0x110000
+
+UNICODE_COMBINING_CLASS_NOT_REORDERED = 0
+UNICODE_COMBINING_CLASS_KANA_VOICING = 8
+UNICODE_COMBINING_CLASS_VIRAMA = 9
+
+BaseCharMapping = namedtuple("BaseCharMapping", ("char", "base_char"))
+BaseCharMappingBlock = namedtuple("BaseCharMappingBlock", ("first", "last", "offset"))
+
+
+# Keep this function in sync with IsCombiningDiacritic in nsUnicodeProperties.h.
+def is_combining_diacritic(char):
+    return combining(char) not in (
+        UNICODE_COMBINING_CLASS_NOT_REORDERED,
+        UNICODE_COMBINING_CLASS_KANA_VOICING,
+        UNICODE_COMBINING_CLASS_VIRAMA,
+        91,
+        129,
+        130,
+        132,
+    )
+
+
+# Keep this function in sync with IsMathOrMusicSymbol in nsUnicodeProperties.h.
+def is_math_or_music_symbol(char):
+    return category(char) in ("Sm", "So")
+
+
+def changes_plane(char, base_char):
+    # Mappings that would change the first 16 bits of a character are not
+    # currently supported. This is because the mapping table only records the
+    # last 16 bits of the base character and also because moving into or out of
+    # the basic multilingual plane would change the length of a UTF-16 string.
+    return ord(char) >> 16 != ord(base_char) >> 16
+
+
+def main(header, fallback_table):
+    mappings = {}
+
+    # Glean mappings from decompositions
+
+    for char in range(UNICODE_LIMIT):
+        char = chr(char)
+        if is_combining_diacritic(char) or is_math_or_music_symbol(char):
+            continue
+        decomposition = normalize("NFD", char)
+        if len(decomposition) < 2:
+            continue
+        base_char = decomposition[0]
+        if changes_plane(char, base_char):
+            continue
+        next_char = decomposition[1]
+        if not is_combining_diacritic(next_char):
+            # Hangul syllables decompose but do not actually have diacritics.
+            # This also excludes decompositions with the Japanese marks U+3099
+            # and U+309A (COMBINING KATAKANA-HIRAGANA [SEMI-]VOICED SOUND
+            # MARK), which we should not ignore for searching (bug 1624244).
+            continue
+        mappings[char] = base_char
+
+    # Add mappings from the ASCII fallback table
+
+    for line in open(fallback_table, encoding="UTF-8"):
+        m = re.match("^(.) → (.+?) ;", line)
+        if not m:
+            continue
+        char = m.group(1)
+        decomposition = m.group(2)
+        if len(decomposition) >= 3:
+            if decomposition.startswith("'") and decomposition.endswith("'"):
+                decomposition = decomposition[1:-1]
+        if len(decomposition) >= 2:
+            if decomposition.startswith("\\"):
+                decomposition = decomposition[1:]
+        if len(decomposition) > 1:
+            continue
+        if changes_plane(char, decomposition):
+            continue
+        mappings[char] = decomposition
+
+    # Organize mappings into contiguous blocks
+
+    mappings = sorted([BaseCharMapping(ord(k), ord(v)) for k, v in mappings.items()])
+    blocks = []
+    i = 0
+    while i < len(mappings) - 1:
+        offset = i
+        first = mappings[i].char & 0xFF
+        while (
+            i < len(mappings) - 1 and mappings[i].char >> 8 == mappings[i + 1].char >> 8
+        ):
+            while (
+                i < len(mappings) - 1
+                and mappings[i].char >> 8 == mappings[i + 1].char >> 8
+                and mappings[i + 1].char - mappings[i].char > 1
+            ):
+                char = mappings[i].char + 1
+                mappings.insert(i + 1, BaseCharMapping(char, char))
+                i += 1
+            i += 1
+        last = mappings[i].char & 0xFF
+        blocks.append(BaseCharMappingBlock(first, last, offset))
+        i += 1
+
+    indexes = []
+    for i, block in enumerate(blocks):
+        while len(indexes) < mappings[block.offset].char >> 8:
+            indexes.append(255)
+        indexes.append(i)
+
+    # Write the mappings to a C header file
+
+    header.write("struct BaseCharMappingBlock {\n")
+    header.write("  uint8_t mFirst;\n")
+    header.write("  uint8_t mLast;\n")
+    header.write("  uint16_t mMappingStartOffset;\n")
+    header.write("};\n")
+    header.write("\n")
+    header.write("static const uint16_t BASE_CHAR_MAPPING_LIST[] = {\n")
+    for char, base_char in mappings:
+        header.write(
+            "  /* {:#06x}".format(char)
+            + " */ "
+            + "{:#06x}".format(base_char & 0xFFFF)
+            + ","
+        )
+        if char != base_char:
+            header.write(" /* " + chr(char) + " → " + chr(base_char) + " */")
+        header.write("\n")
+    header.write("};\n")
+    header.write("\n")
+    header.write(
+        "static const struct BaseCharMappingBlock BASE_CHAR_MAPPING_BLOCKS[] = {\n"
+    )
+    for block in blocks:
+        header.write(
+            "  {"
+            + "{:#04x}".format(block.first)
+            + ", "
+            + "{:#04x}".format(block.last)
+            + ", "
+            + str(block.offset).rjust(4)
+            + "}, // "
+            + "{:#04x}".format(mappings[block.offset].char >> 8)
+            + "xx\n"
+        )
+    header.write("};\n")
+    header.write("\n")
+    header.write("static const uint8_t BASE_CHAR_MAPPING_BLOCK_INDEX[] = {\n")
+    for i, index in enumerate(indexes):
+        header.write(
+            "  " + str(index).rjust(3) + ", // " + "{:#04x}".format(i) + "xx\n"
+        )
+    header.write("};\n")