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#!/usr/bin/env python3
#
# Copyright 2011-2022 The Rust Project Developers. See the COPYRIGHT
# file at the top-level directory of this distribution and at
#
# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
# option. This file may not be copied, modified, or distributed
# except according to those terms.
# This script uses the following Unicode tables:
# - EastAsianWidth.txt
# - ReadMe.txt
# - UnicodeData.txt
#
# Since this should not require frequent updates, we just store this
# out-of-line and check the generated module into git.
import enum
import math
import os
import re
import sys
NUM_CODEPOINTS = 0x110000
"""An upper bound for which `range(0, NUM_CODEPOINTS)` contains Unicode's codespace."""
MAX_CODEPOINT_BITS = math.ceil(math.log2(NUM_CODEPOINTS - 1))
"""The maximum number of bits required to represent a Unicode codepoint."""
class OffsetType(enum.IntEnum):
"""Represents the data type of a lookup table's offsets. Each variant's value represents the
number of bits required to represent that variant's type."""
U2 = 2
"""Offsets are 2-bit unsigned integers, packed four-per-byte."""
U4 = 4
"""Offsets are 4-bit unsigned integers, packed two-per-byte."""
U8 = 8
"""Each offset is a single byte (u8)."""
TABLE_CFGS = [
(13, MAX_CODEPOINT_BITS, OffsetType.U8),
(6, 13, OffsetType.U8),
(0, 6, OffsetType.U2),
]
"""Represents the format of each level of the multi-level lookup table.
A level's entry is of the form `(low_bit, cap_bit, offset_type)`.
This means that every sub-table in that level is indexed by bits `low_bit..cap_bit` of the
codepoint and those tables offsets are stored according to `offset_type`.
If this is edited, you must ensure that `emit_module` reflects your changes."""
MODULE_FILENAME = "tables.rs"
"""The filename of the emitted Rust module (will be created in the working directory)"""
Codepoint = int
BitPos = int
def fetch_open(filename: str):
"""Opens `filename` and return its corresponding file object. If `filename` isn't on disk,
if not os.path.exists(os.path.basename(filename)):
try:
return open(filename, encoding="utf-8")
except OSError:
sys.stderr.write(f"cannot load {filename}")
sys.exit(1)
def load_unicode_version() -> "tuple[int, int, int]":
"""Returns the current Unicode version by fetching and processing `ReadMe.txt`."""
with fetch_open("ReadMe.txt") as readme:
pattern = r"for Version (\d+)\.(\d+)\.(\d+) of the Unicode"
return tuple(map(int, re.search(pattern, readme.read()).groups()))
class EffectiveWidth(enum.IntEnum):
"""Represents the width of a Unicode character. All East Asian Width classes resolve into
either `EffectiveWidth.NARROW`, `EffectiveWidth.WIDE`, or `EffectiveWidth.AMBIGUOUS`."""
ZERO = 0
""" Zero columns wide. """
NARROW = 1
""" One column wide. """
WIDE = 2
""" Two columns wide. """
AMBIGUOUS = 3
""" Two columns wide in a CJK context. One column wide in all other contexts. """
def load_east_asian_widths() -> "list[EffectiveWidth]":
"""Return a list of effective widths, indexed by codepoint.
Widths are determined by fetching and parsing `EastAsianWidth.txt`.
`Neutral`, `Narrow`, and `Halfwidth` characters are assigned `EffectiveWidth.NARROW`.
`Wide` and `Fullwidth` characters are assigned `EffectiveWidth.WIDE`.
`Ambiguous` chracters are assigned `EffectiveWidth.AMBIGUOUS`."""
with fetch_open("EastAsianWidth.txt") as eaw:
# matches a width assignment for a single codepoint, i.e. "1F336;N # ..."
single = re.compile(r"^([0-9A-F]+);(\w+) +# (\w+)")
# matches a width assignment for a range of codepoints, i.e. "3001..3003;W # ..."
multiple = re.compile(r"^([0-9A-F]+)\.\.([0-9A-F]+);(\w+) +# (\w+)")
# map between width category code and condensed width
width_codes = {
**{c: EffectiveWidth.NARROW for c in ["N", "Na", "H"]},
**{c: EffectiveWidth.WIDE for c in ["W", "F"]},
"A": EffectiveWidth.AMBIGUOUS,
}
width_map = []
current = 0
for line in eaw.readlines():
raw_data = None # (low, high, width)
if match := single.match(line):
raw_data = (match.group(1), match.group(1), match.group(2))
elif match := multiple.match(line):
raw_data = (match.group(1), match.group(2), match.group(3))
else:
continue
low = int(raw_data[0], 16)
high = int(raw_data[1], 16)
width = width_codes[raw_data[2]]
assert current <= high
while current <= high:
# Some codepoints don't fall into any of the ranges in EastAsianWidth.txt.
# All such codepoints are implicitly given Neural width (resolves to narrow)
width_map.append(EffectiveWidth.NARROW if current < low else width)
current += 1
while len(width_map) < NUM_CODEPOINTS:
# Catch any leftover codepoints and assign them implicit Neutral/narrow width.
width_map.append(EffectiveWidth.NARROW)
return width_map
def load_zero_widths() -> "list[bool]":
"""Returns a list `l` where `l[c]` is true if codepoint `c` is considered a zero-width
character. `c` is considered a zero-width character if `c` is in general categories
`Cc`, `Cf`, `Mn`, or `Me` (determined by fetching and processing `UnicodeData.txt`)."""
with fetch_open("UnicodeData.txt") as categories:
zw_map = []
current = 0
for line in categories.readlines():
if len(raw_data := line.split(";")) != 15:
continue
[codepoint, name, cat_code] = [
int(raw_data[0], 16),
raw_data[1],
raw_data[2],
]
zero_width = cat_code in ["Cc", "Cf", "Mn", "Me"]
assert current <= codepoint
while current <= codepoint:
if name.endswith(", Last>") or current == codepoint:
# if name ends with Last, we backfill the width value to all codepoints since
# the previous codepoint (aka the start of the range)
zw_map.append(zero_width)
else:
# unassigned characters are implicitly given Neutral width, which is nonzero
zw_map.append(False)
current += 1
while len(zw_map) < NUM_CODEPOINTS:
# Catch any leftover codepoints. They must be unassigned (so nonzero width)
zw_map.append(False)
return zw_map
class Bucket:
"""A bucket contains a group of codepoints and an ordered width list. If one bucket's width
list overlaps with another's width list, those buckets can be merged via `try_extend`."""
def __init__(self):
"""Creates an empty bucket."""
self.entry_set = set()
self.widths = []
def append(self, codepoint: Codepoint, width: EffectiveWidth):
"""Adds a codepoint/width pair to the bucket, and appends `width` to the width list."""
self.entry_set.add((codepoint, width))
self.widths.append(width)
def try_extend(self, attempt: "Bucket") -> bool:
"""If either `self` or `attempt`'s width list starts with the other bucket's width list,
set `self`'s width list to the longer of the two, add all of `attempt`'s codepoints
into `self`, and return `True`. Otherwise, return `False`."""
(less, more) = (self.widths, attempt.widths)
if len(self.widths) > len(attempt.widths):
(less, more) = (attempt.widths, self.widths)
if less != more[: len(less)]:
return False
self.entry_set |= attempt.entry_set
self.widths = more
return True
def entries(self) -> "list[tuple[Codepoint, EffectiveWidth]]":
"""Return a list of the codepoint/width pairs in this bucket, sorted by codepoint."""
result = list(self.entry_set)
result.sort()
return result
def width(self) -> "EffectiveWidth":
"""If all codepoints in this bucket have the same width, return that width; otherwise,
return `None`."""
if len(self.widths) == 0:
return None
potential_width = self.widths[0]
for width in self.widths[1:]:
if potential_width != width:
return None
return potential_width
def make_buckets(entries, low_bit: BitPos, cap_bit: BitPos) -> "list[Bucket]":
"""Partitions the `(Codepoint, EffectiveWidth)` tuples in `entries` into `Bucket`s. All
codepoints with identical bits from `low_bit` to `cap_bit` (exclusive) are placed in the
same bucket. Returns a list of the buckets in increasing order of those bits."""
num_bits = cap_bit - low_bit
assert num_bits > 0
buckets = [Bucket() for _ in range(0, 2 ** num_bits)]
mask = (1 << num_bits) - 1
for (codepoint, width) in entries:
buckets[(codepoint >> low_bit) & mask].append(codepoint, width)
return buckets
class Table:
"""Represents a lookup table. Each table contains a certain number of subtables; each
subtable is indexed by a contiguous bit range of the codepoint and contains a list
of `2**(number of bits in bit range)` entries. (The bit range is the same for all subtables.)
Typically, tables contain a list of buckets of codepoints. Bucket `i`'s codepoints should
be indexed by sub-table `i` in the next-level lookup table. The entries of this table are
indexes into the bucket list (~= indexes into the sub-tables of the next-level table.) The
key to compression is that two different buckets in two different sub-tables may have the
same width list, which means that they can be merged into the same bucket.
If no bucket contains two codepoints with different widths, calling `indices_to_widths` will
discard the buckets and convert the entries into `EffectiveWidth` values."""
def __init__(
self, entry_groups, low_bit: BitPos, cap_bit: BitPos, offset_type: OffsetType
):
"""Create a lookup table with a sub-table for each `(Codepoint, EffectiveWidth)` iterator
in `entry_groups`. Each sub-table is indexed by codepoint bits in `low_bit..cap_bit`,
and each table entry is represented in the format specified by `offset_type`. Asserts
that this table is actually representable with `offset_type`."""
self.low_bit = low_bit
self.cap_bit = cap_bit
self.offset_type = offset_type
self.entries = []
self.indexed = []
buckets = []
for entries in entry_groups:
buckets.extend(make_buckets(entries, self.low_bit, self.cap_bit))
for bucket in buckets:
for (i, existing) in enumerate(self.indexed):
if existing.try_extend(bucket):
self.entries.append(i)
break
else:
self.entries.append(len(self.indexed))
self.indexed.append(bucket)
# Validate offset type
for index in self.entries:
assert index < (1 << int(self.offset_type))
def indices_to_widths(self):
"""Destructively converts the indices in this table to the `EffectiveWidth` values of
their buckets. Assumes that no bucket contains codepoints with different widths."""
self.entries = list(map(lambda i: int(self.indexed[i].width()), self.entries))
del self.indexed
def buckets(self):
"""Returns an iterator over this table's buckets."""
return self.indexed
def to_bytes(self) -> "list[int]":
"""Returns this table's entries as a list of bytes. The bytes are formatted according to
the `OffsetType` which the table was created with, converting any `EffectiveWidth` entries
to their enum variant's integer value. For example, with `OffsetType.U2`, each byte will
contain four packed 2-bit entries."""
entries_per_byte = 8 // int(self.offset_type)
byte_array = []
for i in range(0, len(self.entries), entries_per_byte):
byte = 0
for j in range(0, entries_per_byte):
byte |= self.entries[i + j] << (j * int(self.offset_type))
byte_array.append(byte)
return byte_array
def make_tables(
table_cfgs: "list[tuple[BitPos, BitPos, OffsetType]]", entries
) -> "list[Table]":
"""Creates a table for each configuration in `table_cfgs`, with the first config corresponding
to the top-level lookup table, the second config corresponding to the second-level lookup
table, and so forth. `entries` is an iterator over the `(Codepoint, EffectiveWidth)` pairs
to include in the top-level table."""
tables = []
entry_groups = [entries]
for (low_bit, cap_bit, offset_type) in table_cfgs:
table = Table(entry_groups, low_bit, cap_bit, offset_type)
entry_groups = map(lambda bucket: bucket.entries(), table.buckets())
tables.append(table)
return tables
def emit_module(
out_name: str, unicode_version: "tuple[int, int, int]", tables: "list[Table]"
):
"""Outputs a Rust module to `out_name` using table data from `tables`.
If `TABLE_CFGS` is edited, you may need to edit the included code for `lookup_width`."""
if os.path.exists(out_name):
os.remove(out_name)
with open(out_name, "w", newline="\n", encoding="utf-8") as module:
module.write(
"""// Copyright 2012-2022 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// NOTE: The following code was generated by "scripts/unicode.py", do not edit directly
"""
)
module.write(
f"""
/// that this version of unicode-width is based on.
pub const UNICODE_VERSION: (u8, u8, u8) = {unicode_version};
"""
)
module.write(
"""
pub mod charwidth {
use core::option::Option::{self, None, Some};
/// consulting a multi-level lookup table.
/// If `is_cjk == true`, ambiguous width characters are treated as double width; otherwise,
/// they're treated as single width.
///
/// # Maintenance
/// The tables themselves are autogenerated but this function is hardcoded. You should have
/// nothing to worry about if you re-run `unicode.py` (for example, when updating Unicode.)
/// However, if you change the *actual structure* of the lookup tables (perhaps by editing the
/// `TABLE_CFGS` global in `unicode.py`) you must ensure that this code reflects those changes.
#[inline]
fn lookup_width(c: char, is_cjk: bool) -> usize {
let cp = c as usize;
let t1_offset = TABLES_0[cp >> 13 & 0xFF];
// Each sub-table in TABLES_1 is 7 bits, and each stored entry is a byte,
// so each sub-table is 128 bytes in size.
// (Sub-tables are selected using the computed offset from the previous table.)
let t2_offset = TABLES_1[128 * usize::from(t1_offset) + (cp >> 6 & 0x7F)];
// Each sub-table in TABLES_2 is 6 bits, but each stored entry is 2 bits.
// This is accomplished by packing four stored entries into one byte.
// So each sub-table is 2**(6-2) == 16 bytes in size.
// Since this is the last table, each entry represents an encoded width.
let packed_widths = TABLES_2[16 * usize::from(t2_offset) + (cp >> 2 & 0xF)];
// Extract the packed width
let width = packed_widths >> (2 * (cp & 0b11)) & 0b11;
// A width of 3 signifies that the codepoint is ambiguous width.
if width == 3 {
if is_cjk {
2
} else {
1
}
} else {
width.into()
}
}
"""
)
module.write(
"""
/// `None` if `c` is a control character other than `'\\x00'`.
/// If `is_cjk == true`, ambiguous width characters are treated as double width; otherwise,
/// they're treated as single width.
#[inline]
pub fn width(c: char, is_cjk: bool) -> Option<usize> {
if c < '\\u{7F}' {
if c >= '\\u{20}' {
// U+0020 to U+007F (exclusive) are single-width ASCII codepoints
Some(1)
} else if c == '\\0' {
// U+0000 *is* a control code, but it's special-cased
Some(0)
} else {
// U+0001 to U+0020 (exclusive) are control codes
None
}
} else if c >= '\\u{A0}' {
// No characters >= U+00A0 are control codes, so we can consult the lookup tables
Some(lookup_width(c, is_cjk))
} else {
// U+007F to U+00A0 (exclusive) are control codes
None
}
}
"""
)
subtable_count = 1
for (i, table) in enumerate(tables):
new_subtable_count = len(table.buckets())
if i == len(tables) - 1:
table.indices_to_widths() # for the last table, indices == widths
byte_array = table.to_bytes()
module.write(
f"""
/// Autogenerated. {subtable_count} sub-table(s). Consult [`lookup_width`] for layout info.
static TABLES_{i}: [u8; {len(byte_array)}] = ["""
)
for (j, byte) in enumerate(byte_array):
# Add line breaks for every 15th entry (chosen to match what rustfmt does)
if j % 15 == 0:
module.write("\n ")
module.write(f" 0x{byte:02X},")
module.write("\n ];\n")
subtable_count = new_subtable_count
module.write("}\n")
def main(module_filename: str):
"""Obtain character data from the latest version of Unicode, transform it into a multi-level
lookup table for character width, and write a Rust module utilizing that table to
`module_filename`.
We obey the following rules in decreasing order of importance:
- The soft hyphen (`U+00AD`) is single-width.
- Hangul Jamo medial vowels & final consonants (`U+1160..=U+11FF`) are zero-width.
- All codepoints in general categories `Cc`, `Cf`, `Mn`, and `Me` are zero-width.
- All codepoints with an East Asian Width of `Ambigous` are ambiguous-width.
- All codepoints with an East Asian Width of `Wide` or `Fullwidth` are double-width.
- All other codepoints (including unassigned codepoints and codepoints with an East Asian Width
of `Neutral`, `Narrow`, or `Halfwidth`) are single-width.
These rules are based off of Markus Kuhn's free `wcwidth()` implementation:
version = load_unicode_version()
print(f"Generating module for Unicode {version[0]}.{version[1]}.{version[2]}")
eaw_map = load_east_asian_widths()
zw_map = load_zero_widths()
# Characters marked as zero-width in zw_map should be zero-width in the final map
width_map = list(
map(lambda x: EffectiveWidth.ZERO if x[1] else x[0], zip(eaw_map, zw_map))
)
# Override for soft hyphen
width_map[0x00AD] = EffectiveWidth.NARROW
# Override for Hangul Jamo medial vowels & final consonants
for i in range(0x1160, 0x11FF + 1):
width_map[i] = EffectiveWidth.ZERO
tables = make_tables(TABLE_CFGS, enumerate(width_map))
print("------------------------")
total_size = 0
for (i, table) in enumerate(tables):
size_bytes = len(table.to_bytes())
print(f"Table {i} Size: {size_bytes} bytes")
total_size += size_bytes
print("------------------------")
print(f" Total Size: {total_size} bytes")
emit_module(module_filename, version, tables)
print(f'Wrote to "{module_filename}"')
if __name__ == "__main__":
main(MODULE_FILENAME)