Change example from `%%writeline` to `%%writefile` (#3673)

[etc/vim.git] / src / black / strings.py

diff --git a/src/black/strings.py b/src/black/strings.py
index 3e3bc12fe728cd4a23f3b19395506e88b109723c..ac18aef51ed7d7349f0f0bbb4e2dc3ce338c763b 100644 (file)
--- a/src/black/strings.py
+++ b/src/black/strings.py
@@ -14,6 +14,7 @@ if sys.version_info < (3, 8):
 else:
     from typing import Final
 
+from black._width_table import WIDTH_TABLE
 
 STRING_PREFIX_CHARS: Final = "furbFURB"  # All possible string prefix characters.
 STRING_PREFIX_RE: Final = re.compile(
@@ -278,3 +279,57 @@ def normalize_unicode_escape_sequences(leaf: Leaf) -> None:
             return back_slashes + "N{" + groups["N"].upper() + "}"
 
     leaf.value = re.sub(UNICODE_ESCAPE_RE, replace, text)
+
+
+@lru_cache(maxsize=4096)
+def char_width(char: str) -> int:
+    """Return the width of a single character as it would be displayed in a
+    terminal or editor (which respects Unicode East Asian Width).
+
+    Full width characters are counted as 2, while half width characters are
+    counted as 1.  Also control characters are counted as 0.
+    """
+    table = WIDTH_TABLE
+    codepoint = ord(char)
+    highest = len(table) - 1
+    lowest = 0
+    idx = highest // 2
+    while True:
+        start_codepoint, end_codepoint, width = table[idx]
+        if codepoint < start_codepoint:
+            highest = idx - 1
+        elif codepoint > end_codepoint:
+            lowest = idx + 1
+        else:
+            return 0 if width < 0 else width
+        if highest < lowest:
+            break
+        idx = (highest + lowest) // 2
+    return 1
+
+
+def str_width(line_str: str) -> int:
+    """Return the width of `line_str` as it would be displayed in a terminal
+    or editor (which respects Unicode East Asian Width).
+
+    You could utilize this function to determine, for example, if a string
+    is too wide to display in a terminal or editor.
+    """
+    if line_str.isascii():
+        # Fast path for a line consisting of only ASCII characters
+        return len(line_str)
+    return sum(map(char_width, line_str))
+
+
+def count_chars_in_width(line_str: str, max_width: int) -> int:
+    """Count the number of characters in `line_str` that would fit in a
+    terminal or editor of `max_width` (which respects Unicode East Asian
+    Width).
+    """
+    total_width = 0
+    for i, char in enumerate(line_str):
+        width = char_width(char)
+        if width + total_width > max_width:
+            return i
+        total_width += width
+    return len(line_str)