commit-tree: encourage UTF-8 commit messages.

Introduce is_utf() to check if a text looks like it is encoded
in UTF-8, utf8_width() to count display width, and implements
print_wrapped_text() using them.

git-commit-tree warns if the commit message does not minimally
conform to the UTF-8 encoding when i18n.commitencoding is either
unset, or set to "utf-8".

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 278 insertions, 0 deletions

diff --git a/utf8.c b/utf8.c
new file mode 100644
index 0000000000..8fa62571aa
--- /dev/null
+++ b/utf8.c
@@ -0,0 +1,278 @@
+#include "git-compat-util.h"
+#include "utf8.h"
+
+/* This code is originally from http://www.cl.cam.ac.uk/~mgk25/ucs/ */
+
+struct interval {
+  int first;
+  int last;
+};
+
+/* auxiliary function for binary search in interval table */
+static int bisearch(wchar_t ucs, const struct interval *table, int max) {
+	int min = 0;
+	int mid;
+
+	if (ucs < table[0].first || ucs > table[max].last)
+		return 0;
+	while (max >= min) {
+		mid = (min + max) / 2;
+		if (ucs > table[mid].last)
+			min = mid + 1;
+		else if (ucs < table[mid].first)
+			max = mid - 1;
+		else
+			return 1;
+	}
+
+	return 0;
+}
+
+/* The following two functions define the column width of an ISO 10646
+ * character as follows:
+ *
+ *    - The null character (U+0000) has a column width of 0.
+ *
+ *    - Other C0/C1 control characters and DEL will lead to a return
+ *      value of -1.
+ *
+ *    - Non-spacing and enclosing combining characters (general
+ *      category code Mn or Me in the Unicode database) have a
+ *      column width of 0.
+ *
+ *    - SOFT HYPHEN (U+00AD) has a column width of 1.
+ *
+ *    - Other format characters (general category code Cf in the Unicode
+ *      database) and ZERO WIDTH SPACE (U+200B) have a column width of 0.
+ *
+ *    - Hangul Jamo medial vowels and final consonants (U+1160-U+11FF)
+ *      have a column width of 0.
+ *
+ *    - Spacing characters in the East Asian Wide (W) or East Asian
+ *      Full-width (F) category as defined in Unicode Technical
+ *      Report #11 have a column width of 2.
+ *
+ *    - All remaining characters (including all printable
+ *      ISO 8859-1 and WGL4 characters, Unicode control characters,
+ *      etc.) have a column width of 1.
+ *
+ * This implementation assumes that wchar_t characters are encoded
+ * in ISO 10646.
+ */
+
+static int wcwidth(wchar_t ch)
+{
+	/*
+	 * Sorted list of non-overlapping intervals of non-spacing characters,
+	 * generated by
+	 *   "uniset +cat=Me +cat=Mn +cat=Cf -00AD +1160-11FF +200B c".
+	 */
+	static const struct interval combining[] = {
+		{ 0x0300, 0x0357 }, { 0x035D, 0x036F }, { 0x0483, 0x0486 },
+		{ 0x0488, 0x0489 }, { 0x0591, 0x05A1 }, { 0x05A3, 0x05B9 },
+		{ 0x05BB, 0x05BD }, { 0x05BF, 0x05BF }, { 0x05C1, 0x05C2 },
+		{ 0x05C4, 0x05C4 }, { 0x0600, 0x0603 }, { 0x0610, 0x0615 },
+		{ 0x064B, 0x0658 }, { 0x0670, 0x0670 }, { 0x06D6, 0x06E4 },
+		{ 0x06E7, 0x06E8 }, { 0x06EA, 0x06ED }, { 0x070F, 0x070F },
+		{ 0x0711, 0x0711 }, { 0x0730, 0x074A }, { 0x07A6, 0x07B0 },
+		{ 0x0901, 0x0902 }, { 0x093C, 0x093C }, { 0x0941, 0x0948 },
+		{ 0x094D, 0x094D }, { 0x0951, 0x0954 }, { 0x0962, 0x0963 },
+		{ 0x0981, 0x0981 }, { 0x09BC, 0x09BC }, { 0x09C1, 0x09C4 },
+		{ 0x09CD, 0x09CD }, { 0x09E2, 0x09E3 }, { 0x0A01, 0x0A02 },
+		{ 0x0A3C, 0x0A3C }, { 0x0A41, 0x0A42 }, { 0x0A47, 0x0A48 },
+		{ 0x0A4B, 0x0A4D }, { 0x0A70, 0x0A71 }, { 0x0A81, 0x0A82 },
+		{ 0x0ABC, 0x0ABC }, { 0x0AC1, 0x0AC5 }, { 0x0AC7, 0x0AC8 },
+		{ 0x0ACD, 0x0ACD }, { 0x0AE2, 0x0AE3 }, { 0x0B01, 0x0B01 },
+		{ 0x0B3C, 0x0B3C }, { 0x0B3F, 0x0B3F }, { 0x0B41, 0x0B43 },
+		{ 0x0B4D, 0x0B4D }, { 0x0B56, 0x0B56 }, { 0x0B82, 0x0B82 },
+		{ 0x0BC0, 0x0BC0 }, { 0x0BCD, 0x0BCD }, { 0x0C3E, 0x0C40 },
+		{ 0x0C46, 0x0C48 }, { 0x0C4A, 0x0C4D }, { 0x0C55, 0x0C56 },
+		{ 0x0CBC, 0x0CBC }, { 0x0CBF, 0x0CBF }, { 0x0CC6, 0x0CC6 },
+		{ 0x0CCC, 0x0CCD }, { 0x0D41, 0x0D43 }, { 0x0D4D, 0x0D4D },
+		{ 0x0DCA, 0x0DCA }, { 0x0DD2, 0x0DD4 }, { 0x0DD6, 0x0DD6 },
+		{ 0x0E31, 0x0E31 }, { 0x0E34, 0x0E3A }, { 0x0E47, 0x0E4E },
+		{ 0x0EB1, 0x0EB1 }, { 0x0EB4, 0x0EB9 }, { 0x0EBB, 0x0EBC },
+		{ 0x0EC8, 0x0ECD }, { 0x0F18, 0x0F19 }, { 0x0F35, 0x0F35 },
+		{ 0x0F37, 0x0F37 }, { 0x0F39, 0x0F39 }, { 0x0F71, 0x0F7E },
+		{ 0x0F80, 0x0F84 }, { 0x0F86, 0x0F87 }, { 0x0F90, 0x0F97 },
+		{ 0x0F99, 0x0FBC }, { 0x0FC6, 0x0FC6 }, { 0x102D, 0x1030 },
+		{ 0x1032, 0x1032 }, { 0x1036, 0x1037 }, { 0x1039, 0x1039 },
+		{ 0x1058, 0x1059 }, { 0x1160, 0x11FF }, { 0x1712, 0x1714 },
+		{ 0x1732, 0x1734 }, { 0x1752, 0x1753 }, { 0x1772, 0x1773 },
+		{ 0x17B4, 0x17B5 }, { 0x17B7, 0x17BD }, { 0x17C6, 0x17C6 },
+		{ 0x17C9, 0x17D3 }, { 0x17DD, 0x17DD }, { 0x180B, 0x180D },
+		{ 0x18A9, 0x18A9 }, { 0x1920, 0x1922 }, { 0x1927, 0x1928 },
+		{ 0x1932, 0x1932 }, { 0x1939, 0x193B }, { 0x200B, 0x200F },
+		{ 0x202A, 0x202E }, { 0x2060, 0x2063 }, { 0x206A, 0x206F },
+		{ 0x20D0, 0x20EA }, { 0x302A, 0x302F }, { 0x3099, 0x309A },
+		{ 0xFB1E, 0xFB1E }, { 0xFE00, 0xFE0F }, { 0xFE20, 0xFE23 },
+		{ 0xFEFF, 0xFEFF }, { 0xFFF9, 0xFFFB }, { 0x1D167, 0x1D169 },
+		{ 0x1D173, 0x1D182 }, { 0x1D185, 0x1D18B },
+		{ 0x1D1AA, 0x1D1AD }, { 0xE0001, 0xE0001 },
+		{ 0xE0020, 0xE007F }, { 0xE0100, 0xE01EF }
+	};
+
+	/* test for 8-bit control characters */
+	if (ch == 0)
+		return 0;
+	if (ch < 32 || (ch >= 0x7f && ch < 0xa0))
+		return -1;
+
+	/* binary search in table of non-spacing characters */
+	if (bisearch(ch, combining, sizeof(combining)
+				/ sizeof(struct interval) - 1))
+		return 0;
+
+	/*
+	 * If we arrive here, ch is neither a combining nor a C0/C1
+	 * control character.
+	 */
+
+	return 1 +
+		(ch >= 0x1100 &&
+                    /* Hangul Jamo init. consonants */
+		 (ch <= 0x115f ||
+		  ch == 0x2329 || ch == 0x232a ||
+                  /* CJK ... Yi */
+		  (ch >= 0x2e80 && ch <= 0xa4cf &&
+		   ch != 0x303f) ||
+		  /* Hangul Syllables */
+		  (ch >= 0xac00 && ch <= 0xd7a3) ||
+		  /* CJK Compatibility Ideographs */
+		  (ch >= 0xf900 && ch <= 0xfaff) ||
+		  /* CJK Compatibility Forms */
+		  (ch >= 0xfe30 && ch <= 0xfe6f) ||
+		  /* Fullwidth Forms */
+		  (ch >= 0xff00 && ch <= 0xff60) ||
+		  (ch >= 0xffe0 && ch <= 0xffe6) ||
+		  (ch >= 0x20000 && ch <= 0x2fffd) ||
+		  (ch >= 0x30000 && ch <= 0x3fffd)));
+}
+
+/*
+ * This function returns the number of columns occupied by the character
+ * pointed to by the variable start. The pointer is updated to point at
+ * the next character. If it was not valid UTF-8, the pointer is set to NULL.
+ */
+int utf8_width(const char **start)
+{
+	unsigned char *s = (unsigned char *)*start;
+	wchar_t ch;
+
+	if (*s < 0x80) {
+		/* 0xxxxxxx */
+		ch = *s;
+		*start += 1;
+	} else if ((s[0] & 0xe0) == 0xc0) {
+		/* 110XXXXx 10xxxxxx */
+		if ((s[1] & 0xc0) != 0x80 ||
+				/* overlong? */
+				(s[0] & 0xfe) == 0xc0)
+			goto invalid;
+		ch = ((s[0] & 0x1f) << 6) | (s[1] & 0x3f);
+		*start += 2;
+	} else if ((s[0] & 0xf0) == 0xe0) {
+		/* 1110XXXX 10Xxxxxx 10xxxxxx */
+		if ((s[1] & 0xc0) != 0x80 ||
+				(s[2] & 0xc0) != 0x80 ||
+				/* overlong? */
+				(s[0] == 0xe0 && (s[1] & 0xe0) == 0x80) ||
+				/* surrogate? */
+				(s[0] == 0xed && (s[1] & 0xe0) == 0xa0) ||
+				/* U+FFFE or U+FFFF? */
+				(s[0] == 0xef && s[1] == 0xbf &&
+				 (s[2] & 0xfe) == 0xbe))
+			goto invalid;
+		ch = ((s[0] & 0x0f) << 12) |
+			((s[1] & 0x3f) << 6) | (s[2] & 0x3f);
+		*start += 3;
+	} else if ((s[0] & 0xf8) == 0xf0) {
+		/* 11110XXX 10XXxxxx 10xxxxxx 10xxxxxx */
+		if ((s[1] & 0xc0) != 0x80 ||
+				(s[2] & 0xc0) != 0x80 ||
+				(s[3] & 0xc0) != 0x80 ||
+				/* overlong? */
+				(s[0] == 0xf0 && (s[1] & 0xf0) == 0x80) ||
+				/* > U+10FFFF? */
+				(s[0] == 0xf4 && s[1] > 0x8f) || s[0] > 0xf4)
+			goto invalid;
+		ch = ((s[0] & 0x07) << 18) | ((s[1] & 0x3f) << 12) |
+			((s[2] & 0x3f) << 6) | (s[3] & 0x3f);
+		*start += 4;
+	} else {
+invalid:
+		*start = NULL;
+		return 0;
+	}
+
+	return wcwidth(ch);
+}
+
+int is_utf8(const char *text)
+{
+	while (*text) {
+		if (*text == '\n' || *text == '\t' || *text == '\r') {
+			text++;
+			continue;
+		}
+		utf8_width(&text);
+		if (!text)
+			return 0;
+	}
+	return 1;
+}
+
+static void print_spaces(int count)
+{
+	static const char s[] = "                    ";
+	while (count >= sizeof(s)) {
+		fwrite(s, sizeof(s) - 1, 1, stdout);
+		count -= sizeof(s) - 1;
+	}
+	fwrite(s, count, 1, stdout);
+}
+
+/*
+ * Wrap the text, if necessary. The variable indent is the indent for the
+ * first line, indent2 is the indent for all other lines.
+ */
+void print_wrapped_text(const char *text, int indent, int indent2, int width)
+{
+	int w = indent, assume_utf8 = is_utf8(text);
+	const char *bol = text, *space = NULL;
+
+	for (;;) {
+		char c = *text;
+		if (!c || isspace(c)) {
+			if (w < width || !space) {
+				const char *start = bol;
+				if (space)
+					start = space;
+				else
+					print_spaces(indent);
+				fwrite(start, text - start, 1, stdout);
+				if (!c) {
+					putchar('\n');
+					return;
+				} else if (c == '\t')
+					w |= 0x07;
+				space = text;
+				w++;
+				text++;
+			}
+			else {
+				putchar('\n');
+				text = bol = space + 1;
+				space = NULL;
+				w = indent = indent2;
+			}
+			continue;
+		}
+		if (assume_utf8)
+			w += utf8_width(&text);
+		else {
+			w++;
+			text++;
+		}
+	}
+}