3 files changed, 174 insertions, 0 deletions

diff --git a/include/unicode/string.h b/include/unicode/string.h
index e989380..9ac029a 100644
--- a/include/unicode/string.h
+++ b/include/unicode/string.h
@@ -18,7 +18,10 @@ enum [[clang::flag_enum]] caseflags {
 /* clang-format on */
 
 [[nodiscard]] size_t u8gcnt(const char8_t *, size_t);
+[[nodiscard]] size_t u8wcnt(const char8_t *, size_t);
+
 size_t u8gnext(struct u8view *, const char8_t **, size_t *);
+size_t u8wnext(struct u8view *, const char8_t **, size_t *);
 
 #define mlib_warn_trunc nodiscard("don’t forget to check for truncation")
 [[mlib_warn_trunc]] size_t u8casefold(char8_t *restrict, size_t,
diff --git a/lib/unicode/string/u8wcnt.c b/lib/unicode/string/u8wcnt.c
new file mode 100644
index 0000000..f1b1742
--- /dev/null
+++ b/lib/unicode/string/u8wcnt.c
@@ -0,0 +1,10 @@
+#include "unicode/string.h"
+
+size_t
+u8wcnt(const char8_t *s, size_t n)
+{
+	size_t m = 0;
+	while (u8wnext(nullptr, &s, &n))
+		m++;
+	return m;
+}
diff --git a/lib/unicode/string/u8wnext.c b/lib/unicode/string/u8wnext.c
new file mode 100644
index 0000000..4236cff
--- /dev/null
+++ b/lib/unicode/string/u8wnext.c
@@ -0,0 +1,161 @@
+#include "macros.h"
+#include "mbstring.h"
+#include "unicode/prop.h"
+#include "unicode/string.h"
+
+#define IS_AHLETTER(cp)   ((cp) == WB_LE || (cp) == WB_HL)
+#define IS_MIDNUMLETQ(cp) ((cp) == WB_MB || (cp) == WB_SQ)
+
+#define RET(x) \
+	do { \
+		ws->prev_ap = ap; \
+		return (x); \
+	} while (false)
+
+struct wbrk_state {
+	int ri_parity;
+	enum uprop_wb prev_ap;
+};
+
+static bool u8iswbrk(const char8_t **, size_t *, struct wbrk_state *);
+
+size_t
+u8wnext(struct u8view *w, const char8_t **s, size_t *n)
+{
+	ASSUME(s != nullptr);
+	ASSUME(n != nullptr);
+
+	if (*n == 0)
+		return 0;
+
+	const char8_t *p = *s;
+	if (w != nullptr)
+		w->p = p;
+
+	size_t m = *n;
+	struct wbrk_state ws = {};
+	while (!u8iswbrk(&p, &m, &ws))
+		;
+
+	ptrdiff_t d = p - *s;
+	*n -= d;
+	*s = p;
+	if (w)
+		w->len = d;
+	return d;
+}
+
+bool
+u8iswbrk(const char8_t **s, size_t *n, struct wbrk_state *ws)
+{
+	ASSUME(s != nullptr);
+	ASSUME(n != nullptr);
+	ASSUME(ws != nullptr);
+
+	rune a, b, c;
+	enum uprop_wb ap, bp, cp;
+	a = b = c = ap = bp = cp = 0;
+
+	u8next(&a, s, n);
+
+	{
+		const char8_t *s_cpy = *s;
+		size_t n_cpy = *n;
+		u8next(&b, &s_cpy, &n_cpy);
+		u8next(&c, &s_cpy, &n_cpy);
+	}
+
+	ws->ri_parity = ws->ri_parity == 0 && uprop_is_ri(a);
+
+	/* WB1 & WB2 */
+	if (!a || !b)
+		RET(true);
+
+	/* WB3 */
+	if (a == '\r' && b == '\n')
+		RET(false);
+
+	/* WB3a */
+	if (a == '\r' || a == '\n' || (ap = uprop_get_wb(a)) == WB_NL)
+		RET(true);
+
+	/* WB3b */
+	if (b == '\r' || b == '\n' || (bp = uprop_get_wb(b)) == WB_NL)
+		RET(true);
+
+	/* WB3c */
+	if (ap == WB_ZWJ && uprop_is_extpict(b))
+		RET(false);
+
+	/* WB3d */
+	if (ap == WB_WSEGSPACE && bp == WB_WSEGSPACE)
+		RET(false);
+
+	/* WB4 */
+	if (bp == WB_FO || bp == WB_EXTEND || bp == WB_ZWJ)
+		RET(false);
+
+	/* WB5 */
+	if (IS_AHLETTER(ap) && IS_AHLETTER(bp))
+		RET(false);
+
+	/* WB6 */
+	cp = uprop_get_wb(c);
+	if (IS_AHLETTER(ap) && (bp == WB_ML || IS_MIDNUMLETQ(bp))
+	    && IS_AHLETTER(cp))
+	{
+		RET(false);
+	}
+
+	/* WB7 */
+	if (IS_AHLETTER(ws->prev_ap) && (ap == WB_ML || IS_MIDNUMLETQ(ap))
+	    && IS_AHLETTER(bp))
+	{
+		RET(false);
+	}
+
+	/* WB7a & WB7b */
+	if (ap == WB_HL && (bp == WB_SQ || (bp == WB_DQ && cp == WB_HL)))
+		RET(false);
+
+	/* WB7c */
+	if (ws->prev_ap == WB_HL && ap == WB_DQ && bp == WB_HL)
+		RET(false);
+
+	/* WB8, WB9, & WB10 */
+	if ((ap == WB_NU || IS_AHLETTER(ap)) && (bp == WB_NU || IS_AHLETTER(bp)))
+		RET(false);
+
+	/* WB11 */
+	if (ws->prev_ap == WB_NU && (ap == WB_MN || IS_MIDNUMLETQ(ap))
+	    && bp == WB_NU)
+	{
+		RET(false);
+	}
+
+	/* WB12 */
+	if (ap == WB_NU && (bp == WB_MN || IS_MIDNUMLETQ(bp)) && cp == WB_NU)
+		RET(false);
+
+	/* WB13 */
+	if (ap == WB_KA && bp == WB_KA)
+		RET(false);
+
+	/* WB13a */
+	if ((IS_AHLETTER(ap) || ap == WB_NU || ap == WB_KA || ap == WB_EX)
+	    && bp == WB_EX)
+	{
+		RET(false);
+	}
+
+	/* WB13b */
+	if (ap == WB_EX && (IS_AHLETTER(bp) || bp == WB_NU || bp == WB_KA))
+		RET(false);
+
+	/* WB15 & WB16 */
+	if (ap == WB_RI && bp == WB_RI && ws->ri_parity == 1)
+		RET(false);
+
+	/* WB999 */
+	RET(true);
+}