From c2139e2e03cbcee9a1ae03956b1f06d3a9c269b0 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Sat, 26 Mar 2022 19:42:13 -0400
Subject: util: New xstrwidth() function

---
 util.c | 36 ++++++++++++++++++++++++++++++++++++
 util.h | 10 ++++++++++
 2 files changed, 46 insertions(+)

diff --git a/util.c b/util.c
index f67406c..a62e66c 100644
--- a/util.c
+++ b/util.c
@@ -29,6 +29,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <wchar.h>
 
 #if BFS_HAS_SYS_PARAM
 #	include <sys/param.h>
@@ -252,6 +253,41 @@ int xstrtofflags(const char **str, unsigned long long *set, unsigned long long *
 #endif
 }
 
+size_t xstrwidth(const char *str) {
+	size_t len = strlen(str);
+	size_t ret = 0;
+
+	mbstate_t mb;
+	memset(&mb, 0, sizeof(mb));
+
+	while (len > 0) {
+		wchar_t wc;
+		size_t mblen = mbrtowc(&wc, str, len, &mb);
+		int cwidth;
+		if (mblen == (size_t)-1) {
+			// Invalid byte sequence, assume a single-width '?'
+			mblen = 1;
+			cwidth = 1;
+			memset(&mb, 0, sizeof(mb));
+		} else if (mblen == (size_t)-2) {
+			// Incomplete byte sequence, assume a single-width '?'
+			mblen = len;
+			cwidth = 1;
+		} else {
+			cwidth = wcwidth(wc);
+			if (cwidth < 0) {
+				cwidth = 0;
+			}
+		}
+
+		str += mblen;
+		len -= mblen;
+		ret += cwidth;
+	}
+
+	return ret;
+}
+
 bool is_nonexistence_error(int error) {
 	return error == ENOENT || errno == ENOTDIR;
 }
diff --git a/util.h b/util.h
index b780624..b5c7d80 100644
--- a/util.h
+++ b/util.h
@@ -207,6 +207,16 @@ int xfaccessat(int fd, const char *path, int amode);
  */
 int xstrtofflags(const char **str, unsigned long long *set, unsigned long long *clear);
 
+/**
+ * wcswidth() variant that works on narrow strings.
+ *
+ * @param str
+ *         The string to measure.
+ * @return
+ *         The likely width of that string in a terminal.
+ */
+size_t xstrwidth(const char *str);
+
 /**
  * Return whether an error code is due to a path not existing.
  */
-- 
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