Common (stringUtil): adds ffUtf8CharLenWidth

src/common/stringUtils.h

@@ -5,6 +5,8 @@
 #include <string.h>
 #include <ctype.h>
 
+#include "common/wcwidth.h"
+
 static inline bool ffStrSet(const char* str) {
     if (str == NULL) {
         return false;
@@ -71,6 +73,88 @@ static inline bool ffCharIsDigit(char c) {
     return '0' <= c && c <= '9';
 }
 
+// Parse one UTF-8 character, returning consumed byte count and display width.
+// Invalid / incomplete sequence falls back to one-byte width=1.
+// If the Unicode codepoint is non-printable, width becomes 0.
+static inline uint8_t ffUtf8CharLenWidth(const char* str, uint32_t length, uint8_t* width) {
+    if (__builtin_expect(length == 0 || *str == '\0', false)) {
+        if (width) {
+            *width = 0;
+        }
+        return 0;
+    }
+
+    unsigned char first = (unsigned char) *str;
+    if (__builtin_expect(first < 0x80, true)) {
+        if (width) {
+            *width = 1;
+        }
+        return 1;
+    }
+
+    uint8_t bytes;
+    if ((first & 0xE0) == 0xC0) {
+        bytes = 2;
+    } else if ((first & 0xF0) == 0xE0) {
+        bytes = 3;
+    } else if ((first & 0xF8) == 0xF0) {
+        bytes = 4;
+    } else {
+        if (width) {
+            *width = 1;
+        }
+        return 1;
+    }
+
+    if (length < bytes) {
+        if (width) {
+            *width = 1;
+        }
+        return 1;
+    }
+
+    for (uint8_t i = 1; i < bytes; ++i) {
+        unsigned char continuation = (unsigned char) str[i];
+        if (continuation == '\0' || (continuation & 0xC0) != 0x80) {
+            if (width) {
+                *width = 1;
+            }
+            return 1;
+        }
+    }
+
+    uint32_t ucs = (uint32_t) (first & ((1U << (8 - bytes)) - 1));
+    for (uint8_t i = 1; i < bytes; ++i) {
+        ucs <<= 6;
+        ucs |= (uint32_t) ((unsigned char) str[i] & 0x3F);
+    }
+
+    int wcWidth = mk_wcwidth(ucs);
+    if (width) {
+        *width = (uint8_t) (wcWidth < 0 ? 0 : wcWidth);
+    }
+    return bytes;
+}
+
+static inline uint32_t ffUtf8StrWidth(const char* str, uint32_t length) {
+    uint32_t result = 0;
+    const char* ptr = str;
+
+    while (length > 0 && *ptr != '\0') {
+        uint8_t width = 0;
+        uint8_t bytes = ffUtf8CharLenWidth(ptr, length, &width);
+        if (__builtin_expect(bytes == 0, false)) {
+            break;
+        }
+
+        result += width;
+        ptr += bytes;
+        length -= bytes;
+    }
+
+    return result > 0 ? result : (uint32_t) (ptr - str);
+}
+
 static inline bool ffCharIsHexDigit(char c) {
     return ffCharIsDigit(c) || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F');
 }