feat(unicode): add SUniSGetUTF8

storm/Unicode.cpp

@@ -0,0 +1,59 @@
+#include "storm/Unicode.hpp"
+
+uint32_t SUniSGetUTF8(const uint8_t* strptr, int32_t* chars) {
+    if (chars) {
+        *chars = 0;
+    }
+
+    if (!strptr || !*strptr) {
+        return -1;
+    }
+
+    if (chars) {
+        *chars = *chars + 1;
+    }
+
+    uint32_t value = *strptr;
+    int32_t extra;
+
+    if ((value & 0xFE) == 0xFC) {
+        value &= 0x01;
+        extra = 5;
+    } else if ((value & 0xFC) == 0xF8) {
+        value &= 0x03;
+        extra = 4;
+    } else if ((value & 0xF8) == 0xF0) {
+        value &= 0x07;
+        extra = 3;
+    } else if ((value & 0xF0) == 0xE0) {
+        value &= 0x0F;
+        extra = 2;
+    } else if ((value & 0xE0) == 0xC0) {
+        value &= 0x1F;
+        extra = 1;
+    } else if ((value & 0x80) == 0x00) {
+        return value;
+    } else {
+        return 0x80000000;
+    }
+
+    const uint8_t* next = strptr + 1;
+
+    for (int32_t i = 0; i < extra; i++, next++) {
+        if (!*next) {
+            return -1;
+        }
+
+        if (chars) {
+            *chars = *chars + 1;
+        }
+
+        if ((*next & 0xC0) != 0x80) {
+            return 0x80000000;
+        }
+
+        value = (value << 6) | (*next & 0x3F);
+    }
+
+    return value;
+}