ser_cache add utf8idx to store utf8 chars

Code/thermal_printer/utf8-utils.c

@@ -0,0 +1,83 @@
+/* Freetype GL - A C OpenGL Freetype engine
+ *
+ * Distributed under the OSI-approved BSD 2-Clause License.  See accompanying
+ * file `LICENSE` for more details.
+ */
+#include <string.h>
+#include "utf8-utils.h"
+
+// ----------------------------------------------------- utf8_surrogate_len ---
+size_t
+utf8_surrogate_len( const char* character )
+{
+    size_t result = 0;
+    char test_char;
+
+    if (!character)
+        return 0;
+
+    test_char = character[0];
+
+    if ((test_char & 0x80) == 0)
+        return 1;
+
+    while (test_char & 0x80)
+    {
+        test_char <<= 1;
+        result++;
+    }
+
+    return result;
+}
+
+// ------------------------------------------------------------ utf8_strlen ---
+size_t
+utf8_strlen( const char* string )
+{
+    const char* ptr = string;
+    size_t result = 0;
+
+    while (*ptr)
+    {
+        ptr += utf8_surrogate_len(ptr);
+        result++;
+    }
+
+    return result;
+}
+
+uint32_t
+utf8_to_utf32( const char * character )
+{
+    if( !character )
+    {
+        return -1;
+    }
+
+    if( ( character[0] & 0x80 ) == 0x0 )
+    {
+        return character[0];
+    }
+
+    if( ( character[0] & 0xE0 ) == 0xC0 )
+    {
+        return ( ( character[0] & 0x3F ) << 6 ) | ( character[1] & 0x3F );
+    }
+
+    if( ( character[0] & 0xF0 ) == 0xE0 )
+    {
+        return ( ( character[0] & 0x1F ) << ( 6 + 6 ) ) | ( ( character[1] & 0x3F ) << 6 ) | ( character[2] & 0x3F );
+    }
+
+    if( ( character[0] & 0xF8 ) == 0xF0 )
+    {
+        return ( ( character[0] & 0x0F ) << ( 6 + 6 + 6 ) ) | ( ( character[1] & 0x3F ) << ( 6 + 6 ) ) | ( ( character[2] & 0x3F ) << 6 ) | ( character[3] & 0x3F );
+    }
+
+    if( ( character[0] & 0xFC ) == 0xF8 )
+    {
+        return ( ( character[0] & 0x07 ) << ( 6 + 6 + 6 + 6 ) ) | ( ( character[1] & 0x3F ) << ( 6 + 6 + 6 ) ) | ( ( character[2] & 0x3F ) << ( 6 + 6 ) ) | ( ( character[3] & 0x3F ) << 6 ) | ( character[4] & 0x3F );
+    }
+
+    return 0xFFFD; // invalid character
+}