Threeway converter string between simplified Chinese GBK, UTF-8, and Unicode for an embed system (stm32, x86, or any other little-endian system).

 It also suits for threeway string converting for BIG5, Japanese Shift-JIS or Korean EUC-KR to UTF-8/unicode.

• This library didn't need any other library.
• Only suit for little-endian system. For example x86, stm32.
• This library cost about 180KB ROM space.(Lookup table is supper large.)
• This library only suit for characters whose Unicode index smaller than 0xFFFF. Which means it suits for almost every character.
• This library didn't need malloc or any other dynamic memory. (Suit for embed system.)
• This library is super fast. Searching lookup table only needs 16 comparisons at most. (Normally this kind of search need about 10000 comparisons on average.)
• I only test this library for GBK converting on stm32f4 system.
• The Lookup table is modified from fatfs library. And converter part is enlightened from:  不依赖任何系统API,用c语言实现gbk/utf8/unicode编码转换  and  GB2312转unicode程序

• Add gbk2utf2uni.h, gbk2utf2uni.c and  into your project.

• GBK.c (optional): This file provides a Lookup table. If you use fatfs library and there are already cc936.c file in your project, you don't need this file at all.

Either GBK.c or cc932.c may cost about 180KB ROM space.(Not suit for low-cost MCU.)

• File names of the lookup table for other language, and corresponding file in FatFs library.

• Then convert string like this:

char tmpGBK[128];
memset(tmpGBK,0, sizeof(tmpGBK));
utf82gbk(tmpGBK, "测试一下UTF-8转成GBK.\n");
printf(tmpGBK);

Convert function would detect string end when converting. So GBK string and UTF-8 string for converted must end with '\0'. And Unicode string must end with "\0\0".

• Notice: Immediate string type is according to your code file store mode.

In my case, all code is stored in UTF-8 mode.(Upper code demo.) If your code file is in GBK mode. Then you should test code like this:

char tmpUTF8[128];
memset(tmpUTF8,0, sizeof(tmpUTF8));
gb2utf8(tmpUTF8, "测试一下GBK转成UTF-8.\n");
printf(tmpUTF8);

这本来就是一个简单的功能。不过查了半天资料，居然没有一个库是可以拿来就用的。崩溃。所以就查了资料自己写了个库。自从用了stm32，一个项目还没构建完，居然就造了好几个轮子了。 本来想写个中文的说明，不过今天太晚了。睡了。