Functions to convert string(utf-8 in c++) to \uXXXX unicode escape

clip.cpp

//
// convert utf-8 string to \uXXXX format.
// return actual length of the escaped string.
//
size_t escapeUnicode(const char* fromStr, char* const toStr, const size_t& maxSize)
{
	// initialize iconv
	iconv_t cd = iconv_open("UTF-16BE", "UTF-8");
	// set iconv parameters
	int arg = 1;
	iconvctl(cd, ICONV_SET_TRANSLITERATE, &arg);
	iconvctl(cd, ICONV_SET_DISCARD_ILSEQ, &arg);
	// get the size to be converted.
	size_t fromLen = strlen(fromStr) + 1;
	size_t afromLen = fromLen;
	// set the size to contain the result as twice of utf-8 length
	// (if there is all ascii, twice is needed.)
	size_t toLen = fromLen << 1;
	// prepare a buffer to contain the UTF-16 string.
	char* buff = (char*)calloc(toLen, sizeof(char));
	// because iconv() function will move the pointer, prepare a backup.
	char* abuff = buff;
	size_t size = iconv(cd, (const char**)&fromStr, &afromLen, &abuff, &toLen);
	iconv_close(cd);

	// buffer for escaped string
	char* escBuff = (char*)calloc((fromLen << 1) + 1, sizeof(char));
	// size of the escaped string. 
	size_t n = 0;
	for (size_t i = 0; (buff[i] != 0 || buff[i+1] != 0); i += 2) {
		const size_t UNI_ESC_SIZE = 6;
		char uni[UNI_ESC_SIZE + 1] = {0};	// \uXXXX
		if (buff[i] != 0) {
			// unicode escape format
			sprintf(uni, "\\u%02X%02X", (unsigned char)buff[i], (unsigned char)buff[i+1]);
			// concat escaped unicode
			memcpy(escBuff + n, uni, UNI_ESC_SIZE);
			n += UNI_ESC_SIZE;
		} else {
			// ascii
			escBuff[n++] = buff[i + 1];
		}
	}
	escBuff[n] = '\0';	// terminate the string.

	strncpy(toStr, escBuff, maxSize);

	free(buff);
	buff = 0;
	free(escBuff);
	escBuff = 0;
	return n;
}

JsonUtilities.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Text;

namespace CIS_StdWebServices.Utils
{
    public class JsonUtilities
    {
        private static Encoding unicode = Encoding.BigEndianUnicode;

        public static string escapeUnicode(string uniStr)
        {
            byte[] unicodeBytes = unicode.GetBytes(uniStr);
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < unicodeBytes.Length - 1; i += 2)
            {
                if (unicodeBytes[i] != 0)
                {
                    sb.
                        Append("\\u").
                        Append(unicodeBytes[i].ToString("X2")).
                        Append(unicodeBytes[i + 1].ToString("X2"));
                }
                else
                {
                    char ascii = (char) unicodeBytes[i + 1];
                    sb.Append(ascii);
                }
            }
            return sb.ToString();
        }
    }
}