Win32/C++ 获取GBK编码字符个数

#include <string>

int32_t GetGbkCount(const void* pData, size_t size = -1, std::string* pGbk = nullptr)
{
    const uint8_t* pCpData = (const uint8_t*)pData;
    std::string strOutGbk;      // 输出字符编码
    uint16_t gbkCode = 0;       // GBK编码
    int32_t nByteCount = 0;     // 字节计数
    int32_t nChCount = 0;       // 字符计数
    bool fResult = true;        // 操作结果

    while ((0 != *pCpData) && (0 != size))
    {
        uint8_t ch = *pCpData;

        // ASCII编码 兼容
        if (ch <= 0x7F)
        {
            gbkCode = ch;
            nChCount++;
        }
        else
        {
            // 高字节范围: 0x81 - 0xFE
            if (0 == nByteCount)
            {
                gbkCode = 0;
                if (ch >= 0x81 && ch <= 0xFE)
                {
                    gbkCode = ch;
                    nByteCount = 1;
                }
                else
                {
                    fResult = false;
                    break;
                }
            }
            else
            {
                // 低字节范围: 0x40 - 0xFE (不包括0x7F)
                if (1 == nByteCount)
                {
                    if (!(ch >= 0x40 && ch <= 0xFE) || 0x7F == ch)
                    {
                        fResult = false;
                        break;
                    }
                }

                gbkCode = gbkCode << 8;
                gbkCode |= ch;

                nByteCount--;

                if (0 == nByteCount)
                {
                    nChCount++;
                }
            }
        }

        if (0 == nByteCount)
        {
            if (gbkCode <= 0x7F)
            {
                strOutGbk.push_back((uint8_t)gbkCode);
            }
            else
            {
                strOutGbk.push_back(gbkCode >> 8);
                strOutGbk.push_back(gbkCode & 0xFF);
            }
        }

        pCpData++;

        if (-1 != size)
        {
            size--;
        }
    }

    if (!fResult)
    {
        return -1;
    }

    if (pGbk)
    {
        *pGbk = std::move(strOutGbk);
    }

    return nChCount;
}