二次的密码验证机制

#include <stdio.h>
#include <math.h>
#include <windows.h>

void InputPassword( size_t maxcount, char keys[], double timepoints[] )
{
    LARGE_INTEGER frequency, start_time;
    QueryPerformanceFrequency( &frequency );
    start_time.QuadPart = 0;

    bool keys_down[128] = { false }; // 记录 char 0-127 的按键状态
    HANDLE console = GetStdHandle(STD_INPUT_HANDLE);
    for( size_t i=0; i!=maxcount; )
    {
        INPUT_RECORD input_record;
        DWORD events_read;
        if( !ReadConsoleInput(console,&input_record,1,&events_read) || events_read!=1 || input_record.EventType!=KEY_EVENT ) // 忽略非按键信息
            continue;

        bool bKeyDown = input_record.Event.KeyEvent.bKeyDown!=0;
        char AsciiChar = input_record.Event.KeyEvent.uChar.AsciiChar;
        if( bKeyDown && AsciiChar=='\r' ) // 回车后不再记录
        {
            keys[i++] = 0;
            break;
        }
        if( AsciiChar<' ' || AsciiChar>=127 ) // 忽略无法映射的字符（对应着locale("C")下的isprint）
            continue;
        AsciiChar = (AsciiChar>='a' && AsciiChar<'z') ? (AsciiChar-'a'+'A') : AsciiChar; // 忽略大小写（否则要监控Shift键和Caps键，过于复杂）

        if( bKeyDown && !keys_down[AsciiChar] )
        {
            LARGE_INTEGER timepoint;
            QueryPerformanceCounter( &timepoint );
            if( i == 0 )
                start_time = timepoint;

            keys_down[AsciiChar] = true;
            keys[i] = AsciiChar;
            timepoints[i++] = (timepoint.QuadPart-start_time.QuadPart)/(frequency.QuadPart+0.0);
            putchar( '*' );
        }
        else if( !bKeyDown && keys_down[AsciiChar] )
        {
            LARGE_INTEGER timepoint;
            QueryPerformanceCounter( &timepoint );

            keys_down[AsciiChar] = false;
            keys[i] = AsciiChar;
            timepoints[i++] = (timepoint.QuadPart-start_time.QuadPart)/(frequency.QuadPart+0.0);
        }
    }
    putchar( '\n' );
}

void ShowPassword( size_t maxcount, char keys[], double timepoints[] )
{
    printf( "{\n" );
    bool keys_down[128] = { false };
    for( size_t i=0; i!=maxcount && keys[i]!=0; ++i )
    {
        keys_down[keys[i]] = !keys_down[keys[i]];
        printf( "    '%c' %-4s at %10.6fs\n", keys[i], (keys_down[keys[i]]?"Down":"Up"), timepoints[i] );
    }
    printf( "}\n" );
}

bool ShowDifference( size_t maxcount, char a_keys[], double a_timepoints[], char b_keys[], double b_timepoints[] )
{
    for( size_t i=0; i!=maxcount && a_keys[i]!=0; ++i )
    {
        if( a_keys[i] != b_keys[i] )
        {
            puts( "{ 按键顺序不一致 }" );
            return false;
        }
    }

    printf( "{\n" );
    double a_keys_down[128] = { 0 };
    double b_keys_down[128] = { 0 };
    for( size_t i=0; i!=maxcount && a_keys[i]!=0; ++i )
    {
        if( a_keys_down[a_keys[i]] == 0 )
        {
            a_keys_down[a_keys[i]] = a_timepoints[i] + 1.0;
            b_keys_down[b_keys[i]] = b_timepoints[i] + 1.0;
            if( i == 0 )
                printf( "    '%c' Down:\n", a_keys[i] );
            else
                printf( "    '%c' Down: 按键时刻相差 %10.6fs (%4.2f%%)\n", a_keys[i], fabs(a_timepoints[i]-b_timepoints[i]), fabs(a_timepoints[i]-b_timepoints[i])*100/a_timepoints[i] );
        }
        else
        {
            double d1 = fabs( a_timepoints[i]+1.0 - a_keys_down[a_keys[i]] );
            double d2 = fabs( b_timepoints[i]+1.0 - b_keys_down[b_keys[i]] );
            printf( "    '%c' Up  : 按键时长相差 %10.6fs (%4.2f%%)\n", a_keys[i], fabs(d1-d2), fabs(d1-d2)*100/d1 );
            a_keys_down[a_keys[i]] = 0;
            b_keys_down[b_keys[i]] = 0;
        }
    }
    printf( "}\n" );

    puts( "你认为这个偏差可以接受，就返回true；否则，返回false" );
    return true;
}

int main( void )
{
    char a_keys[50];
    double a_intervals[50];
    InputPassword( 50, a_keys, a_intervals );
    ShowPassword( 50, a_keys, a_intervals );

    char b_keys[50];
    double b_intervals[50];
    InputPassword( 50, b_keys, b_intervals );
    ShowPassword( 50, b_keys, b_intervals );

    ShowDifference( 50, a_keys, a_intervals, b_keys, b_intervals );
}