Helpers File中的TCP IP Stack无限循环

嗨，我现在正在使用TCP IP堆栈V5.42.08，在调试项目时，我发现程序被困在助手循环中。精确地考虑变量VBIT计数，在0初始化，并将它与0值进行比较。这是我不理解的：为什么我们要增加VBIT？在做IF条件之前（++是变量之前，很明显），如果我们希望这个变量保持在0。我是否错过了一些函数，将它放在-- 1之前？这里是帮助文件函数，其中出现问题。



      以下为原文

    Hi,

I'm currently working with the TCP IP Stack v5.42.08 and while debugging the project I found that the program was stuck in Helpers loop.

Precisely regarding the variable vBitCount, initialized at 0, and compared at the end to 0 value.
This is what I don't understand : why do we increment vBitCount BEFORE doing the if condition (++ are before the variable, obviously ), if we want that variable to stay at 0.

Did I miss some function that puts it at -1 right before ?
Here is the Helpers file function where the problem occurs.

DWORD GenerateRandomDWORD(void)
{
BYTE vBitCount;
WORD w, wTime, wLastValue;
DWORD dwTotalTime;
union
{
  DWORD dw;
  WORD w[2];
} randomResult;

#if defined __18CXX
{
//same loop than below but for 18cxx devices
}
#else
{
WORD AD1CON1Save, AD1CON2Save, AD1CON3Save;
WORD T1CONSave, PR1Save;

// Save hardware SFRs
AD1CON1Save = AD1CON1;
AD1CON2Save = AD1CON2;
AD1CON3Save = AD1CON3;
T1CONSave = T1CON;
PR1Save = PR1;

// Set up Timer and A/D converter module
AD1CON1 = 0x0000; // Turn off the ADC so we can write to it
AD1CON3 = 0x9F00; // Frc A/D clock, 31 Tad acquisition
AD1CON2 = 0x003F; // Interrupt after every 16th sample/convert
AD1CON1 = 0x80E4; // Turn on the A/D module, auto-convert
T1CON = 0x8000; // TON = 1, no prescalar
PR1 = 0xFFFF; // Don't clear timer early
vBitCount = 0; /* ---- variable used at the end of the loop to check entropy of packets----- */
dwTotalTime = 0;
wLastValue = 0;
randomResult.dw = LFSRRand();
while(1)
{
  ClrWdt();
  #if defined(__C30__)
   while(!IFS0bits.AD1IF); // A/D interrupt flag bit
  #else
   while(!IEC0bits.AD1IE) // A/D interrupt enable
            {
                //enable interrupt ad1
                IEC0bits.AD1IE=1;
            }
  #endif
  wTime = TMR1;
  TMR1 = 0x0000;

  #if defined(__C30__)
   IFS0bits.AD1IF = 0;
  #else
   IFS1CLR = _IFS0_AD1IF_MASK;
  #endif
  w = LFSRRand();

  // Wait no longer than 1 second obtaining entropy
  dwTotalTime += wTime;
  if(dwTotalTime >= GetInstructionClock())
  {
   randomResult.w[0] ^= LFSRRand();
   randomResult.w[1] ^= LFSRRand();
   break;
  }

  // Keep sampling if minimal entropy was likely obtained this round
  if(wLastValue == wTime)
   continue;

  // Add this entropy into the pseudo random number generator by reseeding
  LFSRSeedRand(w + (wLastValue - wTime));
  wLastValue = wTime;

  // Accumulate at least 32 bits of randomness over time
  randomResult.dw <<= 1;
  if(LFSRRand() & 0x0080)
   randomResult.w[0] |= 0x1;

  // See if we've collected a fair amount of entropy and can quit early
  if(++vBitCount == 0u)
   break;
}


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