Chapter 3 C traps and Defects

Exercise 3.1 assumes that the array element whose subscript is out of bounds is invalid even if the address is obtained, how should the bufwrite program in section 3.6 of the book be written?

The source program in section 3.6 is:

void bufwrite(char *p,int n){     while(n > 0){          int k,rem;          if(bufptr == &buffer[N])               flushbuffer();          rem = N - (bufptr - buffer);          k = n > rem ? rem : n;          memcpy(bufptr,p,k);            bufptr += k;          p += k;          n -= k;     }}

According to your own ideas

if(bufptr == &buffer[N])

Change to the following statement:

if(bufptr > &buffer[N - 1])

Practice 3.2I personally think that the flush function in the exercise will be less efficient and will be compared more steps.

Exercise 3.3 compile a function to perform a binary search for a sorted integer table. Function input includes a pointer to the header, the number of elements in the table, and the value to be searched. The function output is a pointer to elements that meet the search requirements. If no value that meets the requirements is found, a null pointer is output.

The program is as follows:

int *FindNum(int *pTab,int TolNum,int FindNum){     int low = 0,high = TolNum - 1,mid = 0;     if(pTab[low] == FindNum){          return pTab;     }     if(pTab[high] == FindNum){          pTab = pTab + high;          return pTab;     }     while(low <= high){          mid = ((high - low) / 2) + low;          if(pTab[mid] == FindNum){               pTab = pTab + mid;               return pTab;          }          else{               if(pTab[mid] > FindNum)                    high = mid - 1;               else                    low = mid + 1;          }     }     return NULL;}