String--two-block model analysis

Topic:

There is a string beginning or ending with n spaces ("ABCDEFGDDDD") to remove the front and back spaces and return a new string.

1 //string two-block model2 intTRIMSPACESTR (Char*p,Char*buf)3 {4     intRV =0;5     Char*str =p;6     inti =0;//Search pointer variables, starting at the head of the string7     intj = strlen (str)-1;//search for pointer variables, starting at the end of the string8     intLen =0;//valid length of string9 Ten     if(Str==null | | buf==NULL) One     { ARV =-1; -printf"Function trimspacestr () Check (Str==null | | buf==null) Error:%d", RV); -         returnRV; the     } -  -      while(Isspace (Str[i]) && i<j) -     { +i++; -     } +  A      while(Isspace (Str[j]) && j>=0) at     { -j--; -     } -      -Len = j-i+1; -  instrncpy (BUF, str+I, Len); -  toBuf[len] =' /'; +     returnRV; - } the intMain () * { $     intRET =0;Panax Notoginseng  -     //allocated a memory space in the stack and copied a copy of the the     CharStr[] ="abcdefgdddd"; +  A     Charp1[ -]; the  +RET =trimspacestr (str, p1); -  $     if(Ret! =0) $     { -printf"Function delspace () Error:%d \ n", ret); -     } the      -printf"After Delete Space:%s\n", p1);Wuyi  the     return 0; -}

Analysis:First look at the functionint trimspacestr (char *p, char *buf), allocating memory in the main function, passing in the called function, preferably const in front of Char *p, prevents accidental modification of the source string
Then look at int main (), copy the string into the memory block temporarily assigned to the first address in Str, char str[] = "abcdefgdddd", the same as char p1[], will two into functions as arguments < Span style= "color: #008080;" >< Span style= "color: #800080;" > /span>

< Span style= "color: #0000ff;" > note: < Span style= "color: #008080;" >< Span style= "color: #800080;" > "ABCDEFGDDDD", the *p is not modified in the function, the string is in the constant area

Summarize:

1. The string can be in the stack area str[]= "", heap area char *p = malloc, and a constant area to allocate memory char *p = "", Be careful!!

2. Do not easily modify the contents of the memory block from other places, and really want to modify the new self to open up a piece of memory!

String--two-block model analysis