string中c_str()、data()、copy(p,n)函數的用法

標準庫的string類提供了3個成員函數來從一個string得到c類型的字符數組：c_str()、data()、copy(p,n)。

1. c_str()：生成一個const char*指針，指向以空字符終止的數組。

注：

①這個數組的數據是臨時的，當有一個改變這些數據的成員函數被調用後，其中的數據就會失效。因此要麼現用先轉換，要麼把它的數據複製到用戶自己可以管理的內存中。注意。看下例：
const char* c;
string s=”1234”;
c = s.c_str();
cout<

include

include

int main( )
{
using namespace std;
string str1 ( “1234567890” );
basic_string ::iterator str_Iter;
char array1 [ 20 ] = { 0 };
char array2 [ 10 ] = { 0 };
basic_string :: pointer array1Ptr = array1;
basic_string :: value_type *array2Ptr = array2;

cout << "The original string str1 is: ";
for ( str_Iter = str1.begin( ); str_Iter != str1.end( ); str_Iter++ )
    cout << *str_Iter;
cout << endl;

basic_string <char>:: size_type nArray1;
// Note: string::copy is potentially unsafe, consider
// using string::_Copy_s instead.
nArray1 = str1.copy ( array1Ptr , 12 );  // C4996
cout << "The number of copied characters in array1 is: "
    << nArray1 << endl;
cout << "The copied characters array1 is: " << array1Ptr << endl;

basic_string <char>:: size_type nArray2;
// Note: string::copy is potentially unsafe, consider
// using string::_Copy_s instead.
nArray2 = str1.copy ( array2Ptr , 5 , 6  );  // C4996
cout << "The number of copied characters in array2 is: "
    << nArray2 << endl;
cout << "The copied characters array2 is: " << array2Ptr << endl;

////注意一定要使array3有足夠的空間
//char array3[5]={0};
//basic_string<char>::pointer array3Ptr=array3;
//basic_string<char>::size_type nArray3;
//nArray3 = str1.copy(array3,9); //錯誤！！！！
//cout<<"The number of copied characters in array3 is: "
//  <<nArray3<<endl;
//cout<<"The copied characters array3 is: "<<array3Ptr<<endl;

}

上面最後註釋掉的部分，雖然編譯沒有錯誤，但是運行時會產生錯誤：Stack around the variable ‘array3’ was corrupted.