山寨C++ string

string.h

// system string

// 临时如此山寨一下，以后有空再抽象出一个子类。
// 按照ib所说：typedef std::basic_string  string;
class string
{
private:
 char *buf;
 int len;
 int buf_size;
 void init();
 void mksize( int siz );
 void copy( const char* str );
public:
 string();
 string( const char *src );
 //拷贝函数
 string( const string &src );
 ~string();
 //操作符重载
 char& operator [] ( int index );
 string& operator = ( const char *src );
 string& operator = ( const string& s );
 bool operator == ( const char *src );
 bool operator == ( const string& s );
 string& operator + ( const string& add2 );
 string& operator + ( const char* src );
 string& operator += ( const char* src );
 string& operator += ( const string& add2 );
 operator char *();
 operator int();
 //成员函数
 const char *cstr();
 char charAt( int index );
 string& fromInteger( int number );
 int length();
 int find( string substr , int start=0 );
 int rfind( string substr );
 string trim( char part );
 string left( int sublen );
 string right( int sublen );
 string mid( int start , int sublen );
 string replace( string src , string dest );
};

string.c

 string::string()
 {
  //临时分配这么多空间了
  init();
  mksize(16);
 }
 
 string::string( const char *src )
 {
  init();
  copy(src);
 }
 
 //拷贝函数
 string::string( const string &src )
 {
  init();
  copy(src.buf);
 }
 
 string::~string()
 {
  if( buf )
   free(buf);
 }
 
 //初始化私有成员
 void string::init()
 {
  len = 0;
  buf_size = 0;
  buf = (char*)0;
 }
 
 //改变缓冲区大小
 void string::mksize(int siz)
 {
  char* newstr;
  if( siz > buf_size ){
   buf_size = siz;
   newstr = (char*)malloc(siz);
   if(len>0){ //原来有数据，则复制过去
    strcpy( newstr, buf );
   }
   //设置结束符，便于使用strcat等
   newstr[len] = '\0';
   if( buf )
    free(buf);
   buf = newstr;
  }
 }
 
 void string::copy ( const char *src )
 {
  int newlen;
  newlen = strlen(src);
  len = 0; 
  mksize(newlen+1);
  if(!buf)return;
  strcpy( buf, src );
  len = newlen;
 }
 
 //操作符重载
 char& string::operator [] ( int index )
 {
  //如果不做检查，会溢出。。。
  return buf[index];
 }
 
 string& string::operator = ( const char *src )
 {
  copy(src);
  return *this;
 }
 
 string& string::operator = ( const string& s )
 {
  copy(s.buf);
  return *this;
 }
 
 bool string::operator == ( const char *src )
 {
  if( !buf || !src )
   return false;
  return ( strcmp( buf, src )==0 );
 }
 
 bool string::operator == ( const string& s )
 {
  if( !buf || !s.buf )
   return false;
  return ( strcmp( buf, s.buf )==0 );
 }
 
 string& string::operator + ( const string& add2 )
 {
  len += add2.len;
  mksize( len+1 );
  strcat( buf, add2.buf );
  return *this;
 }
 
 string& string::operator + ( const char* src )
 {
  len += strlen(src);
  mksize( len+1 );
  strcat( buf, src );
  return *this;
 }
 
 string& string::operator += ( const string& add2 )
 {
  *this = *this + add2;
  return *this;
 }
 
 string& string::operator += ( const char* src )
 {
  *this = *this + src;
  return *this;
 }
 
 string::operator char *()
 {
  return buf;
 }
 
 // get integer value
 string::operator int()
 {
  int num = 0;
  bool neg = false;
  char* str = buf;
  if((*str>='0'&&*str<='9')||*str=='-'||*str=='+'){
   if(*str=='-'||*str=='+'){
    if(*str=='-')
     neg = true;
    str++;
   } 
  }else
   return 0;
  while(*str>='0'&&*str<='9')
   num = num*10 + (*str++ -'0');
  return neg?-num:num;
 }
 
 //成员函数
 const char * string::cstr()
 {
  return buf;
 }
 
 char string::charAt( int index )
 {
  return buf[index];
 }
 
 string& string::fromInteger( int number )
 {
  mksize(16);
  len = sprintf(buf, "%ld", number);
  return *this;
 }
 
 int string::length()
 {
  return len;
 }
 
 int string::find( string substr , int start )
 {
  char* found;
  if( start>=len )
   return -1;
  found = strstr( &buf[start], substr.buf );
  if(found)
   return (int)(found-buf);
  return -1;
 }
 
 int string::rfind( string substr )
 {
  //not implemented.
  return -1;
 }
 
 string string::trim( char part )
 {
  int beg, end;
  string tmp;
  for(beg=0; buf[beg]==part; beg++);
  for(end=len-1; buf[end]==part; end--);
  if(end-beg>=0){
   tmp.mksize(end-beg+1);
   memcpy(tmp.buf, &buf[beg], end-beg);
   tmp.len = end-beg;
   tmp.buf[tmp.len]='\0';
  }
  return tmp;
 }
 
 string string::left( int sublen )
 {
  string tmp;
  if(sublen>len)
   sublen=len;
  if(sublen>=0){
   tmp.mksize(sublen+1);
   memcpy(tmp.buf, &buf[0], sublen);
   tmp.len = sublen;
   tmp.buf[sublen]='\0';
  }
  return tmp;
 }
 
 string string::right( int sublen )
 {
  string tmp;
  if(sublen>len)
   sublen=len;
  if(sublen>=0){
   tmp.mksize(sublen+1);
   memcpy(tmp.buf, &buf[len-sublen-1], sublen);
   tmp.len = sublen;
   tmp.buf[sublen]='\0';
  }
  return tmp;
 }
 
 string string::mid( int start , int sublen )
 {
  string tmp;
  if(start+sublen>len){
   sublen=len-start;
  }
  if(start>=0&&sublen>0){
   tmp.mksize(sublen+1);
   memcpy(tmp.buf, &buf[start], sublen);
   tmp.len = sublen;
   tmp.buf[sublen]='\0';
  }
  return tmp;
 }
 
 // 
 string string::replace( string src , string dest )
 {
  string tmp;
  int i, j;
  for(j=0,i=find(src.buf,0); i>=0; i=find(src.buf,j) ){
   tmp += mid(j,i-j) + dest;
   j = i + src.len;
  }
  tmp += mid(j, len-j);
  return tmp;
 }