c++ - Copy doesn't work in my string::copy implementation -
following on https://codereview.stackexchange.com/q/126242/23788.
i wrote string class , according feedback have changed stuff. there more should fixed?
+operator doesn't work , not know i've done wrong. have segfault when "str+str".
process finished exit code 139 and str.h
class str { friend std::istream &operator>>(std::istream &, str &); friend void swap(str &s, str &t) { std::swap(s.data, t.data); std::swap(s.length, t.length); std::swap(s.alloc, t.alloc); } public: typedef char *iterator; typedef size_t size_type; str() : data(nullptr), length(0), capacity(0) { } str(size_type length, char char_to_fill) : str() { create(length, char_to_fill); } str(const char *s) : str() { create(s); } template<class in> str(in b, in e) : str() { create(b, e); } ~str() { if (data) alloc.deallocate(data, capacity); data = nullptr; } str(const str &s) { *this = s; } // move constructor? str(str &&other) : str() {// initialize via default constructor, c++11 swap(*this, other); } str &operator+=(const str &s) { size_type new_length = length + s.length - 1; //remove 1 because of 2 nulls if (new_length > capacity) { reallocate(new_length); strcpy(data + length - 1, s.data); //overwrite null s length = new_length; } else {//if there enough space strcpy(data + length - 1, s.data); } return *this; } str &operator=(str rhs) { swap(*this, rhs); return *this; } char &operator[](size_type i) { return data[i]; }; const char &operator[](size_type i) const { return data[i]; }; size_type size() { return length; } const size_type size() const { return length; } const char *c_str() const { return data; } void copy(char *dest, size_type n) { if (n > length) throw std::out_of_range("out of range"); std::copy(data, data + n, dest); } char *begin() { return data; }; char *end() { return data + length; }; void push_back(char c) { if (length == capacity) { reallocate(capacity == 0 ? default_capacity : 2 * capacity); } data[length++] = c; } private: char *data; std::allocator<char> alloc; size_type length; size_type capacity; static const size_type default_capacity = 20; void create(size_type n, char character_to_fill) { capacity = length = n + 1; data = alloc.allocate(capacity); std::uninitialized_fill(data, data + length - 1, character_to_fill); //alloc.construct(data + length - 1, '\0'); //is needed constructed? data[length - 1] = '\0'; } void create(const char *s) { capacity = length = strlen(s) + 1; data = alloc.allocate(capacity); strcpy(data, s); //alloc.construct(data + length - 1, '\0'); data[length - 1] = '\0'; } template<class in> void create(in b, in e) { capacity = e - b + 1; data = alloc.allocate(capacity); while (b != e) { data[length++] = *(b++); } //alloc.construct(data + length -1, '\0'); data[length++] = '\0'; } void reallocate(size_t new_capacity) { char *new_data = alloc.allocate(new_capacity); std::copy(data, data + length, new_data); alloc.deallocate(data, length); data = new_data; capacity = new_capacity; } }; std::istream &operator>>(std::istream &is, str &s) { std::vector<char> buf; char actual_character; while (is.get(actual_character) && isspace(actual_character)) { ; } if (is) { //is correct check "is" ? buf.push_back(actual_character); while (is.get(actual_character) && !isspace(actual_character)); if (is) is.unget(); } s.create(buf.begin(), buf.end()); return is; } std::ostream &operator<<(std::ostream &os, const str &s) { os << s.c_str(); return os; } str operator+(str lhs, const str &rhs) { lhs += rhs; return lhs; } and example main.cpp
#include <iostream> #include <vector> #include "str.h" using std::cout; using std::endl; int main() { str s("siema"); cout<<s.c_str()<<endl; s = "hello"; cout<<s<<endl; s.push_back('a'); cout<<s<<endl; str t = "world"; //cout<<s+t<<endl; //this doesnt work s+=t; cout<<s<<endl; cout<<s[3]<<s[5]<<s[11]<<endl; cout<<s.size()<<endl; cout<<str(s.begin()+3, s.end()-2)<<endl; for(str::iterator = s.begin(); i<s.end() ; i+=2){ cout<<i<<endl; } char copied[3]; t.copy(copied, 4); cout<<copied<<endl; return 0; }
in code
char copied[3]; t.copy(copied, 4); cout<<copied<<endl; "copied" has length of 3 while trying copy 4 characters it. cause problem
check updated codes below. read comments "<--"
str.h
#include <iostream> #include <memory> #include <vector> class str { friend std::istream &operator >> (std::istream &, str &); void swap(str &s, str &t) { std::swap(s.data, t.data); std::swap(s.length, t.length); std::swap(s.alloc, t.alloc); } public: typedef char *iterator; typedef size_t size_type; str() : data(nullptr), length(0), capacity(0) { } str(size_type length, char char_to_fill) : str() { create(length, char_to_fill); } str(const char *s) : str() { create(s); } template<class in> str(in b, in e) : str() { create(b, e); } ~str() { if (data) alloc.deallocate(data, capacity); data = nullptr; } str(const str &s) { *this = s; } // move constructor? str(str &&other) : str() {// initialize via default constructor, c++11 swap(*this, other); } str &operator+=(const str &s) { size_type new_length = length + s.length - 1; //remove 1 because of 2 nulls if (new_length > capacity) { reallocate(new_length); strcpy(data + length - 1, s.data); //overwrite null s //length = new_length; //<-- need update length anyay. move before return } else {//if there enough space strcpy(data + length - 1, s.data); } length = new_length; //<-- update length return *this; } str &operator=(str rhs) { swap(*this, rhs); return *this; } char &operator[](size_type i) { return data[i]; }; const char &operator[](size_type i) const { return data[i]; }; size_type size() { return length; } const size_type size() const { return length; } const char *c_str() const { return data; } void copy(char *dest, size_type n) { if (n > length) throw std::out_of_range("out of range"); std::copy(data, data + n, dest); // <--forgot '\0'? dest[n] = '\0'; // <-- add '\0' } char *begin() { return data; }; char *end() { return data + length; }; void push_back(char c) { if (length == capacity) { reallocate(capacity == 0 ? default_capacity : 2 * capacity); } data[length++ - 1] = c; //<-- length - 1 last position, because length here includes '\0' data[length - 1] = 0; //<-- don't forget add '\0'. it's better if fill unused spaces '\0' after allocate them. } private: char *data; std::allocator<char> alloc; size_type length; size_type capacity; static const size_type default_capacity = 20; void create(size_type n, char character_to_fill) { capacity = length = n + 1; data = alloc.allocate(capacity); std::uninitialized_fill(data, data + length - 1, character_to_fill); //alloc.construct(data + length - 1, '\0'); //is needed constructed? data[length - 1] = '\0'; } void create(const char *s) { capacity = length = strlen(s) + 1; data = alloc.allocate(capacity); strcpy(data, s); //alloc.construct(data + length - 1, '\0'); data[length - 1] = '\0'; } template<class in> void create(in b, in e) { capacity = e - b + 1; data = alloc.allocate(capacity); while (b != e) { data[length++] = *(b++); } //alloc.construct(data + length -1, '\0'); data[length++] = '\0'; } void reallocate(size_t new_capacity) { char *new_data = alloc.allocate(new_capacity); std::copy(data, data + length, new_data); alloc.deallocate(data, length); data = new_data; capacity = new_capacity; } }; std::istream &operator >> (std::istream &is, str &s) { std::vector<char> buf; char actual_character; while (is.get(actual_character) && isspace(actual_character)) { ; } if (is) { //is correct check "is" ? buf.push_back(actual_character); while (is.get(actual_character) && !isspace(actual_character)); if (is) is.unget(); } s.create(buf.begin(), buf.end()); return is; } std::ostream &operator<<(std::ostream &os, const str &s) { os << s.c_str(); return os; } str operator+(str lhs, const str &rhs) { lhs += rhs; return lhs; } and main:
int main() { str s("siema"); cout << s.c_str() << endl; s = "hello"; cout << s << endl; s.push_back('a'); cout << s << endl; str t = "world"; //cout<<s+t<<endl; //this doesnt work s += t; cout << s << endl; cout << s[3] << s[5] << s[11] << endl; cout << s.size() << endl; cout << str(s.begin() + 3, s.end() - 2) << endl; (str::iterator = s.begin(); i<s.end(); += 2) { cout << << endl; } char copied[5]; //<-- 3, not enough space t.copy(copied, 4); cout << copied << endl; return 0; }
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