[CPP] Add vector library

Author: scopeInfinity

src/usr/include/vector.h

@@ -0,0 +1,30 @@
+#pragma once
+
+#include <stddef.h>
+
+namespace std {
+
+template<typename T>
+class vector {
+    std::size_t _capacity, _size;
+    T *_data;
+    void resize_capacity(std::size_t capacity);
+
+public:
+    vector<T>();
+    vector<T>(std::size_t size, const T &_default);
+
+    bool empty();
+    std::size_t size();
+    void push_back(const T &val);
+    void pop_back();
+
+    T& back();
+    T& front();
+    T& at(std::size_t pos);
+    T& operator[](std::size_t pos);
+};
+
+}  // namespace std end
+
+#include <vector.tcc>

src/usr/include/vector.tcc

@@ -0,0 +1,92 @@
+#pragma once
+
+// This is internal headerfile to be included by vector.h only
+
+#include <vector.h>
+#include <new.h>
+#include <stdlib.h>
+#include <string.h>
+
+namespace std {
+
+static std::size_t next_power2(std::size_t size) {
+    // assumes no overflow
+    std::size_t p = 1;
+    while (p && p < size) p <<= 1;
+    return p;
+}
+
+template <typename T>
+vector<T>::vector() : _data(NULL), _size(0) {
+    resize_capacity(1);
+}
+
+template <typename T>
+vector<T>::vector(std::size_t size, const T &_default): _size(size)  {
+    this->_data = NULL;
+    resize_capacity(size);
+    for(std::size_t i = 0; i < size; i++) {
+        this->_data[i] = _default;
+    }
+}
+
+template <typename T>
+void vector<T>::resize_capacity(std::size_t capacity) {
+    // internal; assumes capacity to be power of 2
+    // and will also make a copy of array and move _data pointer.
+    // assumes size<=current_capacity and size<=new_capacity
+    this->_capacity = capacity;
+    const std::size_t data_size = capacity*sizeof(T);
+    T *_new_data = (T*) std::malloc(data_size);
+    if (!_new_data) return;  // malloc failed
+    std::memcpy(_new_data, this->_data, data_size);
+    std::free(this->_data);  // should be no-op if _data == NULL
+    this->_data = _new_data;
+}
+
+template <typename T>
+bool vector<T>::empty() {
+    return this->_size == 0;
+}
+
+template <typename T>
+std::size_t vector<T>::size() {
+    return this->_size;
+}
+
+template <typename T>
+void vector<T>::push_back(const T &val) {
+    if(this->_size == this->_capacity) {
+        resize_capacity(this->_capacity*2);
+    }
+    this->_data[this->_size++] = val;
+}
+
+template <typename T>
+void vector<T>::pop_back() {
+    // not reducing the capacity for now
+    if(this->_size > 0) {
+        this->_size--;
+    }
+}
+
+template <typename T>
+T &vector<T>::back() {
+    return this->_data[this->_size-1];
+}
+template <typename T>
+T &vector<T>::front() {
+    return this->_data[0];
+}
+
+template <typename T>
+T &vector<T>::at(std::size_t pos) {
+    return this->_data[pos];
+}
+
+template <typename T>
+T &vector<T>::operator[](std::size_t pos) {
+    return this->_data[pos];
+}
+
+} // namespace std end

src/usr/local/src/simplecpp.cpp

@@ -1,6 +1,7 @@
 // Simple C++ program
 #include <stdio.h>
 #include <iostream.h>
+#include <vector.h>
 
 namespace geometry {
 
@@ -66,5 +67,13 @@ int main(int argc, char *argv[]) {
     std::cout << "Your name is: " << name << std::endl;
     delete[] name;
 
+    // vector
+    std::vector<int> list(4, 100);
+    list[0] = 0;
+    for(std::size_t i = 0; i < list.size(); i++) {
+        std::cout << "list[" << (int)i << "] = " << list[i] << std::endl;
+    }
+
+    std::cout << "Exiting..." << std::endl;
     return 0;
 }