ule/array.hpp

#ifndef ULE_ARRAY_H
#define ULE_ARRAY_H

#include <new> // operator new, operator delete

#include "config.h"
#include "alloc.h" // allocators...
#include "serialize.h" // serialization
#include "string.h" // String::memcpy
#include "types.h" // type definitions


// this is a dynamic array (grows as needed)
// should work with any data type for T including primitive types
// some initial |capacity| is heap-allocated and a pointer is stored to it as |data|
// the |length| of the array, or number of filled slots is also tracked.
//
// it implements a single constructor, and operator new. no destructor, or operator overloading besides that.
// remember to use ->data or .data to actually access the underlying array.
//
// overhead:
//      size of the struct will be 128 bits on 64-bit platforms
//      note that if you heap allocate this structure and store it on another struct, you will have to chase two pointers to get at the data.
//      to avoid this, I often include this struct in other structs so there's only one pointer dereference,
//      just like including a raw pointer array + length in your struct.
//      because I like to do this, automatic destructors are not useful.
//
template <typename T>
struct Array {
    u32 length;
    u32 capacity;
    T* data;

    Array<T>(u32 _capacity = 8) {
        ULE_TYPES_H_FTAG;
        this->length   = 0;
        this->capacity = _capacity;
        this->data     = (T*) pCalloc(sizeof (T), _capacity);
    }
    void* operator new(size_t size) {
        ULE_TYPES_H_FTAG;
        return pMalloc((u32) size);
    }

    void checkIfShouldGrow() {
        ULE_TYPES_H_FTAG;
        if (this->isFull()) {
            // optimal number as you approach infinite elements approaches PHI, but 1.5 sometimes works better for finite sizes
            //
            // it seems, that a commonly chosen growth rate of '2' is perhaps the worst possible choice.
            // if you grow at a rate of 2x, you end up (likely) never being able to re-use the freed 'hole' in the heap
            // for a future allocation of the same kind.
            // useful reading for those interested in their own dynamic array implementations:
            // (facebook's vector impl, a strictly better std::vector)
            // https://github.com/facebook/folly/blob/main/folly/docs/FBVector.md
            //
            this->capacity = (u32) (this->capacity * 1.5);
            this->data = (T*) pRealloc(data, sizeof(T) * this->capacity);
        }
    }

    // for when the order in the array doesn't matter, move the end of the array into the removed slot
    void removeSwapWithEnd(u32 index) {
        ULE_TYPES_H_FTAG;
        if (this->isEmpty()) return; // overhead, maybe assert instead?

        u32 end = this->length - 1;
        if (index != end) {
            this->data[index] = this->data[end];
        }
        this->pop();
    }

    void removeSwapWithEnd(T* addr) {
        ULE_TYPES_H_FTAG;
        for (u32 i = 0; i < this->length; i++) {
            if ((this->data + i) == addr) {
                removeSwapWithEnd(i);
                return;
            }
        }
    }

    void removeAndShrink(u32 index) {
        ULE_TYPES_H_FTAG;
        for (u32 i = index + 1; i < this->length; i++) {
            String::memcpy(&this->data[i - 1], &this->data[i], sizeof(T));
        }
        this->length--;
    }

    void removeAndShrink(T* elementAddr) {
        ULE_TYPES_H_FTAG;
        s32 index = -1;
        for (u32 i = 0; i < this->length; i++) {
            if ((this->data + i) == elementAddr) {
                index = i;
                break;
            }
        }

        if (index == -1) {
            return;
        }

        for (u32 i = index + 1; i < this->length; i++) {
            String::memcpy((void*)(this->data + i - 1), (void*)(this->data + i), sizeof(T));
        }
        this->length--;
    }

    T pop() {
        ULE_TYPES_H_FTAG;
        if (this->isEmpty()) {
            die("empty");
        }

        return this->data[--this->length];
    }

    // sometimes, you want to copy some POD data on the stack to the next position in the internal array
    // that's what this does
    u32 pushCopy(T* e) {
        ULE_TYPES_H_FTAG;
        this->checkIfShouldGrow();

        String::memcpy((void*) &this->data[this->length++], e, sizeof(T));

        return this->length - 1;
    }

    // returns the next address into which you can store a T. makes sure there's enough room first.
    // it is irresponsible to call this and then not store a T in that address. this increments length,
    // reserving the next spot for you.
    T* pushNextAddrPromise() {
        ULE_TYPES_H_FTAG;
        this->checkIfShouldGrow();

        return &this->data[this->length++];
    }

    u32 push(T e) {
        ULE_TYPES_H_FTAG;
        this->checkIfShouldGrow();

        this->data[this->length++] = e;

        return this->length - 1;
    }

    u32 pushMany(T* elements, u32 count) {
        ULE_TYPES_H_FTAG;
        // ensure we have capacity. if we have to realloc multiple times that can suck,
        // but should be avoidable in practice by having an appropriately large initial capacity
        while (this->capacity < (this->length + count)) {
            this->capacity *= 1.5;
            this->data = (T*) pRealloc(data, sizeof (T) * this->capacity);
        }

        u32 start = this->length;
        for (u32 i1 = start, i2 = 0; i1 < count; i1++, i2++) {
            this->data[this->length++] = elements[i2];
        }

        return start;
    }

    void reverse() {
        ULE_TYPES_H_FTAG;
        u32 count = this->length / 2;

        for (u32 i = 0; i < count; i++) {
            u32 offset = this->length - 1 - i;

            T temp = this->data[i];
            this->data[i] = this->data[offset];
            this->data[offset] = temp;
        }
    }

    T shift() {
        ULE_TYPES_H_FTAG;
        if (this->length == 0) {
            return null;
        }

        T out = this->data[0];
        this->length -= 1;

        for (u32 i = 0; i < this->length; i++) {
            *(this->data + i) = *(this->data + i + 1);
        }

        return out;
    }

    T unshift(T e) {
        ULE_TYPES_H_FTAG;
        this->checkIfShouldGrow();

        for (u32 i = 0; i < this->length; i++) {
            *(this->data + i + 1) = *(this->data + i);
        }

        this->data[0] = e;
        this->length += 1;

        return this->length;
    }

    T peek() const {
        ULE_TYPES_H_FTAG;
        if (this->isEmpty()) {
            return null;
        }

        return this->data[this->length - 1];
    }

    bool isEmpty() const {
        ULE_TYPES_H_FTAG;
        return this->length == 0;
    }

    bool isFull() const {
        ULE_TYPES_H_FTAG;
        return this->length == this->capacity;
    }

    void clear() {
        ULE_TYPES_H_FTAG;
        this->length = 0;
    }
};

#ifdef ULE_CONFIG_OPTION_SERIALIZATION
template <typename T>
static void serialize(String* str, Array<T> array) {
    ULE_TYPES_H_FTAG;
    serialize(str, array.length);
    serialize(str, array.capacity);
    for (u32 i = 0; i < array.length; i++) {
        serialize(str, array.data[i]);
    }
}

template <typename T>
static void serialize(String* str, Array<T>* array) {
    ULE_TYPES_H_FTAG;
    SERIALIZE_HANDLE_NULL(str, array);
    serialize(str, array->length);
    serialize(str, array->capacity);
    for (u32 i = 0; i < array->length; i++) {
        serialize(str, array->data[i]);
    }
}

template <typename T>
static void deserialize(char** buffer, Array<T>* array) {
    ULE_TYPES_H_FTAG;
    deserialize(buffer, &array->length);
    deserialize(buffer, &array->capacity);
    for (u32 i = 0; i < array->length; i++) {
        deserialize(buffer, array->data + i);
    }
}

template <typename T>
static void deserialize(char** buffer, Array<T>** array) {
    ULE_TYPES_H_FTAG;
    DESERIALIZE_HANDLE_NULL(buffer, array);
    u32 length, capacity;
    deserialize(buffer, &length);
    deserialize(buffer, &capacity);
    Array<T>* _array = new Array<T>(capacity);
    _array->length = length;
    for (u32 i = 0; i < _array->length; i++) {
        deserialize(buffer, _array->data + i);
    }
    *array = _array;
}
#endif // ULE_CONFIG_OPTION_SERIALIZATION

#endif