dynamic_array.c

// written by Sam Goodrick
// contact at sdg31@zips.uakron.edu

#include "dynamic_array.h"
#include <malloc.h>

void construct( dynamic_array* arr )
{
	arr->capacity = 4;
	arr->array = malloc( arr->capacity * sizeof( double ) );

	arr->size = 0;
	arr->first = arr->array;
	arr->last = arr->array;
	arr->limit = arr->array + arr->capacity;
}

// 
void destruct( dynamic_array* arr )
{
	free( arr->array );

	arr->array = arr->first = arr->last = arr->limit = NULL;
}

void resize( dynamic_array* arr )
{
	double* temp;
	arr->capacity *= 2;
	
	temp = realloc( arr->array, arr->capacity * sizeof( double ) );

	if( temp == NULL )
	{
		printf( "unable to reallocate array %p\n", arr );
		return;
	}
	
	arr->first = arr->array;
	arr->last = arr->array + arr->size;
	arr->limit = arr->array + arr->capacity;
}

void reserve( dynamic_array* arr, int n )
{
	double* temp;
	temp = realloc( arr->array, arr->capacity * n * sizeof( double ) );

	if( temp == NULL )
	{
		printf( "unable to reserve %d elements in array %p\n", n, arr );
		return;
	}

	arr->first = arr->array;
	arr->last = arr->array + arr->size;
	arr->limit = arr->array + arr->capacity;
}

double* push_back( dynamic_array* arr, double data )
{
	// if the array has run out of space, double it
	if( arr->last == arr->limit )
	{
		resize( arr );
	}

	*(arr->last) = data;
	++arr->size;
	return arr->last++;
}

// remove the last element and decrement the last pointer
double pop_back( dynamic_array* arr )
{
	double r = *back( arr );
	*(arr->last - 1) = 0.0;
	--arr->last;
	return r;
}

double* insert( dynamic_array* arr, int pos, double data )
{
	// data can be inserted anywhere within the array
	// as well as at the front or back
	if( pos > arr->size )
	{
		printf( "error: insertion into unitialized memory.\n" );
		return NULL;
	}
	
	// if the array has run out of space, double it
	if( arr->last == arr->limit )
	{
		resize( arr );
	}

	double* temp = malloc( arr->capacity * sizeof( double ) );
	int i;

	// copy everything before the insertion point into the new array
	for( i = 0; i < pos; ++i )
	{
		temp[i] = arr->array[i];
	}

	// make the insertion at the specified point
	temp[pos] = data;

	// copy the remainder of the array into the new array
	for( i = pos + 1; i <= arr->last - arr->first; ++i )
	{
		temp[i] = arr->array[i - 1];
	}

	arr->array = temp;
	++arr->size;
	
	arr->first = arr->array;
	arr->last = arr->array + arr->size;
	arr->limit = arr->array + arr->capacity;

	// return a pointer to the inserted element
	return arr->array + pos;
}

double index( dynamic_array* arr, int n )
{
	return arr->array[n];
}

double* front( dynamic_array* arr )
{
	return arr->array;
}

double* back( dynamic_array* arr )
{
	return arr->last - 1;
}