#include <stdlib.h> /* free(3), malloc(3), realloc(3), size_t */
#include "libfatptr.h"

struct FatPtr *
FatPtr_append(struct FatPtr *p, FatPtr_scalar_t c){
	FatPtr_vector_t t;

	if(p == NULL || (p->s + (sizeof (FatPtr_scalar_t)) > p->a
			&& FatPtr_grow(p, sizeof (FatPtr_scalar_t)) == NULL))
		return NULL;
	(p->v)[(p->s)++] = c;
	return p;
}

struct FatPtr *
FatPtr_construct(struct FatPtr *p){

	return FatPtr_grow(FatPtr_initialize(p), sizeof (FatPtr_scalar_t));
}

struct FatPtr *
FatPtr_destruct(struct FatPtr *p){

	if(p != NULL){
		free(p->v);
		FatPtr_initialize(p);
	}
	return NULL;
}

struct FatPtr *
FatPtr_grow(struct FatPtr *p, size_t units){
	FatPtr_vector_t t;

	if(p == NULL || (t = realloc(p->v, p->a + units)) == NULL)
		return NULL;
	p->a += units;
	p->v = t;
	return p;
}

struct FatPtr *
FatPtr_initialize(struct FatPtr *p){

	if(p != NULL){
		p->a = 0;
		p->s = 0;
		p->v = NULL;
	}
	return p;
}

FatPtr_vector_t
FatPtr_index(struct FatPtr *p, size_t index){

	return p == NULL
		? NULL
		: &p->v[index];
}

struct FatPtr *
FatPtr_prepend(struct FatPtr *p, FatPtr_vector_t s, size_t units){
	size_t i;

	if(FatPtr_shiftleft(p, units) != NULL)
		for(i = 0; units --> 0; p->v[i] = *s++);
	return p;
}

struct FatPtr *
FatPtr_shiftleft(struct FatPtr *p, size_t units){
	size_t i;

	if(p != NULL)
		for(i = 0; i < p->s; ++i)
			(p->v)[i] = (p->v)[i + units];
	return p;
}

struct FatPtr *
FatPtr_shiftright(struct FatPtr *p, size_t units){
	size_t i;

	if(FatPtr_grow(p, units * (sizeof (FatPtr_scalar_t))) == NULL)
		return NULL;
	for(i = 0; i < p->s; ++i)
		(p->v)[i + units] = (p->v)[i];
	p->s += units;
	return p;
}

struct FatPtr *
FatPtr_trimend(struct FatPtr *p, size_t units){

	if(p != NULL)
		p->s -= units;
	return p;
}

struct FatPtr *
FatPtr_trimfront(struct FatPtr *p, size_t units){

	return FatPtr_trimend(FatPtr_shiftleft(p, units), units);
}