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#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include "vector.h"
#define VECTOR_TOOBIG(alloc,elemsize,arrayoff) ((SIZE_MAX - (arrayoff)) / (alloc) < (elemsize))
#define VECTOR_ALLOCSIZE(alloc,elemsize,arrayoff) ((arrayoff) + (alloc) * (elemsize))
void *vector_init(size_t alloc, size_t elemsize, size_t arrayoff)
{
if (VECTOR_TOOBIG(alloc, elemsize, arrayoff)) return NULL;
struct vector *v = malloc(VECTOR_ALLOCSIZE(alloc, elemsize, arrayoff));
if (!v) return NULL;
*v = (struct vector) {
.alloc = alloc,
.elemsize = elemsize,
.arrayoff = arrayoff,
};
return v;
}
void *vector_append(struct vector **vp)
{
struct vector *v = *vp;
if (v->count >= v->alloc) {
size_t alloc = 2 * v->alloc;
if (VECTOR_TOOBIG(alloc, v->elemsize, v->arrayoff)) return NULL;
v = realloc(v, VECTOR_ALLOCSIZE(alloc, v->elemsize, v->arrayoff));
if (!v) return NULL;
v->alloc = alloc;
*vp = v;
}
return (char*)v + v->arrayoff + v->count++ * v->elemsize;
}
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