/*
 * No free per allocation; freearena releases the whole chain.
 * Aligned to 16 so structs with 8-byte fields and doubles are happy.
 * The chunk size doubles up to a cap so we don't fragment on huge
 * inputs.
 */
#include "ww.h"
#include <stdlib.h>
#include <string.h>

#define ALIGN		16
#define INIT_CHUNK	(64 * 1024)
#define MAX_CHUNK	(4 * 1024 * 1024)

static u64
roundup(u64 n, u64 a)
{
	return (n + a - 1) & ~(a - 1);
}

Arena *
newarena(void)
{
	Arena *a = calloc(1, sizeof *a);
	if (a == NULL)
		fatal("newarena: out of memory");
	a->buf = malloc(INIT_CHUNK);
	if (a->buf == NULL)
		fatal("newarena: out of memory");
	a->cap = INIT_CHUNK;
	return a;
}

static void
grow(Arena *a, u64 need)
{
	u64 ncap = a->cap * 2;
	if (ncap > MAX_CHUNK)
		ncap = MAX_CHUNK;
	if (ncap < need)
		ncap = roundup(need, ALIGN);

	Arena *old = malloc(sizeof *old);
	if (old == NULL)
		fatal("arena: oom");
	*old = *a;
	a->next = old;
	a->buf = malloc(ncap);
	if (a->buf == NULL)
		fatal("arena: oom (chunk=%llu)", (unsigned long long)ncap);
	a->off = 0;
	a->cap = ncap;
}

void *
amalloc(Arena *a, u64 n)
{
	n = roundup(n, ALIGN);
	if (n > a->cap - a->off)
		grow(a, n);
	void *p = a->buf + a->off;
	a->off += n;
	a->total += n;
	memset(p, 0, n);
	return p;
}

char *
astrdup(Arena *a, const char *s)
{
	u64 n = strlen(s);
	char *p = amalloc(a, n + 1);
	memcpy(p, s, n);
	return p;
}

char *
astrndup(Arena *a, const char *s, u64 n)
{
	char *p = amalloc(a, n + 1);
	memcpy(p, s, n);
	return p;
}

char *
aprintf(Arena *a, const char *fmt, ...)
{
	va_list ap;
	va_start(ap, fmt);
	int n = vsnprintf(NULL, 0, fmt, ap);
	va_end(ap);
	if (n < 0)
		fatal("aprintf: vsnprintf failed");
	char *p = amalloc(a, (u64)n + 1);
	va_start(ap, fmt);
	vsnprintf(p, (size_t)n + 1, fmt, ap);
	va_end(ap);
	return p;
}

void
freearena(Arena *a)
{
	while (a) {
		Arena *next = a->next;
		free(a->buf);
		/* The head Arena was returned by newarena() and is the only
		 * one we should free as a struct; the linked older ones were
		 * allocated by grow() and are also freeable. */
		free(a);
		a = next;
	}
}