#include "moar.h"

/* Allocates a new call stack region, not incorporated into the regions double

 * linked list yet. */

static MVMCallStackRegion * create_region() {

    MVMCallStackRegion *region = MVM_malloc(MVM_CALLSTACK_REGION_SIZE);

    region->prev = region->next = NULL;

    region->alloc = (char *)region + sizeof(MVMCallStackRegion);

    region->alloc_limit = (char *)region + MVM_CALLSTACK_REGION_SIZE;

    return region;

}

/* Called upon thread creation to set up an initial callstack region for the

 * thread. */

void MVM_callstack_region_init(MVMThreadContext *tc) {

    tc->stack_first = tc->stack_current = create_region();

}

/* Moves the current call stack region we're allocating/freeing in along to

 * the next one in the region chain, allocating that next one if needed. */

MVMCallStackRegion * MVM_callstack_region_next(MVMThreadContext *tc) {

    MVMCallStackRegion *next_region = tc->stack_current->next;

    if (!next_region) {

        next_region = create_region();

        tc->stack_current->next = next_region;

        next_region->prev = tc->stack_current;

    }

    tc->stack_current = next_region;

    return next_region;

}

/* Switches to the previous call stack region, if any. Otherwise, stays in

 * the current region. */

MVMCallStackRegion * MVM_callstack_region_prev(MVMThreadContext *tc) {

    MVMCallStackRegion *prev_region = tc->stack_current->prev;

    if (prev_region)

        tc->stack_current = prev_region;

    else

        prev_region = tc->stack_current;

    return prev_region;

}

/* Resets a threads's callstack to be empty. Used when its contents has been

 * promoted to the heap. */

void MVM_callstack_reset(MVMThreadContext *tc) {

    MVMCallStackRegion *cur_region = tc->stack_current;

    while (cur_region) {

        cur_region->alloc = (char *)cur_region + sizeof(MVMCallStackRegion);

        cur_region = cur_region->prev;

    }

    tc->stack_current = tc->stack_first;

}

/* Called at thread exit to destroy all callstack regions the thread has. */

void MVM_callstack_region_destroy_all(MVMThreadContext *tc) {

    MVMCallStackRegion *cur = tc->stack_first;

    while (cur) {

        MVMCallStackRegion *next = cur->next;

        MVM_free(cur);

        cur = next;

    }

    tc->stack_first = NULL;

}