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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright 2016 Olaf Wintermann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "stack.h"
#include <string.h>

static size_t ucx_stack_align(size_t n) {
    int align = n % sizeof(void*);
    if (align) {
        n += sizeof(void*) - align;
    }
    return n;
}

void ucx_stack_init(UcxStack *stack, char* space, size_t size) {
    stack->size = size - size % sizeof(void*);
    stack->space = space;
    stack->top = NULL;
    
    stack->allocator.pool = stack;
    stack->allocator.malloc = (ucx_allocator_malloc) ucx_stack_malloc;
    stack->allocator.calloc = (ucx_allocator_calloc) ucx_stack_calloc;
    stack->allocator.realloc = (ucx_allocator_realloc) ucx_stack_realloc;
    stack->allocator.free = (ucx_allocator_free) ucx_stack_free;
}

void *ucx_stack_malloc(UcxStack *stack, size_t n) {

    if (ucx_stack_avail(stack) < ucx_stack_align(n)) {
        return NULL;
    } else {
        char *prev = stack->top;
        if (stack->top) {
            stack->top += ucx_stack_align(ucx_stack_topsize(stack));
        } else {
            stack->top = stack->space;
        }
        
        ((struct ucx_stack_metadata*)stack->top)->prev = prev;
        ((struct ucx_stack_metadata*)stack->top)->size = n;
        stack->top += sizeof(struct ucx_stack_metadata);
        
        return stack->top;
    }
}

void *ucx_stack_calloc(UcxStack *stack, size_t nelem, size_t elsize) {
    void *mem = ucx_stack_malloc(stack, nelem*elsize);
    memset(mem, 0, nelem*elsize);
    return mem;
}

void *ucx_stack_realloc(UcxStack *stack, void *ptr, size_t n) {
    if (ptr == stack->top) {
        if (stack->size - (stack->top - stack->space) < ucx_stack_align(n)) {
            return NULL;
        } else {
            ((struct ucx_stack_metadata*)stack->top - 1)->size = n;
            return ptr;
        }
    } else {
        if (ucx_stack_align(((struct ucx_stack_metadata*)ptr - 1)->size) <
                ucx_stack_align(n)) {
            void *nptr = ucx_stack_malloc(stack, n);
            if (nptr) {
                memcpy(nptr, ptr, n);
                ucx_stack_free(stack, ptr);
                
                return nptr;
            } else {
                return NULL;
            }
        } else {
            ((struct ucx_stack_metadata*)ptr - 1)->size = n;
            return ptr;
        }
    }
}

void ucx_stack_free(UcxStack *stack, void *ptr) {
    if (ptr == stack->top) {
        stack->top = ((struct ucx_stack_metadata*) stack->top - 1)->prev;
    } else {
        struct ucx_stack_metadata *next = (struct ucx_stack_metadata*)(
            (char*)ptr +
            ucx_stack_align(((struct ucx_stack_metadata*) ptr - 1)->size)
        );
        next->prev = ((struct ucx_stack_metadata*) ptr - 1)->prev;
    }
}

void ucx_stack_popn(UcxStack *stack, void *dest, size_t n) {
    if (ucx_stack_empty(stack)) {
        return;
    }
    
    size_t len = ucx_stack_topsize(stack);
    if (len > n) {
        len = n;
    }
    
    memcpy(dest, stack->top, len);
    
    ucx_stack_free(stack, stack->top);
}

size_t ucx_stack_avail(UcxStack *stack) {
    size_t avail = ((stack->top ? (stack->size
                    - (stack->top - stack->space)
                    - ucx_stack_align(ucx_stack_topsize(stack)))
                    : stack->size));
    
    if (avail > sizeof(struct ucx_stack_metadata)) {
        return avail - sizeof(struct ucx_stack_metadata);
    } else {
        return 0;
    }
}