stack.h

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/*
  Copyright 2011-2020 David Robillard <d@drobilla.net>
 
  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.
 
  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
 
#ifndef SERD_STACK_H
#define SERD_STACK_H
 
#include <assert.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>

#define SERD_STACK_BOTTOM sizeof(void*)

typedef struct {
  uint8_t* buf;      
  size_t   buf_size; 
  size_t   size;     
} SerdStack;

#define SERD_STACK_BOTTOM sizeof(void*)
 
static inline SerdStack
serd_stack_new(size_t size)
{
  SerdStack stack;
  stack.buf      = (uint8_t*)calloc(size, 1);
  stack.buf_size = size;
  stack.size     = SERD_STACK_BOTTOM;
  return stack;
}
 
static inline bool
serd_stack_is_empty(SerdStack* stack)
{
  return stack->size <= SERD_STACK_BOTTOM;
}
 
static inline void
serd_stack_free(SerdStack* stack)
{
  free(stack->buf);
  stack->buf      = NULL;
  stack->buf_size = 0;
  stack->size     = 0;
}
 
static inline void*
serd_stack_push(SerdStack* stack, size_t n_bytes)
{
  const size_t new_size = stack->size + n_bytes;
  if (stack->buf_size < new_size) {
    stack->buf_size += (stack->buf_size >> 1); // *= 1.5
    stack->buf = (uint8_t*)realloc(stack->buf, stack->buf_size);
  }
 
  uint8_t* const ret = (stack->buf + stack->size);
 
  stack->size = new_size;
  return ret;
}
 
static inline void
serd_stack_pop(SerdStack* stack, size_t n_bytes)
{
  assert(stack->size >= n_bytes);
  stack->size -= n_bytes;
}
 
static inline void*
serd_stack_push_aligned(SerdStack* stack, size_t n_bytes, size_t align)
{
  // Push one byte to ensure space for a pad count
  serd_stack_push(stack, 1);
 
  // Push padding if necessary
  const size_t pad = align - stack->size % align;
  if (pad > 0) {
    serd_stack_push(stack, pad);
  }
 
  // Set top of stack to pad count so we can properly pop later
  assert(pad < UINT8_MAX);
  stack->buf[stack->size - 1] = (uint8_t)pad;
 
  // Push requested space at aligned location
  return serd_stack_push(stack, n_bytes);
}
 
static inline void
serd_stack_pop_aligned(SerdStack* stack, size_t n_bytes)
{
  // Pop requested space down to aligned location
  serd_stack_pop(stack, n_bytes);
 
  // Get amount of padding from top of stack
  const uint8_t pad = stack->buf[stack->size - 1];
 
  // Pop padding and pad count
  serd_stack_pop(stack, pad + 1u);
}
 
#endif // SERD_STACK_H