1. File Header and Includes

c
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/*--------------------------------------------------------------------*/
/* heapmgr1.c (from heapmrgbase.c)                                    */
/* Author: Donghwi Kim, KyoungSoo Park, Kim Chanwoo                   */
/*--------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

#include "chunk.h"

• Lines 1–4: File name, origin, authors.
• Lines 6–8: Pulls in:
  • <stdio.h> for fprintf().
  • <stdlib.h> for exit(), size_t.
  • <assert.h> for runtime sanity checks.
• Line 10: Includes our opaque chunk API.

2. Constants & Globals

c
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#define FALSE 0
#define TRUE  1

enum {
   MEMALLOC_MIN = 1024,
};

/* g_free_head: head of the free‑chunk list */
static Chunk_T g_free_head = NULL;

/* g_heap_start, g_heap_end: current heap bounds */
static void *g_heap_start = NULL, *g_heap_end = NULL;

• FALSE/TRUE: Simple boolean constants.
• MEMALLOC_MIN: Minimum number of units to request from the OS at once (to avoid tiny sbrk calls).
• g_free_head: Points to the first free chunk (a singly‑linked list via chunk_get_next_free_chunk).
• g_heap_start/g_heap_end: Track the start and end of the heap region as returned by sbrk(0).

3. Debug: check_heap_validity

c
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#ifndef NDEBUG
static int check_heap_validity(void) {
   Chunk_T w;
   if (g_heap_start == NULL) {
      fprintf(stderr, "Uninitialized heap start\\n");
      return FALSE;
   }
   if (g_heap_end == NULL) {
      fprintf(stderr, "Uninitialized heap end\\n");
      return FALSE;
   }
   if (g_heap_start == g_heap_end) {
      if (g_free_head == NULL) return TRUE;
      fprintf(stderr, "Inconsistent empty heap\\n");
      return FALSE;
   }
   /* Walk every chunk in memory, ensure it's valid */
   for (w = (Chunk_T)g_heap_start; w && w < (Chunk_T)g_heap_end;
        w = chunk_get_next_adjacent(w, g_heap_start, g_heap_end)) {
      if (!chunk_is_valid(w, g_heap_start, g_heap_end))
         return FALSE;
   }
   /* Walk free‑list, ensure chunks are flagged free, valid, and coalesced */
   for (w = g_free_head; w; w = chunk_get_next_free_chunk(w)) {
      if (chunk_get_status(w) != CHUNK_FREE) {
         fprintf(stderr, "Non-free chunk in the free chunk list\\n");
         return FALSE;
      }
      if (!chunk_is_valid(w, g_heap_start, g_heap_end))
         return FALSE;
      Chunk_T n = chunk_get_next_adjacent(w, g_heap_start, g_heap_end);
      if (n != NULL && n == chunk_get_next_free_chunk(w)) {
         fprintf(stderr, "Uncoalesced chunks\\n");
         return FALSE;
      }
   }
   return TRUE;
}
#endif

4. Utility Functions

4.1 size_to_units

c
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static size_t size_to_units(size_t size) {
  return (size + (CHUNK_UNIT-1)) / CHUNK_UNIT;
}

• Converts a byte‐count request into the number of CHUNK_UNIT‑sized units needed (rounding up).