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/*
* Very simple heap manager.
* Allocation Strategy: The lower end of the heap, is the end of the BSS.
*
* During an alloc, if there is enough space below the high end of heap,
* we return a pointer to the allocated space and move curr.
* Space once allocated is never deallocated!
* We run out of space if we get within BUFSIZE bytes of the stack pointer.
*/
#include "heap.h"
#include "string.h"
#include "biosio.h"
#ifndef NULL
#define NULL ((void *)0)
#endif
extern char _end[];
static unsigned int heap_curr = (unsigned int)_end;
static inline unsigned int currsp(void)
{
unsigned int esp;
asm("movl %%esp,%0 " : "=rm" (esp));
return esp;
}
static inline void _checkheap(void)
{
if (currsp() < heap_curr) // Heap corrupted
{
csprint("\r\nHeap overflow, aborting!\r\n",0x07);
asm volatile("int $0x21" : : "a" (0x4C7f)); /* Exit with error */
return;
}
}
void * malloc(unsigned int num) // Allocate so much space
{
unsigned int ans, heap_max;
_checkheap();
heap_max = currsp() - STACKSIZE;
ans = (heap_curr+3) & ~3; // Align to 4-byte boundary
if ( ans+num > heap_max )
return NULL;
heap_curr = ans+num;
return (void *) ans;
}
/* We don't actually ever use these; if enabled,
probably _checkheap() shouldn't be inline.*/
#if 0
int checkalloc(unsigned int num)
{
_checkheap();
return (heap_curr + num < heap_max);
}
void free(void * ptr)
{
_checkheap();
return;
}
#endif
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