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#include <stdlib.h>
#include <unistd.h>
#include <sys/syscall.h>
#define HEAP_HEADER 16UL
#define HEAP_ALIGN 16UL
#define HEAP_MIN 32UL
#define HEAP_CHUNK (64UL * 1024UL)
static unsigned long heap_start = 0;
static unsigned long heap_end = 0;
static unsigned long heap_rover = 0;
static unsigned long heap_block_size(unsigned long block)
{
return *(unsigned long*)block & ~15UL;
}
static int heap_block_used(unsigned long block)
{
return (int)(*(unsigned long*)block & 1UL);
}
static void heap_set(unsigned long block, unsigned long size, int used)
{
*(unsigned long*)block = size | (used ? 1UL : 0UL);
}
static unsigned long heap_align(unsigned long value)
{
return (value + HEAP_ALIGN - 1UL) & ~(HEAP_ALIGN - 1UL);
}
// pull another hunk off sbrk and drop a free block over it
static int heap_grow(unsigned long need)
{
unsigned long want = heap_align(need);
if (want < HEAP_CHUNK)
want = HEAP_CHUNK;
unsigned long got = (unsigned long)sbrk((long)want);
if ((long)got < 0)
return 0;
if (heap_start == 0)
{
heap_start = got;
heap_end = got;
heap_rover = got;
}
heap_set(heap_end, want, 0);
heap_end += want;
return 1;
}
// fire O(n) malloc implementation frfr
void* malloc(size_t length)
{
if (length == 0)
return NULL;
unsigned long need = heap_align(HEAP_HEADER + length);
if (need < HEAP_MIN)
need = HEAP_MIN;
for (;;)
{
if (heap_rover < heap_start || heap_rover >= heap_end)
heap_rover = heap_start;
unsigned long block = heap_rover;
unsigned long limit = heap_end;
for (int pass = 0; pass < 2; pass++)
{
while (block < limit)
{
if (!heap_block_used(block))
{
// lazily coalesce the free run starting here
unsigned long size = heap_block_size(block);
while (block + size < heap_end && !heap_block_used(block + size))
size += heap_block_size(block + size);
heap_set(block, size, 0);
if (size >= need)
{
if (size >= need + HEAP_MIN)
{
heap_set(block, need, 1);
heap_set(block + need, size - need, 0);
heap_rover = block + need;
}
else
{
heap_set(block, size, 1);
heap_rover = block + size;
}
if (heap_rover >= heap_end)
heap_rover = heap_start;
return (void*)(block + HEAP_HEADER);
}
}
block += heap_block_size(block);
}
block = heap_start;
limit = heap_rover;
}
if (!heap_grow(need))
return NULL;
}
}
void free(void* pointer)
{
if (pointer == NULL)
return;
unsigned long block = (unsigned long)pointer - HEAP_HEADER;
heap_set(block, heap_block_size(block), 0);
}
void* calloc(size_t count, size_t size)
{
unsigned long total = (unsigned long)count * (unsigned long)size;
unsigned char* bytes = malloc(total);
if (bytes)
for (unsigned long i = 0; i < total; i++)
bytes[i] = 0;
return bytes;
}
void* realloc(void* pointer, size_t length)
{
if (pointer == NULL)
return malloc(length);
if (length == 0)
{
free(pointer);
return NULL;
}
unsigned long block = (unsigned long)pointer - HEAP_HEADER;
unsigned long have = heap_block_size(block) - HEAP_HEADER;
if (length <= have)
return pointer;
unsigned char* grown = malloc(length);
if (!grown)
return NULL;
unsigned char* source = pointer;
for (unsigned long i = 0; i < have; i++)
grown[i] = source[i];
free(pointer);
return grown;
}
void exit(int code)
{
__syscall1(SYS_exit, code);
for (;;)
;
}
long atol(const char* string)
{
while (*string == ' ' || *string == '\t')
string++;
int negative = 0;
if (*string == '-')
{
negative = 1;
string++;
}
else if (*string == '+')
string++;
long value = 0;
while (*string >= '0' && *string <= '9')
{
value = value * 10 + (*string - '0');
string++;
}
return negative ? -value : value;
}
int atoi(const char* string)
{
return (int)atol(string);
}
int abs(int value)
{
return value < 0 ? -value : value;
}
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