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libkernaux/src/pfa.c

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2020-11-30 06:40:33 -05:00
#include "config.h"
#include <kernaux/pfa.h>
#include <kernaux/stdlib.h>
void KernAux_PFA_initialize(struct KernAux_PFA *const pfa)
{
kernaux_memset(pfa->pages, KERNAUX_FALSE, sizeof(pfa->pages));
}
void KernAux_PFA_mark_available(
struct KernAux_PFA *const pfa,
unsigned int start,
unsigned int end
) {
if (start >= end) {
return;
}
const unsigned int start_rem = start % KERNAUX_PFA_PAGE_SIZE;
const unsigned int end_rem = (end + 1) % KERNAUX_PFA_PAGE_SIZE;
if (start_rem != 0) {
start = start - start_rem + KERNAUX_PFA_PAGE_SIZE;
}
if (end_rem != 0) {
end = end - end_rem;
}
const unsigned int start_index = start / KERNAUX_PFA_PAGE_SIZE;
const unsigned int end_index = end / KERNAUX_PFA_PAGE_SIZE;
for (unsigned int index = start_index; index <= end_index; ++index) {
pfa->pages[index] = KERNAUX_TRUE;
}
}
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unsigned int KernAux_PFA_alloc_page(struct KernAux_PFA *pfa)
{
// We start from 1 because 0 indicates failure.
// It is not very usefull to alloc page at address 0;
//
for (unsigned int index = 1; index < KERNAUX_PFA_PAGES_COUNT_MAX; ++index) {
if (pfa->pages[index]) {
pfa->pages[index] = KERNAUX_FALSE;
return index * KERNAUX_PFA_PAGE_SIZE;
}
}
return 0;
}
void KernAux_PFA_free_page(struct KernAux_PFA *pfa, unsigned int page_addr)
{
if (page_addr % KERNAUX_PFA_PAGE_SIZE != 0) {
return;
}
pfa->pages[page_addr / KERNAUX_PFA_PAGE_SIZE] = KERNAUX_TRUE;
}