From c987d0e63da46e2927507cbf2b986d592a841d52 Mon Sep 17 00:00:00 2001
From: Alex Kotov <kotovalexarian@gmail.com>
Date: Tue, 14 Dec 2021 06:21:47 +0500
Subject: [PATCH] Rewrite PFA

---
 include/kernaux/pfa.h | 11 +++++------
 src/pfa.c             | 43 +++++++++++++------------------------------
 2 files changed, 18 insertions(+), 36 deletions(-)

diff --git a/include/kernaux/pfa.h b/include/kernaux/pfa.h
index 8fe0af2..7276b8f 100644
--- a/include/kernaux/pfa.h
+++ b/include/kernaux/pfa.h
@@ -11,6 +11,11 @@ extern "C" {
 #define KERNAUX_PFA_PAGE_SIZE (4 * 1024)
 #define KERNAUX_PFA_PAGES_COUNT_MAX (1024 * 1024)
 
+#define KernAux_PFA_alloc_page(pfa) \
+    (KernAux_PFA_alloc_pages((pfa), KERNAUX_PFA_PAGE_SIZE))
+#define KernAux_PFA_free_page(pfa, page_addr) \
+    (KernAux_PFA_free_pages((pfa), (page_addr), KERNAUX_PFA_PAGE_SIZE))
+
 typedef struct KernAux_PFA *KernAux_PFA;
 
 struct KernAux_PFA {
@@ -29,15 +34,9 @@ __attribute__((nonnull));
 void KernAux_PFA_mark_unavailable(KernAux_PFA pfa, size_t start, size_t end)
 __attribute__((nonnull));
 
-size_t KernAux_PFA_alloc_page(KernAux_PFA pfa)
-__attribute__((nonnull));
-
 size_t KernAux_PFA_alloc_pages(KernAux_PFA pfa, size_t mem_size)
 __attribute__((nonnull));
 
-void KernAux_PFA_free_page(KernAux_PFA pfa, size_t page_addr)
-__attribute__((nonnull));
-
 void KernAux_PFA_free_pages(KernAux_PFA pfa, size_t page_addr, size_t mem_size)
 __attribute__((nonnull));
 
diff --git a/src/pfa.c b/src/pfa.c
index 82c9ece..3e3da51 100644
--- a/src/pfa.c
+++ b/src/pfa.c
@@ -68,53 +68,36 @@ void KernAux_PFA_mark(
     }
 }
 
-size_t KernAux_PFA_alloc_page(const KernAux_PFA pfa)
-{
-    // We start from 1 because 0 indicates failure.
-    // It is not very useful to alloc page at address 0;
-    for (size_t index = 1; index < KERNAUX_PFA_PAGES_COUNT_MAX; ++index) {
-        if (pfa->pages[index]) {
-            pfa->pages[index] = false;
-            return index * KERNAUX_PFA_PAGE_SIZE;
-        }
-    }
-
-    return 0;
-}
-
 size_t KernAux_PFA_alloc_pages(const KernAux_PFA pfa, const size_t mem_size)
 {
     if (mem_size % KERNAUX_PFA_PAGE_SIZE != 0) return 0;
 
-    const size_t pages_count = mem_size  / KERNAUX_PFA_PAGE_SIZE;
+    const size_t pages_count = mem_size / KERNAUX_PFA_PAGE_SIZE;
 
     // We start from 1 because 0 indicates failure.
     // It is not very useful to alloc page at address 0;
-    for (size_t start = 1; start < KERNAUX_PFA_PAGES_COUNT_MAX;) {
-        size_t end = start;
-        for (; end < start + pages_count; ++end) {
-            if (!pfa->pages[end]) break;
+    for (size_t index = 1, start = 0;
+            index < KERNAUX_PFA_PAGES_COUNT_MAX;
+            ++index)
+    {
+        if (!pfa->pages[index]) {
+            start = 0;
+            continue;
         }
-        if (end >= KERNAUX_PFA_PAGES_COUNT_MAX) return 0;
-        if (end == start + pages_count - 1) {
-            for (size_t index = start; index <= end; ++index) {
+
+        if (start == 0) start = index;
+
+        if (index - start + 1 == pages_count) {
+            for (; index >= start; --index) {
                 pfa->pages[index] = false;
             }
             return start * KERNAUX_PFA_PAGE_SIZE;
         }
-        start = end + 1;
     }
 
     return 0;
 }
 
-void KernAux_PFA_free_page(const KernAux_PFA pfa, size_t page_addr)
-{
-    if (page_addr % KERNAUX_PFA_PAGE_SIZE != 0) return;
-
-    pfa->pages[page_addr / KERNAUX_PFA_PAGE_SIZE] = true;
-}
-
 void KernAux_PFA_free_pages(
     const KernAux_PFA pfa,
     const size_t page_addr,