From 2d8c689ac1f417abd963444e443ec0a64ed18967 Mon Sep 17 00:00:00 2001
From: Alex Kotov <kotovalexarian@gmail.com>
Date: Tue, 1 Dec 2020 04:38:55 +0500
Subject: [PATCH] Alloc and free pages in PFA

---
 include/kernaux/pfa.h | 10 +++++++---
 src/pfa.c             | 24 ++++++++++++++++++++++++
 tests/test_pfa.c      | 10 ++++++++++
 3 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/include/kernaux/pfa.h b/include/kernaux/pfa.h
index b80e355..2a63f6d 100644
--- a/include/kernaux/pfa.h
+++ b/include/kernaux/pfa.h
@@ -14,9 +14,7 @@ struct KernAux_PFA {
     kernaux_bool pages[KERNAUX_PFA_PAGES_COUNT_MAX];
 };
 
-void KernAux_PFA_initialize(
-    struct KernAux_PFA *pfa
-)
+void KernAux_PFA_initialize(struct KernAux_PFA *pfa)
 __attribute__((nonnull));
 
 void KernAux_PFA_mark_available(
@@ -26,6 +24,12 @@ void KernAux_PFA_mark_available(
 )
 __attribute__((nonnull));
 
+unsigned int KernAux_PFA_alloc_page(struct KernAux_PFA *pfa)
+__attribute__((nonnull));
+
+void KernAux_PFA_free_page(struct KernAux_PFA *pfa, unsigned int page_addr)
+__attribute__((nonnull));
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/pfa.c b/src/pfa.c
index 3a5b46e..360a1da 100644
--- a/src/pfa.c
+++ b/src/pfa.c
@@ -35,3 +35,27 @@ void KernAux_PFA_mark_available(
         pfa->pages[index] = KERNAUX_TRUE;
     }
 }
+
+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;
+}
diff --git a/tests/test_pfa.c b/tests/test_pfa.c
index bd07e25..96811a3 100644
--- a/tests/test_pfa.c
+++ b/tests/test_pfa.c
@@ -35,5 +35,15 @@ int main()
         assert(pfa.pages[index] == KERNAUX_FALSE);
     }
 
+    unsigned int page_addr = KernAux_PFA_alloc_page(&pfa);
+
+    assert(page_addr != 0);
+    assert(page_addr % KERNAUX_PFA_PAGE_SIZE == 0);
+    assert(!pfa.pages[page_addr / KERNAUX_PFA_PAGE_SIZE]);
+
+    KernAux_PFA_free_page(&pfa, page_addr);
+
+    assert(pfa.pages[page_addr / KERNAUX_PFA_PAGE_SIZE]);
+
     return 0;
 }