From 36457f775f375381bd9ed6ed8b99b449fc9854dd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nils=20O=2E=20Sel=C3=A5sdal?= <nos@utel.tech>
Date: Tue, 21 Apr 2026 13:20:07 +0200
Subject: [PATCH] Improve sarena.h

---
 include/ucore/sarena.h | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/include/ucore/sarena.h b/include/ucore/sarena.h
index 4c66720..a712de8 100644
--- a/include/ucore/sarena.h
+++ b/include/ucore/sarena.h
@@ -40,7 +40,7 @@ struct UCSTmpAlloc {
  * Use as
  * @code
  * _Alignas(16) char v[128];
- * UCSArena a = UC_BV_STATIC_INITIALIZER(v);
+ * UCSArena a = UC_SAR_STATIC_INITIALIZER(v);
  * @endcode
  */
 #define UC_SAR_STATIC_INITIALIZER(data) UC_SAR_INITIALIZER((data), sizeof(data))
@@ -49,15 +49,20 @@ struct UCSTmpAlloc {
  * Use as
  * @code
  * char v[128];
- * UCSArena a = UC_BV_STATIC_INITIALIZER(v, sizeof v);
+ * UCSArena a = UC_SAR_INITIALIZER(v, sizeof v);
  * @endcode
  * or
  * @code
  * char *m = malloc(128);
- * UCSArena a = UC_BV_INIT(m, 128);
+ * UCSArena a = UC_SAR_INITIALIZER(m, 128);
  * @endcode
  */
-#define UC_SAR_INITIALIZER(data, sz) {(data), (data), (data) + sz}
+#define UC_SAR_INITIALIZER(data, sz) {\
+    .start = (data),\
+    .curr = (data),\
+    .end=(data) + sz,\
+    .tmp_allocs = 0\
+}
 
 /** Initialize a UCSArena with an array as the backing memory to allocate from.
  * The macro can be used at local scope to allocate memory automatic on the stack,
@@ -111,7 +116,7 @@ static inline UCSTmpAlloc uc_sar_tmp_begin(UCSArena *arena)
     return state;
 }
 
-// end temporary allocations, releaseing all allocations since the most recent uc_sar_tmp_begin
+// end temporary allocations, releasing all allocations since the most recent uc_sar_tmp_begin
 static inline void uc_sar_tmp_end(const UCSTmpAlloc *state)
 {
     UCSArena *arena = state->arena;
@@ -121,9 +126,9 @@ static inline void uc_sar_tmp_end(const UCSTmpAlloc *state)
 }
 
 // Allocate @sz bytes from the UCSArena. Returns NULL if not enough space
-void *uc_sar_alloc(UCSArena *arena, size_t sz)
+static inline void *uc_sar_alloc(UCSArena *arena, size_t sz)
 {
-    if (arena->curr + sz > arena->end) {
+    if (sz > (arena->curr - arena->end)) {
         return NULL;
     }
     void *start = arena->curr;
@@ -133,7 +138,7 @@ void *uc_sar_alloc(UCSArena *arena, size_t sz)
 
 // Allocate @sz bytes from the UCSArena, returned pointer is aligned to @align
 // Returns NULL if not enough space
-void *uc_sar_alloc_aligned(UCSArena *arena, size_t sz, unsigned int align) [[gnu::alloc_align(3)]]
+static inline void *uc_sar_alloc_aligned(UCSArena *arena, size_t sz, unsigned int align) [[gnu::alloc_align(3)]]
 {
     assert(align != 0);
     assert((align & (align - 1)) == 0);  // power of 2
@@ -142,7 +147,8 @@ void *uc_sar_alloc_aligned(UCSArena *arena, size_t sz, unsigned int align) [[gnu
     uintptr_t aligned = (curr + (align - (uintptr_t)1)) & ~(align - (uintptr_t)1);
     unsigned char *start = (unsigned char *)aligned;
 
-    if (start + sz > arena->end) {
+    if (sz > (arena->curr - arena->end)) {
+
         return NULL;
     }
 
@@ -151,6 +157,8 @@ void *uc_sar_alloc_aligned(UCSArena *arena, size_t sz, unsigned int align) [[gnu
     return start;
 }
 
+// reset arena, making all memory available for allocation
+// also invalidates any UCSTmpAlloc instances.
 static inline void uc_sar_reset(UCSArena *arena)
 {
     arena->curr = arena->start;