From fe98a513bc11e2934e4ca1e39a5d204d2d3ad77a Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Thu, 29 Jul 2021 15:27:48 +0900
Subject: [PATCH] [util] Add a function to check hunk pointers

Its only real utility is to check that a pointer is not pointing into
freed space.
---
 include/QF/zone.h |  1 +
 libs/util/zone.c  | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/include/QF/zone.h b/include/QF/zone.h
index 0cd55c66d..93dbc8089 100644
--- a/include/QF/zone.h
+++ b/include/QF/zone.h
@@ -119,6 +119,7 @@ size_t Hunk_LowMark (memhunk_t *hunk) __attribute__((pure));
 void Hunk_RawFreeToLowMark (memhunk_t *hunk, size_t mark) __attribute__((nonnull(1)));
 void Hunk_FreeToLowMark (memhunk_t *hunk, size_t mark);
 void *Hunk_TempAlloc (memhunk_t *hunk, size_t size);
+int Hunk_PointerIsValid (memhunk_t *hunk, void *ptr) __attribute__((pure));
 
 
 
diff --git a/libs/util/zone.c b/libs/util/zone.c
index 275948126..a2b68d754 100644
--- a/libs/util/zone.c
+++ b/libs/util/zone.c
@@ -715,6 +715,30 @@ Hunk_TempAlloc (memhunk_t *hunk, size_t size)
 	return buf;
 }
 
+VISIBLE int
+Hunk_PointerIsValid (memhunk_t *hunk, void *ptr)
+{
+	if (!hunk) { hunk = global_hunk; } //FIXME clean up callers
+
+	size_t      offset = (byte *) ptr - hunk->base;
+	if (offset >= hunk->size) {
+		return 0;
+	}
+	if (offset < hunk->low_used) {
+		// the pointer is somewhere in the lower space of the hunk
+		// FIXME better checking?
+		return 1;
+	}
+	if (offset >= hunk->size - hunk->high_used + sizeof (hunkblk_t)) {
+		// the pointer is somewhere in the upper space of the hunk
+		// FIXME better checking?
+		return 1;
+	}
+	// the pointer is somewhere in between the two marks, so it has probably
+	// been freed
+	return 0;
+}
+
 /* CACHE MEMORY */