From: Christopher Faulet <cfaulet@haproxy.com>
Date: Wed, 8 Jul 2026 08:38:12 +0000 (+0200)
Subject: MEDIUM: htx: Skip UNUSED blocs when getting previous,next and first blocks
X-Git-Url: https://git.kaiwu.me/?a=commitdiff_plain;h=b680af702c1700a36e792e484d692bab737890c7;p=haproxy.git

MEDIUM: htx: Skip UNUSED blocs when getting previous,next and first blocks

htx_get_prev_blk(), htx_get_next_blk() and htx_get_first_blk() functions
were modified to automatically skip UNUSED blocks. So now, a valid block or
NULL is returned.  In addition, htx_remove_blk() was adapted accordingly to
also skip UNUSED blocks.

Thanks to this change, the loops on HTX messages could be simplified by
removing test on UNUSED blocks, while it remains harmless.
---

diff --git a/include/haproxy/htx.h b/include/haproxy/htx.h
index 4b7b9834f..b48d87df6 100644
--- a/include/haproxy/htx.h
+++ b/include/haproxy/htx.h
@@ -272,16 +272,22 @@ static inline int32_t htx_get_prev(const struct htx *htx, uint32_t pos)
 	return (pos - 1);
 }
 
-/* Returns the HTX block before <blk> in the HTX message <htx>. If <blk> is the
- * head, NULL returned.
+/* Returns the HTX block before <blk> in the HTX message <htx>, skipping all
+ * UNUSED blocks. If <blk> is the head, NULL returned.
  */
 static inline struct htx_blk *htx_get_prev_blk(const struct htx *htx,
 					       const struct htx_blk *blk)
 {
-	int32_t pos;
+	struct htx_blk *pblk = NULL;
+	int32_t pos = htx_get_blk_pos(htx, blk);
 
-	pos = htx_get_prev(htx, htx_get_blk_pos(htx, blk));
-	return ((pos == -1) ? NULL : htx_get_blk(htx, pos));
+	for (pos = htx_get_prev(htx, pos); pos != -1; pos = htx_get_prev(htx, pos)) {
+		pblk = htx_get_blk(htx, pos);
+		if (htx_get_blk_type(pblk) != HTX_BLK_UNUSED)
+			break;
+		pblk = NULL;
+	}
+	return pblk;
 }
 
 /* Returns the position of block immediately after the one pointed by <pos>. If
@@ -295,18 +301,25 @@ static inline int32_t htx_get_next(const struct htx *htx, uint32_t pos)
 
 }
 
-/* Returns the HTX block after <blk> in the HTX message <htx>. If <blk> is the
- * tail, NULL returned.
+/* Returns the HTX block after <blk> in the HTX message <htx>, skipping UNUSED
+ * blocks. If <blk> is the tail, NULL returned.
  */
 static inline struct htx_blk *htx_get_next_blk(const struct htx *htx,
 					       const struct htx_blk *blk)
 {
-	int32_t pos;
+	struct htx_blk *nblk = NULL;
+	int32_t pos = htx_get_blk_pos(htx, blk);
 
-	pos = htx_get_next(htx, htx_get_blk_pos(htx, blk));
-	return ((pos == -1) ? NULL : htx_get_blk(htx, pos));
+	for (pos = htx_get_next(htx, pos); pos != -1; pos = htx_get_next(htx, pos)) {
+		nblk = htx_get_blk(htx, pos);
+		if (htx_get_blk_type(nblk) != HTX_BLK_UNUSED)
+			break;
+		nblk = NULL;
+	}
+	return nblk;
 }
 
+
 /* Returns the position of the first block in the HTX message <htx>. -1 means
  * the first block is unset or the HTS is empty.
  */
@@ -315,15 +328,21 @@ static inline int32_t htx_get_first(const struct htx *htx)
 	return htx->first;
 }
 
-/* Returns the first HTX block in the HTX message <htx>. If unset or if <htx> is
- * empty, NULL returned.
+/* Returns the first HTX block in the HTX message <htx>, skipping UNUSED
+ * blocks. If unset or if <htx> is empty, NULL returned.
  */
 static inline struct htx_blk *htx_get_first_blk(const struct htx *htx)
 {
+	struct htx_blk *fblk = NULL;
 	int32_t pos;
 
-	pos = htx_get_first(htx);
-	return ((pos == -1) ? NULL : htx_get_blk(htx, pos));
+	for (pos = htx_get_first(htx); pos != -1; pos = htx_get_next(htx, pos)) {
+		fblk = htx_get_blk(htx, pos);
+		if (htx_get_blk_type(fblk) != HTX_BLK_UNUSED)
+			break;
+		fblk = NULL;
+	}
+	return fblk;
 }
 
 /* Returns the type of the first block in the HTX message <htx>. If unset or if
diff --git a/src/htx.c b/src/htx.c
index 3a05dc42f..fff828932 100644
--- a/src/htx.c
+++ b/src/htx.c
@@ -368,6 +368,7 @@ struct htx_blk *htx_add_blk(struct htx *htx, enum htx_blk_type type, uint32_t bl
  */
 struct htx_blk *htx_remove_blk(struct htx *htx, struct htx_blk *blk)
 {
+	struct htx_blk *prevblk, *nextblk;
 	enum htx_blk_type type;
 	uint32_t pos, addr, sz;
 
@@ -382,6 +383,15 @@ struct htx_blk *htx_remove_blk(struct htx *htx, struct htx_blk *blk)
 		return NULL;
 	}
 
+	/* Get prev and next blocks, skipping all UNUSED blocks.
+	 *   <prevblk> may NULL if the head is removed otherwise it must exists
+	 *   <nextblk> may NULL if the tail is removed otherwise it must exists
+	 */
+	prevblk = htx_get_prev_blk(htx, blk);
+	nextblk = htx_get_next_blk(htx, blk);
+
+	/* There is at least 2 used blocks, so (head != tail and tail > 0) */
+
 	type = htx_get_blk_type(blk);
 	pos  = htx_get_blk_pos(htx, blk);
 	sz   = htx_get_blksz(blk);
@@ -394,26 +404,24 @@ struct htx_blk *htx_remove_blk(struct htx *htx, struct htx_blk *blk)
 		blk->info = ((uint32_t)HTX_BLK_UNUSED << 28);
 	}
 
-	/* There is at least 2 blocks, so tail is always > 0 */
+
 	if (pos == htx->head) {
 		/* move the head forward */
-		htx->head++;
+		BUG_ON_HOT(prevblk != NULL || nextblk == NULL);
+		htx->head = htx_get_blk_pos(htx, nextblk);
 	}
 	else if (pos == htx->tail) {
-		/* remove the tail. this was the last inserted block so
-		 * return NULL. */
-		htx->tail--;
-		blk = NULL;
+		/* remove the tail */
+		BUG_ON_HOT(prevblk == NULL || nextblk != NULL);
+		htx->tail = htx_get_blk_pos(htx, prevblk);
 		goto end;
 	}
 	else
 		htx->flags |= HTX_FL_FRAGMENTED;
 
-	blk = htx_get_blk(htx, pos+1);
-
   end:
 	if (pos == htx->first)
-		htx->first = (blk ? htx_get_blk_pos(htx, blk) : -1);
+		htx->first = (nextblk ? htx_get_blk_pos(htx, nextblk) : -1);
 
 	if (htx->head == htx->tail) {
 		/* If there is just one block in the HTX message, free space can
@@ -443,7 +451,7 @@ struct htx_blk *htx_remove_blk(struct htx *htx, struct htx_blk *blk)
 	BUG_ON((int32_t)htx->head_addr < 0);
 	BUG_ON(htx->end_addr > htx->tail_addr);
 	BUG_ON(htx->head_addr > htx->end_addr);
-	return blk;
+	return nextblk;
 }
 
 /* Looks for the HTX block containing the offset <offset>, starting at the HTX