From 24ed835129e09fc547af2b77fefbee71ef20ab5d Mon Sep 17 00:00:00 2001
From: Christopher Faulet <cfaulet@haproxy.com>
Date: Thu, 22 Nov 2018 11:20:43 +0100
Subject: [PATCH] MINOR: htx: Add function to add an HTX block just before
 another one

The function htx_add_data_before() can be used to add an HTX block before
another one. For instance, it could be used to add some data before the
end-of-message marker.
---
 include/proto/htx.h |  1 +
 src/htx.c           | 31 +++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/include/proto/htx.h b/include/proto/htx.h
index 2f7aaf742..7db2059c2 100644
--- a/include/proto/htx.h
+++ b/include/proto/htx.h
@@ -57,6 +57,7 @@ struct htx_blk *htx_add_endof(struct htx *htx, enum htx_blk_type type);
 struct htx_blk *htx_add_data(struct htx *htx, const struct ist data);
 struct htx_blk *htx_add_trailer(struct htx *htx, const struct ist tlr);
 struct htx_blk *htx_add_oob(struct htx *htx, const struct ist oob);
+struct htx_blk *htx_add_data_before(struct htx *htx, const struct htx_blk *ref, const struct ist data);
 
 int htx_reqline_to_str(const union htx_sl *sl, struct buffer *chk);
 int htx_stline_to_str(const union htx_sl *sl, struct buffer *chk);
diff --git a/src/htx.c b/src/htx.c
index f04214318..0c9646739 100644
--- a/src/htx.c
+++ b/src/htx.c
@@ -788,6 +788,37 @@ struct htx_blk *htx_add_oob(struct htx *htx, const struct ist oob)
         return blk;
 }
 
+struct htx_blk *htx_add_data_before(struct htx *htx, const struct htx_blk *ref,
+				    const struct ist data)
+{
+	struct htx_blk *blk;
+	int32_t prev;
+
+        /* FIXME: check data.len (< 256MB) */
+        blk = htx_add_blk(htx, HTX_BLK_DATA, data.len);
+        if (!blk)
+                return NULL;
+
+        blk->info += data.len;
+        memcpy(htx_get_blk_ptr(htx, blk), data.ptr, data.len);
+
+	for (prev = htx_get_prev(htx, htx->tail); prev != -1; prev = htx_get_prev(htx, prev)) {
+		struct htx_blk *pblk = htx_get_blk(htx, prev);
+
+		/* Swap .addr and .info fields */
+		blk->addr ^= pblk->addr; pblk->addr ^= blk->addr; blk->addr ^= pblk->addr;
+		blk->info ^= pblk->info; pblk->info ^= blk->info; blk->info ^= pblk->info;
+
+		if (blk->addr == pblk->addr)
+			blk->addr += htx_get_blksz(pblk);
+		htx->front = prev;
+
+		if (pblk == ref)
+			break;
+		blk = pblk;
+	}
+	return blk;
+}
 
 /* Appends the string representation of the request line block <blk> to the
  * chunk <chk>. It returns 1 if data are successfully appended, otherwise it