diff --git a/include/types/htx.h b/include/types/htx.h
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+++ b/include/types/htx.h
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+/*
+ * include/types/htx.h
+ * This file contains the internal HTTP definitions.
+ *
+ * Copyright (C) 2018 HAProxy Technologies, Christopher Faulet <cfaulet@haproxy.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#ifndef _TYPES_HTX_H
+#define _TYPES_HTX_H
+
+#include <common/ist.h>
+#include <types/sample.h>
+
+/*
+ * The internal representation of an HTTP message is a contiguous array
+ * containing both the blocks (htx_blk) and their contents. Blocks are stored
+ * starting from the end of the array while their contents are stored at the
+ * beginning.
+ *
+ * As data are sent to the peer, blocks and contents are released at the
+ * edges. This free space is reused when no more space left. So blocks and
+ * contents may wrap, not necessarily the same time.
+ *
+ * An HTTP block is as well a header as a body part or a trailer part. For all
+ * these types of block, a content is attached to the block. It can also be a
+ * mark, like the end-of-headers or end-of-message. For these blocks, there is
+ * no content but it count for a byte. It is important to not skip it when data
+ * are forwarded. An HTTP block is composed of 2 fields:
+ *
+ *     - .info : It a 32 bits field containing the block's type on 4 bits
+ *               followed by content' length. See below for details.
+ *
+ *     - .addr : The content's address, if any, relatively to the beginning the
+ *               array used to store the HTTP message itself.
+ *
+ * htx_blk.info representation:
+ *
+ *   0b 0000 0000 0000 0000 0000 0000 0000 0000
+ *      ---- ------------------------ ---------
+ *      type     value (1 MB max)     name length (header)
+ *           ----------------------------------
+ *                data length (256 MB max)
+ *    (body, method, path, version, status, reason, trailers)
+ *
+ *   types:
+ *     - 0000 = request  start-line
+ *     - 0001 = response start-line
+ *     - 0010 = header
+ *     - 0011 = pseudo-header ou "special" header
+ *     - 0100 = end-of-headers
+ *     - 0101 = data
+ *     - 0110 = end-of-data
+ *     - 0111 = trailer
+ *     - 1000 = end-of-message
+ *       ...
+ *     - 1101 = out-of-band
+ *     - 1110 = error
+ *     - 1111 = unused
+ *
+ */
+
+/* HTX flags */
+#define HTX_FL_NONE              0x00000000
+#define HTX_FL_PARSING_ERROR     0x00000001
+
+
+/* Pseudo header types (max 255). */
+enum htx_phdr_type {
+	HTX_PHDR_UNKNOWN =  0,
+	HTX_PHDR_SIZE,
+};
+
+/* HTTP block's type (max 15). */
+enum htx_blk_type {
+	HTX_BLK_REQ_SL =  0, /* Request start-line */
+	HTX_BLK_RES_SL =  1, /* Response start-line */
+	HTX_BLK_HDR    =  2, /* header name/value block */
+	HTX_BLK_PHDR   =  3, /* pseudo header block */
+	HTX_BLK_EOH    =  4, /* end-of-headers block */
+	HTX_BLK_DATA   =  5, /* data block */
+	HTX_BLK_EOD    =  6, /* end-of-data block */
+	HTX_BLK_TLR    =  7, /* trailer name/value block */
+	HTX_BLK_EOM    =  8, /* end-of-message block */
+	/* 9 .. 13 unused */
+	HTX_BLK_OOB    = 14, /* Out of band block, don't alter the parser */
+	HTX_BLK_UNUSED = 15, /* unused/removed block */
+};
+
+/* One HTTP block descriptor */
+struct htx_blk {
+	uint32_t addr; /* relative storage address of a data block */
+	uint32_t info; /* information about data stored */
+};
+
+struct htx_ret {
+	int32_t ret;
+	struct htx_blk *blk;
+};
+
+union htx_sl {
+	struct {
+		enum http_meth_t meth; /* method */
+		int m_len;             /* METHOD length */
+		int u_len;             /* URI length */
+		int v_len;             /* VERSION length */
+		char l[0];
+	} rq;                          /* request line : field, length, data */
+	struct {
+		uint16_t status;       /* status code */
+		int v_len;             /* VERSION length */
+		int c_len;             /* CODE length */
+		int r_len;             /* REASON length */
+		char l[0];
+	} st;                          /* status line : field, length, data */
+};
+
+/* Internal representation of an HTTP message */
+struct htx {
+	uint32_t size;   /* the array size, in bytes, used to store the HTTP message itself */
+	uint32_t data;   /* the data size, in bytes. To known to total size used by all allocated
+			  * blocks (blocks and their contents), you need to add size used by blocks,
+			  * i.e. [ used * sizeof(struct htx_blk *) ] */
+
+	uint32_t used;   /* number of blocks in use */
+	uint32_t tail;   /* last inserted block */
+	uint32_t front;  /* block's position of the first content before the blocks table */
+	uint32_t wrap;   /* the position were the blocks table wraps, if any */
+
+	uint64_t extra;  /* known bytes amount remaining to receive */
+	uint32_t flags;  /* HTX_FL_* */
+
+	struct htx_blk blocks[0]; /* Blocks representing the HTTP message itself */
+};
+
+#endif /* _TYPES_HTX_H */
+
+/*
+ * Local variables:
+ *  c-indent-level: 8
+ *  c-basic-offset: 8
+ * End:
+ */