diff --git a/include/common/hpack-tbl.h b/include/common/hpack-tbl.h
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+++ b/include/common/hpack-tbl.h
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+/*
+ * HPACK header table management (RFC7541) - type definitions and prototypes
+ *
+ * Copyright (C) 2014-2017 Willy Tarreau <willy@haproxy.org>
+ * Copyright (C) 2017 HAProxy Technologies
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+#ifndef _COMMON_HPACK_TBL_H
+#define _COMMON_HPACK_TBL_H
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <common/config.h>
+#include <common/http-hdr.h>
+#include <common/ist.h>
+
+/* Dynamic Headers Table, usable for tables up to 4GB long and values of 64kB-1.
+ * The model can be improved by using offsets relative to the table entry's end
+ * or to the end of the area, or by moving the descriptors at the end of the
+ * table and the data at the beginning. This entry is 8 bytes long, which is 1/4
+ * of the bookkeeping planned by the HPACK spec. Thus it saves 24 bytes per
+ * header field, meaning that even with a single header, 24 extra bytes can be
+ * stored (ie one such descriptor). At 29.2 average bytes per header field as
+ * found in the hpack test case, that's slightly more than 1.5kB of space saved
+ * from a 4kB block, resulting in contiguous space almost always being
+ * available.
+ *
+ * Principle: the table is stored in a contiguous array containing both the
+ * descriptors and the contents. Descriptors are stored at the beginning of the
+ * array while contents are stored starting from the end. Most of the time there
+ * is enough room left in the table to insert a new header field, thanks to the
+ * savings on the descriptor size. Thus by inserting headers from the end it's
+ * possible to maximize the delay before a collision of DTEs and data. In order
+ * to always insert from the right, we need to keep a reference to the latest
+ * inserted element and look before it. The last inserted cell's address defines
+ * the lowest konwn address still in use, unless the area wraps in which case
+ * the available space lies between the end of the tail and the beginning of the
+ * head.
+ *
+ * In order to detect collisions between data blocks and DTEs, we also maintain
+ * an index to the lowest element facing the DTE table, called "front". This one
+ * is updated each time an element is inserted before it. Once the buffer wraps,
+ * this element doesn't have to be updated anymore until it is released, in
+ * which case the buffer doesn't wrap anymore and the front element becomes the
+ * head again.
+ *
+ * Various heuristics are possible concerning the opportunity to wrap the
+ * entries to limit the risk of collisions with the DTE, but experimentation
+ * shows that thanks to the important savings made on the descriptors, the
+ * likeliness of finding a large amount of free space at the end of the area is
+ * much higher than the risk of colliding, so in the end the most naive
+ * algorithms work pretty fine. Typical ratios of 1 collision per 2000 requests
+ * have been observed.
+ *
+ * The defragmentation should be rare ; a study on live data shows on average
+ * 29.2 bytes used per header field. This plus the 32 bytes overhead fix an
+ * average of 66.9 header fields per 4kB table. This brings a 1606 bytes saving
+ * using the current storage description, ensuring that oldest headers are
+ * linearly removed by the sender before fragmentation occurs. This means that
+ * for all smaller header fields there will not be any requirement to defragment
+ * the area and most of the time it will even be possible to copy the old values
+ * directly within the buffer after creating a new entry. On average within the
+ * available space there will be enough room to store 1606/(29.2+8)=43 extra
+ * header fields without switching to another place.
+ *
+ * The table header fits in the table itself, it only takes 16 bytes, so in the
+ * worst case (1 single header) it's possible to store 4096 - 16 - 8 = 4072
+ * data bytes, which is larger than the 4064 the protocol requires (4096 - 32).
+ */
+
+/* One dynamic table entry descriptor */
+struct hpack_dte {
+	uint32_t addr;  /* storage address, relative to the dte address */
+	uint16_t nlen;  /* header name length */
+	uint16_t vlen;  /* header value length */
+};
+
+/* Note: the table's head plus a struct hpack_dte must be smaller than or equal to 32
+ * bytes so that a single large header can always fit. Here that's 16 bytes for
+ * the header, plus 8 bytes per slot.
+ * Note that when <used> == 0, front, head, and wrap are undefined.
+ */
+struct hpack_dht {
+	uint32_t size;  /* allocated table size in bytes */
+	uint32_t total; /* sum of nlen + vlen in bytes */
+	uint16_t front; /* slot number of the first node after the idx table */
+	uint16_t wrap;  /* number of allocated slots, wraps here */
+	uint16_t head;  /* last inserted slot number */
+	uint16_t used;  /* number of slots in use */
+	struct hpack_dte dte[0]; /* dynamic table entries */
+};
+
+/* supported hpack encoding/decoding errors */
+enum {
+	HPACK_ERR_NONE = 0,           /* no error */
+	HPACK_ERR_ALLOC_FAIL,         /* memory allocation error */
+	HPACK_ERR_UNKNOWN_OPCODE,     /* invalid first byte */
+	HPACK_ERR_TRUNCATED,          /* truncated stream */
+	HPACK_ERR_HUFFMAN,            /* huffman decoding error */
+	HPACK_ERR_INVALID_PHDR,       /* invalid pseudo header field name */
+	HPACK_ERR_MISPLACED_PHDR,     /* pseudo header field after a regular header field */
+	HPACK_ERR_DUPLICATE_PHDR,     /* duplicate pseudo header field */
+	HPACK_ERR_DHT_INSERT_FAIL,    /* failed to insert into DHT */
+	HPACK_ERR_TOO_LARGE,          /* decoded request/response is too large */
+	HPACK_ERR_MISSING_METHOD,     /* :method is missing */
+	HPACK_ERR_MISSING_SCHEME,     /* :scheme is missing */
+	HPACK_ERR_MISSING_PATH,       /* :path is missing */
+	HPACK_ERR_MISSING_AUTHORITY,  /* :authority is missing with CONNECT */
+	HPACK_ERR_SCHEME_NOT_ALLOWED, /* :scheme not allowed with CONNECT */
+	HPACK_ERR_PATH_NOT_ALLOWED,   /* :path not allowed with CONNECT */
+};
+
+/* static header table as in RFC7541 Appendix A. [0] unused. */
+#define HPACK_SHT_SIZE 62
+extern const struct http_hdr hpack_sht[HPACK_SHT_SIZE];
+
+extern int __hpack_dht_make_room(struct hpack_dht *dht, unsigned int needed);
+extern int hpack_dht_insert(struct hpack_dht *dht, struct ist name, struct ist value);
+
+/* return a pointer to the entry designated by index <idx> (starting at 1) or
+ * NULL if this index is not there.
+ */
+static inline const struct hpack_dte *hpack_get_dte(const struct hpack_dht *dht, uint16_t idx)
+{
+	idx--;
+
+	if (idx >= dht->used)
+		return NULL;
+
+	if (idx <= dht->head)
+		idx = dht->head - idx;
+	else
+		idx = dht->head - idx + dht->wrap;
+
+	return &dht->dte[idx];
+}
+
+/* return a pointer to the header name for entry <dte>. */
+static inline struct ist hpack_get_name(const struct hpack_dht *dht, const struct hpack_dte *dte)
+{
+	struct ist ret = {
+		.ptr = (void *)dht + dte->addr,
+		.len = dte->nlen,
+	};
+	return ret;
+}
+
+/* return a pointer to the header value for entry <dte>. */
+static inline struct ist hpack_get_value(const struct hpack_dht *dht, const struct hpack_dte *dte)
+{
+	struct ist ret = {
+		.ptr = (void *)dht + dte->addr + dte->nlen,
+		.len = dte->vlen,
+	};
+	return ret;
+}
+
+/* takes an idx, returns the associated name */
+static inline struct ist hpack_idx_to_name(const struct hpack_dht *dht, int idx)
+{
+	const struct hpack_dte *dte;
+
+	if (idx < HPACK_SHT_SIZE)
+		return hpack_sht[idx].n;
+
+	dte = hpack_get_dte(dht, idx - HPACK_SHT_SIZE + 1);
+	if (!dte)
+		return ist("### ERR ###"); // error
+
+	return hpack_get_name(dht, dte);
+}
+
+/* takes an idx, returns the associated value */
+static inline struct ist hpack_idx_to_value(const struct hpack_dht *dht, int idx)
+{
+	const struct hpack_dte *dte;
+
+	if (idx < HPACK_SHT_SIZE)
+		return hpack_sht[idx].v;
+
+	dte = hpack_get_dte(dht, idx - HPACK_SHT_SIZE + 1);
+	if (!dte)
+		return ist("### ERR ###"); // error
+
+	return hpack_get_value(dht, dte);
+}
+
+/* Purges table dht until a header field of <needed> bytes fits according to
+ * the protocol (adding 32 bytes overhead). Returns non-zero on success, zero
+ * on failure (ie: table empty but still not sufficient).
+ */
+static inline int hpack_dht_make_room(struct hpack_dht *dht, unsigned int needed)
+{
+	if (!dht->used || dht->used * 32 + dht->total + needed + 32 <= dht->size)
+		return 1;
+
+	return __hpack_dht_make_room(dht, needed);
+}
+
+/* allocate a dynamic headers table of <size> bytes and return it initialized */
+static inline void hpack_dht_init(struct hpack_dht *dht, uint32_t size)
+{
+	dht->size = size;
+	dht->total = 0;
+	dht->used = 0;
+}
+
+/* allocate a dynamic headers table of <size> bytes and return it initialized */
+static inline struct hpack_dht *hpack_dht_alloc(uint32_t size)
+{
+	struct hpack_dht *dht;
+
+	dht = malloc(size);
+	if (!dht)
+		return dht;
+
+	hpack_dht_init(dht, size);
+	return dht;
+}
+
+/* free a dynamic headers table */
+static inline void hpack_dht_free(struct hpack_dht *dht)
+{
+	free(dht);
+}
+
+#endif /* _COMMON_HPACK_TBL_H */