nghttp2_hd: Implement local header table size limit for encoder

lib/includes/nghttp2/nghttp2.h

@@ -389,6 +389,14 @@ typedef enum {
  * The SETTINGS ID.
  */
 typedef enum {
+  /**
+   * SETTINGS_HEADER_TABLE_SIZE
+   */
+  NGHTTP2_SETTINGS_HEADER_TABLE_SIZE = 1,
+  /**
+   * SETTINGS_ENABLE_PUSH
+   */
+  NGHTTP2_SETTINGS_ENABLE_PUSH = 2,
   /**
    * SETTINGS_MAX_CONCURRENT_STREAMS
    */

lib/nghttp2_hd.c

@@ -187,6 +187,31 @@ static nghttp2_hd_entry* nghttp2_hd_ringbuf_get(nghttp2_hd_ringbuf *ringbuf,
   return ringbuf->buffer[(ringbuf->first + index) & ringbuf->mask];
 }
 
+static int nghttp2_hd_ringbuf_reserve(nghttp2_hd_ringbuf *ringbuf,
+                                      size_t bufsize)
+{
+  size_t i;
+  size_t size;
+  nghttp2_hd_entry **buffer;
+
+  if(ringbuf->mask + 1 >= bufsize) {
+    return 0;
+  }
+  for(size = 1; size < bufsize; size <<= 1);
+  buffer = malloc(sizeof(nghttp2_hd_entry*) * size);
+  if(buffer == NULL) {
+    return NGHTTP2_ERR_NOMEM;
+  }
+  for(i = 0; i < ringbuf->len; ++i) {
+    buffer[i] = nghttp2_hd_ringbuf_get(ringbuf, i);
+  }
+  free(ringbuf->buffer);
+  ringbuf->buffer = buffer;
+  ringbuf->mask = size - 1;
+  ringbuf->first = 0;
+  return 0;
+}
+
 static void nghttp2_hd_ringbuf_free(nghttp2_hd_ringbuf *ringbuf)
 {
   size_t i;
@@ -220,15 +245,16 @@ static void nghttp2_hd_ringbuf_pop_back(nghttp2_hd_ringbuf *ringbuf)
 static int nghttp2_hd_context_init(nghttp2_hd_context *context,
                                    nghttp2_hd_role role,
                                    nghttp2_hd_side side,
-                                   size_t hd_table_bufsize_max)
+                                   size_t local_hd_table_bufsize_max)
 {
   int rv;
   context->role = role;
   context->side = side;
   context->bad = 0;
-  context->hd_table_bufsize_max = hd_table_bufsize_max;
+  context->hd_table_bufsize_max = NGHTTP2_HD_DEFAULT_MAX_BUFFER_SIZE;
-  rv = nghttp2_hd_ringbuf_init(&context->hd_table,
+  rv = nghttp2_hd_ringbuf_init
-                               hd_table_bufsize_max/NGHTTP2_HD_ENTRY_OVERHEAD);
+    (&context->hd_table,
+     context->hd_table_bufsize_max/NGHTTP2_HD_ENTRY_OVERHEAD);
   if(rv != 0) {
     return rv;
   }
@@ -255,6 +281,9 @@ static int nghttp2_hd_context_init(nghttp2_hd_context *context,
     context->buf_track = NULL;
     context->buf_track_capacity = 0;
   }
+  context->local_hd_table_bufsize_max = local_hd_table_bufsize_max;
+  context->local_hd_table_bufsize = 0;
+  context->local_hd_tablelen = 0;
   context->emit_setlen = 0;
   context->buf_tracklen = 0;
   context->hd_table_bufsize = 0;
@@ -269,29 +298,20 @@ static int nghttp2_hd_context_init(nghttp2_hd_context *context,
 int nghttp2_hd_deflate_init(nghttp2_hd_context *deflater, nghttp2_hd_side side)
 {
   return nghttp2_hd_context_init(deflater, NGHTTP2_HD_ROLE_DEFLATE, side,
-                                 NGHTTP2_HD_DEFAULT_MAX_BUFFER_SIZE);
+                                 NGHTTP2_HD_DEFAULT_LOCAL_MAX_BUFFER_SIZE);
 }
 
 int nghttp2_hd_deflate_init2(nghttp2_hd_context *deflater,
                              nghttp2_hd_side side,
-                             size_t hd_table_bufsize_max)
+                             size_t local_hd_table_bufsize_max)
 {
   return nghttp2_hd_context_init(deflater, NGHTTP2_HD_ROLE_DEFLATE, side,
-                                 hd_table_bufsize_max);
+                                 local_hd_table_bufsize_max);
 }
 
 int nghttp2_hd_inflate_init(nghttp2_hd_context *inflater, nghttp2_hd_side side)
 {
-  return nghttp2_hd_context_init(inflater, NGHTTP2_HD_ROLE_INFLATE, side,
+  return nghttp2_hd_context_init(inflater, NGHTTP2_HD_ROLE_INFLATE, side, 0);
-                                 NGHTTP2_HD_DEFAULT_MAX_BUFFER_SIZE);
-}
-
-int nghttp2_hd_inflate_init2(nghttp2_hd_context *inflater,
-                             nghttp2_hd_side side,
-                             size_t hd_table_bufsize_max)
-{
-  return nghttp2_hd_context_init(inflater, NGHTTP2_HD_ROLE_INFLATE, side,
-                                 hd_table_bufsize_max);
 }
 
 static void nghttp2_hd_context_free(nghttp2_hd_context *context)
@@ -680,20 +700,25 @@ static nghttp2_hd_entry* add_hd_table_incremental(nghttp2_hd_context *context,
   int rv;
   nghttp2_hd_entry *new_ent;
   size_t room = entry_room(nv->namelen, nv->valuelen);
-  context->hd_table_bufsize += room;
+  while(context->hd_table_bufsize + room > context->hd_table_bufsize_max &&
-  while(context->hd_table_bufsize > context->hd_table_bufsize_max &&
         context->hd_table.len > 0) {
     size_t index = context->hd_table.len - 1;
     nghttp2_hd_entry* ent = nghttp2_hd_ringbuf_get(&context->hd_table, index);
     context->hd_table_bufsize -= entry_room(ent->nv.namelen, ent->nv.valuelen);
-    if(context->role == NGHTTP2_HD_ROLE_DEFLATE &&
+    if(context->role == NGHTTP2_HD_ROLE_DEFLATE) {
-       (ent->flags & NGHTTP2_HD_FLAG_IMPLICIT_EMIT)) {
+      if(context->hd_table_bufsize < context->local_hd_table_bufsize) {
-      /* Emit common header just before it slips away from the
+        context->local_hd_table_bufsize -= entry_room(ent->nv.namelen,
-         table. If we don't do this, we have to emit it in literal
+                                                      ent->nv.valuelen);
-         representation which hurts compression. */
+        --context->local_hd_tablelen;
-      rv = emit_implicit(buf_ptr, buflen_ptr, offset_ptr, index);
+      }
-      if(rv != 0) {
+      if(ent->flags & NGHTTP2_HD_FLAG_IMPLICIT_EMIT) {
-        return NULL;
+        /* Emit common header just before it slips away from the
+           table. If we don't do this, we have to emit it in literal
+           representation which hurts compression. */
+        rv = emit_implicit(buf_ptr, buflen_ptr, offset_ptr, index);
+        if(rv != 0) {
+          return NULL;
+        }
       }
     }
     nghttp2_hd_ringbuf_pop_back(&context->hd_table);
@@ -702,22 +727,94 @@ static nghttp2_hd_entry* add_hd_table_incremental(nghttp2_hd_context *context,
       free(ent);
     }
   }
+  if(context->role == NGHTTP2_HD_ROLE_DEFLATE) {
+    while(context->local_hd_table_bufsize + room >
+          context->local_hd_table_bufsize_max
+          && context->local_hd_tablelen > 0) {
+      size_t index = context->local_hd_tablelen - 1;
+      nghttp2_hd_entry *ent =
+        nghttp2_hd_ringbuf_get(&context->hd_table, index);
+      context->local_hd_table_bufsize -= entry_room(ent->nv.namelen,
+                                                    ent->nv.valuelen);
+      --context->local_hd_tablelen;
+      if(ent->flags & NGHTTP2_HD_FLAG_IMPLICIT_EMIT) {
+        /* Just like a normal eviction, implicit header must be
+           emitted twice. */
+        rv = emit_implicit(buf_ptr, buflen_ptr, offset_ptr, index);
+        if(rv != 0) {
+          return NULL;
+        }
+        ent->flags ^= NGHTTP2_HD_FLAG_IMPLICIT_EMIT;
+      }
+      if(ent->flags & NGHTTP2_HD_FLAG_REFSET) {
+        /* We need to drop entry from reference set. */
+        rv = emit_indexed_block(buf_ptr, buflen_ptr, offset_ptr, index);
+        if(rv != 0) {
+          return NULL;
+        }
+        ent->flags ^= NGHTTP2_HD_FLAG_REFSET;
+      }
+      /* Release memory. We don't remove entry from the header table
+         at this moment. */
+      if(ent->flags & NGHTTP2_HD_FLAG_NAME_ALLOC) {
+        free(ent->nv.name);
+        ent->nv.name = NULL;
+        ent->flags ^= NGHTTP2_HD_FLAG_NAME_ALLOC;
+      }
+      if(ent->flags & NGHTTP2_HD_FLAG_VALUE_ALLOC) {
+        free(ent->nv.value);
+        ent->nv.value = NULL;
+        ent->flags ^= NGHTTP2_HD_FLAG_VALUE_ALLOC;
+      }
+    }
+  }
+
   new_ent = malloc(sizeof(nghttp2_hd_entry));
   if(new_ent == NULL) {
     return NULL;
   }
-  rv = nghttp2_hd_entry_init(new_ent,
+
-                             entry_flags,
+  if(context->role == NGHTTP2_HD_ROLE_DEFLATE &&
-                             nv->name, nv->namelen, nv->value, nv->valuelen);
+     room > context->local_hd_table_bufsize_max) {
-  if(rv != 0) {
+    uint8_t flags = entry_flags &
-    free(new_ent);
+      ~(NGHTTP2_HD_FLAG_NAME_ALLOC | NGHTTP2_HD_FLAG_VALUE_ALLOC |
-    return NULL;
+        NGHTTP2_HD_FLAG_NAME_GIFT | NGHTTP2_HD_FLAG_VALUE_GIFT);
+    rv = nghttp2_hd_entry_init(new_ent, flags,
+                               NULL, nv->namelen, NULL, nv->valuelen);
+    if(rv != 0) {
+      free(new_ent);
+      return NULL;
+    }
+    if(flags & NGHTTP2_HD_FLAG_NAME_GIFT) {
+      free(nv->name);
+      nv->name = NULL;
+    }
+    if(flags & NGHTTP2_HD_FLAG_VALUE_GIFT) {
+      free(nv->value);
+      nv->value = NULL;
+    }
+    /* caller must emit indexed repr to toggle off new_ent from
+       reference set. We cannot do it here because it may break the
+       indexing. */
+  } else {
+    rv = nghttp2_hd_entry_init(new_ent,
+                               entry_flags,
+                               nv->name, nv->namelen, nv->value, nv->valuelen);
+    if(rv != 0) {
+      free(new_ent);
+      return NULL;
+    }
+    if(context->role == NGHTTP2_HD_ROLE_DEFLATE) {
+      context->local_hd_table_bufsize += room;
+      ++context->local_hd_tablelen;
+    }
   }
   if(room > context->hd_table_bufsize_max) {
     /* The entry taking more than NGHTTP2_HD_MAX_BUFFER_SIZE is
        immediately evicted. */
     --new_ent->ref;
   } else {
+    context->hd_table_bufsize += room;
     new_ent->flags |= NGHTTP2_HD_FLAG_REFSET;
     nghttp2_hd_ringbuf_push_front(&context->hd_table, new_ent);
   }
@@ -727,7 +824,9 @@ static nghttp2_hd_entry* add_hd_table_incremental(nghttp2_hd_context *context,
 static ssize_t find_in_hd_table(nghttp2_hd_context *context, nghttp2_nv *nv)
 {
   size_t i;
-  for(i = 0; i < context->hd_table.len; ++i) {
+  size_t max = context->role == NGHTTP2_HD_ROLE_DEFLATE ?
+    context->local_hd_tablelen : context->hd_table.len;
+  for(i = 0; i < max; ++i) {
     nghttp2_hd_entry *ent = nghttp2_hd_ringbuf_get(&context->hd_table, i);
     if(nghttp2_nv_equal(&ent->nv, nv)) {
       return i;
@@ -746,7 +845,9 @@ static ssize_t find_name_in_hd_table(nghttp2_hd_context *context,
                                      nghttp2_nv *nv)
 {
   size_t i;
-  for(i = 0; i < context->hd_table.len; ++i) {
+  size_t max = context->role == NGHTTP2_HD_ROLE_DEFLATE ?
+    context->local_hd_tablelen : context->hd_table.len;
+  for(i = 0; i < max; ++i) {
     nghttp2_hd_entry *ent = nghttp2_hd_ringbuf_get(&context->hd_table, i);
     if(ent->nv.namelen == nv->namelen &&
        memcmp(ent->nv.name, nv->name, nv->namelen) == 0) {
@@ -763,6 +864,37 @@ static ssize_t find_name_in_hd_table(nghttp2_hd_context *context,
   return -1;
 }
 
+int nghttp2_hd_change_table_size(nghttp2_hd_context *context,
+                                 size_t hd_table_bufsize_max)
+{
+  int rv;
+  rv = nghttp2_hd_ringbuf_reserve
+    (&context->hd_table, hd_table_bufsize_max / NGHTTP2_HD_ENTRY_OVERHEAD);
+  if(rv != 0) {
+    return rv;
+  }
+  context->hd_table_bufsize_max = hd_table_bufsize_max;
+  while(context->hd_table_bufsize > context->hd_table_bufsize_max &&
+        context->hd_table.len > 0) {
+    size_t index = context->hd_table.len - 1;
+    nghttp2_hd_entry* ent = nghttp2_hd_ringbuf_get(&context->hd_table, index);
+    context->hd_table_bufsize -= entry_room(ent->nv.namelen, ent->nv.valuelen);
+    if(context->role == NGHTTP2_HD_ROLE_DEFLATE) {
+      if(context->hd_table_bufsize < context->local_hd_table_bufsize) {
+        context->local_hd_table_bufsize -= entry_room(ent->nv.namelen,
+                                                      ent->nv.valuelen);
+        --context->local_hd_tablelen;
+      }
+    }
+    nghttp2_hd_ringbuf_pop_back(&context->hd_table);
+    if(--ent->ref == 0) {
+      nghttp2_hd_entry_free(ent);
+      free(ent);
+    }
+  }
+  return 0;
+}
+
 static int check_index_range(nghttp2_hd_context *context, size_t index)
 {
   return index < context->hd_table.len + STATIC_TABLE_LENGTH;
@@ -804,7 +936,10 @@ static int deflate_nv(nghttp2_hd_context *deflater,
       if(new_ent->ref == 0) {
         nghttp2_hd_entry_free(new_ent);
         free(new_ent);
-      } else {
+        new_ent = NULL;
+      } else if(new_ent->nv.name != NULL) {
+        /* new_ent->ref > 0 and nv.name is not NULL means that new_ent is
+           in the reference set and in local_hd_table_bufsize */
         new_ent->flags |= NGHTTP2_HD_FLAG_EMIT;
       }
       rv = emit_indexed_block(buf_ptr, buflen_ptr, offset_ptr, index);
@@ -877,7 +1012,9 @@ static int deflate_nv(nghttp2_hd_context *deflater,
       if(new_ent->ref == 0) {
         nghttp2_hd_entry_free(new_ent);
         free(new_ent);
-      } else {
+      } else if(new_ent->nv.name != NULL) {
+        /* new_ent->ref > 0 and nv.name is not NULL means that new_ent is
+           in the reference set and in local_hd_table_bufsize */
         new_ent->flags |= NGHTTP2_HD_FLAG_EMIT;
       }
       incidx = 1;

lib/nghttp2_hd.h

@@ -38,6 +38,11 @@
 #define NGHTTP2_HD_MAX_ENTRY_SIZE 3072
 #define NGHTTP2_HD_ENTRY_OVERHEAD 32
 
+/* Default size of maximum table buffer size for encoder. Even if
+   remote decoder notifies larger buffer size for its decoding,
+   encoder only uses the memory up to this value. */
+#define NGHTTP2_HD_DEFAULT_LOCAL_MAX_BUFFER_SIZE (1 << 12)
+
 typedef enum {
   NGHTTP2_HD_SIDE_REQUEST = 0,
   NGHTTP2_HD_SIDE_RESPONSE = 1
@@ -85,6 +90,24 @@ typedef struct {
 typedef struct {
   /* dynamic header table */
   nghttp2_hd_ringbuf hd_table;
+  /* The header table size for decoding. If the context is initialized
+     as encoder, this value is advertised by remote endpoint
+     decoder. */
+  size_t hd_table_bufsize_max;
+  /* The current effective header table size for encoding. This value
+     is meaningful iff this context is initialized as
+     encoder. |local_hd_table_bufsize| <= |hd_table_bufsize| must be
+     hold. */
+  size_t local_hd_table_bufsize;
+  /* The maximum effective header table for encoding. Although header
+     table size is bounded by |hd_table_bufsize_max|, the encoder can
+     use smaller buffer by not retaining the header name/values beyond
+     the |local_hd_table_bufsize_max| and not referencing those
+     entries. This value is meaningful iff this context is initialized
+     as encoder. */
+  size_t local_hd_table_bufsize_max;
+  /* The number of effective entry in |hd_table|. */
+  size_t local_hd_tablelen;
   /* Holding emitted entry in deflating header block to retain
      reference count. */
   nghttp2_hd_entry **emit_set;
@@ -105,8 +128,6 @@ typedef struct {
   /* NGHTTP2_HD_SIDE_REQUEST for processing request, otherwise
      response. */
   nghttp2_hd_side side;
-  /* Maximum header table size */
-  size_t hd_table_bufsize_max;
   /* Keep track of allocated buffers in inflation */
   uint8_t **buf_track;
   /* The capacity of |buf_track| */
@@ -137,6 +158,11 @@ void nghttp2_hd_entry_free(nghttp2_hd_entry *ent);
 /*
  * Initializes |deflater| for deflating name/values pairs.
  *
+ * The encoder only uses up to
+ * NGHTTP2_HD_DEFAULT_LOCAL_MAX_BUFFER_SIZE bytes for header table
+ * even if the larger value is specified later in
+ * nghttp2_hd_change_table_size().
+ *
  * This function returns 0 if it succeeds, or one of the following
  * negative error codes:
  *
@@ -146,9 +172,22 @@ void nghttp2_hd_entry_free(nghttp2_hd_entry *ent);
 int nghttp2_hd_deflate_init(nghttp2_hd_context *deflater,
                             nghttp2_hd_side side);
 
+/*
+ * Initializes |deflater| for deflating name/values pairs.
+ *
+ * The encoder only uses up to |local_hd_table_bufsize_max| bytes for
+ * header table even if the larger value is specified later in
+ * nghttp2_hd_change_table_size().
+ *
+ * This function returns 0 if it succeeds, or one of the following
+ * negative error codes:
+ *
+ * NGHTTP2_ERR_NOMEM
+ *     Out of memory.
+ */
 int nghttp2_hd_deflate_init2(nghttp2_hd_context *deflater,
                              nghttp2_hd_side side,
-                             size_t hd_table_bufsize_max);
+                             size_t local_hd_table_bufsize_max);
 
 /*
  * Initializes |inflater| for inflating name/values pairs.
@@ -162,10 +201,6 @@ int nghttp2_hd_deflate_init2(nghttp2_hd_context *deflater,
 int nghttp2_hd_inflate_init(nghttp2_hd_context *inflater,
                             nghttp2_hd_side side);
 
-int nghttp2_hd_inflate_init2(nghttp2_hd_context *inflater,
-                             nghttp2_hd_side side,
-                             size_t hd_table_bufsize_max);
-
 /*
  * Deallocates any resources allocated for |deflater|.
  */
@@ -176,6 +211,20 @@ void nghttp2_hd_deflate_free(nghttp2_hd_context *deflater);
  */
 void nghttp2_hd_inflate_free(nghttp2_hd_context *inflater);
 
+
+/*
+ * Changes header table size in |context|. This may trigger eviction
+ * in the dynamic table.
+ *
+ * This function returns 0 if it succeeds, or one of the following
+ * negative error codes:
+ *
+ * NGHTTP2_ERR_NOMEM
+ *     Out of memory.
+ */
+int nghttp2_hd_change_table_size(nghttp2_hd_context *context,
+                                 size_t hd_table_bufsize_max);
+
 /*
  * Deflates the |nva|, which has the |nvlen| name/value pairs, into
  * the buffer pointed by the |*buf_ptr| with the length |*buflen_ptr|.

tests/main.c

@@ -231,6 +231,8 @@ int main(int argc, char* argv[])
                    test_nghttp2_hd_deflate_same_indexed_repr) ||
       !CU_add_test(pSuite, "hd_deflate_common_header_eviction",
                    test_nghttp2_hd_deflate_common_header_eviction) ||
+      !CU_add_test(pSuite, "hd_deflate_local_buffer",
+                   test_nghttp2_hd_deflate_local_buffer) ||
       !CU_add_test(pSuite, "hd_inflate_indname_inc",
                    test_nghttp2_hd_inflate_indname_inc) ||
       !CU_add_test(pSuite, "hd_inflate_indname_inc_eviction",
@@ -239,6 +241,8 @@ int main(int argc, char* argv[])
                    test_nghttp2_hd_inflate_newname_inc) ||
       !CU_add_test(pSuite, "hd_inflate_clearall_inc",
                    test_nghttp2_hd_inflate_clearall_inc) ||
+      !CU_add_test(pSuite, "hd_change_table_size",
+                   test_nghttp2_hd_change_table_size) ||
       !CU_add_test(pSuite, "hd_deflate_inflate",
                    test_nghttp2_hd_deflate_inflate) ||
       !CU_add_test(pSuite, "gzip_inflate", test_nghttp2_gzip_inflate) ||

tests/nghttp2_hd_test.c

@@ -247,6 +247,197 @@ void test_nghttp2_hd_deflate_common_header_eviction(void)
   nghttp2_hd_deflate_free(&deflater);
 }
 
+void test_nghttp2_hd_deflate_local_buffer(void)
+{
+  nghttp2_hd_context deflater, inflater;
+  size_t i;
+  ssize_t rv, blocklen;
+  uint8_t *buf = NULL;
+  size_t buflen = 0;
+  nghttp2_nv nva1[] = { MAKE_NV("k1", "v1"), /* 36 */
+                        MAKE_NV("k10", "v10"), /* 38 */
+                        MAKE_NV("k100", "v100"), /* 40 */
+                        MAKE_NV("k1000", "v1000") /* 42 */
+  }; /* Total: 156 */
+  nghttp2_nv nva2[] = { MAKE_NV("k10", "v10"), /* 38 */
+                        MAKE_NV("k1", "v1") /* 36 */
+  };
+  nghttp2_nv nv3;
+  uint8_t val[256];
+  nghttp2_nv nva4[] = { MAKE_NV(":method", "GET"),
+                        MAKE_NV(":scheme", "http")
+  };
+  nghttp2_nv *resnva;
+  nghttp2_hd_entry *ent;
+
+  memset(val, 'a', sizeof(val));
+  nv3.name = nv3.value = val;
+  nv3.namelen = nv3.valuelen = sizeof(val);
+
+  /* Check the case where entry from static table is inserted to
+     dynamic header table. And it is out of local header table
+     size. */
+  nghttp2_hd_deflate_init2(&deflater, NGHTTP2_HD_SIDE_REQUEST, 32);
+  nghttp2_hd_inflate_init(&inflater, NGHTTP2_HD_SIDE_REQUEST);
+  blocklen = nghttp2_hd_deflate_hd(&deflater, &buf, &buflen, 0,
+                                   nva4, ARRLEN(nva4));
+  CU_ASSERT(blocklen > 0);
+  /* Now header table should look like this:
+   *
+   *  0: :scheme, http (-)
+   *  1: :method, GET (-)
+   *
+   * name/value of all entries must be NULL.
+   */
+  CU_ASSERT(2 == deflater.hd_table.len);
+  CU_ASSERT(0 == deflater.local_hd_tablelen);
+  CU_ASSERT(0 == deflater.local_hd_table_bufsize);
+  for(i = 0; i < 2; ++i) {
+    ent = nghttp2_hd_table_get(&deflater, i);
+    CU_ASSERT(ent->nv.name == NULL);
+    CU_ASSERT(ent->nv.value == NULL);
+    CU_ASSERT(0 == (ent->flags & NGHTTP2_HD_FLAG_REFSET));
+  }
+
+  rv = nghttp2_hd_inflate_hd(&inflater, &resnva, buf, blocklen);
+  CU_ASSERT(2 == rv);
+  assert_nv_equal(nva4, resnva, 2);
+  nghttp2_hd_end_headers(&inflater);
+  nghttp2_nv_array_del(resnva);
+
+  nghttp2_hd_deflate_free(&deflater);
+  nghttp2_hd_inflate_free(&inflater);
+
+  /* 156 buffer size can hold all headers in local region */
+  nghttp2_hd_deflate_init2(&deflater, NGHTTP2_HD_SIDE_REQUEST,
+                           156);
+  blocklen = nghttp2_hd_deflate_hd(&deflater, &buf, &buflen, 0,
+                                   nva1, ARRLEN(nva1));
+  CU_ASSERT(blocklen > 0);
+  /* Now header table should look like this:
+   *
+   *  0: k1000, v100
+   *  1: k100, v100
+   *  2: k10, v10
+   *  3: k1, v1
+   */
+  CU_ASSERT(4 == deflater.hd_table.len);
+  CU_ASSERT(4 == deflater.local_hd_tablelen);
+  CU_ASSERT(156 == deflater.local_hd_table_bufsize);
+  for(i = 0; i < 4; ++i) {
+    CU_ASSERT(nghttp2_hd_table_get(&deflater, i)->nv.name != NULL);
+    CU_ASSERT(nghttp2_hd_table_get(&deflater, i)->nv.value != NULL);
+  }
+
+  CU_ASSERT(0 == nghttp2_hd_change_table_size(&deflater, 156));
+  CU_ASSERT(4 == deflater.hd_table.len);
+  CU_ASSERT(4 == deflater.local_hd_tablelen);
+  CU_ASSERT(156 == deflater.local_hd_table_bufsize);
+
+  blocklen = nghttp2_hd_deflate_hd(&deflater, &buf, &buflen, 0, &nv3, 1);
+  CU_ASSERT(blocklen > 0);
+  /* Now header table should be empty */
+  CU_ASSERT(0 == deflater.hd_table.len);
+  CU_ASSERT(0 == deflater.local_hd_tablelen);
+  CU_ASSERT(0 == deflater.local_hd_table_bufsize);
+
+  nghttp2_hd_deflate_free(&deflater);
+
+  /* Check more complex use case */
+  nghttp2_hd_deflate_init2(&deflater, NGHTTP2_HD_SIDE_REQUEST,
+                           155);
+  nghttp2_hd_inflate_init(&inflater, NGHTTP2_HD_SIDE_REQUEST);
+  blocklen = nghttp2_hd_deflate_hd(&deflater, &buf, &buflen, 0,
+                                   nva1, ARRLEN(nva1));
+  CU_ASSERT(blocklen > 0);
+  /* Now header table should look like this:
+   *
+   *  0: k1000, v100 (R)
+   *  1: k100, v100 (R)
+   *  2: k10, v10 (R)
+   *  3: k1, v1 (-)  <- name, value must be NULL and not in reference set
+   *
+   * But due to the local table size limit, name/value of index=3 must
+   * be NULL.
+   */
+  CU_ASSERT(4 == deflater.hd_table.len);
+  CU_ASSERT(3 == deflater.local_hd_tablelen);
+  CU_ASSERT(120 == deflater.local_hd_table_bufsize);
+  for(i = 0; i < 3; ++i) {
+    CU_ASSERT(nghttp2_hd_table_get(&deflater, i)->nv.name != NULL);
+    CU_ASSERT(nghttp2_hd_table_get(&deflater, i)->nv.value != NULL);
+  }
+  ent = nghttp2_hd_table_get(&deflater, 3);
+  CU_ASSERT(ent->nv.name == NULL);
+  CU_ASSERT(ent->nv.value == NULL);
+  CU_ASSERT(0 == (ent->flags & NGHTTP2_HD_FLAG_REFSET));
+
+  rv = nghttp2_hd_inflate_hd(&inflater, &resnva, buf, blocklen);
+  CU_ASSERT(4 == rv);
+  assert_nv_equal(nva1, resnva, 4);
+  nghttp2_hd_end_headers(&inflater);
+  nghttp2_nv_array_del(resnva);
+
+  blocklen = nghttp2_hd_deflate_hd(&deflater, &buf, &buflen, 0,
+                                   nva2, ARRLEN(nva2));
+  CU_ASSERT(blocklen > 0);
+  /* Now header table should look like this:
+   *
+   *  0: k1, v1 (R)
+   *  1: k1000, v100 (R)
+   *  2: k100, v100 (R)
+   *  3: k10, v10 (-) <- name, value must be NULL
+   *  4: k1, v1   (-) <- name, value must be NULL
+   */
+  CU_ASSERT(5 == deflater.hd_table.len);
+  CU_ASSERT(3 == deflater.local_hd_tablelen);
+  CU_ASSERT(118 == deflater.local_hd_table_bufsize);
+  ent = nghttp2_hd_table_get(&deflater, 3);
+  CU_ASSERT(0 == (ent->flags & NGHTTP2_HD_FLAG_REFSET));
+  ent = nghttp2_hd_table_get(&deflater, 3);
+  CU_ASSERT(0 == (ent->flags & NGHTTP2_HD_FLAG_REFSET));
+
+  rv = nghttp2_hd_inflate_hd(&inflater, &resnva, buf, blocklen);
+  CU_ASSERT(2 == rv);
+  /* Sort before comparison */
+  nghttp2_nv_array_sort(nva2, 2);
+  assert_nv_equal(nva2, resnva, 2);
+  nghttp2_hd_end_headers(&inflater);
+  nghttp2_nv_array_del(resnva);
+
+  blocklen = nghttp2_hd_deflate_hd(&deflater, &buf, &buflen, 0, &nv3, 1);
+  CU_ASSERT(blocklen > 0);
+  /* Now header table should look like this:
+   *
+   *  0: a..a, a..a (-)
+   *  1: k1, v1 (-)
+   *  2: k1000, v100 (-)
+   *  3: k100, v100 (-)
+   *  4: k10, v10 (-)
+   *  5: k1, v1   (-)
+   *
+   *  name/value of all entries must be NULL.
+   */
+  CU_ASSERT(6 == deflater.hd_table.len);
+  CU_ASSERT(0 == deflater.local_hd_tablelen);
+  CU_ASSERT(0 == deflater.local_hd_table_bufsize);
+  for(i = 0; i < 6; ++i) {
+    ent = nghttp2_hd_table_get(&deflater, i);
+    CU_ASSERT(0 == (ent->flags & NGHTTP2_HD_FLAG_REFSET));
+  }
+
+  rv = nghttp2_hd_inflate_hd(&inflater, &resnva, buf, blocklen);
+  CU_ASSERT(1 == rv);
+  assert_nv_equal(&nv3, resnva, 1);
+  nghttp2_hd_end_headers(&inflater);
+  nghttp2_nv_array_del(resnva);
+
+  free(buf);
+  nghttp2_hd_inflate_free(&inflater);
+  nghttp2_hd_deflate_free(&deflater);
+
+}
+
 void test_nghttp2_hd_inflate_indname_inc(void)
 {
   nghttp2_hd_context inflater;
@@ -389,6 +580,40 @@ void test_nghttp2_hd_inflate_clearall_inc(void)
   nghttp2_hd_inflate_free(&inflater);
 }
 
+void test_nghttp2_hd_change_table_size(void)
+{
+  nghttp2_hd_context deflater;
+  nghttp2_nv nva[] = { MAKE_NV(":method", "GET"),
+                       MAKE_NV(":path", "/") };
+  uint8_t *buf = NULL;
+  size_t buflen = 0;
+  ssize_t rv;
+
+  nghttp2_hd_deflate_init(&deflater, NGHTTP2_HD_SIDE_REQUEST);
+  CU_ASSERT(0 == nghttp2_hd_change_table_size(&deflater, 8000));
+  CU_ASSERT(255 == deflater.hd_table.mask);
+  CU_ASSERT(8000 == deflater.hd_table_bufsize_max);
+
+  rv = nghttp2_hd_deflate_hd(&deflater, &buf, &buflen, 0, nva, 2);
+  CU_ASSERT(rv > 0);
+  CU_ASSERT(2 == deflater.hd_table.len);
+
+  CU_ASSERT(0 == nghttp2_hd_change_table_size(&deflater, 16384));
+  CU_ASSERT(511 == deflater.hd_table.mask);
+  CU_ASSERT(2 == deflater.hd_table.len);
+  CU_ASSERT(2 == deflater.local_hd_tablelen);
+  CU_ASSERT(5 ==
+            deflater.hd_table.buffer[deflater.hd_table.first]->nv.namelen);
+
+  CU_ASSERT(0 == nghttp2_hd_change_table_size(&deflater, 0));
+  CU_ASSERT(511 == deflater.hd_table.mask);
+  CU_ASSERT(0 == deflater.hd_table.len);
+  CU_ASSERT(0 == deflater.local_hd_tablelen);
+
+  free(buf);
+  nghttp2_hd_deflate_free(&deflater);
+}
+
 static void check_deflate_inflate(nghttp2_hd_context *deflater,
                                   nghttp2_hd_context *inflater,
                                   nghttp2_nv *nva, size_t nvlen)

tests/nghttp2_hd_test.h

@@ -28,10 +28,12 @@
 void test_nghttp2_hd_deflate(void);
 void test_nghttp2_hd_deflate_same_indexed_repr(void);
 void test_nghttp2_hd_deflate_common_header_eviction(void);
+void test_nghttp2_hd_deflate_local_buffer(void);
 void test_nghttp2_hd_inflate_indname_inc(void);
 void test_nghttp2_hd_inflate_indname_inc_eviction(void);
 void test_nghttp2_hd_inflate_newname_inc(void);
 void test_nghttp2_hd_inflate_clearall_inc(void);
+void test_nghttp2_hd_change_table_size(void);
 void test_nghttp2_hd_deflate_inflate(void);
 
 #endif /* NGHTTP2_HD_TEST_H */