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1 /*
2  *
3  * Copyright 2015 gRPC authors.
4  *
5  * Licensed under the Apache License, Version 2.0 (the "License");
6  * you may not use this file except in compliance with the License.
7  * You may obtain a copy of the License at
8  *
9  *     http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  *
17  */
18 
19 #ifndef GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_HPACK_ENCODER_H
20 #define GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_HPACK_ENCODER_H
21 
22 #include <grpc/support/port_platform.h>
23 
24 #include <grpc/slice.h>
25 #include <grpc/slice_buffer.h>
26 #include "src/core/ext/transport/chttp2/transport/frame.h"
27 #include "src/core/lib/transport/metadata.h"
28 #include "src/core/lib/transport/metadata_batch.h"
29 #include "src/core/lib/transport/transport.h"
30 
31 // This should be <= 8. We use 6 to save space.
32 #define GRPC_CHTTP2_HPACKC_NUM_VALUES_BITS 6
33 #define GRPC_CHTTP2_HPACKC_NUM_VALUES (1 << GRPC_CHTTP2_HPACKC_NUM_VALUES_BITS)
34 /* initial table size, per spec */
35 #define GRPC_CHTTP2_HPACKC_INITIAL_TABLE_SIZE 4096
36 /* maximum table size we'll actually use */
37 #define GRPC_CHTTP2_HPACKC_MAX_TABLE_SIZE (1024 * 1024)
38 
39 extern grpc_core::TraceFlag grpc_http_trace;
40 
41 typedef struct {
42   uint32_t filter_elems_sum;
43   uint32_t max_table_size;
44   uint32_t max_table_elems;
45   uint32_t cap_table_elems;
46   /** if non-zero, advertise to the decoder that we'll start using a table
47       of this size */
48   uint8_t advertise_table_size_change;
49   /** maximum number of bytes we'll use for the decode table (to guard against
50       peers ooming us by setting decode table size high) */
51   uint32_t max_usable_size;
52   /* one before the lowest usable table index */
53   uint32_t tail_remote_index;
54   uint32_t table_size;
55   uint32_t table_elems;
56 
57   /* filter tables for elems: this tables provides an approximate
58      popularity count for particular hashes, and are used to determine whether
59      a new literal should be added to the compression table or not.
60      They track a single integer that counts how often a particular value has
61      been seen. When that count reaches max (255), all values are halved. */
62   uint8_t filter_elems[GRPC_CHTTP2_HPACKC_NUM_VALUES];
63 
64   /* entry tables for keys & elems: these tables track values that have been
65      seen and *may* be in the decompressor table */
66   grpc_slice entries_keys[GRPC_CHTTP2_HPACKC_NUM_VALUES];
67   grpc_mdelem entries_elems[GRPC_CHTTP2_HPACKC_NUM_VALUES];
68   uint32_t indices_keys[GRPC_CHTTP2_HPACKC_NUM_VALUES];
69   uint32_t indices_elems[GRPC_CHTTP2_HPACKC_NUM_VALUES];
70 
71   uint16_t* table_elem_size;
72 } grpc_chttp2_hpack_compressor;
73 
74 void grpc_chttp2_hpack_compressor_init(grpc_chttp2_hpack_compressor* c);
75 void grpc_chttp2_hpack_compressor_destroy(grpc_chttp2_hpack_compressor* c);
76 void grpc_chttp2_hpack_compressor_set_max_table_size(
77     grpc_chttp2_hpack_compressor* c, uint32_t max_table_size);
78 void grpc_chttp2_hpack_compressor_set_max_usable_size(
79     grpc_chttp2_hpack_compressor* c, uint32_t max_table_size);
80 
81 typedef struct {
82   uint32_t stream_id;
83   bool is_eof;
84   bool use_true_binary_metadata;
85   size_t max_frame_size;
86   grpc_transport_one_way_stats* stats;
87 } grpc_encode_header_options;
88 
89 void grpc_chttp2_encode_header(grpc_chttp2_hpack_compressor* c,
90                                grpc_mdelem** extra_headers,
91                                size_t extra_headers_size,
92                                grpc_metadata_batch* metadata,
93                                const grpc_encode_header_options* options,
94                                grpc_slice_buffer* outbuf);
95 
96 #endif /* GRPC_CORE_EXT_TRANSPORT_CHTTP2_TRANSPORT_HPACK_ENCODER_H */
97