1.. Licensed to the Apache Software Foundation (ASF) under one
2   or more contributor license agreements.  See the NOTICE file
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4   regarding copyright ownership.  The ASF licenses this file
5   to you under the Apache License, Version 2.0 (the
6   "License"); you may not use this file except in compliance
7   with the License.  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,
12   software distributed under the License is distributed on an
13   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
14   KIND, either express or implied.  See the License for the
15   specific language governing permissions and limitations
16   under the License.
17
18.. include:: ../../../common.defs
19
20.. _developer-plugins-http-headers-functions:
21
22Header Functions
23****************
24
25The Traffic Server API HTTP header functions enable you to work with
26HTTP header data stored in marshal buffers.
27
28The HTTP header data structure is a parsed version of the HTTP header
29defined in the HTTP protocol specification. An HTTP header is composed
30of a request or response line followed by zero or more MIME fields. In
31fact, an HTTP header is a subclass of a MIME header; all of the MIME
32header routines operate on HTTP headers.
33
34An HTTP **request line** is composed of a method, a URL, and version. A
35**response line** is composed of a version, status code, and reason
36phrase. See `About HTTP Headers <../http-headers#AboutHTTPHeaders>`__
37for additional details and examples.
38
39To facilitate fast comparisons and reduce storage size, Traffic Server
40defines several pre-allocated method names. These names correspond to
41the methods defined in the HTTP 1.1 specification
42
43``TS_HTTP_METHOD_CONNECT``
44   "CONNECT"
45
46``TS_HTTP_METHOD_DELETE``
47   "DELETE"
48
49``TS_HTTP_METHOD_GE``
50   "GET"
51
52``TS_HTTP_METHOD_HEAD``
53   "HEAD"
54
55``TS_HTTP_METHOD_OPTIONS``
56   "OPTIONS"
57
58``TS_HTTP_METHOD_POST``
59   "POST"
60
61``TS_HTTP_METHOD_PURGE``
62   "PURGE"
63
64``TS_HTTP_METHOD_PUT``
65   "PUT"
66
67``TS_HTTP_METHOD_TRACE``
68   "TRACE"
69
70``TS_HTTP_METHOD_PUSH``
71   "PUSH"
72
73Traffic Server also defines several common values that appear in HTTP
74headers.
75
76``TS_HTTP_VALUE_BYTES``
77   "bytes"
78
79``TS_HTTP_VALUE_CHUNKED``
80   "chunked"
81
82``TS_HTTP_VALUE_CLOSE``
83   "close"
84
85``TS_HTTP_VALUE_COMPRESS``
86   "compress"
87
88``TS_HTTP_VALUE_DEFLATE``
89   "deflate"
90
91``TS_HTTP_VALUE_GZIP``
92   "gzip"
93
94``TS_HTTP_VALUE_IDENTITY``
95   "identity"
96
97``TS_HTTP_VALUE_KEEP_ALIVE``
98   "keep-alive"
99
100``TS_HTTP_VALUE_MAX_AGE``
101   "max-age"
102
103``TS_HTTP_VALUE_MAX_STALE``
104   "max-stale"
105
106``TS_HTTP_VALUE_MIN_FRESH``
107   "min-fresh"
108
109``TS_HTTP_VALUE_MUST_REVALIDATE``
110   "must-revalidate"
111
112``TS_HTTP_VALUE_NONE``
113   "none"
114
115``TS_HTTP_VALUE_NO_CACHE``
116   "no-cache"
117
118``TS_HTTP_VALUE_NO_STORE``
119   "no-store"
120
121``TS_HTTP_VALUE_NO_TRANSFORM``
122   "no-transform"
123
124``TS_HTTP_VALUE_ONLY_IF_CACHED``
125   "only-if-cached"
126
127``TS_HTTP_VALUE_PRIVATE``
128   "private"
129
130``TS_HTTP_VALUE_PROXY_REVALIDATE``
131   "proxy-revalidate"
132
133``TS_HTTP_VALUE_PUBLIC``
134   "public"
135
136``TS_HTTP_VALUE_S_MAX_AGE``
137   "s-maxage"
138
139The method names and header values above are defined in ``ts.h`` as
140``const char*`` strings. When Traffic Server sets a method or a header
141value, it checks to make sure that the new value is one of the known
142values. If it is, then it stores a pointer into a global table (instead
143of storing the known value in the marshal buffer). The method names and
144header values listed above are also pointers into this table. This
145allows simple pointer comparison of the value returned from
146``TSHttpMethodGet`` with one of the values listed above. It is also
147recommended that you use the above values when referring to one of the
148known schemes, since this removes the possibility of a spelling error.
149
150The **HTTP Header Functions** are listed below:
151
152-  :c:func:`TSHttpHdrClone`
153-  :c:func:`TSHttpHdrCopy`
154-  :c:func:`TSHttpHdrCreate`
155-  :c:func:`TSHttpHdrDestroy`
156-  :c:func:`TSHttpHdrLengthGet`
157-  :c:func:`TSHttpHdrMethodGet`
158-  :c:func:`TSHttpHdrMethodSet`
159-  :c:func:`TSHttpHdrPrint`
160-  :c:func:`TSHttpHdrReasonGet`
161-  :c:func:`TSHttpHdrReasonLookup`
162-  :c:func:`TSHttpHdrReasonSet`
163-  :c:func:`TSHttpHdrStatusGet`
164-  :c:func:`TSHttpHdrStatusSet`
165-  :c:func:`TSHttpHdrTypeGet`
166-  :c:func:`TSHttpHdrTypeSet`
167-  :c:func:`TSHttpHdrUrlGet`
168-  :c:func:`TSHttpHdrUrlSet`
169-  :c:func:`TSHttpHdrVersionGet`
170-  :c:func:`TSHttpHdrVersionSet`
171-  :c:func:`TSHttpParserClear`
172-  :c:func:`TSHttpParserCreate`
173-  :c:func:`TSHttpParserDestroy`
174-  :c:func:`TSHttpHdrParseReq`
175-  :c:func:`TSHttpHdrParseResp`
176
177