http-parser replaced to llhttp.

src/3rdparty/llhttp/README.md

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+# llhttp
+[![CI](https://github.com/nodejs/llhttp/workflows/CI/badge.svg)](https://github.com/nodejs/llhttp/actions?query=workflow%3ACI)
+
+Port of [http_parser][0] to [llparse][1].
+
+## Why?
+
+Let's face it, [http_parser][0] is practically unmaintainable. Even
+introduction of a single new method results in a significant code churn.
+
+This project aims to:
+
+* Make it maintainable
+* Verifiable
+* Improving benchmarks where possible
+
+More details in [Fedor Indutny's talk at JSConf EU 2019](https://youtu.be/x3k_5Mi66sY)
+
+## How?
+
+Over time, different approaches for improving [http_parser][0]'s code base
+were tried. However, all of them failed due to resulting significant performance
+degradation.
+
+This project is a port of [http_parser][0] to TypeScript. [llparse][1] is used
+to generate the output C source file, which could be compiled and
+linked with the embedder's program (like [Node.js][7]).
+
+## Performance
+
+So far llhttp outperforms http_parser:
+
+|                 | input size |  bandwidth   |  reqs/sec  |   time  |
+|:----------------|-----------:|-------------:|-----------:|--------:|
+| **llhttp**      | 8192.00 mb | 1777.24 mb/s | 3583799.39 req/sec | 4.61 s |
+| **http_parser** | 8192.00 mb | 694.66 mb/s | 1406180.33 req/sec | 11.79 s |
+
+llhttp is faster by approximately **156%**.
+
+## Maintenance
+
+llhttp project has about 1400 lines of TypeScript code describing the parser
+itself and around 450 lines of C code and headers providing the helper methods.
+The whole [http_parser][0] is implemented in approximately 2500 lines of C, and
+436 lines of headers.
+
+All optimizations and multi-character matching in llhttp are generated
+automatically, and thus doesn't add any extra maintenance cost. On the contrary,
+most of http_parser's code is hand-optimized and unrolled. Instead describing
+"how" it should parse the HTTP requests/responses, a maintainer should
+implement the new features in [http_parser][0] cautiously, considering
+possible performance degradation and manually optimizing the new code.
+
+## Verification
+
+The state machine graph is encoded explicitly in llhttp. The [llparse][1]
+automatically checks the graph for absence of loops and correct reporting of the
+input ranges (spans) like header names and values. In the future, additional
+checks could be performed to get even stricter verification of the llhttp.
+
+## Usage
+
+```C
+#include "llhttp.h"
+
+llhttp_t parser;
+llhttp_settings_t settings;
+
+/* Initialize user callbacks and settings */
+llhttp_settings_init(&settings);
+
+/* Set user callback */
+settings.on_message_complete = handle_on_message_complete;
+
+/* Initialize the parser in HTTP_BOTH mode, meaning that it will select between
+ * HTTP_REQUEST and HTTP_RESPONSE parsing automatically while reading the first
+ * input.
+ */
+llhttp_init(&parser, HTTP_BOTH, &settings);
+
+/* Parse request! */
+const char* request = "GET / HTTP/1.1\r\n\r\n";
+int request_len = strlen(request);
+
+enum llhttp_errno err = llhttp_execute(&parser, request, request_len);
+if (err == HPE_OK) {
+  /* Successfully parsed! */
+} else {
+  fprintf(stderr, "Parse error: %s %s\n", llhttp_errno_name(err),
+          parser.reason);
+}
+```
+
+---
+
+### Bindings to other languages
+
+* Python: [pallas/pyllhttp][8]
+* Ruby: [metabahn/llhttp][9]
+
+#### LICENSE
+
+This software is licensed under the MIT License.
+
+Copyright Fedor Indutny, 2018.
+
+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.
+
+[0]: https://github.com/nodejs/http-parser
+[1]: https://github.com/nodejs/llparse
+[2]: https://en.wikipedia.org/wiki/Register_allocation#Spilling
+[3]: https://en.wikipedia.org/wiki/Tail_call
+[4]: https://llvm.org/docs/LangRef.html
+[5]: https://llvm.org/docs/LangRef.html#call-instruction
+[6]: https://clang.llvm.org/
+[7]: https://github.com/nodejs/node
+[8]: https://github.com/pallas/pyllhttp
+[9]: https://github.com/metabahn/llhttp