130 lines
4.6 KiB
Markdown
130 lines
4.6 KiB
Markdown
# llhttp
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[](http://travis-ci.org/nodejs/llhttp)
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Port of [http_parser][0] to [llparse][1].
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## Why?
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Let's face it, [http_parser][0] is practically unmaintainable. Even
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introduction of a single new method results in a significant code churn.
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This project aims to:
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* Make it maintainable
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* Verifiable
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* Improving benchmarks where possible
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## How?
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Over time, different approaches for improving [http_parser][0]'s code base
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were tried. However, all of them failed due to resulting significant performance
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degradation.
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This project is a port of [http_parser][0] to TypeScript. [llparse][1] is used
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to generate the output C and/or bitcode artifacts, which could be compiled and
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linked with the embedder's program (like [Node.js][7]).
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## Performance
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So far llhttp outperforms http_parser:
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| | input size | bandwidth | reqs/sec | time |
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|:----------------|-----------:|-------------:|-----------:|--------:|
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| **llhttp** _(C)_ | 8192.00 mb | 1497.88 mb/s | 3020458.87 ops/sec | 5.47 s |
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| **llhttp** _(bitcode)_ | 8192.00 mb | 1131.75 mb/s | 2282171.24 ops/sec | 7.24 s |
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| **http_parser** | 8192.00 mb | 694.66 mb/s | 1406180.33 req/sec | 11.79 s |
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llhttp is faster by approximately **116%**.
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## Maintenance
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llhttp project has about 1400 lines of TypeScript code describing the parser
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itself and around 450 lines of C code and headers providing the helper methods.
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The whole [http_parser][0] is implemented in approximately 2500 lines of C, and
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436 lines of headers.
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All optimizations and multi-character matching in llhttp are generated
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automatically, and thus doesn't add any extra maintenance cost. On the contrary,
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most of http_parser's code is hand-optimized and unrolled. Instead describing
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"how" it should parse the HTTP requests/responses, a maintainer should
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implement the new features in [http_parser][0] cautiously, considering
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possible performance degradation and manually optimizing the new code.
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## Verification
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The state machine graph is encoded explicitly in llhttp. The [llparse][1]
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automatically checks the graph for absence of loops and correct reporting of the
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input ranges (spans) like header names and values. In the future, additional
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checks could be performed to get even stricter verification of the llhttp.
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## Usage
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```C
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#include "llhttp.h"
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llhttp_t parser;
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llhttp_settings_t settings;
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/* Initialize user callbacks and settings */
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llhttp_settings_init(&settings);
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/* Set user callback */
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settings.on_message_complete = handle_on_message_complete;
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/* Initialize the parser in HTTP_BOTH mode, meaning that it will select between
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* HTTP_REQUEST and HTTP_RESPONSE parsing automatically while reading the first
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* input.
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*/
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llhttp_init(&parser, HTTP_BOTH, &settings);
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/* Use `llhttp_set_type(&parser, HTTP_REQUEST);` to override the mode */
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/* Parse request! */
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const char* request = "GET / HTTP/1.1\r\n\r\n";
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int request_len = strlen(request);
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enum llhttp_errno err = llhttp_execute(&parser, request, request_len);
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if (err == HPE_OK) {
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/* Successfully parsed! */
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} else {
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fprintf(stderr, "Parse error: %s %s\n", llhttp_errno_name(err),
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parser.reason);
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}
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```
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---
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#### LICENSE
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This software is licensed under the MIT License.
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Copyright Fedor Indutny, 2018.
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Permission is hereby granted, free of charge, to any person obtaining a
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copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to permit
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persons to whom the Software is furnished to do so, subject to the
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following conditions:
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The above copyright notice and this permission notice shall be included
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in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
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NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
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OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
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USE OR OTHER DEALINGS IN THE SOFTWARE.
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[0]: https://github.com/nodejs/http-parser
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[1]: https://github.com/nodejs/llparse
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[2]: https://en.wikipedia.org/wiki/Register_allocation#Spilling
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[3]: https://en.wikipedia.org/wiki/Tail_call
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[4]: https://llvm.org/docs/LangRef.html
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[5]: https://llvm.org/docs/LangRef.html#call-instruction
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[6]: https://clang.llvm.org/
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[7]: https://github.com/nodejs/node
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