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54 lines
1.8 KiB
Markdown
54 lines
1.8 KiB
Markdown
---
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title: "S08. Return a Compressed Response"
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order: 27
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status: "draft"
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---
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cpp-httplib automatically compresses response bodies when the client indicates support via `Accept-Encoding`. The handler doesn't need to do anything special. Supported encodings are gzip, Brotli, and Zstd.
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## Build-time setup
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To enable compression, define the relevant macros before including `httplib.h`:
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```cpp
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#define CPPHTTPLIB_ZLIB_SUPPORT // gzip
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#define CPPHTTPLIB_BROTLI_SUPPORT // brotli
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#define CPPHTTPLIB_ZSTD_SUPPORT // zstd
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#include <httplib.h>
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```
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You'll also need to link `zlib`, `brotli`, and `zstd` respectively. Enable only what you need.
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## Usage
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```cpp
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svr.Get("/api/data", [](const httplib::Request &req, httplib::Response &res) {
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std::string body = build_large_response();
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res.set_content(body, "application/json");
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});
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```
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That's it. If the client sent `Accept-Encoding: gzip`, cpp-httplib compresses the response with gzip automatically. `Content-Encoding: gzip` and `Vary: Accept-Encoding` are added for you.
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## Encoding priority
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When the client accepts multiple encodings, cpp-httplib picks in this order (among those enabled at build time): Brotli → Zstd → gzip. Your code doesn't need to care — you always get the most efficient option available.
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## Streaming responses are compressed too
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Streaming responses via `set_chunked_content_provider()` get the same automatic compression.
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```cpp
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svr.Get("/events", [](const httplib::Request &req, httplib::Response &res) {
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res.set_chunked_content_provider(
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"text/plain",
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[](size_t offset, httplib::DataSink &sink) {
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// ...
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});
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});
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```
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> **Note:** Tiny responses barely benefit from compression and just waste CPU time. cpp-httplib skips compression for bodies that are too small to bother with.
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> For the client-side counterpart, see [C15. Enable compression](c15-compression).
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