Add zstd support (#2088)

* Add zstd support

* Add zstd to CI tests

* Use use zstd cmake target instead of ZSTD. Use cmake variable for found packages

* Add missing comment for HTTPLIB_REQUIRE_ZSTD

* Fix test.yaml rebase error

* Use zstd::libzstd target

* Add include and library paths to ZSTD args

* Run clang-format

* Add zstd to httplibConfig.cmake.in

httplib.h

@@ -312,6 +312,10 @@ using socket_t = int;
 #include <brotli/encode.h>
 #endif
 
+#ifdef CPPHTTPLIB_ZSTD_SUPPORT
+#include <zstd.h>
+#endif
+
 /*
  * Declaration
  */
@@ -2445,7 +2449,7 @@ ssize_t send_socket(socket_t sock, const void *ptr, size_t size, int flags);
 
 ssize_t read_socket(socket_t sock, void *ptr, size_t size, int flags);
 
-enum class EncodingType { None = 0, Gzip, Brotli };
+enum class EncodingType { None = 0, Gzip, Brotli, Zstd };
 
 EncodingType encoding_type(const Request &req, const Response &res);
 
@@ -2558,6 +2562,34 @@ private:
 };
 #endif
 
+#ifdef CPPHTTPLIB_ZSTD_SUPPORT
+class zstd_compressor : public compressor {
+public:
+  zstd_compressor();
+  ~zstd_compressor();
+
+  bool compress(const char *data, size_t data_length, bool last,
+                Callback callback) override;
+
+private:
+  ZSTD_CCtx *ctx_ = nullptr;
+};
+
+class zstd_decompressor : public decompressor {
+public:
+  zstd_decompressor();
+  ~zstd_decompressor();
+
+  bool is_valid() const override;
+
+  bool decompress(const char *data, size_t data_length,
+                  Callback callback) override;
+
+private:
+  ZSTD_DCtx *ctx_ = nullptr;
+};
+#endif
+
 // NOTE: until the read size reaches `fixed_buffer_size`, use `fixed_buffer`
 // to store data. The call can set memory on stack for performance.
 class stream_line_reader {
@@ -3949,6 +3981,12 @@ inline EncodingType encoding_type(const Request &req, const Response &res) {
   if (ret) { return EncodingType::Gzip; }
 #endif
 
+#ifdef CPPHTTPLIB_ZSTD_SUPPORT
+  // TODO: 'Accept-Encoding' has zstd, not zstd;q=0
+  ret = s.find("zstd") != std::string::npos;
+  if (ret) { return EncodingType::Zstd; }
+#endif
+
   return EncodingType::None;
 }
 
@@ -4157,6 +4195,61 @@ inline bool brotli_decompressor::decompress(const char *data,
 }
 #endif
 
+#ifdef CPPHTTPLIB_ZSTD_SUPPORT
+inline zstd_compressor::zstd_compressor() {
+  ctx_ = ZSTD_createCCtx();
+  ZSTD_CCtx_setParameter(ctx_, ZSTD_c_compressionLevel, ZSTD_fast);
+}
+
+inline zstd_compressor::~zstd_compressor() { ZSTD_freeCCtx(ctx_); }
+
+inline bool zstd_compressor::compress(const char *data, size_t data_length,
+                                      bool last, Callback callback) {
+  std::array<char, CPPHTTPLIB_COMPRESSION_BUFSIZ> buff{};
+
+  ZSTD_EndDirective mode = last ? ZSTD_e_end : ZSTD_e_continue;
+  ZSTD_inBuffer input = {data, data_length, 0};
+
+  bool finished;
+  do {
+    ZSTD_outBuffer output = {buff.data(), CPPHTTPLIB_COMPRESSION_BUFSIZ, 0};
+    size_t const remaining = ZSTD_compressStream2(ctx_, &output, &input, mode);
+
+    if (ZSTD_isError(remaining)) { return false; }
+
+    if (!callback(buff.data(), output.pos)) { return false; }
+
+    finished = last ? (remaining == 0) : (input.pos == input.size);
+
+  } while (!finished);
+
+  return true;
+}
+
+inline zstd_decompressor::zstd_decompressor() { ctx_ = ZSTD_createDCtx(); }
+
+inline zstd_decompressor::~zstd_decompressor() { ZSTD_freeDCtx(ctx_); }
+
+inline bool zstd_decompressor::is_valid() const { return ctx_ != nullptr; }
+
+inline bool zstd_decompressor::decompress(const char *data, size_t data_length,
+                                          Callback callback) {
+  std::array<char, CPPHTTPLIB_COMPRESSION_BUFSIZ> buff{};
+  ZSTD_inBuffer input = {data, data_length, 0};
+
+  while (input.pos < input.size) {
+    ZSTD_outBuffer output = {buff.data(), CPPHTTPLIB_COMPRESSION_BUFSIZ, 0};
+    size_t const remaining = ZSTD_decompressStream(ctx_, &output, &input);
+
+    if (ZSTD_isError(remaining)) { return false; }
+
+    if (!callback(buff.data(), output.pos)) { return false; }
+  }
+
+  return true;
+}
+#endif
+
 inline bool has_header(const Headers &headers, const std::string &key) {
   return headers.find(key) != headers.end();
 }
@@ -4397,6 +4490,13 @@ bool prepare_content_receiver(T &x, int &status,
 #else
       status = StatusCode::UnsupportedMediaType_415;
       return false;
+#endif
+    } else if (encoding == "zstd") {
+#ifdef CPPHTTPLIB_ZSTD_SUPPORT
+      decompressor = detail::make_unique<zstd_decompressor>();
+#else
+      status = StatusCode::UnsupportedMediaType_415;
+      return false;
 #endif
     }
 
@@ -6634,6 +6734,10 @@ Server::write_content_with_provider(Stream &strm, const Request &req,
       } else if (type == detail::EncodingType::Brotli) {
 #ifdef CPPHTTPLIB_BROTLI_SUPPORT
         compressor = detail::make_unique<detail::brotli_compressor>();
+#endif
+      } else if (type == detail::EncodingType::Zstd) {
+#ifdef CPPHTTPLIB_ZSTD_SUPPORT
+        compressor = detail::make_unique<detail::zstd_compressor>();
 #endif
       } else {
         compressor = detail::make_unique<detail::nocompressor>();
@@ -7049,6 +7153,8 @@ inline void Server::apply_ranges(const Request &req, Response &res,
             res.set_header("Content-Encoding", "gzip");
           } else if (type == detail::EncodingType::Brotli) {
             res.set_header("Content-Encoding", "br");
+          } else if (type == detail::EncodingType::Zstd) {
+            res.set_header("Content-Encoding", "zstd");
           }
         }
       }
@@ -7088,6 +7194,11 @@ inline void Server::apply_ranges(const Request &req, Response &res,
 #ifdef CPPHTTPLIB_BROTLI_SUPPORT
         compressor = detail::make_unique<detail::brotli_compressor>();
         content_encoding = "br";
+#endif
+      } else if (type == detail::EncodingType::Zstd) {
+#ifdef CPPHTTPLIB_ZSTD_SUPPORT
+        compressor = detail::make_unique<detail::zstd_compressor>();
+        content_encoding = "zstd";
 #endif
       }
 
@@ -7812,6 +7923,10 @@ inline bool ClientImpl::write_request(Stream &strm, Request &req,
 #ifdef CPPHTTPLIB_ZLIB_SUPPORT
       if (!accept_encoding.empty()) { accept_encoding += ", "; }
       accept_encoding += "gzip, deflate";
+#endif
+#ifdef CPPHTTPLIB_ZSTD_SUPPORT
+      if (!accept_encoding.empty()) { accept_encoding += ", "; }
+      accept_encoding += "zstd";
 #endif
       req.set_header("Accept-Encoding", accept_encoding);
     }
@@ -10377,4 +10492,4 @@ inline SSL_CTX *Client::ssl_context() const {
 
 } // namespace httplib
 
-#endif // CPPHTTPLIB_HTTPLIB_H
+#endif // CPPHTTPLIB_HTTPLIB_H