Add C++ modules support

.github/workflows/update-module-exports.yml

 if(HTTPLIB_COMPILE) 
 if(HTTPLIB_COMPILE) 
@@ -0,0 +1,81 @@
+name: Update Module Exports
+
+on:
+  pull_request:
+    paths:
+      - 'httplib.h'
+  push:
+    branches:
+      - master
+      - main
+    paths:
+      - 'httplib.h'
+
+jobs:
+  update-exports:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0  # Fetch all history for proper diff
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Check for changes in httplib.h
+        id: check_changes
+        run: |
+          if git diff --name-only HEAD~1 HEAD | grep -q "httplib.h"; then
+            echo "changes=true" >> $GITHUB_OUTPUT
+          else
+            echo "changes=false" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Update module exports
+        if: steps.check_changes.outputs.changes == 'true'
+        run: |
+          python3 update_modules.py
+
+      - name: Check if module file was modified
+        if: steps.check_changes.outputs.changes == 'true'
+        id: check_module_changes
+        run: |
+          if git diff --quiet modules/httplib.cppm; then
+            echo "modified=false" >> $GITHUB_OUTPUT
+          else
+            echo "modified=true" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Commit changes
+        if: steps.check_module_changes.outputs.modified == 'true'
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git add modules/httplib.cppm
+          git commit -m "chore: update module exports for httplib.h changes"
+
+      - name: Push changes (for push events)
+        if: steps.check_module_changes.outputs.modified == 'true' && github.event_name == 'push'
+        run: |
+          git push
+
+      - name: Push changes (for pull requests)
+        if: steps.check_module_changes.outputs.modified == 'true' && github.event_name == 'pull_request'
+        run: |
+          git push origin HEAD:${{ github.head_ref }}
+
+      - name: Add comment to PR
+        if: steps.check_module_changes.outputs.modified == 'true' && github.event_name == 'pull_request'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: '✅ Module exports have been automatically updated based on changes to `httplib.h`.'
+            })

CMakeLists.txt

@@ -110,6 +110,7 @@ option(HTTPLIB_USE_CERTS_FROM_MACOSX_KEYCHAIN "Enable feature to load system cer
 option(HTTPLIB_USE_NON_BLOCKING_GETADDRINFO "Enables the non-blocking alternatives for getaddrinfo." ON)
 option(HTTPLIB_REQUIRE_ZSTD "Requires ZSTD to be found & linked, or fails build." OFF)
 option(HTTPLIB_USE_ZSTD_IF_AVAILABLE "Uses ZSTD (if available) to enable zstd support." ON)
+option(HTTPLIB_BUILD_MODULES "Build httplib modules (requires HTTPLIB_COMPILE to be ON)." OFF)
 # Defaults to static library but respects standard BUILD_SHARED_LIBS if set
 include(CMakeDependentOption)
 cmake_dependent_option(HTTPLIB_SHARED "Build the library as a shared library instead of static. Has no effect if using header-only."
@@ -365,3 +366,10 @@ if(HTTPLIB_TEST)
 	include(CTest)
 	add_subdirectory(test)
 endif()
+
+if(HTTPLIB_BUILD_MODULES)
+	if(NOT HTTPLIB_COMPILE)
+		message(FATAL_ERROR "HTTPLIB_BUILD_MODULES requires HTTPLIB_COMPILE to be ON.")
+	endif()
+	add_subdirectory(modules)
+endif()

README.md

@@ -1253,6 +1253,43 @@ $ ./split.py
 Wrote out/httplib.h and out/httplib.cc
 ```
 
+Build C++ Modules
+-----------------
+
+If using CMake, it is possible to build this as a C++20 module using the `HTTPLIB_BUILD_MODULES` option (which requires `HTTPLIB_COMPILE` to be enabled).
+
+#### Server (Multi-threaded)
+```cpp
+import httplib;
+
+using httplib::Request;
+using httplib::Response;
+using httplib::SSLServer;
+
+SSLServer svr;
+
+svr.Get("/hi", []([[maybe_unused]] const Request& req, Response& res) -> void {
+  res.set_content("Hello World!", "text/plain");
+});
+
+svr.listen("0.0.0.0", 8080);
+```
+
+#### Client
+```cpp
+import httplib;
+
+using httplib::Client;
+using httplib::Result;
+
+Client cli("https://yhirose.github.io");
+
+if (Result res = cli.Get("/hi")) {
+  res->status;
+  res->body;
+}
+```
+
 Dockerfile for Static HTTP Server
 ---------------------------------
 

modules/CMakeLists.txt

@@ -0,0 +1,25 @@
+add_library(httplib_module)
+
+target_sources(httplib_module
+    PUBLIC
+        FILE_SET CXX_MODULES FILES
+            httplib.cppm
+)
+
+target_compile_features(httplib_module PUBLIC cxx_std_20)
+
+target_include_directories(httplib_module PUBLIC
+    $<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
+    $<INSTALL_INTERFACE:include>
+)
+
+add_library(httplib::module ALIAS httplib_module)
+
+# Installation
+install(TARGETS httplib_module
+    EXPORT ${PROJECT_NAME}Targets
+    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
+    FILE_SET CXX_MODULES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/httplib/modules
+)

modules/httplib.cppm

@@ -0,0 +1,93 @@
+//
+//  httplib.cppm
+//
+//  Copyright (c) 2025 Yuji Hirose. All rights reserved.
+//  MIT License
+//
+
+module;
+
+#include "../httplib.h"
+
+export module httplib;
+
+export namespace httplib {
+    using httplib::SSLVerifierResponse;
+    using httplib::StatusCode;
+    using httplib::Headers;
+    using httplib::Params;
+    using httplib::Match;
+    using httplib::DownloadProgress;
+    using httplib::UploadProgress;
+    using httplib::Response;
+    using httplib::ResponseHandler;
+    using httplib::FormData;
+    using httplib::FormField;
+    using httplib::FormFields;
+    using httplib::FormFiles;
+    using httplib::MultipartFormData;
+    using httplib::UploadFormData;
+    using httplib::UploadFormDataItems;
+    using httplib::DataSink;
+    using httplib::ContentProvider;
+    using httplib::ContentProviderWithoutLength;
+    using httplib::ContentProviderResourceReleaser;
+    using httplib::FormDataProvider;
+    using httplib::FormDataProviderItems;
+    using httplib::ContentReceiverWithProgress;
+    using httplib::ContentReceiver;
+    using httplib::FormDataHeader;
+    using httplib::ContentReader;
+    using httplib::Range;
+    using httplib::Ranges;
+    using httplib::Request;
+    using httplib::Response;
+    using httplib::Error;
+    using httplib::to_string;
+    using httplib::operator<<;
+    using httplib::Stream;
+    using httplib::TaskQueue;
+    using httplib::ThreadPool;
+    using httplib::Logger;
+    using httplib::ErrorLogger;
+    using httplib::SocketOptions;
+    using httplib::default_socket_options;
+    using httplib::status_message;
+    using httplib::get_bearer_token_auth;
+    using httplib::Server;
+    using httplib::Result;
+    using httplib::ClientConnection;
+    using httplib::ClientImpl;
+    using httplib::Client;
+
+    #ifdef CPPHTTPLIB_OPENSSL_SUPPORT
+    using httplib::SSLServer;
+    using httplib::SSLClient;
+    #endif
+
+    using httplib::hosted_at;
+    using httplib::encode_uri_component;
+    using httplib::encode_uri;
+    using httplib::decode_uri_component;
+    using httplib::decode_uri;
+    using httplib::encode_path_component;
+    using httplib::decode_path_component;
+    using httplib::encode_query_component;
+    using httplib::decode_query_component;
+    using httplib::append_query_params;
+    using httplib::make_range_header;
+    using httplib::make_basic_authentication_header;
+
+    using httplib::get_client_ip;
+
+    namespace stream {
+        using httplib::stream::Result;
+        using httplib::stream::Get;
+        using httplib::stream::Post;
+        using httplib::stream::Put;
+        using httplib::stream::Patch;
+        using httplib::stream::Delete;
+        using httplib::stream::Head;
+        using httplib::stream::Options;
+    }
+}

split.py

@@ -2,66 +2,74 @@
 
 """This script splits httplib.h into .h and .cc parts."""
 
-import argparse
 import os
 import sys
+from argparse import ArgumentParser, Namespace
+from typing import List
 
-border = '// ----------------------------------------------------------------------------'
 
-args_parser = argparse.ArgumentParser(description=__doc__)
-args_parser.add_argument(
-    "-e", "--extension", help="extension of the implementation file (default: cc)",
-    default="cc"
-)
-args_parser.add_argument(
-    "-o", "--out", help="where to write the files (default: out)", default="out"
-)
-args = args_parser.parse_args()
+def main() -> None:
+    """Main entry point for the script."""
+    BORDER: str = '// ----------------------------------------------------------------------------'
 
-cur_dir = os.path.dirname(sys.argv[0])
-lib_name = 'httplib'
-header_name = '/' + lib_name + '.h'
-source_name = '/' + lib_name + '.' + args.extension
-# get the input file
-in_file = cur_dir + header_name
-# get the output file
-h_out = args.out + header_name
-cc_out = args.out + source_name
+    args_parser: ArgumentParser = ArgumentParser(description=__doc__)
+    args_parser.add_argument(
+        "-e", "--extension", help="extension of the implementation file (default: cc)",
+        default="cc"
+    )
+    args_parser.add_argument(
+        "-o", "--out", help="where to write the files (default: out)", default="out"
+    )
+    args: Namespace = args_parser.parse_args()
 
-# if the modification time of the out file is after the in file,
-# don't split (as it is already finished)
-do_split = True
+    cur_dir: str = os.path.dirname(sys.argv[0])
+    lib_name: str = 'httplib'
+    header_name: str = f"/{lib_name}.h"
+    source_name: str = f"/{lib_name}.{args.extension}"
+    # get the input file
+    in_file: str = cur_dir + header_name
+    # get the output file
+    h_out: str = args.out + header_name
+    cc_out: str = args.out + source_name
 
-if os.path.exists(h_out):
-    in_time = os.path.getmtime(in_file)
-    out_time = os.path.getmtime(h_out)
-    do_split = in_time > out_time
+    # if the modification time of the out file is after the in file,
+    # don't split (as it is already finished)
+    do_split: bool = True
 
-if do_split:
-    with open(in_file) as f:
-        lines = f.readlines()
+    if os.path.exists(h_out):
+        in_time: float = os.path.getmtime(in_file)
+        out_time: float = os.path.getmtime(h_out)
+        do_split: bool = in_time > out_time
 
-    python_version = sys.version_info[0]
-    if python_version < 3:
-        os.makedirs(args.out)
+    if do_split:
+        with open(in_file) as f:
+            lines: List[str] = f.readlines()
+
+        python_version: int = sys.version_info[0]
+        if python_version < 3:
+            os.makedirs(args.out)
+        else:
+            os.makedirs(args.out, exist_ok=True)
+
+        in_implementation: bool = False
+        cc_out: str = args.out + source_name
+        with open(h_out, 'w') as fh, open(cc_out, 'w') as fc:
+            fc.write('#include "httplib.h"\n')
+            fc.write('namespace httplib {\n')
+            for line in lines:
+                is_border_line: bool = BORDER in line
+                if is_border_line:
+                    in_implementation: bool = not in_implementation
+                elif in_implementation:
+                    fc.write(line.replace('inline ', ''))
+                else:
+                    fh.write(line)
+            fc.write('} // namespace httplib\n')
+
+        print(f"Wrote {h_out} and {cc_out}")
     else:
-        os.makedirs(args.out, exist_ok=True)
+        print(f"{h_out} and {cc_out} are up to date")
 
-    in_implementation = False
-    cc_out = args.out + source_name
-    with open(h_out, 'w') as fh, open(cc_out, 'w') as fc:
-        fc.write('#include "httplib.h"\n')
-        fc.write('namespace httplib {\n')
-        for line in lines:
-            is_border_line = border in line
-            if is_border_line:
-                in_implementation = not in_implementation
-            elif in_implementation:
-                fc.write(line.replace('inline ', ''))
-            else:
-                fh.write(line)
-        fc.write('} // namespace httplib\n')
 
-    print("Wrote {} and {}".format(h_out, cc_out))
-else:
-    print("{} and {} are up to date".format(h_out, cc_out))
+if __name__ == "__main__":
+    main()