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‎.clang-format

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---
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Language: Cpp
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Standard: c++17
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BasedOnStyle: Microsoft
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IndentExternBlock: NoIndent
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PointerAlignment: Left

‎.github/workflows/ci.yml

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name: CI
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on: [push, pull_request]
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jobs:
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build:
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runs-on: ${{ matrix.runner }}
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strategy:
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matrix:
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os: [linux, windows, macos]
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build_type: [Debug, RelWithDebInfo]
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arch: [x86, x64]
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cmake: [minimal, latest]
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exclude:
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- os: linux
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arch: x86
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- os: windows
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cmake: minimal
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- os: macos
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arch: x86
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- os: macos
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cmake: minimal
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include:
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- cmake: minimal
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cmake_url_part: v3.5/cmake-3.5.2
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- os: linux
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runner: ubuntu-latest
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- os: windows
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runner: windows-latest
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- os: windows
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arch: x86
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cmake_args: -A Win32
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- os: windows
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arch: x64
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cmake_args: -A x64
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- os: macos
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runner: macos-latest
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steps:
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- name: Checkout
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uses: actions/checkout@v1
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- name: Install dependencies (linux)
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if: matrix.os == 'linux'
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run: |
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set -ex
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cmake_url="https://cmake.org/files"
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cmake_url_part="${{ matrix.cmake_url_part }}"
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if [ -n "$cmake_url_part" ]; then
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cmake_url_part="${cmake_url_part}-Linux-x86_64.tar.gz"
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else
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cmake_url_part="LatestRelease/$(wget --quiet --no-check-certificate "${cmake_url}/LatestRelease/cmake-latest-files-v1.json" -O - | jq -r '[.files[] | select(.class == "archive" and (.os[] | contains("linux")) and (.architecture[] | contains("x86_64")))] | .[0] | .name')"
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fi
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wget --no-check-certificate "${cmake_url}/${cmake_url_part}" -O /tmp/cmake.tar.gz
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sudo tar xf /tmp/cmake.tar.gz -C /usr/local --strip-components 1
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- name: CMake version
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run: cmake --version
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- name: Configure
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run: cmake -E make_directory _build && cmake -E chdir _build cmake .. -DCMAKE_BUILD_TYPE=${{ matrix.build_type }} ${{ matrix.cmake_args }}
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- name: Build
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run: cmake --build _build --config ${{ matrix.build_type }}
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- name: Test
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run: cmake -E chdir _build ctest --build-config ${{ matrix.build_type }} --output-on-failure

‎CMakeLists.txt

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cmake_minimum_required(VERSION 3.5)
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project(arc4 VERSION 1.0 LANGUAGES C)
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set(ARC4_STANDALONE_BUILD OFF)
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if(PROJECT_SOURCE_DIR STREQUAL CMAKE_SOURCE_DIR)
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set(ARC4_STANDALONE_BUILD ON)
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endif()
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option(ARC4_ENABLE_INSTALL "${PROJECT_NAME}: Enable install" ${ARC4_STANDALONE_BUILD})
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option(ARC4_ENABLE_TESTS "${PROJECT_NAME}: Enable tests" ${ARC4_STANDALONE_BUILD})
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option(ARC4_ENABLE_WERROR "${PROJECT_NAME}: Treat warnings as errors" ${ARC4_STANDALONE_BUILD})
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if(ARC4_ENABLE_INSTALL)
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include(GNUInstallDirs)
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include(CMakePackageConfigHelpers)
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endif()
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if(ARC4_ENABLE_TESTS)
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enable_testing()
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endif()
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if(ARC4_STANDALONE_BUILD)
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if(NOT CMAKE_C_STANDARD)
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set(CMAKE_C_STANDARD 99)
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set(CMAKE_C_STANDARD_REQUIRED ON)
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set(CMAKE_C_EXTENSIONS OFF)
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endif()
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if(CMAKE_C_COMPILER_ID MATCHES "GNU|Clang")
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add_compile_options(
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-Wall
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-Wextra
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-pedantic
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$<$<BOOL:${ARC4_ENABLE_WERROR}>:-Werror>)
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elseif(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
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add_compile_options(
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/W4
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$<$<BOOL:${ARC4_ENABLE_WERROR}>:/WX>)
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endif()
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endif()
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add_subdirectory(src)
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if(ARC4_ENABLE_TESTS)
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add_subdirectory(test)
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endif()
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if(ARC4_ENABLE_INSTALL)
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write_basic_package_version_file(
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${PROJECT_BINARY_DIR}/${PROJECT_NAME}-config-version.cmake
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VERSION ${PROJECT_VERSION}
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COMPATIBILITY AnyNewerVersion)
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configure_file(
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config.cmake.in
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${PROJECT_NAME}-config.cmake
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@ONLY)
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install(
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EXPORT ${PROJECT_NAME}-targets
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DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}
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NAMESPACE ${PROJECT_NAME}::)
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install(
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FILES
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${PROJECT_BINARY_DIR}/${PROJECT_NAME}-config.cmake
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${PROJECT_BINARY_DIR}/${PROJECT_NAME}-config-version.cmake
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DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
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install(
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FILES
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LICENSE
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README.md
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DESTINATION ${CMAKE_INSTALL_DOCDIR})
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endif()

‎LICENSE

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BSD 3-Clause License
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Copyright (c) 2021, Mike Gelfand
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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3. Neither the name of the copyright holder nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

‎README.md

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# ARC4: Alleged RC4 implementation
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This is a tiny and reusable implementation of [alleged RC4](https://en.wikipedia.org/wiki/RC4) cipher.
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The use of RC4 is declining due to various security concerns.
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A number of popular cryptographic libraries have started to mark it as deprecated or remove it completely:
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* **OpenSSL**: not built by default in 1.1, moved to "legacy" provider in 3.0
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* **WolfSSL (CyaSSL)**: not built by default in 3.4.6
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* **MbedTLS (PolarSSL)**: removed in 3.0
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Nonetheless, it's still used in e.g. BitTorrent software, and forcing people to do some more work to make RC4 available in the aforementioned libraries is not always possible or desirable.

‎config.cmake.in

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include(${CMAKE_CURRENT_LIST_DIR}/@[email protected])

‎src/CMakeLists.txt

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add_library(arc4 STATIC
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arc4.c
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arc4.h)
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if(NOT ARC4_STANDALONE_BUILD)
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add_library(${PROJECT_NAME}::arc4 ALIAS arc4)
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endif()
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target_include_directories(arc4
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PUBLIC
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$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
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$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
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if(ARC4_ENABLE_INSTALL)
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install(
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TARGETS arc4
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EXPORT ${PROJECT_NAME}-targets
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RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
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ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
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LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR})
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install(
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FILES arc4.h
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DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
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endif()

‎src/arc4.c

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#include "arc4.h"
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#include <assert.h>
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#define ARC4_MAGIC 0x34637261 // 'arc4' (LE)
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static inline void arc4_swap(struct arc4_context* ctx, size_t i, size_t j)
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{
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assert(ctx != NULL);
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assert(i < 256);
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assert(j < 256);
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uint8_t const t = ctx->s[i];
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ctx->s[i] = ctx->s[j];
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ctx->s[j] = t;
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}
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static inline uint8_t arc4_next(struct arc4_context* ctx)
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{
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assert(ctx != NULL);
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ctx->i += 1;
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ctx->j += ctx->s[ctx->i];
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arc4_swap(ctx, ctx->i, ctx->j);
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return ctx->s[(uint8_t)(ctx->s[ctx->i] + ctx->s[ctx->j])];
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}
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void arc4_init(struct arc4_context* ctx, void const* key, size_t key_length)
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{
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assert(ctx != NULL);
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assert(key != NULL);
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assert(key_length < 256);
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#ifndef NDEBUG
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ctx->magic = ARC4_MAGIC;
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#endif
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ctx->i = 0;
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ctx->j = 0;
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for (size_t i = 0; i < 256; ++i)
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{
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ctx->s[i] = (uint8_t)i;
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}
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for (size_t i = 0, j = 0; i < 256; ++i)
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{
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j = (uint8_t)(j + ctx->s[i] + ((uint8_t const*)key)[i % key_length]);
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arc4_swap(ctx, i, j);
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}
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}
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void arc4_process(struct arc4_context* ctx, void const* src_data, void* dst_data, size_t data_length)
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{
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assert(ctx != NULL);
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assert(ctx->magic == ARC4_MAGIC);
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if (data_length == 0)
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{
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return;
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}
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assert(src_data != NULL);
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assert(dst_data != NULL);
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assert(data_length < SIZE_MAX);
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for (size_t i = 0; i < data_length; ++i)
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{
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((uint8_t*)dst_data)[i] = ((uint8_t const*)src_data)[i] ^ arc4_next(ctx);
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}
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}
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void arc4_discard(struct arc4_context* ctx, size_t length)
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{
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assert(ctx != NULL);
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assert(ctx->magic == ARC4_MAGIC);
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assert(length < SIZE_MAX);
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for (size_t i = 0; i < length; ++i)
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{
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arc4_next(ctx);
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}
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}

‎src/arc4.h

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#pragma once
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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struct arc4_context
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{
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#ifndef NDEBUG
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uint32_t magic;
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#endif
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uint8_t i;
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uint8_t j;
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uint8_t s[256];
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};
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void arc4_init(struct arc4_context* ctx, void const* key, size_t key_length);
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void arc4_process(struct arc4_context* ctx, void const* src_data, void* dst_data, size_t data_length);
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void arc4_discard(struct arc4_context* ctx, size_t length);
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#ifdef __cplusplus
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}
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#endif

‎test/CMakeLists.txt

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add_executable(arc4_test
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test.c)
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target_link_libraries(arc4_test
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PRIVATE
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arc4)
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add_test(
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NAME arc4_test
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COMMAND arc4_test)

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