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Android NDK JNI 入门笔记-day04-NDK实现Hash算法

binglingziyu 人气:2
[* Android NDK JNI 入门笔记目录 *](https://www.ihubin.com/blog/android-ndk-jni-basic-catagory/) # 开头 前面的学习,我们已经掌握了 NDK 开发的必备知识。 下一步就要多实践,通过创造问题并解决问题,来增加熟练度,提升经验。 日常开发中,经常会用到 `MD5` `SHA1` `SHA256` 等 HASH 算法,我们可以在 Native 实现这些功能。 # Hash 算法 > HASH 主要用于信息安全领域中加密算法,他把一些不同长度的信息转化成杂乱的 128 位的编码里,叫做 HASH 值。也可以说,hash 就是找到一种数据内容和数据存放地址之间的映射关系。 Android 开发中,查看证书指纹: ![android-cert-fingerprint](http://cloudstorage.ihubin.com/blog/Android/ndk-jnihttps://img.qb5200.com/download-x/day04/android-cert-fingerprint.jpg) # 动手实践 像之前一样[创建一个 Native C++ 模板项目](https://www.ihubin.com/blog/android-ndk-jni-basic-day01/) ## 项目准备 ![day04-example-preview](http://cloudstorage.ihubin.com/blog/Android/ndk-jnihttps://img.qb5200.com/download-x/day04https://img.qb5200.com/download-x/day04-example-preview.jpeg) ## 选用 C++ 开源 HASH 算法实现库 > [Portable C++ hashing library](https://github.com/stbrumme/hash-library) ![cpp-hash-library](http://cloudstorage.ihubin.com/blog/Android/ndk-jnihttps://img.qb5200.com/download-x/day04/cpp-hash-library-file-tree.png) ## Android 工程引入 C++ 库源码 ![android-use-cpp-library-source](http://cloudstorage.ihubin.com/blog/Android/ndk-jnihttps://img.qb5200.com/download-x/day04/android-use-cpp-library-source.png) ## CMakeLists.txt ``` cmake_minimum_required(VERSION 3.4.1) # 该命令会查找指定目录下的所有源文件,然后将结果存进指定变量名 aux_source_directory(hash-library HASH_LIBRARY_SRC) # 添加头文件搜索目录 include_directories(hash-library) add_library( native-lib SHARED # 将 hash-library 源文件添加进来 native-lib.cpp ${HASH_LIBRARY_SRC}) find_library( log-lib log ) target_link_libraries( native-lib ${log-lib} ) ``` ## 实现功能 ### MD5 > Java 版本: ```java public static String md5(String plainText) { try { MessageDigest md5 = MessageDigest.getInstance("MD5"); byte[] md5Byte = md5.digest(plainText.getBytes()); return byteArrayToString(md5Byte); } catch (Exception e) { return ""; } } ``` > Native 版本: ```c++ extern "C" JNIEXPORT jstring JNICALL Java_com_ihubin_ndkjni_NativeUtil_md5(JNIEnv *env, jclass clazz, jstring plaintext) { const char * plaintextChar = env->GetStringUTFChars(plaintext, 0); std::string plaintextStr = std::string(plaintextChar); MD5 md5; std::string md5String = md5(plaintextStr); char * tabStr = new char [md5String.length()+1]; strcpy(tabStr, md5String.c_str()); char md5Result[128] = {0}; formatSignature(tabStr, md5Result); return env->NewStringUTF(md5Result); } ``` ### SHA1 > Java 版本: ```java public static String sha1(String plainText) { try { MessageDigest sha1 = MessageDigest.getInstance("SHA1"); byte[] sha1Byte = sha1.digest(plainText.getBytes()); return byteArrayToString(sha1Byte); } catch (Exception e) { return ""; } } ``` > Native 版本: ```c++ extern "C" JNIEXPORT jstring JNICALL Java_com_ihubin_ndkjni_NativeUtil_sha1(JNIEnv *env, jclass clazz, jstring plaintext) { const char * plaintextChar = env->GetStringUTFChars(plaintext, 0); std::string plaintextStr = std::string(plaintextChar); SHA1 sha1; std::string sha1String = sha1(plaintextStr); char * tabStr = new char [sha1String.length()+1]; strcpy(tabStr, sha1String.c_str()); char sha1Result[128] = {0}; formatSignature(tabStr, sha1Result); return env->NewStringUTF(sha1Result); } ``` ### SHA256 > Java 版本: ``` public static String sha256(String plainText) { try { MessageDigest sha256 = MessageDigest.getInstance("SHA256"); byte[] sha256Byte = sha256.digest(plainText.getBytes()); return byteArrayToString(sha256Byte); } catch (Exception e) { return ""; } } ``` > Native 版本: ``` extern "C" JNIEXPORT jstring JNICALL Java_com_ihubin_ndkjni_NativeUtil_sha256(JNIEnv *env, jclass clazz, jstring plaintext) { const char * plaintextChar = env->GetStringUTFChars(plaintext, 0); std::string plaintextStr = std::string(plaintextChar); SHA256 sha256; std::string sha256String = sha256(plaintextStr); char * tabStr = new char [sha256String.length()+1]; strcpy(tabStr, sha256String.c_str()); char sha256Result[128] = {0}; formatSignature(tabStr, sha256Result); return env->NewStringUTF(sha256Result); } ``` ## 最终效果 ![day04-example-result](http://cloudstorage.ihubin.com/blog/Android/ndk-jnihttps://img.qb5200.com/download-x/day04https://img.qb5200.com/download-x/day04-example-result.jpeg) > 至此,我们已经学会了在 Android 项目中引用开源 C++ 库,同时我们也实现在 Native 实现 HASH 算法。 ----- 代码: [NDKJNIday04](https://github.com/binglingziyu/NDK-JNI/tree/master/NDKJNIday04) 参考资料: [Oracle - JNI Types and Data Structures](https:/https://img.qb5200.com/download-x/docs.oracle.com/javase/7https://img.qb5200.com/download-x/docs/technotes/guides/jni/spec/types.html) [C++ hash-library](https://github.com/stbrumme/hash-library) [CMake入门](https://www.cnblogs.com/binglingziyu/tag/CMake/) -----

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