* Android NDK JNI directory entry notes *

beginning

Previous study, we have mastered the necessary knowledge NDK development.

The next step is more practice, through the creation of the problem and solve the problem, to increase proficiency to enhance the experience.

Daily development, often used MD5 SHA1 SHA256such as HASH algorithm, we can implement these functions in Native.

Hash algorithm

HASH mainly used in the field of information security encryption algorithms, some of the information he converted to different lengths of 128-bit code in messy called HASH value. It can be said, hash is to find a mapping relationship between data content and data storage address.

Android development, review the certificate thumbprint:

android-cert-fingerprint

Hands

As before create a Native C ++ project template

Project Preparation

day04-example-preview

Selection of open source C ++ library HASH algorithm

Portable C++ hashing library

cpp-hash-library

Android project to introduce C ++ source code library

android-use-cpp-library-source

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} )

Realize the function

MD5

Java version:

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 version:

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 version:

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 version:

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 version:

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 version:

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);
}