diff --git a/Core/MMKV.cpp b/Core/MMKV.cpp
index 1440620e..29df7839 100644
--- a/Core/MMKV.cpp
+++ b/Core/MMKV.cpp
@@ -332,7 +332,7 @@ string MMKV::cryptKey() const {
     if (m_crypter) {
         char key[AES_KEY_LEN];
         m_crypter->getKey(key);
-        return string(key, strnlen(key, AES_KEY_LEN));
+        return {key, strnlen(key, AES_KEY_LEN)};
     }
     return "";
 }
@@ -1220,7 +1220,7 @@ static string md5(const basic_string<T> &value) {
         snprintf(tmp, sizeof(tmp), "%2.2x", ch);
         strcat(buf, tmp);
     }
-    return string(buf);
+    return {buf};
 }
 
 static MMKVPath_t encodeFilePath(const string &mmapID) {
diff --git a/Core/MemoryFile.cpp b/Core/MemoryFile.cpp
index 6feca033..67fbee7f 100644
--- a/Core/MemoryFile.cpp
+++ b/Core/MemoryFile.cpp
@@ -303,16 +303,106 @@ size_t getPageSize() {
 
 #ifndef MMKV_APPLE
 
+static pair<MMKVPath_t, int> createUniqueTempFile(const char *prefix) {
+    char path[PATH_MAX];
+    snprintf(path, PATH_MAX, "%s%s.XXXXX", P_tmpdir, prefix);
+
+    auto fd = mkstemp(path);
+    if (fd < 0) {
+        MMKVError("fail to create unique temp file %s, %d(%s)", path, errno, strerror(errno));
+        return {"", fd};
+    }
+    return {MMKVPath_t(path), fd};
+}
+
 bool copyFile(const MMKVPath_t &srcPath, const MMKVPath_t &dstPath) {
-    return false;
+    auto pair = createUniqueTempFile("MMKV");
+    auto tmpFD = pair.second;
+    auto &tmpPath = pair.first;
+    if (tmpFD < 0) {
+        return false;
+    }
+
+    bool ret = false;
+    if (copyFileContent(srcPath, tmpFD)) {
+        MMKVInfo("copyfile [%s] to [%s]", srcPath.c_str(), tmpPath.c_str());
+        ret = (::rename(tmpPath.c_str(), dstPath.c_str()) == 0);
+        if (ret) {
+            MMKVInfo("copyfile [%s] to [%s] finish.", srcPath.c_str(), dstPath.c_str());
+        } else {
+            MMKVError("fail to rename [%s] to [%s]", tmpPath.c_str(), dstPath.c_str());
+        }
+    }
+
+    ::close(tmpFD);
+    ::unlink(tmpPath.c_str());
+
+    return ret;
 }
 
 bool copyFileContent(const MMKVPath_t &srcPath, const MMKVPath_t &dstPath) {
-    return false;
+    auto dstFd = open(dstPath.c_str(), O_WRONLY | O_CREAT | O_TRUNC, S_IRWXU);
+    if (dstFd < 0) {
+        MMKVError("fail to open [%s], %d(%s)", dstPath.c_str(), errno, strerror(errno));
+        return false;
+    }
+    auto ret = copyFileContent(srcPath, dstFd);
+    if (!ret) {
+        MMKVError("fail to copyfile(): target file %s", dstPath.c_str());
+    } else {
+        MMKVInfo("copy content from %s to [%s] finish", srcPath.c_str(), dstPath.c_str());
+    }
+    ::close(dstFd);
+    return ret;
 }
 
 bool copyFileContent(const MMKVPath_t &srcPath, MMKVFileHandle_t dstFD) {
-    return false;
+    if (dstFD < 0) {
+        return false;
+    }
+    bool ret = false;
+    char *buffer = nullptr;
+    auto bufferSize = getPageSize();
+    auto srcFd = open(srcPath.c_str(), O_RDONLY, S_IRWXU);
+    if (srcFd < 0) {
+        MMKVError("fail to open [%s], %d(%s)", srcPath.c_str(), errno, strerror(errno));
+        return false;
+    }
+    buffer = (char *)malloc(bufferSize);
+    if (!buffer) {
+        MMKVError("fail to malloc size %zu, %d(%s)", bufferSize, errno, strerror(errno));
+        goto errorOut;
+    }
+
+    // the POSIX standard don't have sendfile()/fcopyfile() equivalent, have to do it the hard way
+    while (true) {
+        auto sizeRead = read(srcFd, buffer, bufferSize);
+        if (sizeRead < 0) {
+            MMKVError("fail to read file [%s], %d(%s)", srcPath.c_str(), errno, strerror(errno));
+            goto errorOut;
+        }
+
+        size_t totalWrite = 0;
+        do {
+            auto sizeWrite = write(dstFD, buffer + totalWrite, sizeRead - totalWrite);
+            if (sizeWrite < 0) {
+                MMKVError("fail to write fd [%d], %d(%s)", dstFD, errno, strerror(errno));
+                goto errorOut;
+            }
+            totalWrite += sizeWrite;
+        } while (totalWrite < sizeRead);
+
+        if (sizeRead < bufferSize) {
+            break;
+        }
+    }
+    ret = true;
+    MMKVInfo("copy content from %s to fd[%d] finish", srcPath.c_str(), dstFD);
+
+    errorOut:
+    free(buffer);
+    ::close(srcFd);
+    return ret;
 }
 
 #endif
diff --git a/Core/MemoryFile_Android.cpp b/Core/MemoryFile_Android.cpp
index c005151d..60bb4b8c 100644
--- a/Core/MemoryFile_Android.cpp
+++ b/Core/MemoryFile_Android.cpp
@@ -180,7 +180,7 @@ string ASharedMemory_getName(int fd) {
         MMKVError("fail to get ashmem name:%d, %s", fd, strerror(errno));
         return "";
     }
-    return string(name);
+    return {name};
 }
 
 } // namespace mmkv
diff --git a/Core/MemoryFile_OSX.cpp b/Core/MemoryFile_OSX.cpp
index 09702d2b..b1e9a3c8 100644
--- a/Core/MemoryFile_OSX.cpp
+++ b/Core/MemoryFile_OSX.cpp
@@ -110,9 +110,10 @@ bool copyFileContent(const MMKVPath_t &srcPath, const MMKVPath_t &dstPath) {
     auto ret = copyFileContent(srcPath, dstFD);
     if (!ret) {
         MMKVError("fail to copyfile(): target file %s", dstPath.c_str());
+    } else {
+        MMKVInfo("copy content from %s to fd[%s] finish", srcPath.c_str(), dstPath.c_str());
     }
     ::close(dstFD);
-    MMKVInfo("copy content from %s to fd[%s] finish", srcPath.c_str(), dstPath.c_str());
 
     return ret;
 }