diff --git a/lib/files.cpp b/lib/files.cpp
index 9f6027f..86c53a5 100644
--- a/lib/files.cpp
+++ b/lib/files.cpp
@@ -452,8 +452,30 @@ int FilesOperation::fischl_write(const char *path, const char *buf, size_t size,
     // FileNode *get_file;
     // if((get_file = fischl_find_entry(root_node, path)) == NULL)
     //     return -ENOENT;
+    // Caution! this based on content in file are multiple of IO_BLOCK_SIZE, not the exact write size.
+    // based on current write_datablock API implement, when write_datablock pass with actual size not index this function should be fixed
+    INode inode;
+    // Assuming inode is correctly initialized here based on 'path'
+    inode.inode_construct(fi->fh, disk);
+    size_t len = inode.size * IO_BLOCK_SIZE;  // Assuming each block is 4096 bytes
 
-    return size;
+    size_t bytes_write = 0;
+    size_t block_index = offset / IO_BLOCK_SIZE;  // Starting block index
+    size_t block_offset = offset % IO_BLOCK_SIZE; // Offset within the first block
+    while (bytes_write < size) {
+        char block_buffer[IO_BLOCK_SIZE];  // Temporary buffer for each block
+        size_t copy_size = std::min(size - bytes_write, IO_BLOCK_SIZE - block_offset);
+        memcpy(block_buffer + block_offset, buf + bytes_write, copy_size);
+        write_datablock(inode, block_index, block_buffer);
+        fprintf(stderr,"[%s ,%d] inode.size %d\n",__func__,__LINE__, inode.size);
+        fprintf(stderr,"[%s ,%d] block_index %d\n",__func__,__LINE__, block_index);
+        fprintf(stderr,"[%s ,%d] buf %s, block_buffer %s\n",__func__,__LINE__, buf, block_buffer);
+        bytes_write += copy_size;
+        block_index++;
+        block_offset = 0;  // Only the first block might have a non-zero offset
+    }
+
+    return bytes_write;  // Return the actual number of bytes read
 }
 
 int FilesOperation::fischl_read(const char *path, char *buf, size_t size, off_t offset, struct fuse_file_info *fi){
diff --git a/test/layer2_API_dir.cpp b/test/layer2_API_dir.cpp
index 4b87f89..1b84951 100644
--- a/test/layer2_API_dir.cpp
+++ b/test/layer2_API_dir.cpp
@@ -62,12 +62,18 @@ TEST(FileOperationTest, WriteTest) {
     char buffer[IO_BLOCK_SIZE] = {0};
     INode inode;
     u_int64_t get_disk_inum;
+    struct fuse_file_info fi;
+    
     //file test
     get_disk_inum = fsop->disk_namei("/test");
     inode.inode_construct(get_disk_inum, *H);
     buffer[0] = '1';
     fsop->write_datablock(inode, 0, buffer);
     inode.inode_save(*H);
+    /*with fischl_write API*/
+    // fsop->fischl_open("/test", &fi);
+    // EXPECT_EQ(fi.fh, get_disk_inum);
+    // fsop->fischl_write("/test", buffer, sizeof(buffer), 0, &fi);
     //other file baz
     get_disk_inum = fsop->disk_namei("/foo/bar/baz");
     inode.inode_construct(get_disk_inum, *H);
@@ -77,6 +83,13 @@ TEST(FileOperationTest, WriteTest) {
     fsop->write_datablock(inode, 101, buffer);
     inode.inode_save(*H);
     // TODO: guard against overwriting directory datablocks
+    /*with new API*/
+    // buffer[0] = '4';
+    // fsop->fischl_open("/foo/bar/baz", &fi);
+    // EXPECT_EQ(fi.fh, get_disk_inum);
+    // fsop->fischl_write("/foo/bar/baz", buffer, sizeof(buffer), 3*IO_BLOCK_SIZE, &fi);
+    // buffer[0] = '5';
+    // fsop->fischl_write("/foo/bar/baz", buffer, sizeof(buffer), 101*IO_BLOCK_SIZE, &fi);
 }
 
 TEST(FileOperationTest, RamDiskTest) {
@@ -135,10 +148,18 @@ TEST(FileOperationTest, ReadTest) {
 
     //read baz file
     get_file_inum= fsop->namei("/foo/bar/baz");
-    inode.inode_construct(get_file_inum, *H);
-    fsop->read_datablock(inode, 3, read_buffer);
+    // inode.inode_construct(get_file_inum, *H);
+    // fsop->read_datablock(inode, 3, read_buffer);
+    // EXPECT_EQ(read_buffer[0], '4');
+    // fsop->read_datablock(inode, 101, read_buffer);
+    // EXPECT_EQ(read_buffer[0], '5');
+
+    //read baz file again with fischl_read API
+    fsop->fischl_open("/foo/bar/baz", &fi);
+    EXPECT_EQ(fi.fh, get_file_inum);
+    fsop->fischl_read("/foo/bar/baz", read_buffer, sizeof(read_buffer), 3*IO_BLOCK_SIZE, &fi);
     EXPECT_EQ(read_buffer[0], '4');
-    fsop->read_datablock(inode, 101, read_buffer);
+    fsop->fischl_read("/foo/bar/baz", read_buffer, sizeof(read_buffer), 101*IO_BLOCK_SIZE, &fi);
     EXPECT_EQ(read_buffer[0], '5');
 }