Ultracopier 0.3

Hello, here I will speak about file transfer to do copy/move. You need understand some basic therms.

I have discover which each OS and FS is different.

• Windows/ntfs have correct fs layer, asynchronous inode and data layer, synchronous is not allowed and then flush return instantly regardless if is really written on the disk (prevent freeze the application, in all case data in memory lost application blocked or not). 
• Linux/ext4 with partial asynchronous for data layer (in loop read/write the read block the write, and the write block the read), inode creations and manipulations are synchronous but due to low volume the aggressive access can be done without big lost of performance.

Ultracopier 0.1

While { read (position); write (position) }

• Advantage: Very simple, and used by the most of developer to have simple copy file.
  
• Disadvantage: The missing cache do read blocking, then if buffer is not full, the write can be down without blocking but the loop and thread is blocked at read function and the contrary.
• Implementation mistake: The slow down in interface slow down the copy.
  

Ultracopier 0.2

Thread 1: While { read (position); } , Thread pool for write: While { write (position); } close(); , and pipe like communication

• Advantage: The close function is blocked in thread, and while is blocked another write thread is used. The read not block anymore the write, and the contrary (the different media have advantage, and the buffer and cache level can change separately and be in concurrency).
• Disadvantage: It’s complicated on some programming aspect, I have need use goto to minimize the code, and have great big read function. The write thread decision is can be complicated too. The list parsing and read is same code for intuitive programming. Not parallel the extra programming like variable initialization, to prevent slow down for not real copy operation. Not parallel inode and data parallel operation possible. Can’t recovery destination file write corruption. 
• Implementation mistake: Do with thread and lot of blocking function (not event to have cleaner design), based on 0.1 design. The slow down in interface slow down the copy.

Ultracopier 0.3

Thead 1: Copy list send/receive event (start transfer, stop transfer event), Thread list of {Read thread, Write thread, transfer thread} with pipe like communication.

• Advantage: Can parallel the inode and data access, prevent no copy operation to slow down the copy. Can group inode access via parallel access, but data parallel is bad in general. Have asynchronous behavior like for all OS/FS (included synchronous OS/FS like linux/ext4). Very cleaner design, possible separate control on each transfer. Can recovery destination file write corruption. 
• Disadvantage: Need master multi-thread, data locality, and lot of advanced algorithm.