batch Read&Write api

[izouxv]

hi
go-journal is very good
I have two suggestions

1: the disk function maybe need a error return

orignal Disk interface

type Disk interface { 
	Read(a uint64) (Block, error) 
	ReadTo(a uint64, b Block) error 
	Write(a uint64, v Block) error 
	Size() (uint64, error) 
	Barrier() error
	Close() error
}

the Disk can be mem fs, file fs, or network fs (ths fs implement the Disk interface with smb client)

2: batch read & write to resuse IO

the io is very intensive when WRITE a big file
writing a data, it will make 4 write operates

• 1 write log block(journal data)
• 2 update block0(disk addrs)
• 3 update block1(start pos),
• 4 write data back.

if writing a big data consecutively, Batch interfaces can be used to reduce IO in the setp 1 and 4
if reading a big data consecutiveley, It's the same with writing
the interface about like this.

type DiskWriteBatch interface {
	WriteBatch(startPos uint64, blocks []Block) error
}
type DiskReadBatch interface {
	ReadBatch(startPos uint64, blockLen int) ([]Block, error)
}

could you add a batch WRITE api, or give me some advice
thank you