Refactor out the model into a subpackage

blocks.go

@@ -1,67 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"crypto/sha256"
-	"io"
-)
-
-type BlockList []Block
-
-type Block struct {
-	Offset uint64
-	Length uint32
-	Hash   []byte
-}
-
-// Blocks returns the blockwise hash of the reader.
-func Blocks(r io.Reader, blocksize int) (BlockList, error) {
-	var blocks BlockList
-	var offset uint64
-	for {
-		lr := &io.LimitedReader{r, int64(blocksize)}
-		hf := sha256.New()
-		n, err := io.Copy(hf, lr)
-		if err != nil {
-			return nil, err
-		}
-
-		if n == 0 {
-			break
-		}
-
-		b := Block{
-			Offset: offset,
-			Length: uint32(n),
-			Hash:   hf.Sum(nil),
-		}
-		blocks = append(blocks, b)
-		offset += uint64(n)
-	}
-
-	return blocks, nil
-}
-
-// To returns the list of blocks necessary to transform src into dst.
-// Both block lists must have been created with the same block size.
-func (src BlockList) To(tgt BlockList) (have, need BlockList) {
-	if len(tgt) == 0 && len(src) != 0 {
-		return nil, nil
-	}
-
-	if len(tgt) != 0 && len(src) == 0 {
-		// Copy the entire file
-		return nil, tgt
-	}
-
-	for i := range tgt {
-		if i >= len(src) || bytes.Compare(tgt[i].Hash, src[i].Hash) != 0 {
-			// Copy differing block
-			need = append(need, tgt[i])
-		} else {
-			have = append(have, tgt[i])
-		}
-	}
-
-	return have, need
-}