Vendor aws-sdk-go (dep ensure) (#178)

vendor/github.com/aws/aws-sdk-go/service/glacier/treehash.go

@@ -0,0 +1,79 @@
+package glacier
+
+import (
+	"crypto/sha256"
+	"io"
+
+	"github.com/aws/aws-sdk-go/internal/sdkio"
+)
+
+const bufsize = 1024 * 1024
+
+// Hash contains information about the tree-hash and linear hash of a
+// Glacier payload. This structure is generated by ComputeHashes().
+type Hash struct {
+	TreeHash   []byte
+	LinearHash []byte
+}
+
+// ComputeHashes computes the tree-hash and linear hash of a seekable reader r.
+//
+// See http://docs.aws.amazon.com/amazonglacier/latest/dev/checksum-calculations.html for more information.
+func ComputeHashes(r io.ReadSeeker) Hash {
+	start, _ := r.Seek(0, sdkio.SeekCurrent) // Read the whole stream
+	defer r.Seek(start, sdkio.SeekStart)     // Rewind stream at end
+
+	buf := make([]byte, bufsize)
+	hashes := [][]byte{}
+	hsh := sha256.New()
+
+	for {
+		// Build leaf nodes in 1MB chunks
+		n, err := io.ReadAtLeast(r, buf, bufsize)
+		if n == 0 {
+			break
+		}
+
+		tmpHash := sha256.Sum256(buf[:n])
+		hashes = append(hashes, tmpHash[:])
+		hsh.Write(buf[:n]) // Track linear hash while we're at it
+
+		if err != nil {
+			break // This is the last chunk
+		}
+	}
+
+	return Hash{
+		LinearHash: hsh.Sum(nil),
+		TreeHash:   ComputeTreeHash(hashes),
+	}
+}
+
+// ComputeTreeHash builds a tree hash root node given a slice of
+// hashes. Glacier tree hash to be derived from SHA256 hashes of 1MB
+// chucks of the data.
+//
+// See http://docs.aws.amazon.com/amazonglacier/latest/dev/checksum-calculations.html for more information.
+func ComputeTreeHash(hashes [][]byte) []byte {
+	if hashes == nil || len(hashes) == 0 {
+		return nil
+	}
+
+	for len(hashes) > 1 {
+		tmpHashes := [][]byte{}
+
+		for i := 0; i < len(hashes); i += 2 {
+			if i+1 <= len(hashes)-1 {
+				tmpHash := append(append([]byte{}, hashes[i]...), hashes[i+1]...)
+				tmpSum := sha256.Sum256(tmpHash)
+				tmpHashes = append(tmpHashes, tmpSum[:])
+			} else {
+				tmpHashes = append(tmpHashes, hashes[i])
+			}
+		}
+
+		hashes = tmpHashes
+	}
+
+	return hashes[0]
+}