1 files changed, 41 insertions, 0 deletions
diff --git a/core/verification.go b/core/verification.go
new file mode 100644
index 0000000..5023d06
--- /dev/null
+++ b/core/verification.go
@@ -0,0 +1,41 @@
+package core
+
+import (
+	"bufio"
+	"fmt"
+	"strings"
+)
+
+func ReadBlock(node Node, part *bufio.Reader) ([]byte, error) {
+	block := make([]byte, node.BlockEnd-node.BlockStart)
+	blockSize := node.BlockEnd - node.BlockStart
+	_, err := part.Discard(node.BlockStart)
+	if err != nil {
+		return []byte{}, err
+	}
+	block, err = part.Peek(blockSize)
+	return block, err
+}
+
+func VerifyBlock(block []byte, node Node) error {
+	calculatedBlockHash, err := CalculateBlockHash(block)
+	if err != nil {
+		return err
+	}
+	wantedBlockHash := node.BlockSum
+	if strings.Compare(calculatedBlockHash, strings.TrimSpace(wantedBlockHash)) == 0 {
+		return nil
+	}
+	return fmt.Errorf("Error: Node %s ranging from %d to %d does not match block", node.PrevNodeSum, node.BlockStart, node.BlockEnd)
+}
+
+func VerifyNode(node Node, nextNode Node) error {
+	nodeHash, err := calculateStringHash(fmt.Sprintf("%d%d%s%s", node.BlockStart, node.BlockEnd, node.BlockSum, node.PrevNodeSum))
+	if err != nil {
+		return err
+	}
+	if strings.Compare(nodeHash, nextNode.PrevNodeSum) != 0 {
+		return fmt.Errorf("Node %s is not valid!", node.PrevNodeSum)
+	}
+	return nil
+}