src/backup/data_blob.rs: move parts into single files

src/backup/checksum_reader.rs

@@ -0,0 +1,47 @@
+use failure::*;
+use std::io::Read;
+
+pub struct ChecksumReader<'a, R> {
+    reader: R,
+    hasher: crc32fast::Hasher,
+    signer: Option<openssl::sign::Signer<'a>>,
+}
+
+impl <'a, R: Read> ChecksumReader<'a, R> {
+
+    pub fn new(reader: R, signer: Option<openssl::sign::Signer<'a>>) -> Self {
+        let hasher = crc32fast::Hasher::new();
+        Self { reader, hasher, signer }
+    }
+
+    pub fn finish(mut self) -> Result<(R, u32, Option<[u8; 32]>), Error> {
+        let crc = self.hasher.finalize();
+
+        if let Some(ref mut signer) = self.signer {
+            let mut tag = [0u8; 32];
+            signer.sign(&mut tag)?;
+            Ok((self.reader, crc, Some(tag)))
+        } else {
+            Ok((self.reader, crc, None))
+        }
+    }
+}
+
+impl <'a, R: Read> Read for ChecksumReader<'a, R> {
+
+    fn read(&mut self, buf: &mut [u8]) -> Result<usize, std::io::Error> {
+        let count = self.reader.read(buf)?;
+        if count > 0 {
+            self.hasher.update(&buf[..count]);
+            if let Some(ref mut signer) = self.signer {
+                signer.update(&buf[..count])
+                    .map_err(|err| {
+                        std::io::Error::new(
+                            std::io::ErrorKind::Other,
+                            format!("hmac update failed - {}", err))
+                    })?;
+            }
+        }
+        Ok(count)
+    }
+}