1 files changed, 81 insertions, 0 deletions
diff --git a/src/block/block.rs b/src/block/block.rs
new file mode 100644
index 00000000..4d3fbcb8
--- /dev/null
+++ b/src/block/block.rs
@@ -0,0 +1,81 @@
+use serde::{Deserialize, Serialize};
+use zstd::stream::{decode_all as zstd_decode, Encoder};
+
+use garage_util::data::*;
+use garage_util::error::*;
+
+/// A possibly compressed block of data
+#[derive(Debug, Serialize, Deserialize)]
+pub enum DataBlock {
+	/// Uncompressed data
+	Plain(#[serde(with = "serde_bytes")] Vec<u8>),
+	/// Data compressed with zstd
+	Compressed(#[serde(with = "serde_bytes")] Vec<u8>),
+}
+
+impl DataBlock {
+	/// Query whether this block is compressed
+	pub fn is_compressed(&self) -> bool {
+		matches!(self, DataBlock::Compressed(_))
+	}
+
+	/// Get the inner, possibly compressed buffer. You should probably use [`DataBlock::verify_get`]
+	/// instead
+	pub fn inner_buffer(&self) -> &[u8] {
+		use DataBlock::*;
+		let (Plain(ref res) | Compressed(ref res)) = self;
+		res
+	}
+
+	/// Get the buffer, possibly decompressing it, and verify it's integrity.
+	/// For Plain block, data is compared to hash, for Compressed block, zstd checksumming system
+	/// is used instead.
+	pub fn verify_get(self, hash: Hash) -> Result<Vec<u8>, Error> {
+		match self {
+			DataBlock::Plain(data) => {
+				if blake2sum(&data) == hash {
+					Ok(data)
+				} else {
+					Err(Error::CorruptData(hash))
+				}
+			}
+			DataBlock::Compressed(data) => {
+				zstd_decode(&data[..]).map_err(|_| Error::CorruptData(hash))
+			}
+		}
+	}
+
+	/// Verify data integrity. Allocate less than [`DataBlock::verify_get`] and don't consume self, but
+	/// does not return the buffer content.
+	pub fn verify(&self, hash: Hash) -> Result<(), Error> {
+		match self {
+			DataBlock::Plain(data) => {
+				if blake2sum(data) == hash {
+					Ok(())
+				} else {
+					Err(Error::CorruptData(hash))
+				}
+			}
+			DataBlock::Compressed(data) => zstd::stream::copy_decode(&data[..], std::io::sink())
+				.map_err(|_| Error::CorruptData(hash)),
+		}
+	}
+
+	pub fn from_buffer(data: Vec<u8>, level: Option<i32>) -> DataBlock {
+		if let Some(level) = level {
+			if let Ok(data) = zstd_encode(&data[..], level) {
+				return DataBlock::Compressed(data);
+			}
+		}
+		DataBlock::Plain(data)
+	}
+}
+
+fn zstd_encode<R: std::io::Read>(mut source: R, level: i32) -> std::io::Result<Vec<u8>> {
+	let mut result = Vec::<u8>::new();
+	let mut encoder = Encoder::new(&mut result, level)?;
+	encoder.include_checksum(true)?;
+	std::io::copy(&mut source, &mut encoder)?;
+	encoder.finish()?;
+	Ok(result)
+}