From 577cfd5550c1b5e2dec43b25785f5cd59cb9bd66 Mon Sep 17 00:00:00 2001
From: Jiang Liu <gerry@linux.alibaba.com>
Date: Thu, 13 Apr 2023 10:53:33 +0800
Subject: [PATCH] storage: refine the way to define compression algorithms

Reserve 4 bits to store toc compression algorithms, and use enumeration
instead of bitmask for algorithms.

Signed-off-by: Jiang Liu <gerry@linux.alibaba.com>
---
 storage/src/meta/toc.rs | 30 +++++++++++++++++-------------
 1 file changed, 17 insertions(+), 13 deletions(-)

diff --git a/storage/src/meta/toc.rs b/storage/src/meta/toc.rs
index e759bd95f8c..a7f724f59f5 100644
--- a/storage/src/meta/toc.rs
+++ b/storage/src/meta/toc.rs
@@ -45,6 +45,8 @@ bitflags! {
         const COMPRESSION_ZSTD = 0x0002;
         /// Entry data is compressed with lz4.
         const COMPRESSION_LZ4_BLOCK = 0x0004;
+        /// Bit mask for compression algorithms.
+        const COMPRESSION_MASK = 0x000f;
     }
 }
 
@@ -129,23 +131,23 @@ impl TocEntry {
     }
 
     /// Get compression algorithm to process entry  data.
-    pub fn compressor(&self) -> compress::Algorithm {
-        if self.flags & TocEntryFlags::COMPRESSION_ZSTD.bits() != 0 {
-            compress::Algorithm::Zstd
-        } else if self.flags & TocEntryFlags::COMPRESSION_LZ4_BLOCK.bits() != 0 {
-            compress::Algorithm::Lz4Block
-        } else {
-            compress::Algorithm::None
-        }
+    pub fn compressor(&self) -> Result<compress::Algorithm> {
+        let flags = TocEntryFlags::from_bits(self.flags)
+            .ok_or_else(|| einval!("unknown compression algorithm for TOC entry"))?;
+        let algo = match flags & TocEntryFlags::COMPRESSION_MASK {
+            TocEntryFlags::COMPRESSION_ZSTD => compress::Algorithm::Zstd,
+            TocEntryFlags::COMPRESSION_LZ4_BLOCK => compress::Algorithm::Lz4Block,
+            TocEntryFlags::COMPRESSION_NONE => compress::Algorithm::None,
+            _ => return Err(einval!("unknown compression algorithm for TOC entry")),
+        };
+        Ok(algo)
     }
 
     /// Set compression algorithm to process entry data.
     pub fn set_compressor(&mut self, compressor: compress::Algorithm) -> Result<()> {
         let c: TocEntryFlags = compressor.try_into()?;
 
-        self.flags &= !TocEntryFlags::COMPRESSION_NONE.bits();
-        self.flags &= !TocEntryFlags::COMPRESSION_ZSTD.bits();
-        self.flags &= !TocEntryFlags::COMPRESSION_LZ4_BLOCK.bits();
+        self.flags &= !TocEntryFlags::COMPRESSION_MASK.bits();
         self.flags |= c.bits();
 
         Ok(())
@@ -528,7 +530,8 @@ impl TocEntryList {
             let bootstrap = self
                 .get_entry(TOC_ENTRY_BOOTSTRAP)
                 .ok_or_else(|| enoent!("`image.boot` doesn't exist in the ToC list"))?;
-            if bootstrap.compressor() == compress::Algorithm::None
+            let compressor = bootstrap.compressor()?;
+            if compressor == compress::Algorithm::None
                 && bootstrap.compressed_size() != bootstrap.uncompressed_size()
             {
                 return Err(einval!("invalid ToC entry for `image.boot`"));
@@ -569,7 +572,8 @@ impl TocEntryList {
             let cda = self
                 .get_entry(TOC_ENTRY_BLOB_DIGEST)
                 .ok_or_else(|| enoent!("`blob.digest` doesn't exist in the ToC list"))?;
-            if cda.compressor() == compress::Algorithm::None
+            let compressor = cda.compressor()?;
+            if compressor == compress::Algorithm::None
                 && cda.compressed_size() != cda.uncompressed_size()
             {
                 return Err(einval!("invalid ToC entry for `blob.digest`"));