From e8cb4a8d53ff544931b0d9dd7734381bc28abc8c Mon Sep 17 00:00:00 2001
From: Andrew Gunnerson <accounts+github@chiller3.com>
Date: Sun, 23 Mar 2025 18:50:44 -0400
Subject: [PATCH] Fix incorrect compression input for gzip CoW size estimation

Instead of compressing the 64 MiB input in 2 MiB chunks, each loop
iteration was compressing the full 64 MiB. This massively slowed down
the patching process from seconds to potentially hours and would
temporarily waste a bunch of space during OTA installation.

Fixes: #433

Signed-off-by: Andrew Gunnerson <accounts+github@chiller3.com>
---
 avbroot/src/cli/ota.rs        | 4 ++--
 avbroot/src/format/payload.rs | 8 +++++---
 e2e/e2e.toml                  | 8 ++++----
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/avbroot/src/cli/ota.rs b/avbroot/src/cli/ota.rs
index 427a73b..b3a80be 100644
--- a/avbroot/src/cli/ota.rs
+++ b/avbroot/src/cli/ota.rs
@@ -683,8 +683,6 @@ pub fn compress_image(
     // update the CoW size estimate or else the CoW block device may run out of
     // space during flashing.
     let vabc_algo = if partition.estimate_cow_size.is_some() {
-        info!("Needs updated CoW size estimate: {name}");
-
         // Only CoW v2 seems to exist in the wild currently, so that is all we
         // support.
         let Some(dpm) = &header.manifest.dynamic_partition_metadata else {
@@ -705,6 +703,8 @@ pub fn compress_image(
             bail!("Unsupported VABC compression: {compression}");
         };
 
+        info!("Needs updated {vabc_algo} CoW size estimate: {name}");
+
         Some(vabc_algo)
     } else {
         None
diff --git a/avbroot/src/format/payload.rs b/avbroot/src/format/payload.rs
index 21f448b..b7a9db4 100644
--- a/avbroot/src/format/payload.rs
+++ b/avbroot/src/format/payload.rs
@@ -965,20 +965,22 @@ impl VabcAlgo {
 
         while !raw_data.is_empty() {
             let n = raw_data.len().min(block_size as usize);
+            let (chunk, remaining) = raw_data.split_at(n);
+
             // This should match CompressWorker::GetDefaultCompressionLevel() in
             // AOSP's libsnapshot.
             let compressed = match self {
-                Self::Lz4 => lz4_flex::block::compress(&raw_data[..n]),
+                Self::Lz4 => lz4_flex::block::compress(chunk),
                 Self::Gzip => {
                     let mut encoder = GzEncoder::new(Vec::new(), Compression::best());
-                    encoder.write_all(raw_data).map_err(Error::GzCompress)?;
+                    encoder.write_all(chunk).map_err(Error::GzCompress)?;
                     encoder.finish().map_err(Error::GzCompress)?
                 }
             };
 
             total += compressed.len().min(n) as u64;
 
-            raw_data = &raw_data[n..];
+            raw_data = remaining;
         }
 
         Ok(total)
diff --git a/e2e/e2e.toml b/e2e/e2e.toml
index c87f48c..5f4b20b 100644
--- a/e2e/e2e.toml
+++ b/e2e/e2e.toml
@@ -168,9 +168,9 @@ data.type = "vbmeta"
 data.deps = ["system"]
 
 [profile.pixel_v2.hashes_streaming]
-original = "4b7e5675f834ac56bf3459628adfe1425c2346a1c224ee6ea0a3be9f996db254"
-patched = "4a7ca99808b4e49a2dc77a620d4fb7d8219b974ab5b3d5b5709084942805dc9a"
+original = "bd2f19cf3d2285e35e8b36d44f75ed910e8e0be44c3ebd29f17a812521ba754b"
+patched = "cf65d5b90500af54cd1204a646379bb852825061bc7c3f973b7a042f353f75ad"
 
 [profile.pixel_v2.hashes_seekable]
-original = "66b44b148b35a8a998214e0ae36470b42ffd6d2974e18cd8fa12cd8af0c98540"
-patched = "5ddec4bb56dd78a49fbc49e9ad3de7710b0b008b031ff4dfce8fdc775e753ad1"
+original = "7f96ebf7366e0b60c91ac1e5f196a2189ffdb0bbc73f77804a736466fcab7315"
+patched = "c2d9d60d73c038da39f82073ffadb459c96b901d66db7af11f59da58e0dd53e4"