From b6893b13cdbfd92fc5e5553777747dd9dd317358 Mon Sep 17 00:00:00 2001
From: Park Joon-Kyu <segfault87@gmail.com>
Date: Sat, 10 May 2025 17:23:13 +0900
Subject: [PATCH] fix broken compression when feeding data larger than 64 KiB

---
 Cargo.lock                   | 13 +++++++++++++
 actix-http/src/ws/deflate.rs | 10 +++++++---
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 63de68fe8..3afa9f6f8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1320,6 +1320,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7ced92e76e966ca2fd84c8f7aa01a4aea65b0eb6648d72f7c8f3e2764a67fece"
 dependencies = [
  "crc32fast",
+ "libz-sys",
  "miniz_oxide",
 ]
 
@@ -1922,6 +1923,18 @@ dependencies = [
  "windows-targets 0.52.6",
 ]
 
+[[package]]
+name = "libz-sys"
+version = "1.1.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b70e7a7df205e92a1a4cd9aaae7898dac0aa555503cc0a649494d0d60e7651d"
+dependencies = [
+ "cc",
+ "libc",
+ "pkg-config",
+ "vcpkg",
+]
+
 [[package]]
 name = "linked-hash-map"
 version = "0.5.6"
diff --git a/actix-http/src/ws/deflate.rs b/actix-http/src/ws/deflate.rs
index 76bfebb35..239ebec2e 100644
--- a/actix-http/src/ws/deflate.rs
+++ b/actix-http/src/ws/deflate.rs
@@ -530,8 +530,8 @@ impl DeflateCompressionContext {
         let mut buf = [0u8; BUF_SIZE];
 
         loop {
-            let total_in = self.compress.total_in() - self.total_bytes_read;
-            let res = if total_in >= payload.len() as u64 {
+            let bytes_in = self.compress.total_in() - self.total_bytes_read;
+            let res = if bytes_in >= payload.len() as u64 {
                 self.compress
                     .compress(&[], &mut buf, flate2::FlushCompress::Sync)
                     .map_err(|err| {
@@ -540,7 +540,11 @@ impl DeflateCompressionContext {
                     })?
             } else {
                 self.compress
-                    .compress(&payload, &mut buf, flate2::FlushCompress::None)
+                    .compress(
+                        &payload[bytes_in as usize..],
+                        &mut buf,
+                        flate2::FlushCompress::None,
+                    )
                     .map_err(|err| {
                         self.reset();
                         ProtocolError::Io(err.into())