adb: implement LZ4 compression.

Add support for LZ4 compression, which compresses and decompresses far
more quickly than brotli, at the cost of worse compression ratio.

`adb sync -d system` speeds (in MB/s) on aosp_blueline-eng:

           none    brotli    lz4
USB 3.0     120       110    190
USB 2.0      38        75     63

Bug: https://issuetracker.google.com/150827486
Test: python3 -m unittest test_device.FileOperationsTest{Uncompressed,Brotli,LZ4}
Change-Id: Ibef6ac15a76b4e5dcd02d7fb9433cbb1c02b8382

1 files changed, 28 insertions, 2 deletions

diff --git a/adb/daemon/file_sync_service.cpp b/adb/daemon/file_sync_service.cpp
index 3138ab497..3436e32c0 100644
--- a/adb/daemon/file_sync_service.cpp
+++ b/adb/daemon/file_sync_service.cpp
@@ -272,7 +272,7 @@ static bool handle_send_file_data(borrowed_fd s, unique_fd fd, uint32_t* timesta
     syncmsg msg;
     Block buffer(SYNC_DATA_MAX);
     std::span<char> buffer_span(buffer.data(), buffer.size());
-    std::variant<std::monostate, NullDecoder, BrotliDecoder> decoder_storage;
+    std::variant<std::monostate, NullDecoder, BrotliDecoder, LZ4Decoder> decoder_storage;
     Decoder* decoder = nullptr;
 
     switch (compression) {
@@ -284,6 +284,10 @@ static bool handle_send_file_data(borrowed_fd s, unique_fd fd, uint32_t* timesta
             decoder = &decoder_storage.emplace<BrotliDecoder>(buffer_span);
             break;
 
+        case CompressionType::LZ4:
+            decoder = &decoder_storage.emplace<LZ4Decoder>(buffer_span);
+            break;
+
         case CompressionType::Any:
             LOG(FATAL) << "unexpected CompressionType::Any";
     }
@@ -569,6 +573,15 @@ static bool do_send_v2(int s, const std::string& path, std::vector<char>& buffer
         }
         compression = CompressionType::Brotli;
     }
+    if (msg.send_v2_setup.flags & kSyncFlagLZ4) {
+        msg.send_v2_setup.flags &= ~kSyncFlagLZ4;
+        if (compression) {
+            SendSyncFail(s, android::base::StringPrintf("multiple compression flags received: %d",
+                                                        orig_flags));
+            return false;
+        }
+        compression = CompressionType::LZ4;
+    }
 
     if (msg.send_v2_setup.flags) {
         SendSyncFail(s, android::base::StringPrintf("unknown flags: %d", msg.send_v2_setup.flags));
@@ -598,7 +611,7 @@ static bool recv_impl(borrowed_fd s, const char* path, CompressionType compressi
     syncmsg msg;
     msg.data.id = ID_DATA;
 
-    std::variant<std::monostate, NullEncoder, BrotliEncoder> encoder_storage;
+    std::variant<std::monostate, NullEncoder, BrotliEncoder, LZ4Encoder> encoder_storage;
     Encoder* encoder;
 
     switch (compression) {
@@ -610,6 +623,10 @@ static bool recv_impl(borrowed_fd s, const char* path, CompressionType compressi
             encoder = &encoder_storage.emplace<BrotliEncoder>(SYNC_DATA_MAX);
             break;
 
+        case CompressionType::LZ4:
+            encoder = &encoder_storage.emplace<LZ4Encoder>(SYNC_DATA_MAX);
+            break;
+
         case CompressionType::Any:
             LOG(FATAL) << "unexpected CompressionType::Any";
     }
@@ -688,6 +705,15 @@ static bool do_recv_v2(borrowed_fd s, const char* path, std::vector<char>& buffe
         }
         compression = CompressionType::Brotli;
     }
+    if (msg.recv_v2_setup.flags & kSyncFlagLZ4) {
+        msg.recv_v2_setup.flags &= ~kSyncFlagLZ4;
+        if (compression) {
+            SendSyncFail(s, android::base::StringPrintf("multiple compression flags received: %d",
+                                                        orig_flags));
+            return false;
+        }
+        compression = CompressionType::LZ4;
+    }
 
     if (msg.recv_v2_setup.flags) {
         SendSyncFail(s, android::base::StringPrintf("unknown flags: %d", msg.recv_v2_setup.flags));