commit 76622d444d94b620089707528dd98337bf2671fd
author David Anderson <dvander@google.com> Tue Jun 13 16:51:22 2023 -0700
committer David Anderson <dvander@google.com> Wed Jun 14 12:03:59 2023 -0700
tree 828e8f403b75d5e6499465f010f57cd87305e726
parent 5eae2cb4508282b1ae8f7f376a07645c650557d0

libsnapshot: Remove dependence between CowWriterV2 and CowReader.

The plan of record for the new CowOperation layout is to automatically
translate from CowOperationV2. However, CowWriterV2 currently imports
directly from CowReader, which means we'd need two translation steps.

Luckily we now have CowParserV2, which means we can directly import into
CowWriterV2.

Bug: 280529365
Test: vts_libsnapshot_test
Test: cow_api_test
Change-Id: I11863dcb483f0448686d6c492d8eb128840ce18c

fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp

diff --git a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
index b6603da..c549969 100644
--- a/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
+++ b/fs_mgr/libsnapshot/libsnapshot_cow/writer_v2.cpp
@@ -14,6 +14,8 @@
 // limitations under the License.
 //
 
+#include "writer_v2.h"
+
 #include <sys/types.h>
 #include <sys/uio.h>
 #include <unistd.h>
@@ -37,7 +39,7 @@
 #include <sys/ioctl.h>
 #include <unistd.h>
 
-#include "writer_v2.h"
+#include "parser_v2.h"
 
 // The info messages here are spammy, but as useful for update_engine. Disable
 // them when running on the host.
@@ -252,14 +254,20 @@
 }
 
 bool CowWriterV2::OpenForAppend(uint64_t label) {
-    auto reader = std::make_unique<CowReader>();
-    std::queue<CowOperation> toAdd;
-
-    if (!reader->Parse(fd_, {label})) {
+    if (!ReadCowHeader(fd_, &header_)) {
         return false;
     }
 
-    header_ = reader->GetHeader();
+    CowParserV2 parser;
+    if (!parser.Parse(fd_, header_, {label})) {
+        return false;
+    }
+    if (header_.prefix.major_version > 2) {
+        LOG(ERROR) << "CowWriterV2 tried to open incompatible version "
+                   << header_.prefix.major_version;
+        return false;
+    }
+
     options_.block_size = header_.block_size;
     options_.cluster_ops = header_.cluster_ops;
 
@@ -267,16 +275,10 @@
     footer_.op.num_ops = 0;
     InitPos();
 
-    auto iter = reader->GetOpIter();
-
-    while (!iter->AtEnd()) {
-        AddOperation(*iter->Get());
-        iter->Next();
+    for (const auto& op : *parser.ops()) {
+        AddOperation(op);
     }
 
-    // Free reader so we own the descriptor position again.
-    reader = nullptr;
-
     if (lseek(fd_.get(), next_op_pos_, SEEK_SET) < 0) {
         PLOG(ERROR) << "lseek failed";
         return false;