mandoline filesystem: add a sqlite3 vfs to proxy filesystem usage.

sql/connection.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sql/connection.h"
 
 #include <string.h>
 
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
@@ skipping 133 matching lines @@
 // This should match UMA_HISTOGRAM_MEDIUM_TIMES().
 base::HistogramBase* GetMediumTimeHistogram(const std::string& name) {
   return base::Histogram::FactoryTimeGet(
       name,
       base::TimeDelta::FromMilliseconds(10),
       base::TimeDelta::FromMinutes(3),
       50,
       base::HistogramBase::kUmaTargetedHistogramFlag);
 }
 
+std::string AsUTF8ForSQL(const base::FilePath& path) {
+#if defined(OS_WIN)
+  return base::WideToUTF8(path.value());
+#elif defined(OS_POSIX)
+  return path.value();
+#endif
+}
+
 }  // namespace
 
 namespace sql {
 
 // static
 Connection::ErrorIgnorerCallback* Connection::current_ignorer_cb_ = NULL;
 
 // static
 bool Connection::ShouldIgnoreSqliteError(int error) {
   if (!current_ignorer_cb_)
@@ skipping 141 matching lines @@
       std::string full_histogram_name = "Sqlite.SizeKB." + histogram_tag_;
       base::HistogramBase* histogram =
           base::Histogram::FactoryGet(
               full_histogram_name, 1, 1000000, 50,
               base::HistogramBase::kUmaTargetedHistogramFlag);
       if (histogram)
         histogram->Add(sample);
     }
   }
 
-#if defined(OS_WIN)
-  return OpenInternal(base::WideToUTF8(path.value()), RETRY_ON_POISON);
-#elif defined(OS_POSIX)
-  return OpenInternal(path.value(), RETRY_ON_POISON);
-#endif
+  return OpenInternal(AsUTF8ForSQL(path), RETRY_ON_POISON);

[Scott Hess - ex-Googler, 2015/06/19 20:48:02]

+1!  The placement of this #if has annoyed me for so long.

 }
 
 bool Connection::OpenInMemory() {
   in_memory_ = true;
   return OpenInternal(":memory:", NO_RETRY);
 }
 
 bool Connection::OpenTemporary() {
   return OpenInternal("", NO_RETRY);
 }
@@ skipping 287 matching lines @@
 // junk to prevent other processes from opening it successfully (like
 // Gears "SQLite poison 3" trick).
 //
 // static
 bool Connection::Delete(const base::FilePath& path) {
   base::ThreadRestrictions::AssertIOAllowed();
 
   base::FilePath journal_path(path.value() + FILE_PATH_LITERAL("-journal"));
   base::FilePath wal_path(path.value() + FILE_PATH_LITERAL("-wal"));
 
-  base::DeleteFile(journal_path, false);
-  base::DeleteFile(wal_path, false);
-  base::DeleteFile(path, false);
+  std::string journal_str = AsUTF8ForSQL(journal_path);
+  std::string wal_str = AsUTF8ForSQL(wal_path);
+  std::string path_str = AsUTF8ForSQL(path);
 
-  return !base::PathExists(journal_path) &&
-      !base::PathExists(wal_path) &&
-      !base::PathExists(path);
+  sqlite3_vfs* vfs = sqlite3_vfs_find(NULL);
+  CHECK(vfs);
+  CHECK(vfs->xDelete);
+  CHECK(vfs->xAccess);
+
+  // We only work with unix, win32 and mojo filesystems. If you're trying to
+  // use this code with any other VFS, you're not in a good place.
+  CHECK(strncmp(vfs->zName, "unix", 4) == 0 ||
+        strncmp(vfs->zName, "win32", 5) == 0 ||
+        strcmp(vfs->zName, "mojo") == 0);
+
+  vfs->xDelete(vfs, journal_str.c_str(), 0);
+  vfs->xDelete(vfs, wal_str.c_str(), 0);
+  vfs->xDelete(vfs, path_str.c_str(), 0);
+
+  int journal_exists = 0;
+  vfs->xAccess(vfs, journal_str.c_str(), SQLITE_ACCESS_EXISTS,
+               &journal_exists);
+
+  int wal_exists = 0;
+  vfs->xAccess(vfs, wal_str.c_str(), SQLITE_ACCESS_EXISTS,
+               &wal_exists);
+
+  int path_exists = 0;
+  vfs->xAccess(vfs, path_str.c_str(), SQLITE_ACCESS_EXISTS,
+               &path_exists);
+
+  return !journal_exists && !wal_exists && !path_exists;
 }
 
 bool Connection::BeginTransaction() {
   if (needs_rollback_) {
     DCHECK_GT(transaction_nesting_, 0);
 
     // When we're going to rollback, fail on this begin and don't actually
     // mark us as entering the nested transaction.
     return false;
   }
@@ skipping 663 matching lines @@
   ignore_result(Execute(kNoWritableSchema));
 
   return ret;
 }
 
 base::TimeTicks TimeSource::Now() {
   return base::TimeTicks::Now();
 }
 
 }  // namespace sql