[sql] Rewrite sqlite patching "system".

third_party/sqlite/webdb.patch

-The WebDatabase implementation in the renderer users a custom vfs to
-broker file open and other requests.  This modifies the built-in vfs
-implementation to let that code share much of the implementation
-details.
-
-diff --git src/os_unix.c src/os_unix.c
-index ef04a72..e5e1509 100644
---- src/os_unix.c
-+++ src/os_unix.c
-@@ -3496,9 +3496,16 @@ typedef const sqlite3_io_methods *(*finder_type)(const char*,unixFile*);
- */
- 
- /*
-+** Initializes a unixFile structure with zeros.
-+*/
-+void initUnixFile(sqlite3_file* file) {
-+  memset(file, 0, sizeof(unixFile));
-+}
-+
-+/*
- ** Initialize the contents of the unixFile structure pointed to by pId.
- */
--static int fillInUnixFile(
-+int fillInUnixFile(
-   sqlite3_vfs *pVfs,      /* Pointer to vfs object */
-   int h,                  /* Open file descriptor of file being opened */
-   int dirfd,              /* Directory file descriptor */
-@@ -3812,6 +3819,73 @@ static UnixUnusedFd *findReusableFd(const char *zPath, int flags){
- }
- 
- /*
-+** Initializes a unixFile structure with zeros.
-+*/
-+void chromium_sqlite3_initialize_unix_sqlite3_file(sqlite3_file* file) {
-+  memset(file, 0, sizeof(unixFile));
-+}
-+
-+int chromium_sqlite3_fill_in_unix_sqlite3_file(sqlite3_vfs* vfs,
-+                                               int fd,
-+                                               int dirfd,
-+                                               sqlite3_file* file,
-+                                               const char* fileName,
-+                                               int noLock,
-+                                               int isDelete) {
-+  return fillInUnixFile(vfs, fd, dirfd, file, fileName, noLock, isDelete, 0);
-+}
-+
-+/*
-+** Search for an unused file descriptor that was opened on the database file.
-+** If a suitable file descriptor if found, then it is stored in *fd; otherwise,
-+** *fd is not modified.
-+**
-+** If a reusable file descriptor is not found, and a new UnixUnusedFd cannot
-+** be allocated, SQLITE_NOMEM is returned. Otherwise, SQLITE_OK is returned.
-+*/
-+int chromium_sqlite3_get_reusable_file_handle(sqlite3_file* file,
-+                                              const char* fileName,
-+                                              int flags,
-+                                              int* fd) {
-+  unixFile* unixSQLite3File = (unixFile*)file;
-+  int fileType = flags & 0xFFFFFF00;
-+  if (fileType == SQLITE_OPEN_MAIN_DB) {
-+    UnixUnusedFd *unusedFd = findReusableFd(fileName, flags);
-+    if (unusedFd) {
-+      *fd = unusedFd->fd;
-+    } else {
-+      unusedFd = sqlite3_malloc(sizeof(*unusedFd));
-+      if (!unusedFd) {
-+        return SQLITE_NOMEM;
-+      }
-+    }
-+    unixSQLite3File->pUnused = unusedFd;
-+  }
-+  return SQLITE_OK;
-+}
-+
-+/*
-+** Marks 'fd' as the unused file descriptor for 'pFile'.
-+*/
-+void chromium_sqlite3_update_reusable_file_handle(sqlite3_file* file,
-+                                                  int fd,
-+                                                  int flags) {
-+  unixFile* unixSQLite3File = (unixFile*)file;
-+  if (unixSQLite3File->pUnused) {
-+    unixSQLite3File->pUnused->fd = fd;
-+    unixSQLite3File->pUnused->flags = flags;
-+  }
-+}
-+
-+/*
-+** Destroys pFile's field that keeps track of the unused file descriptor.
-+*/
-+void chromium_sqlite3_destroy_reusable_file_handle(sqlite3_file* file) {
-+  unixFile* unixSQLite3File = (unixFile*)file;
-+  sqlite3_free(unixSQLite3File->pUnused);
-+}
-+
-+/*
- ** Open the file zPath.
- ** 
- ** Previously, the SQLite OS layer used three functions in place of this
-@@ -3893,20 +3967,13 @@ static int unixOpen(
-        || eType==SQLITE_OPEN_TRANSIENT_DB
-   );
- 
--  memset(p, 0, sizeof(unixFile));
-+  chromium_sqlite3_initialize_unix_sqlite3_file(pFile);
- 
-   if( eType==SQLITE_OPEN_MAIN_DB ){
--    UnixUnusedFd *pUnused;
--    pUnused = findReusableFd(zName, flags);
--    if( pUnused ){
--      fd = pUnused->fd;
--    }else{
--      pUnused = sqlite3_malloc(sizeof(*pUnused));
--      if( !pUnused ){
--        return SQLITE_NOMEM;
--      }
-+    rc = chromium_sqlite3_get_reusable_file_handle(pFile, zName, flags, &fd);
-+    if( rc!=SQLITE_OK ){
-+      return rc;
-     }
--    p->pUnused = pUnused;
-   }else if( !zName ){
-     /* If zName is NULL, the upper layer is requesting a temp file. */
-     assert(isDelete && !isOpenDirectory);
-@@ -3949,10 +4016,7 @@ static int unixOpen(
-     *pOutFlags = flags;
-   }
- 
--  if( p->pUnused ){
--    p->pUnused->fd = fd;
--    p->pUnused->flags = flags;
--  }
-+  chromium_sqlite3_update_reusable_file_handle(pFile, fd, flags);
- 
-   if( isDelete ){
- #if OS_VXWORKS
-@@ -4028,7 +4092,7 @@ static int unixOpen(
-   rc = fillInUnixFile(pVfs, fd, dirfd, pFile, zPath, noLock, isDelete);
- open_finished:
-   if( rc!=SQLITE_OK ){
--    sqlite3_free(p->pUnused);
-+    chromium_sqlite3_destroy_reusable_file_handle(pFile);
-   }
-   return rc;
- }
-diff --git src/os_win.c src/os_win.c
-index bc03a4b..06539d7 100644
---- src/os_win.c
-+++ src/os_win.c
-@@ -1890,4 +1890,11 @@ int sqlite3_os_end(void){
-   return SQLITE_OK;
- }
- 
-+void chromium_sqlite3_initialize_win_sqlite3_file(sqlite3_file* file, HANDLE handle) {
-+  winFile* winSQLite3File = (winFile*)file;
-+  memset(file, 0, sizeof(*file));
-+  winSQLite3File->pMethod = &winIoMethod;
-+  winSQLite3File->h = handle;
-+}
-+
- #endif /* SQLITE_OS_WIN */