Replace flags argument to Sql.open with single bool

Previously, "flags" argument of Sql.open was of type libc::c_int, but
only one bit was used: whether to open database read-only. This commit
makes it explicit by changing type to bool and renaming argument.

src/context.rs

@@ -150,7 +150,7 @@ impl Context {
         };
 
         ensure!(
-            ctx.sql.open(&ctx, &ctx.dbfile, 0),
+            ctx.sql.open(&ctx, &ctx.dbfile, false),
             "Failed opening sqlite database"
         );
 

src/imex.rs

@@ -87,7 +87,7 @@ pub fn has_backup(context: &Context, dir_name: impl AsRef<Path>) -> Result<Strin
                 let name = name.to_string_lossy();
                 if name.starts_with("delta-chat") && name.ends_with(".bak") {
                     let sql = Sql::new();
-                    if sql.open(context, &path, 0x1) {
+                    if sql.open(context, &path, true) {
                         let curr_backup_time =
                             sql.get_raw_config_int(context, "backup_time")
                                 .unwrap_or_default() as u64;
@@ -413,7 +413,7 @@ fn import_backup(context: &Context, backup_to_import: impl AsRef<Path>) -> Resul
     /* error already logged */
     /* re-open copied database file */
     ensure!(
-        context.sql.open(&context, &context.get_dbfile(), 0),
+        context.sql.open(&context, &context.get_dbfile(), false),
         "could not re-open db"
     );
 
@@ -496,7 +496,7 @@ fn export_backup(context: &Context, dir: impl AsRef<Path>) -> Result<()> {
         dest_path_filename.display(),
     );
     let copied = dc_copy_file(context, context.get_dbfile(), &dest_path_filename);
-    context.sql.open(&context, &context.get_dbfile(), 0);
+    context.sql.open(&context, &context.get_dbfile(), false);
     if !copied {
         let s = dest_path_filename.to_string_lossy().to_string();
         bail!(
@@ -526,7 +526,7 @@ fn add_files_to_export(context: &Context, dest_path_filename: &PathBuf) -> Resul
     // the source to be locked, neigher the destination as it is used only here)
     let sql = Sql::new();
     ensure!(
-        sql.open(context, &dest_path_filename, 0),
+        sql.open(context, &dest_path_filename, false),
         "could not open db"
     );
     if !sql.table_exists("backup_blobs") {

src/sql.rs

@@ -11,8 +11,6 @@ use crate::error::{Error, Result};
 use crate::param::*;
 use crate::peerstate::*;
 
-const DC_OPEN_READONLY: usize = 0x01;
-
 /// A wrapper around the underlying Sqlite3 object.
 #[derive(DebugStub)]
 pub struct Sql {
@@ -42,8 +40,8 @@ impl Sql {
     }
 
     // return true on success, false on failure
-    pub fn open(&self, context: &Context, dbfile: &std::path::Path, flags: libc::c_int) -> bool {
-        match open(context, self, dbfile, flags) {
+    pub fn open(&self, context: &Context, dbfile: &std::path::Path, readonly: bool) -> bool {
+        match open(context, self, dbfile, readonly) {
             Ok(_) => true,
             Err(Error::SqlAlreadyOpen) => false,
             Err(_) => {
@@ -320,7 +318,7 @@ fn open(
     context: &Context,
     sql: &Sql,
     dbfile: impl AsRef<std::path::Path>,
-    flags: libc::c_int,
+    readonly: bool,
 ) -> Result<()> {
     if sql.is_open() {
         error!(
@@ -332,7 +330,7 @@ fn open(
     }
 
     let mut open_flags = OpenFlags::SQLITE_OPEN_NO_MUTEX;
-    if 0 != (flags & DC_OPEN_READONLY as i32) {
+    if readonly {
         open_flags.insert(OpenFlags::SQLITE_OPEN_READ_ONLY);
     } else {
         open_flags.insert(OpenFlags::SQLITE_OPEN_READ_WRITE);
@@ -351,7 +349,7 @@ fn open(
         *sql.pool.write().unwrap() = Some(pool);
     }
 
-    if 0 == flags & DC_OPEN_READONLY as i32 {
+    if !readonly {
         let mut exists_before_update = 0;
         let mut dbversion_before_update = 0;
         /* Init tables to dbversion=0 */