mdbx: добавление опции MDBX_CP_OVERWRITE в API копирования БД.

mdbx.h

@@ -1666,7 +1666,7 @@ DEFINE_ENUM_FLAG_OPERATORS(MDBX_put_flags)
 
 /** \brief Environment copy flags
  * \ingroup c_extra
- * \see mdbx_env_copy() \see mdbx_env_copy2fd() */
+ * \see mdbx_env_copy() \see mdbx_env_copy2fd() \see mdbx_txn_copy2pathname() */
 typedef enum MDBX_copy_flags {
   MDBX_CP_DEFAULTS = 0,
 
@@ -1691,7 +1691,11 @@ typedef enum MDBX_copy_flags {
   /** Enable renew/restart read transaction in case it use outdated
    * MVCC shapshot, otherwise the \ref MDBX_MVCC_RETARDED will be returned
    * \see mdbx_txn_copy2fd() \see mdbx_txn_copy2pathname() */
-  MDBX_CP_RENEW_TXN = 32u
+  MDBX_CP_RENEW_TXN = 32u,
+
+  /** Silently overwrite the target file, if it exists, instead of returning an error
+   * \see mdbx_txn_copy2pathname() \see mdbx_env_copy() */
+  MDBX_CP_OVERWRITE = 64u
 
 } MDBX_copy_flags_t;
 DEFINE_ENUM_FLAG_OPERATORS(MDBX_copy_flags)

src/api-copy.c

@@ -748,7 +748,8 @@ __cold static int copy2pathname(MDBX_txn *txn, const pathchar_t *dest_path, MDBX
    * We don't want the OS to cache the writes, since the source data is
    * already in the OS cache. */
   mdbx_filehandle_t newfd = INVALID_HANDLE_VALUE;
-  int rc = osal_openfile(MDBX_OPEN_COPY, txn->env, dest_path, &newfd,
+  int rc = osal_openfile((flags & MDBX_CP_OVERWRITE) ? MDBX_OPEN_COPY_OVERWRITE : MDBX_OPEN_COPY_EXCL, txn->env,
+                         dest_path, &newfd,
 #if defined(_WIN32) || defined(_WIN64)
                          (mdbx_mode_t)-1
 #else

src/osal.c

@@ -1198,29 +1198,29 @@ MDBX_INTERNAL int osal_openfile(const enum osal_openfile_purpose purpose, const
     break;
   case MDBX_OPEN_DXB_OVERLAPPED_DIRECT:
     FlagsAndAttributes |= FILE_FLAG_NO_BUFFERING;
-    /* fall through */
-    __fallthrough;
+    __fallthrough /* fall through */;
   case MDBX_OPEN_DXB_OVERLAPPED:
     FlagsAndAttributes |= FILE_FLAG_OVERLAPPED;
-    /* fall through */
-    __fallthrough;
+    __fallthrough /* fall through */;
   case MDBX_OPEN_DXB_DSYNC:
     CreationDisposition = OPEN_EXISTING;
     DesiredAccess |= GENERIC_WRITE | GENERIC_READ;
     FlagsAndAttributes |= FILE_FLAG_WRITE_THROUGH;
     break;
-  case MDBX_OPEN_COPY:
-    CreationDisposition = CREATE_NEW;
-    ShareMode = 0;
-    DesiredAccess |= GENERIC_WRITE;
-    if (env->ps >= globals.sys_pagesize)
-      FlagsAndAttributes |= FILE_FLAG_NO_BUFFERING;
-    break;
   case MDBX_OPEN_DELETE:
     CreationDisposition = OPEN_EXISTING;
     ShareMode |= FILE_SHARE_DELETE;
     DesiredAccess = FILE_READ_ATTRIBUTES | FILE_WRITE_ATTRIBUTES | DELETE | SYNCHRONIZE;
     break;
+  case MDBX_OPEN_COPY_EXCL:
+    CreationDisposition = CREATE_NEW;
+    __fallthrough /* fall through */;
+  case MDBX_OPEN_COPY_OVERWRITE:
+    ShareMode = 0;
+    DesiredAccess |= GENERIC_WRITE;
+    if (env->ps >= globals.sys_pagesize)
+      FlagsAndAttributes |= FILE_FLAG_NO_BUFFERING;
+    break;
   }
 
   *fd = CreateFileW(pathname, DesiredAccess, ShareMode, nullptr, CreationDisposition, FlagsAndAttributes, nullptr);
@@ -1260,9 +1260,6 @@ MDBX_INTERNAL int osal_openfile(const enum osal_openfile_purpose purpose, const
   case MDBX_OPEN_DXB_LAZY:
     flags |= O_RDWR;
     break;
-  case MDBX_OPEN_COPY:
-    flags = O_CREAT | O_WRONLY | O_EXCL;
-    break;
   case MDBX_OPEN_DXB_DSYNC:
     flags |= O_WRONLY;
 #if defined(O_DSYNC)
@@ -1276,9 +1273,14 @@ MDBX_INTERNAL int osal_openfile(const enum osal_openfile_purpose purpose, const
   case MDBX_OPEN_DELETE:
     flags = O_RDWR;
     break;
+  case MDBX_OPEN_COPY_EXCL:
+    flags |= O_EXCL;
+    __fallthrough /* fall through */;
+  case MDBX_OPEN_COPY_OVERWRITE:
+    flags |= O_WRONLY;
   }
 
-  const bool direct_nocache_for_copy = env->ps >= globals.sys_pagesize && purpose == MDBX_OPEN_COPY;
+  const bool direct_nocache_for_copy = env->ps >= globals.sys_pagesize && purpose >= MDBX_OPEN_COPY_EXCL;
   if (direct_nocache_for_copy) {
 #if defined(O_DIRECT)
     flags |= O_DIRECT;

src/osal.h

@@ -446,8 +446,9 @@ enum osal_openfile_purpose {
   MDBX_OPEN_DXB_OVERLAPPED_DIRECT,
 #endif /* Windows */
   MDBX_OPEN_LCK,
-  MDBX_OPEN_COPY,
-  MDBX_OPEN_DELETE
+  MDBX_OPEN_DELETE,
+  MDBX_OPEN_COPY_EXCL,
+  MDBX_OPEN_COPY_OVERWRITE,
 };
 
 MDBX_MAYBE_UNUSED static inline bool osal_isdirsep(pathchar_t c) {