MDEV-20453 add class similar to std::string_view (non owning string reference)

This version is not optimized yet. It could have bugs because I didn't
check it with unit tests. Also, std::char_traits are not really supported.
So, now it's not possible to create f.ex. a case insensitive string_view.

fil_path_to_space_name(): renamed, moved to another file
and refactored to use string_view

sql/CMakeLists.txt

@@ -143,7 +143,7 @@ SET (SQL_SOURCE
                opt_trace.cc
 	       ${WSREP_SOURCES}
                table_cache.cc encryption.cc temporary_tables.cc
-               proxy_protocol.cc backup.cc xa.cc
+               proxy_protocol.cc backup.cc xa.cc string_view.cc
                ${CMAKE_CURRENT_BINARY_DIR}/sql_builtin.cc
                ${CMAKE_CURRENT_BINARY_DIR}/sql_yacc.cc
                ${CMAKE_CURRENT_BINARY_DIR}/sql_yacc_ora.cc

sql/string_view.cc

+/*****************************************************************************
+
+Copyright (c) 2020 MariaDB Corporation.
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; version 2 of the License.
+
+This program is distributed in the hope that it will be useful, but WITHOUT
+ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License along with
+this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA
+
+*****************************************************************************/
+
+#include "string_view.h"
+
+#include <ostream>
+
+std::basic_ostream<char> &operator<<(std::basic_ostream<char> &os,
+                                     string_view v)
+{
+  // TODO standard requires a much more complicated code here.
+  auto size= static_cast<std::streamsize>(v.size());
+  os.write(v.data(), size);
+  return os;
+}

storage/innobase/fil/fil0fil.cc

@@ -3487,53 +3487,6 @@ fil_space_read_name_and_filepath(
 	return(success);
 }
 
-/** Convert a file name to a tablespace name.
-@param[in]	filename	directory/databasename/tablename.ibd
-@return database/tablename string, to be freed with ut_free() */
-char*
-fil_path_to_space_name(
-	const char*	filename)
-{
-	/* Strip the file name prefix and suffix, leaving
-	only databasename/tablename. */
-	ulint		filename_len	= strlen(filename);
-	const char*	end		= filename + filename_len;
-#ifdef HAVE_MEMRCHR
-	const char*	tablename	= 1 + static_cast<const char*>(
-		memrchr(filename, OS_PATH_SEPARATOR,
-			filename_len));
-	const char*	dbname		= 1 + static_cast<const char*>(
-		memrchr(filename, OS_PATH_SEPARATOR,
-			tablename - filename - 1));
-#else /* HAVE_MEMRCHR */
-	const char*	tablename	= filename;
-	const char*	dbname		= NULL;
-
-	while (const char* t = static_cast<const char*>(
-		       memchr(tablename, OS_PATH_SEPARATOR,
-			      ulint(end - tablename)))) {
-		dbname = tablename;
-		tablename = t + 1;
-	}
-#endif /* HAVE_MEMRCHR */
-
-	ut_ad(dbname != NULL);
-	ut_ad(tablename > dbname);
-	ut_ad(tablename < end);
-	ut_ad(end - tablename > 4);
-	ut_ad(memcmp(end - 4, DOT_IBD, 4) == 0);
-
-	char*	name = mem_strdupl(dbname, ulint(end - dbname) - 4);
-
-	ut_ad(name[tablename - dbname - 1] == OS_PATH_SEPARATOR);
-#if OS_PATH_SEPARATOR != '/'
-	/* space->name uses '/', not OS_PATH_SEPARATOR. */
-	name[tablename - dbname - 1] = '/';
-#endif
-
-	return(name);
-}
-
 /** Discover the correct IBD file to open given a remote or missing
 filepath from the REDO log. Administrators can move a crashed
 database to another location on the same machine and try to recover it.

storage/innobase/fsp/fsp0file.cc

@@ -258,6 +258,28 @@ Datafile::same_as(
 #endif /* WIN32 */
 }
 
+/** Convert a file name to a tablespace name.
+@param[in]	filename	directory/databasename/tablename.ibd
+@return database/tablename string, to be freed with ut_free() */
+static char *fsp_path_to_space_name(string_view filename)
+{
+  auto last_slash= filename.rfind(OS_PATH_SEPARATOR);
+  auto prev_last_slash=
+      filename.substr(0, last_slash).rfind(OS_PATH_SEPARATOR);
+  filename.remove_prefix(prev_last_slash + 1);
+  ut_ad(filename.ends_with(DOT_IBD));
+  filename.remove_suffix(strlen(DOT_IBD));
+
+  char *name= mem_strdupl(filename.data(), filename.size());
+
+#if OS_PATH_SEPARATOR != '/'
+  /* space->name uses '/', not OS_PATH_SEPARATOR. */
+  name[last_slash - prev_last_slash - 1]= '/';
+#endif
+
+  return name;
+}
+
 /** Allocate and set the datafile or tablespace name in m_name.
 If a name is provided, use it; else extract a file-per-table
 tablespace name from m_filepath. The value of m_name
@@ -271,7 +293,7 @@ Datafile::set_name(const char*	name)
 	if (name != NULL) {
 		m_name = mem_strdup(name);
 	} else {
-		m_name = fil_path_to_space_name(m_filepath);
+		m_name = fsp_path_to_space_name(m_filepath);
 	}
 }
 

storage/innobase/include/fil0fil.h

@@ -34,6 +34,7 @@ Created 10/25/1995 Heikki Tuuri
 #include "log0recv.h"
 #include "dict0types.h"
 #include "ilist.h"
+#include "string_view.h"
 #ifdef UNIV_LINUX
 # include <set>
 #endif
@@ -1495,13 +1496,6 @@ fil_space_read_name_and_filepath(
 	char**	name,
 	char**	filepath);
 
-/** Convert a file name to a tablespace name.
-@param[in]	filename	directory/databasename/tablename.ibd
-@return database/tablename string, to be freed with ut_free() */
-char*
-fil_path_to_space_name(
-	const char*	filename);
-
 /** Generate redo log for swapping two .ibd files
 @param[in]	old_table	old table
 @param[in]	new_table	new table