Revert MDEV-20453 (string_view)

In fsp_path_to_space_name(), we would access a byte right before
the start of the string, tripping AddressSanitizer.

This reverts commit d87006a1c1e775ac75b6cc21c8a243b8b4e61571
and commit a7634281aa64a549d19cd20ead7e80d0267271ee.

3 files changed, 55 insertions, 24 deletions

diff --git a/storage/innobase/fil/fil0fil.cc b/storage/innobase/fil/fil0fil.cc
index ae579ce46ba..f076f32e50f 100644
--- a/storage/innobase/fil/fil0fil.cc
+++ b/storage/innobase/fil/fil0fil.cc
@@ -3487,6 +3487,53 @@ 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.
diff --git a/storage/innobase/fsp/fsp0file.cc b/storage/innobase/fsp/fsp0file.cc
index 670beac2579..653b74c73be 100644
--- a/storage/innobase/fsp/fsp0file.cc
+++ b/storage/innobase/fsp/fsp0file.cc
@@ -30,7 +30,6 @@ Created 2013-7-26 by Kevin Lewis
 #include "page0page.h"
 #include "srv0start.h"
 
-#include "string_view.h"
 /** Initialize the name, size and order of this datafile
 @param[in]	name	tablespace name, will be copied
 @param[in]	flags	tablespace flags */
@@ -259,28 +258,6 @@ 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
@@ -294,7 +271,7 @@ Datafile::set_name(const char*	name)
 	if (name != NULL) {
 		m_name = mem_strdup(name);
 	} else {
-		m_name = fsp_path_to_space_name(m_filepath);
+		m_name = fil_path_to_space_name(m_filepath);
 	}
 }
 
diff --git a/storage/innobase/include/fil0fil.h b/storage/innobase/include/fil0fil.h
index ecba2db8e06..21f21d95ebc 100644
--- a/storage/innobase/include/fil0fil.h
+++ b/storage/innobase/include/fil0fil.h
@@ -1495,6 +1495,13 @@ 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