Fix for bug#41486: extra character appears in BLOB for every

~40Mb after mysqldump/import 
        
When the input string exceeds the maximum allowed size for the 
internal buffer, batch_readline() returns a truncated string. 
Since there was no way for a caller to determine whether the 
string was truncated or not, the command line client assumed 
batch_readline() to always return the whole input string and 
appended a newline character. This resulted in garbled data 
when importing dumps containing strings longer than the 
maximum input buffer size. 
  
Fixed by adding a flag to the batch_readline() interface to 
signal a truncated string to the caller. 
  
Other minor problems fixed during patch implementation: 
 
- The maximum allowed buffer size for batch_readline() was set 
up depending on the client's max_allowed_packet value. It does 
not actully make any sense, as those variables are not 
related. The input buffer size limit is now always set to 1 
MB. 
  
- fill_buffer() did not always set the EOF flag. 
 
- The input buffer could actually grow twice as the specified 
limit due to insufficient checks in intern_read_line().

mysql-test/t/mysql.test

@@ -331,4 +331,31 @@ EOF
 
 remove_file $MYSQLTEST_VARDIR/tmp/bug31060.sql;
 
+#  
+# Bug #41486: extra character appears in BLOB for every ~40Mb after   
+#             mysqldump/import   
+#  
+  
+# Have to change the global variable as the mysql client will use 
+# a separate session 
+set @old_max_allowed_packet = @@global.max_allowed_packet; 
+# 2 MB blob length + some space for the rest of INSERT query
+set @@global.max_allowed_packet = 2 * 1024 * 1024 + 1024; 
+set @@max_allowed_packet = @@global.max_allowed_packet;
+
+CREATE TABLE t1(data LONGBLOB);  
+INSERT INTO t1 SELECT REPEAT('1', 2*1024*1024);  
+  
+--exec $MYSQL_DUMP test t1 >$MYSQLTEST_VARDIR/tmp/bug41486.sql  
+# Check that the mysql client does not insert extra newlines when loading  
+# strings longer than client's max_allowed_packet  
+--exec $MYSQL --max_allowed_packet=1M test < $MYSQLTEST_VARDIR/tmp/bug41486.sql 2>&1  
+SELECT LENGTH(data) FROM t1;  
+  
+remove_file $MYSQLTEST_VARDIR/tmp/bug41486.sql; 
+DROP TABLE t1;  
+
+set @@global.max_allowed_packet = @old_max_allowed_packet; 
+set @@max_allowed_packet = @@global.max_allowed_packet;
+ 
 --echo End of 5.0 tests