8325600: Better symbol storage

Reviewed-by: mbalao, andrew
Backport-of: da06689bf6fde7b6dd8efc2f0c39fc95adcdb69d

Author: Aleksei Voitylov

hotspot/src/share/vm/classfile/symbolTable.cpp

@@ -237,17 +237,22 @@ unsigned int SymbolTable::hash_symbol(const char* s, int len) {
 // safepoints).
 
 // Symbols should represent entities from the constant pool that are
-// limited to 64K in length, but usage errors creep in allowing Symbols
+// limited to <64K in length, but usage errors creep in allowing Symbols
 // to be used for arbitrary strings. For debug builds we will assert if
 // a string is too long, whereas product builds will truncate it.
-Symbol* SymbolTable::lookup(const char* name, int len, TRAPS) {
+static int check_length(const char* name, int len) {
   assert(len <= Symbol::max_length(),
          "String length exceeds the maximum Symbol length");
   if (len > Symbol::max_length()) {
     warning("A string \"%.80s ... %.80s\" exceeds the maximum Symbol "
             "length of %d and has been truncated", name, (name + len - 80), Symbol::max_length());
     len = Symbol::max_length();
   }
+  return len;
+}
+
+Symbol* SymbolTable::lookup(const char* name, int len, TRAPS) {
+  len = check_length(name, len);
   unsigned int hashValue = hash_symbol(name, len);
   int index = the_table()->hash_to_index(hashValue);
 
@@ -387,7 +392,8 @@ void SymbolTable::add(ClassLoaderData* loader_data, constantPoolHandle cp,
 
 Symbol* SymbolTable::new_permanent_symbol(const char* name, TRAPS) {
   unsigned int hash;
-  Symbol* result = SymbolTable::lookup_only((char*)name, (int)strlen(name), hash);
+  int len = check_length(name, (int)strlen(name));
+  Symbol* result = SymbolTable::lookup_only((char*)name, len, hash);
   if (result != NULL) {
     return result;
   }
@@ -396,7 +402,7 @@ Symbol* SymbolTable::new_permanent_symbol(const char* name, TRAPS) {
 
   SymbolTable* table = the_table();
   int index = table->hash_to_index(hash);
-  return table->basic_add(index, (u1*)name, (int)strlen(name), hash, false, THREAD);
+  return table->basic_add(index, (u1*)name, len, hash, false, THREAD);
 }
 
 Symbol* SymbolTable::basic_add(int index_arg, u1 *name, int len,