Create a top-level "third_party" directory

This directory now contains third_party software that is vendored into
the Servo source tree. The idea is that it would eventually hold
webrender and other crates from mozilla-central as well with a standard
patch management approach for each.

third_party/ply/example/yply/yparse.py

@@ -0,0 +1,244 @@
+# parser for Unix yacc-based grammars
+#
+# Author: David Beazley (dave@dabeaz.com)
+# Date  : October 2, 2006
+
+import ylex
+tokens = ylex.tokens
+
+from ply import *
+
+tokenlist = []
+preclist = []
+
+emit_code = 1
+
+
+def p_yacc(p):
+    '''yacc : defsection rulesection'''
+
+
+def p_defsection(p):
+    '''defsection : definitions SECTION
+                  | SECTION'''
+    p.lexer.lastsection = 1
+    print("tokens = ", repr(tokenlist))
+    print()
+    print("precedence = ", repr(preclist))
+    print()
+    print("# -------------- RULES ----------------")
+    print()
+
+
+def p_rulesection(p):
+    '''rulesection : rules SECTION'''
+
+    print("# -------------- RULES END ----------------")
+    print_code(p[2], 0)
+
+
+def p_definitions(p):
+    '''definitions : definitions definition
+                   | definition'''
+
+
+def p_definition_literal(p):
+    '''definition : LITERAL'''
+    print_code(p[1], 0)
+
+
+def p_definition_start(p):
+    '''definition : START ID'''
+    print("start = '%s'" % p[2])
+
+
+def p_definition_token(p):
+    '''definition : toktype opttype idlist optsemi '''
+    for i in p[3]:
+        if i[0] not in "'\"":
+            tokenlist.append(i)
+    if p[1] == '%left':
+        preclist.append(('left',) + tuple(p[3]))
+    elif p[1] == '%right':
+        preclist.append(('right',) + tuple(p[3]))
+    elif p[1] == '%nonassoc':
+        preclist.append(('nonassoc',) + tuple(p[3]))
+
+
+def p_toktype(p):
+    '''toktype : TOKEN
+               | LEFT
+               | RIGHT
+               | NONASSOC'''
+    p[0] = p[1]
+
+
+def p_opttype(p):
+    '''opttype : '<' ID '>'
+               | empty'''
+
+
+def p_idlist(p):
+    '''idlist  : idlist optcomma tokenid
+               | tokenid'''
+    if len(p) == 2:
+        p[0] = [p[1]]
+    else:
+        p[0] = p[1]
+        p[1].append(p[3])
+
+
+def p_tokenid(p):
+    '''tokenid : ID 
+               | ID NUMBER
+               | QLITERAL
+               | QLITERAL NUMBER'''
+    p[0] = p[1]
+
+
+def p_optsemi(p):
+    '''optsemi : ';'
+               | empty'''
+
+
+def p_optcomma(p):
+    '''optcomma : ','
+                | empty'''
+
+
+def p_definition_type(p):
+    '''definition : TYPE '<' ID '>' namelist optsemi'''
+    # type declarations are ignored
+
+
+def p_namelist(p):
+    '''namelist : namelist optcomma ID
+                | ID'''
+
+
+def p_definition_union(p):
+    '''definition : UNION CODE optsemi'''
+    # Union declarations are ignored
+
+
+def p_rules(p):
+    '''rules   : rules rule
+               | rule'''
+    if len(p) == 2:
+        rule = p[1]
+    else:
+        rule = p[2]
+
+    # Print out a Python equivalent of this rule
+
+    embedded = []      # Embedded actions (a mess)
+    embed_count = 0
+
+    rulename = rule[0]
+    rulecount = 1
+    for r in rule[1]:
+        # r contains one of the rule possibilities
+        print("def p_%s_%d(p):" % (rulename, rulecount))
+        prod = []
+        prodcode = ""
+        for i in range(len(r)):
+            item = r[i]
+            if item[0] == '{':    # A code block
+                if i == len(r) - 1:
+                    prodcode = item
+                    break
+                else:
+                    # an embedded action
+                    embed_name = "_embed%d_%s" % (embed_count, rulename)
+                    prod.append(embed_name)
+                    embedded.append((embed_name, item))
+                    embed_count += 1
+            else:
+                prod.append(item)
+        print("    '''%s : %s'''" % (rulename, " ".join(prod)))
+        # Emit code
+        print_code(prodcode, 4)
+        print()
+        rulecount += 1
+
+    for e, code in embedded:
+        print("def p_%s(p):" % e)
+        print("    '''%s : '''" % e)
+        print_code(code, 4)
+        print()
+
+
+def p_rule(p):
+    '''rule : ID ':' rulelist ';' '''
+    p[0] = (p[1], [p[3]])
+
+
+def p_rule2(p):
+    '''rule : ID ':' rulelist morerules ';' '''
+    p[4].insert(0, p[3])
+    p[0] = (p[1], p[4])
+
+
+def p_rule_empty(p):
+    '''rule : ID ':' ';' '''
+    p[0] = (p[1], [[]])
+
+
+def p_rule_empty2(p):
+    '''rule : ID ':' morerules ';' '''
+
+    p[3].insert(0, [])
+    p[0] = (p[1], p[3])
+
+
+def p_morerules(p):
+    '''morerules : morerules '|' rulelist
+                 | '|' rulelist
+                 | '|'  '''
+
+    if len(p) == 2:
+        p[0] = [[]]
+    elif len(p) == 3:
+        p[0] = [p[2]]
+    else:
+        p[0] = p[1]
+        p[0].append(p[3])
+
+#   print("morerules", len(p), p[0])
+
+
+def p_rulelist(p):
+    '''rulelist : rulelist ruleitem
+                | ruleitem'''
+
+    if len(p) == 2:
+        p[0] = [p[1]]
+    else:
+        p[0] = p[1]
+        p[1].append(p[2])
+
+
+def p_ruleitem(p):
+    '''ruleitem : ID
+                | QLITERAL
+                | CODE
+                | PREC'''
+    p[0] = p[1]
+
+
+def p_empty(p):
+    '''empty : '''
+
+
+def p_error(p):
+    pass
+
+yacc.yacc(debug=0)
+
+
+def print_code(code, indent):
+    if not emit_code:
+        return
+    codelines = code.splitlines()
+    for c in codelines:
+        print("%s# %s" % (" " * indent, c))