LFF files grammar

This page shows the syntactic level and lexical level which the LFF parser uses to analyze LFF files.

Syntactic level

The following grammar is presented in the YACC format. The terminal symbol are written as capital letters, while the not terminal symbol are written as small letters.

   1  file : header packet_formats trailer
   2  hdr_init : HEADER
   3  header : hdr_init structs ENDHH hdefs
   4  trailer : TRAILER structs ENDHT
   6  packet_formats : pheader pdefs psdefs pudefs pwdefs pddefs $$1 ptrailer
   8  packet_formats : packet_formats pheader pdefs psdefs pudefs pwdefs pddefs $$2 ptrailer
   9  pheader : PHEADER structs ENDPH
  10  ptrailer : PTRAILER structs ENDPT
  11  str : str def
  12      | def
  13  structs : str
  14          |
  15  def : BYTE NAME
  16      | WORD NAME
  17      | DWORD NAME
  18  hdefs : hdefs1 hdefs2
  19  hdefs1 : MUSTINVERT ':' expression
  20  hdefs2 : LINKTYPE ':' expression
  21  string : STRING
  22  pdefs : PLEN ':' expression LEN ':' expression TYPE ':' expression CHECK ':' expression FIRSTPROTOCOL ':' stringa
  23  psdefs : SECS ':' expression
  24         |
  25  pudefs : USECS ':' expression
  26         |
  27  pwdefs : WRITTEN ':' expression
  28         |
  29  pddefs : DISCARDED ':' expression
  30         |
  31  expression : NAME
  32              | NUMBER
  33              | NUMBER_H
  34              | '(' expression ')'
  35              | expression '+' expression
  36              | expression MIU expression
  37              | expression MAU expression
  38              | expression '<' expression
  39              | expression '>' expression
  40              | expression NOT_EQ expression
  41              | expression '=' expression
  42              | expression AND expression
  43              | expression OR expression
  44              | expression '-' expression
  45              | expression '*' expression
  46              | expression '/' expression
  47              | expression '%' expression
  48              | '-' expression
  49              | NOT expression

'file' is the beginning symbol.

Here it is the table which shows the priority order of the operators in the expressions:

The lexical level

Here it is a summary of the scanner which recognize the file tokens. This summary is presented in the LEX format.

SPACE ([\t\r\n ])
SPACES ({SPACE}*)
LETTER ([a-zA-Z])
DIGIT ([0-9])
F_DIGIT ([1-9])
DECIMAL ({DIGIT}*{F_DIGIT}|0)
HEX ((("0x")|("0X"))([a-fA-F]|{DIGIT})+)
INTEGER ({F_DIGIT}{DIGIT}*)
VAR_NAME ((("_")|{LETTER})({LETTER}|{DIGIT}|("_"))*)
COST_INT_CORTO ({INTERO}|[0])
OP	([-+=*/%()<>:])
VAR ({VAR_NAME})
COMMENT ("/*"([^*]*|"*"+[^*/])"*"+\/)
COST_STRING (\"[^\"\n]*\")

%%
BYTE {return BYTE;}
WORD {return WORD;}
DWORD {return DWORD;}
AND {return AND;}
"&" {return AND;}
"&&" {return AND;}
OR {return OR;}
"|" {return OR;}
"||" {return OR;}
NOT {return NOT;}
"!" {return NOT;}
"~" {return NOT;}
TYPE {return TYPE;}
CHECK {return CHECK;}
PLEN {return PLEN;}
L'EN {return L'EN;}
SECS {return SECS;}
USECS {return USECS;}
WRITTEN {return WRITTEN;}
DISCARDED {return DISCARDED;}
FIRSTPROTOCOL {return FIRSTPROTOCOL;}
HEADER {return HEADER;}
TRAILER {return TRAILER;}
PHEADER {return PHEADER;}
PTRAILER {return PTRAILER;}
ENDHH {return ENDHH;}
ENDPH {return ENDPH;}
ENDHT {return ENDHT;}
ENDPT {return ENDPT;}
NOT {return NOT;}
"!=" {return NOT_EQ;}
"<=" {return MIU;}
">=" {return MAU;}
MUSTINVERT {return MUSTINVERT;}
LINKTYPE {return LINKTYPE;}
{HEX} {return NUMBER_H;}
{COST_INT_CORTO} {return NUMBER;}
{COMMENT}	{/*the comments are ignored*/ }
{OP} {return yytext[0];}
{VAR}	{return NAME;}
{COST_STRING}	{return STRING;}
{SPACE}+ {/*the spaces are ignored*/}
. {printf("Scanner error at line %d\n",yylineno);return (-1);}
%%

'AND' can be written : 'AND', '&&', '&'

'OR' can be written : 'OR', '||', '|'

'NOT' can be written : 'NOT', '!', '~'

'=' can be written : '==', '='