parse.y

nedit 是一款linux下的开发源码的功能强大的编辑器

            | numexpr GT numexpr  {
                ADD_OP(OP_GT);
            }
            | numexpr GE numexpr  {
                ADD_OP(OP_GE);
            }
            | numexpr LT numexpr  {
                ADD_OP(OP_LT);
            }
            | numexpr LE numexpr  {
                ADD_OP(OP_LE);
            }
            | numexpr EQ numexpr  {
                ADD_OP(OP_EQ);
            }
            | numexpr NE numexpr  {
                ADD_OP(OP_NE);
            }
            | numexpr '&' numexpr {
                ADD_OP(OP_BIT_AND);
            }
            | numexpr '|' numexpr  {
                ADD_OP(OP_BIT_OR);
            }
            | numexpr and numexpr %prec AND {
                ADD_OP(OP_AND); SET_BR_OFF($2, GetPC());
            }
            | numexpr or numexpr %prec OR {
                ADD_OP(OP_OR); SET_BR_OFF($2, GetPC());
            }
            | NOT numexpr {
                ADD_OP(OP_NOT);
            }
            | INCR SYMBOL {
                ADD_OP(OP_PUSH_SYM); ADD_SYM($2); ADD_OP(OP_INCR);
                ADD_OP(OP_DUP); ADD_OP(OP_ASSIGN); ADD_SYM($2);
            }
            | SYMBOL INCR {
                ADD_OP(OP_PUSH_SYM); ADD_SYM($1); ADD_OP(OP_DUP);
                ADD_OP(OP_INCR); ADD_OP(OP_ASSIGN); ADD_SYM($1);
            }
            | DECR SYMBOL {
                ADD_OP(OP_PUSH_SYM); ADD_SYM($2); ADD_OP(OP_DECR);
                ADD_OP(OP_DUP); ADD_OP(OP_ASSIGN); ADD_SYM($2);
            }
            | SYMBOL DECR {
                ADD_OP(OP_PUSH_SYM); ADD_SYM($1); ADD_OP(OP_DUP);
                ADD_OP(OP_DECR); ADD_OP(OP_ASSIGN); ADD_SYM($1);
            }
            | numexpr IN numexpr {
                ADD_OP(OP_IN_ARRAY);
            }
            ;
while:  WHILE {
            $$ = GetPC(); StartLoopAddrList();
        }
        ;
for:    FOR {
            StartLoopAddrList(); $$ = GetPC();
        }
        ;
else:   ELSE {
            ADD_OP(OP_BRANCH); $$ = GetPC(); ADD_BR_OFF(0);
        }
        ;
cond:   /* nothing */ {
            ADD_OP(OP_BRANCH_NEVER); $$ = GetPC(); ADD_BR_OFF(0);
        }
        | numexpr {
            ADD_OP(OP_BRANCH_FALSE); $$ = GetPC(); ADD_BR_OFF(0);
        }
        ;
and:    AND {
            ADD_OP(OP_DUP); ADD_OP(OP_BRANCH_FALSE); $$ = GetPC();
            ADD_BR_OFF(0);
        }
        ;
or:     OR {
            ADD_OP(OP_DUP); ADD_OP(OP_BRANCH_TRUE); $$ = GetPC();
            ADD_BR_OFF(0);
        }
        ;
blank:  /* nothing */
        | blank '\n'
        ;

%% /* User Subroutines Section */


/*
** Parse a null terminated string and create a program from it (this is the
** parser entry point).  The program created by this routine can be
** executed using ExecuteProgram.  Returns program on success, or NULL
** on failure.  If the command failed, the error message is returned
** as a pointer to a static string in msg, and the length of the string up
** to where parsing failed in stoppedAt.
*/
Program *ParseMacro(char *expr, char **msg, char **stoppedAt)
{
    Program *prog;

    BeginCreatingProgram();

    /* call yyparse to parse the string and check for success.  If the parse
       failed, return the error message and string index (the grammar aborts
       parsing at the first error) */
    InPtr = expr;
    if (yyparse()) {
        *msg = ErrMsg;
        *stoppedAt = InPtr;
        FreeProgram(FinishCreatingProgram());
        return NULL;
    }

    /* get the newly created program */
    prog = FinishCreatingProgram();

    /* parse succeeded */
    *msg = "";
    *stoppedAt = InPtr;
    return prog;
}


static int yylex(void)
{
    int i, len;
    Symbol *s;
    static DataValue value = {NO_TAG, {0}};
    static char escape[] = "\\\"ntbrfav";
    static char replace[] = "\\\"\n\t\b\r\f\a\v";

    /* skip whitespace, backslash-newline combinations, and comments, which are
       all considered whitespace */
    for (;;) {
        if (*InPtr == '\\' && *(InPtr + 1) == '\n')
            InPtr += 2;
        else if (*InPtr == ' ' || *InPtr == '\t')
            InPtr++;
        else if (*InPtr == '#')
            while (*InPtr != '\n' && *InPtr != '\0') {
                /* Comments stop at escaped newlines */
                if (*InPtr == '\\' && *(InPtr + 1) == '\n') {
                    InPtr += 2;
                    break;
                }
                InPtr++;
            }        else
            break;
    }


    /* return end of input at the end of the string */
    if (*InPtr == '\0') {
        return 0;
    }

    /* process number tokens */
    if (isdigit((unsigned char)*InPtr))  { /* number */
        char name[28];
        sscanf(InPtr, "%d%n", &value.val.n, &len);
        sprintf(name, "const %d", value.val.n);
        InPtr += len;
        value.tag = INT_TAG;
        if ((yylval.sym=LookupSymbol(name)) == NULL)
            yylval.sym = InstallSymbol(name, CONST_SYM, value);
        return NUMBER;
    }

    /* process symbol tokens.  "define" is a special case not handled
       by this parser, considered end of input.  Another special case
       is action routine names which are allowed to contain '-' despite
       the ambiguity, handled in matchesActionRoutine. */
    if (isalpha((unsigned char)*InPtr) || *InPtr == '$') {
        if ((s=matchesActionRoutine(&InPtr)) == NULL) {
            char symName[MAX_SYM_LEN+1], *p = symName;
            *p++ = *InPtr++;
            while (isalnum((unsigned char)*InPtr) || *InPtr=='_') {
                if (p >= symName + MAX_SYM_LEN)
                    InPtr++;
                else
                    *p++ = *InPtr++;
            }
            *p = '\0';
            if (!strcmp(symName, "while")) return WHILE;
            if (!strcmp(symName, "if")) return IF;
            if (!strcmp(symName, "else")) return ELSE;
            if (!strcmp(symName, "for")) return FOR;
            if (!strcmp(symName, "break")) return BREAK;
            if (!strcmp(symName, "continue")) return CONTINUE;
            if (!strcmp(symName, "return")) return RETURN;
        if (!strcmp(symName, "in")) return IN;
        if (!strcmp(symName, "delete") && follow_non_whitespace('(', SYMBOL, DELETE) == DELETE) return DELETE;
            if (!strcmp(symName, "define")) {
                InPtr -= 6;
                return 0;
            }
            if ((s=LookupSymbol(symName)) == NULL) {
                s = InstallSymbol(symName, symName[0]=='$' ?
                        (isdigit((unsigned char)symName[1]) ?
                        ARG_SYM : GLOBAL_SYM) : LOCAL_SYM, value);
                s->value.tag = NO_TAG;
            }
        }
        yylval.sym = s;
        return SYMBOL;
    }

    /* process quoted strings w/ embedded escape sequences */
    if (*InPtr == '\"') {
        char string[MAX_STRING_CONST_LEN], *p = string;
        InPtr++;
        while (*InPtr != '\0' && *InPtr != '\"' && *InPtr != '\n') {
            if (p >= string + MAX_STRING_CONST_LEN) {
                InPtr++;
                continue;
            }
            if (*InPtr == '\\') {
                InPtr++;
                if (*InPtr == '\n') {
                    InPtr++;
                    continue;
                }
                for (i=0; escape[i]!='\0'; i++) {
                    if (escape[i] == '\0') {
                        *p++= *InPtr++;
                        break;
                    } else if (escape[i] == *InPtr) {
                        *p++ = replace[i];
                        InPtr++;
                        break;
                    }
                }
            } else
                *p++= *InPtr++;
        }
        *p = '\0';
        InPtr++;
        yylval.sym = InstallStringConstSymbol(string);
        return STRING;
    }

    /* process remaining two character tokens or return single char as token */
    switch(*InPtr++) {
    case '>':   return follow('=', GE, GT);
    case '<':   return follow('=', LE, LT);
    case '=':   return follow('=', EQ, '=');
    case '!':   return follow('=', NE, NOT);
    case '+':   return follow2('+', INCR, '=', ADDEQ, '+');
    case '-':   return follow2('-', DECR, '=', SUBEQ, '-');
    case '|':   return follow2('|', OR, '=', OREQ, '|');
    case '&':   return follow2('&', AND, '=', ANDEQ, '&');
    case '*':   return follow2('*', POW, '=', MULEQ, '*');
    case '/':   return follow('=', DIVEQ, '/');
    case '%':   return follow('=', MODEQ, '%');
    case '^':   return POW;
    default:    return *(InPtr-1);
    }
}

/*
** look ahead for >=, etc.
*/
static int follow(char expect, int yes, int no)
{
    if (*InPtr++ == expect)
        return yes;
    InPtr--;
    return no;
}
static int follow2(char expect1, int yes1, char expect2, int yes2, int no)
{
    char next = *InPtr++;
    if (next == expect1)
        return yes1;
    if (next == expect2)
        return yes2;
    InPtr--;
    return no;
}

static int follow_non_whitespace(char expect, int yes, int no)
{
    char *localInPtr = InPtr;

    while (1) {
        if (*localInPtr == ' ' || *localInPtr == '\t') {
            ++localInPtr;
        }
        else if (*localInPtr == '\\' && *(localInPtr + 1) == '\n') {
            localInPtr += 2;
        }
        else if (*localInPtr == expect) {
            return(yes);
        }
        else {
            return(no);
        }
    }
}

/*
** Look (way) ahead for hyphenated routine names which begin at inPtr.  A
** hyphenated name is allowed if it is pre-defined in the global symbol
** table.  If a matching name exists, returns the symbol, and update "inPtr".
**
** I know this is horrible language design, but existing nedit action routine
** names contain hyphens.  Handling them here in the lexical analysis process
** is much easier than trying to deal with it in the parser itself.  (sorry)
*/
static Symbol *matchesActionRoutine(char **inPtr)
{
    char *c, *symPtr;
    int hasDash = False;
    char symbolName[MAX_SYM_LEN+1];
    Symbol *s;

    symPtr = symbolName;
    for (c = *inPtr; isalnum((unsigned char)*c) || *c=='_' ||
            ( *c=='-' && isalnum((unsigned char)(*(c+1)))); c++) {
        if (*c == '-')
            hasDash = True;
        *symPtr++ = *c;
    }
    if (!hasDash)
        return NULL;
    *symPtr = '\0';
    s = LookupSymbol(symbolName);
    if (s != NULL)
        *inPtr = c;
    return s;
}

/*
** Called by yacc to report errors (just stores for returning when
** parsing is aborted.  The error token action is to immediate abort
** parsing, so this message is immediately reported to the caller
** of ParseExpr)
*/
static int yyerror(char *s)
{
    ErrMsg = s;
    return 0;
}