tclexpr.c

tcl源码详细资料

#ifndef EXCLUDE_TCL

/* 
 * tclExpr.c --
 *
 *	This file contains the code to evaluate expressions for
 *	Tcl.
 *
 *	This implementation of floating-point support was modelled
 *	after an initial implementation by Bill Carpenter.
 *
 * Copyright 1987-1991 Regents of the University of California
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies.  The University of California
 * makes no representations about the suitability of this
 * software for any purpose.  It is provided "as is" without
 * express or implied warranty.
 */

#include "tclInt.h"

/*
 * The stuff below is a bit of a hack so that this file can be used
 * in environments that include no UNIX, i.e. no errno.  Just define
 * errno here.
 */

#ifndef TCL_GENERIC_ONLY
#include "tclUnix.h"
#endif

/*
 * The data structure below is used to describe an expression value,
 * which can be either an integer (the usual case), a double-precision
 * floating-point value, or a string.  A given number has only one
 * value at a time.
 */

#define STATIC_STRING_SPACE 150

typedef struct {
    long intValue;		/* Integer value, if any. */
    double  doubleValue;	/* Floating-point value, if any. */
    ParseValue pv;		/* Used to hold a string value, if any. */
    char staticSpace[STATIC_STRING_SPACE];
				/* Storage for small strings;  large ones
				 * are malloc-ed. */
    int type;			/* Type of value:  TYPE_INT, TYPE_DOUBLE,
				 * or TYPE_STRING. */
} Value;

/*
 * Valid values for type:
 */

#define TYPE_INT	0
#define TYPE_DOUBLE	1
#define TYPE_STRING	2


/*
 * The data structure below describes the state of parsing an expression.
 * It's passed among the routines in this module.
 */

typedef struct {
    char *originalExpr;		/* The entire expression, as originally
				 * passed to Tcl_Expr. */
    char *expr;			/* Position to the next character to be
				 * scanned from the expression string. */
    int token;			/* Type of the last token to be parsed from
				 * expr.  See below for definitions.
				 * Corresponds to the characters just
				 * before expr. */
} ExprInfo;

/*
 * The token types are defined below.  In addition, there is a table
 * associating a precedence with each operator.  The order of types
 * is important.  Consult the code before changing it.
 */

#define VALUE		0
#define OPEN_PAREN	1
#define CLOSE_PAREN	2
#define END		3
#define UNKNOWN		4

/*
 * Binary operators:
 */

#define MULT		8
#define DIVIDE		9
#define MOD		10
#define PLUS		11
#define MINUS		12
#define LEFT_SHIFT	13
#define RIGHT_SHIFT	14
#define LESS		15
#define GREATER		16
#define LEQ		17
#define GEQ		18
#define EQUAL		19
#define NEQ		20
#define BIT_AND		21
#define BIT_XOR		22
#define BIT_OR		23
#define AND		24
#define OR		25
#define QUESTY		26
#define COLON		27

/*
 * Unary operators:
 */

#define	UNARY_MINUS	28
#define NOT		29
#define BIT_NOT		30

/*
 * Precedence table.  The values for non-operator token types are ignored.
 */

int precTable[] = {
    0, 0, 0, 0, 0, 0, 0, 0,
    11, 11, 11,				/* MULT, DIVIDE, MOD */
    10, 10,				/* PLUS, MINUS */
    9, 9,				/* LEFT_SHIFT, RIGHT_SHIFT */
    8, 8, 8, 8,				/* LESS, GREATER, LEQ, GEQ */
    7, 7,				/* EQUAL, NEQ */
    6,					/* BIT_AND */
    5,					/* BIT_XOR */
    4,					/* BIT_OR */
    3,					/* AND */
    2,					/* OR */
    1, 1,				/* QUESTY, COLON */
    12, 12, 12				/* UNARY_MINUS, NOT, BIT_NOT */
};

/*
 * Mapping from operator numbers to strings;  used for error messages.
 */

char *operatorStrings[] = {
    "VALUE", "(", ")", "END", "UNKNOWN", "5", "6", "7",
    "*", "/", "%", "+", "-", "<<", ">>", "<", ">", "<=",
    ">=", "==", "!=", "&", "^", "|", "&&", "||", "?", ":",
    "-", "!", "~"
};

/*
 * Declarations for local procedures to this file:
 */

static int		ExprGetValue _ANSI_ARGS_((Tcl_Interp *interp,
			    ExprInfo *infoPtr, int prec, Value *valuePtr));
static int		ExprLex _ANSI_ARGS_((Tcl_Interp *interp,
			    ExprInfo *infoPtr, Value *valuePtr));
static void		ExprMakeString _ANSI_ARGS_((Value *valuePtr));
static int		ExprParseString _ANSI_ARGS_((Tcl_Interp *interp,
			    char *string, Value *valuePtr));
static int		ExprTopLevel _ANSI_ARGS_((Tcl_Interp *interp,
			    char *string, Value *valuePtr));

/*
 *--------------------------------------------------------------
 *
 * ExprParseString --
 *
 *	Given a string (such as one coming from command or variable
 *	substitution), make a Value based on the string.  The value
 *	will be a floating-point or integer, if possible, or else it
 *	will just be a copy of the string.
 *
 * Results:
 *	TCL_OK is returned under normal circumstances, and TCL_ERROR
 *	is returned if a floating-point overflow or underflow occurred
 *	while reading in a number.  The value at *valuePtr is modified
 *	to hold a number, if possible.
 *
 * Side effects:
 *	None.
 *
 *--------------------------------------------------------------
 */

static int
ExprParseString(interp, string, valuePtr)
    Tcl_Interp *interp;		/* Where to store error message. */
    char *string;		/* String to turn into value. */
    Value *valuePtr;		/* Where to store value information. 
				 * Caller must have initialized pv field. */
{
    register char c;

    /*
     * Try to convert the string to a number.
     */

    c = *string;
    if (((c >= '0') && (c <= '9')) || (c == '-') || (c == '.')) {
	char *term;

	valuePtr->type = TYPE_INT;
	errno = 0;
	valuePtr->intValue = strtol(string, &term, 0);
	c = *term;
	if ((c == '\0') && (errno != ERANGE)) {
	    return TCL_OK;
	}
	if ((c == '.') || (c == 'e') || (c == 'E') || (errno == ERANGE)) {
	    errno = 0;
	    valuePtr->doubleValue = strtod(string, &term);
	    if (errno == ERANGE) {
		Tcl_ResetResult(interp);
		if (valuePtr->doubleValue == 0.0) {
		    Tcl_AppendResult(interp, "floating-point value \"",
			    string, "\" too small to represent",
			    (char *) NULL);
		} else {
		    Tcl_AppendResult(interp, "floating-point value \"",
			    string, "\" too large to represent",
			    (char *) NULL);
		}
		return TCL_ERROR;
	    }
	    if (*term == '\0') {
		valuePtr->type = TYPE_DOUBLE;
		return TCL_OK;
	    }
	}
    }

    /*
     * Not a valid number.  Save a string value (but don't do anything
     * if it's already the value).
     */

    valuePtr->type = TYPE_STRING;
    if (string != valuePtr->pv.buffer) {
	int length, shortfall;

	length = strlen(string);
	valuePtr->pv.next = valuePtr->pv.buffer;
	shortfall = length - (valuePtr->pv.end - valuePtr->pv.buffer);
	if (shortfall > 0) {
	    (*valuePtr->pv.expandProc)(&valuePtr->pv, shortfall);
	}
	strcpy(valuePtr->pv.buffer, string);
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * ExprLex --
 *
 *	Lexical analyzer for expression parser:  parses a single value,
 *	operator, or other syntactic element from an expression string.
 *
 * Results:
 *	TCL_OK is returned unless an error occurred while doing lexical
 *	analysis or executing an embedded command.  In that case a
 *	standard Tcl error is returned, using interp->result to hold
 *	an error message.  In the event of a successful return, the token
 *	and field in infoPtr is updated to refer to the next symbol in
 *	the expression string, and the expr field is advanced past that
 *	token;  if the token is a value, then the value is stored at
 *	valuePtr.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
ExprLex(interp, infoPtr, valuePtr)
    Tcl_Interp *interp;			/* Interpreter to use for error
					 * reporting. */
    register ExprInfo *infoPtr;		/* Describes the state of the parse. */
    register Value *valuePtr;		/* Where to store value, if that is
					 * what's parsed from string.  Caller
					 * must have initialized pv field
					 * correctly. */
{
    register char *p, c;
    char *var, *term;
    int result;

    p = infoPtr->expr;
    c = *p;
    while (isspace(c)) {
	p++;
	c = *p;
    }
    infoPtr->expr = p+1;
    switch (c) {
	case '0':
	case '1':
	case '2':
	case '3':
	case '4':
	case '5':
	case '6':
	case '7':
	case '8':
	case '9':
	case '.':

	    /*
	     * Number.  First read an integer.  Then if it looks like
	     * there's a floating-point number (or if it's too big a
	     * number to fit in an integer), parse it as a floating-point
	     * number.
	     */

	    infoPtr->token = VALUE;
	    valuePtr->type = TYPE_INT;
	    errno = 0;
	    valuePtr->intValue = strtoul(p, &term, 0);
	    c = *term;
	    if ((c == '.') || (c == 'e') || (c == 'E') || (errno == ERANGE)) {
		char *term2;

		errno = 0;
		valuePtr->doubleValue = strtod(p, &term2);
		if (errno == ERANGE) {
		    Tcl_ResetResult(interp);
		    if (valuePtr->doubleValue == 0.0) {
			interp->result =
				"floating-point value too small to represent";
		    } else {
			interp->result =
				"floating-point value too large to represent";
		    }
		    return TCL_ERROR;
		}
		if (term2 == infoPtr->expr) {
		    interp->result = "poorly-formed floating-point value";
		    return TCL_ERROR;
		}
		valuePtr->type = TYPE_DOUBLE;
		infoPtr->expr = term2;
	    } else {
		infoPtr->expr = term;
	    }
	    return TCL_OK;

	case '$':

	    /*
	     * Variable.  Fetch its value, then see if it makes sense
	     * as an integer or floating-point number.
	     */

	    infoPtr->token = VALUE;
	    var = Tcl_ParseVar(interp, p, &infoPtr->expr);
	    if (var == NULL) {
		return TCL_ERROR;
	    }
	    if (((Interp *) interp)->noEval) {
		valuePtr->type = TYPE_INT;
		valuePtr->intValue = 0;
		return TCL_OK;
	    }
	    return ExprParseString(interp, var, valuePtr);

	case '[':
	    infoPtr->token = VALUE;
	    result = Tcl_Eval(interp, p+1, TCL_BRACKET_TERM,
		    &infoPtr->expr);
	    if (result != TCL_OK) {
		return result;
	    }
	    infoPtr->expr++;
	    if (((Interp *) interp)->noEval) {
		valuePtr->type = TYPE_INT;
		valuePtr->intValue = 0;
		Tcl_ResetResult(interp);
		return TCL_OK;
	    }
	    result = ExprParseString(interp, interp->result, valuePtr);
	    if (result != TCL_OK) {
		return result;
	    }
	    Tcl_ResetResult(interp);
	    return TCL_OK;

	case '"':
	    infoPtr->token = VALUE;
	    result = TclParseQuotes(interp, infoPtr->expr, '"', 0,
		    &infoPtr->expr, &valuePtr->pv);
	    if (result != TCL_OK) {
		return result;
	    }
	    return ExprParseString(interp, valuePtr->pv.buffer, valuePtr);

	case '{':
	    infoPtr->token = VALUE;
	    result = TclParseBraces(interp, infoPtr->expr, &infoPtr->expr,
		    &valuePtr->pv);
	    if (result != TCL_OK) {
		return result;
	    }
	    return ExprParseString(interp, valuePtr->pv.buffer, valuePtr);

	case '(':
	    infoPtr->token = OPEN_PAREN;
	    return TCL_OK;

	case ')':
	    infoPtr->token = CLOSE_PAREN;
	    return TCL_OK;

	case '*':
	    infoPtr->token = MULT;
	    return TCL_OK;

	case '/':
	    infoPtr->token = DIVIDE;
	    return TCL_OK;

	case '%':
	    infoPtr->token = MOD;
	    return TCL_OK;

	case '+':
	    infoPtr->token = PLUS;
	    return TCL_OK;

	case '-':
	    infoPtr->token = MINUS;
	    return TCL_OK;

	case '?':
	    infoPtr->token = QUESTY;
	    return TCL_OK;

	case ':':
	    infoPtr->token = COLON;