LXR busybox/coreutils/expr.c

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Mini expr implementation for busybox
   4 *
   5 * based on GNU expr Mike Parker.
   6 * Copyright (C) 86, 1991-1997, 1999 Free Software Foundation, Inc.
   7 *
   8 * Busybox modifications
   9 * Copyright (c) 2000  Edward Betts <edward@debian.org>.
  10 * Copyright (C) 2003-2005  Vladimir Oleynik <dzo@simtreas.ru>
  11 *  - reduced 464 bytes.
  12 *  - 64 math support
  13 *
  14 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
  15 */
  16
  17/* This program evaluates expressions.  Each token (operator, operand,
  18 * parenthesis) of the expression must be a separate argument.  The
  19 * parser used is a reasonably general one, though any incarnation of
  20 * it is language-specific.  It is especially nice for expressions.
  21 *
  22 * No parse tree is needed; a new node is evaluated immediately.
  23 * One function can handle multiple operators all of equal precedence,
  24 * provided they all associate ((x op x) op x). */
  25
  26/* no getopt needed */
  27
  28#include "libbb.h"
  29#include "xregex.h"
  30
  31#if ENABLE_EXPR_MATH_SUPPORT_64
  32typedef int64_t arith_t;
  33
  34#define PF_REZ      "ll"
  35#define PF_REZ_TYPE (long long)
  36#define STRTOL(s, e, b) strtoll(s, e, b)
  37#else
  38typedef long arith_t;
  39
  40#define PF_REZ      "l"
  41#define PF_REZ_TYPE (long)
  42#define STRTOL(s, e, b) strtol(s, e, b)
  43#endif
  44
  45/* TODO: use bb_strtol[l]? It's easier to check for errors... */
  46
  47/* The kinds of value we can have.  */
  48enum {
  49        INTEGER,
  50        STRING
  51};
  52
  53/* A value is.... */
  54struct valinfo {
  55        smallint type;                  /* Which kind. */
  56        union {                         /* The value itself. */
  57                arith_t i;
  58                char *s;
  59        } u;
  60};
  61typedef struct valinfo VALUE;
  62
  63/* The arguments given to the program, minus the program name.  */
  64struct globals {
  65        char **args;
  66};
  67#define G (*(struct globals*)&bb_common_bufsiz1)
  68
  69/* forward declarations */
  70static VALUE *eval(void);
  71
  72
  73/* Return a VALUE for I.  */
  74
  75static VALUE *int_value(arith_t i)
  76{
  77        VALUE *v;
  78
  79        v = xzalloc(sizeof(VALUE));
  80        if (INTEGER) /* otherwise xzaaloc did it already */
  81                v->type = INTEGER;
  82        v->u.i = i;
  83        return v;
  84}
  85
  86/* Return a VALUE for S.  */
  87
  88static VALUE *str_value(const char *s)
  89{
  90        VALUE *v;
  91
  92        v = xzalloc(sizeof(VALUE));
  93        if (STRING) /* otherwise xzaaloc did it already */
  94                v->type = STRING;
  95        v->u.s = xstrdup(s);
  96        return v;
  97}
  98
  99/* Free VALUE V, including structure components.  */
 100
 101static void freev(VALUE *v)
 102{
 103        if (v->type == STRING)
 104                free(v->u.s);
 105        free(v);
 106}
 107
 108/* Return nonzero if V is a null-string or zero-number.  */
 109
 110static int null(VALUE *v)
 111{
 112        if (v->type == INTEGER)
 113                return v->u.i == 0;
 114        /* STRING: */
 115        return v->u.s[0] == '\0' || LONE_CHAR(v->u.s, '0');
 116}
 117
 118/* Coerce V to a STRING value (can't fail).  */
 119
 120static void tostring(VALUE *v)
 121{
 122        if (v->type == INTEGER) {
 123                v->u.s = xasprintf("%" PF_REZ "d", PF_REZ_TYPE v->u.i);
 124                v->type = STRING;
 125        }
 126}
 127
 128/* Coerce V to an INTEGER value.  Return 1 on success, 0 on failure.  */
 129
 130static bool toarith(VALUE *v)
 131{
 132        if (v->type == STRING) {
 133                arith_t i;
 134                char *e;
 135
 136                /* Don't interpret the empty string as an integer.  */
 137                /* Currently does not worry about overflow or int/long differences. */
 138                i = STRTOL(v->u.s, &e, 10);
 139                if ((v->u.s == e) || *e)
 140                        return 0;
 141                free(v->u.s);
 142                v->u.i = i;
 143                v->type = INTEGER;
 144        }
 145        return 1;
 146}
 147
 148/* Return str[0]+str[1] if the next token matches STR exactly.
 149   STR must not be NULL.  */
 150
 151static int nextarg(const char *str)
 152{
 153        if (*G.args == NULL || strcmp(*G.args, str) != 0)
 154                return 0;
 155        return (unsigned char)str[0] + (unsigned char)str[1];
 156}
 157
 158/* The comparison operator handling functions.  */
 159
 160static int cmp_common(VALUE *l, VALUE *r, int op)
 161{
 162        arith_t ll, rr;
 163
 164        ll = l->u.i;
 165        rr = r->u.i;
 166        if (l->type == STRING || r->type == STRING) {
 167                tostring(l);
 168                tostring(r);
 169                ll = strcmp(l->u.s, r->u.s);
 170                rr = 0;
 171        }
 172        /* calculating ll - rr and checking the result is prone to overflows.
 173         * We'll do it differently: */
 174        if (op == '<')
 175                return ll < rr;
 176        if (op == ('<' + '='))
 177                return ll <= rr;
 178        if (op == '=' || (op == '=' + '='))
 179                return ll == rr;
 180        if (op == '!' + '=')
 181                return ll != rr;
 182        if (op == '>')
 183                return ll > rr;
 184        /* >= */
 185        return ll >= rr;
 186}
 187
 188/* The arithmetic operator handling functions.  */
 189
 190static arith_t arithmetic_common(VALUE *l, VALUE *r, int op)
 191{
 192        arith_t li, ri;
 193
 194        if (!toarith(l) || !toarith(r))
 195                bb_error_msg_and_die("non-numeric argument");
 196        li = l->u.i;
 197        ri = r->u.i;
 198        if (op == '+')
 199                return li + ri;
 200        if (op == '-')
 201                return li - ri;
 202        if (op == '*')
 203                return li * ri;
 204        if (ri == 0)
 205                bb_error_msg_and_die("division by zero");
 206        if (op == '/')
 207                return li / ri;
 208        return li % ri;
 209}
 210
 211/* Do the : operator.
 212   SV is the VALUE for the lhs (the string),
 213   PV is the VALUE for the rhs (the pattern).  */
 214
 215static VALUE *docolon(VALUE *sv, VALUE *pv)
 216{
 217        VALUE *v;
 218        regex_t re_buffer;
 219        const int NMATCH = 2;
 220        regmatch_t re_regs[NMATCH];
 221
 222        tostring(sv);
 223        tostring(pv);
 224
 225        if (pv->u.s[0] == '^') {
 226                bb_error_msg("\
 227warning: unportable BRE: `%s': using `^' as the first character\n\
 228of a basic regular expression is not portable; it is being ignored", pv->u.s);
 229        }
 230
 231        memset(&re_buffer, 0, sizeof(re_buffer));
 232        memset(re_regs, 0, sizeof(*re_regs));
 233        xregcomp(&re_buffer, pv->u.s, 0);
 234
 235        /* expr uses an anchored pattern match, so check that there was a
 236         * match and that the match starts at offset 0. */
 237        if (regexec(&re_buffer, sv->u.s, NMATCH, re_regs, 0) != REG_NOMATCH
 238         && re_regs[0].rm_so == 0
 239        ) {
 240                /* Were \(...\) used? */
 241                if (re_buffer.re_nsub > 0) {
 242                        sv->u.s[re_regs[1].rm_eo] = '\0';
 243                        v = str_value(sv->u.s + re_regs[1].rm_so);
 244                } else {
 245                        v = int_value(re_regs[0].rm_eo);
 246                }
 247        } else {
 248                /* Match failed -- return the right kind of null.  */
 249                if (re_buffer.re_nsub > 0)
 250                        v = str_value("");
 251                else
 252                        v = int_value(0);
 253        }
 254//FIXME: sounds like here is a bit missing: regfree(&re_buffer);
 255        return v;
 256}
 257
 258/* Handle bare operands and ( expr ) syntax.  */
 259
 260static VALUE *eval7(void)
 261{
 262        VALUE *v;
 263
 264        if (!*G.args)
 265                bb_error_msg_and_die("syntax error");
 266
 267        if (nextarg("(")) {
 268                G.args++;
 269                v = eval();
 270                if (!nextarg(")"))
 271                        bb_error_msg_and_die("syntax error");
 272                G.args++;
 273                return v;
 274        }
 275
 276        if (nextarg(")"))
 277                bb_error_msg_and_die("syntax error");
 278
 279        return str_value(*G.args++);
 280}
 281
 282/* Handle match, substr, index, length, and quote keywords.  */
 283
 284static VALUE *eval6(void)
 285{
 286        static const char keywords[] ALIGN1 =
 287                "quote\0""length\0""match\0""index\0""substr\0";
 288
 289        VALUE *r, *i1, *i2;
 290        VALUE *l = l; /* silence gcc */
 291        VALUE *v = v; /* silence gcc */
 292        int key = *G.args ? index_in_strings(keywords, *G.args) + 1 : 0;
 293
 294        if (key == 0) /* not a keyword */
 295                return eval7();
 296        G.args++; /* We have a valid token, so get the next argument.  */
 297        if (key == 1) { /* quote */
 298                if (!*G.args)
 299                        bb_error_msg_and_die("syntax error");
 300                return str_value(*G.args++);
 301        }
 302        if (key == 2) { /* length */
 303                r = eval6();
 304                tostring(r);
 305                v = int_value(strlen(r->u.s));
 306                freev(r);
 307        } else
 308                l = eval6();
 309
 310        if (key == 3) { /* match */
 311                r = eval6();
 312                v = docolon(l, r);
 313                freev(l);
 314                freev(r);
 315        }
 316        if (key == 4) { /* index */
 317                r = eval6();
 318                tostring(l);
 319                tostring(r);
 320                v = int_value(strcspn(l->u.s, r->u.s) + 1);
 321                if (v->u.i == (arith_t) strlen(l->u.s) + 1)
 322                        v->u.i = 0;
 323                freev(l);
 324                freev(r);
 325        }
 326        if (key == 5) { /* substr */
 327                i1 = eval6();
 328                i2 = eval6();
 329                tostring(l);
 330                if (!toarith(i1) || !toarith(i2)
 331                 || i1->u.i > (arith_t) strlen(l->u.s)
 332                 || i1->u.i <= 0 || i2->u.i <= 0)
 333                        v = str_value("");
 334                else {
 335                        v = xmalloc(sizeof(VALUE));
 336                        v->type = STRING;
 337                        v->u.s = xstrndup(l->u.s + i1->u.i - 1, i2->u.i);
 338                }
 339                freev(l);
 340                freev(i1);
 341                freev(i2);
 342        }
 343        return v;
 344
 345}
 346
 347/* Handle : operator (pattern matching).
 348   Calls docolon to do the real work.  */
 349
 350static VALUE *eval5(void)
 351{
 352        VALUE *l, *r, *v;
 353
 354        l = eval6();
 355        while (nextarg(":")) {
 356                G.args++;
 357                r = eval6();
 358                v = docolon(l, r);
 359                freev(l);
 360                freev(r);
 361                l = v;
 362        }
 363        return l;
 364}
 365
 366/* Handle *, /, % operators.  */
 367
 368static VALUE *eval4(void)
 369{
 370        VALUE *l, *r;
 371        int op;
 372        arith_t val;
 373
 374        l = eval5();
 375        while (1) {
 376                op = nextarg("*");
 377                if (!op) { op = nextarg("/");
 378                 if (!op) { op = nextarg("%");
 379                  if (!op) return l;
 380                }}
 381                G.args++;
 382                r = eval5();
 383                val = arithmetic_common(l, r, op);
 384                freev(l);
 385                freev(r);
 386                l = int_value(val);
 387        }
 388}
 389
 390/* Handle +, - operators.  */
 391
 392static VALUE *eval3(void)
 393{
 394        VALUE *l, *r;
 395        int op;
 396        arith_t val;
 397
 398        l = eval4();
 399        while (1) {
 400                op = nextarg("+");
 401                if (!op) {
 402                        op = nextarg("-");
 403                        if (!op) return l;
 404                }
 405                G.args++;
 406                r = eval4();
 407                val = arithmetic_common(l, r, op);
 408                freev(l);
 409                freev(r);
 410                l = int_value(val);
 411        }
 412}
 413
 414/* Handle comparisons.  */
 415
 416static VALUE *eval2(void)
 417{
 418        VALUE *l, *r;
 419        int op;
 420        arith_t val;
 421
 422        l = eval3();
 423        while (1) {
 424                op = nextarg("<");
 425                if (!op) { op = nextarg("<=");
 426                 if (!op) { op = nextarg("=");
 427                  if (!op) { op = nextarg("==");
 428                   if (!op) { op = nextarg("!=");
 429                    if (!op) { op = nextarg(">=");
 430                     if (!op) { op = nextarg(">");
 431                      if (!op) return l;
 432                }}}}}}
 433                G.args++;
 434                r = eval3();
 435                toarith(l);
 436                toarith(r);
 437                val = cmp_common(l, r, op);
 438                freev(l);
 439                freev(r);
 440                l = int_value(val);
 441        }
 442}
 443
 444/* Handle &.  */
 445
 446static VALUE *eval1(void)
 447{
 448        VALUE *l, *r;
 449
 450        l = eval2();
 451        while (nextarg("&")) {
 452                G.args++;
 453                r = eval2();
 454                if (null(l) || null(r)) {
 455                        freev(l);
 456                        freev(r);
 457                        l = int_value(0);
 458                } else
 459                        freev(r);
 460        }
 461        return l;
 462}
 463
 464/* Handle |.  */
 465
 466static VALUE *eval(void)
 467{
 468        VALUE *l, *r;
 469
 470        l = eval1();
 471        while (nextarg("|")) {
 472                G.args++;
 473                r = eval1();
 474                if (null(l)) {
 475                        freev(l);
 476                        l = r;
 477                } else
 478                        freev(r);
 479        }
 480        return l;
 481}
 482
 483int expr_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 484int expr_main(int argc, char **argv)
 485{
 486        VALUE *v;
 487
 488        if (argc == 1) {
 489                bb_error_msg_and_die("too few arguments");
 490        }
 491
 492        G.args = argv + 1;
 493
 494        v = eval();
 495        if (*G.args)
 496                bb_error_msg_and_die("syntax error");
 497
 498        if (v->type == INTEGER)
 499                printf("%" PF_REZ "d\n", PF_REZ_TYPE v->u.i);
 500        else
 501                puts(v->u.s);
 502
 503        fflush_stdout_and_exit(null(v));
 504}
 505