summaryrefslogtreecommitdiff
path: root/src/lstrlib.js
blob: 56fcc11d0a987249bf4485f8fcf9e945b5cc2974 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
"use strict";

const assert  = require('assert');
const sprintf = require('sprintf');

const lapi    = require('./lapi.js');
const lauxlib = require('./lauxlib.js');
const lobject = require('./lobject.js');
const lua     = require('./lua.js');
const luaconf = require('./luaconf.js');
const CT      = lua.constant_types;

const L_ESC   = '%'.charCodeAt(0);

// (sizeof(size_t) < sizeof(int) ? MAX_SIZET : (size_t)(INT_MAX))
const MAXSIZE = Number.MAX_SAFE_INTEGER;


/* translate a relative string position: negative means back from end */
const posrelat = function(pos, len) {
    if (pos >= 0) return pos;
    else if (0 - pos > len) return 0;
    else return len + pos + 1;
};

const str_sub = function(L) {
    let s = lauxlib.luaL_checkstring(L, 1);
    let l = s.length;
    let start = posrelat(lauxlib.luaL_checkinteger(L, 2), l);
    let end = posrelat(lauxlib.luaL_optinteger(L, 3, -1), l);
    if (start < 1) start = 1;
    if (end > l) end = l;
    if (start <= end)
        lapi.lua_pushstring(L, s.slice(start - 1, (start - 1) + (end - start + 1)));
    else lapi.lua_pushliteral(L, "");
    return 1;
};

const str_len = function(L) {
    lapi.lua_pushinteger(L, lauxlib.luaL_checkstring(L, 1).length);
    return 1;
};

const str_char = function(L) {
    let n = lapi.lua_gettop(L);  /* number of arguments */
    let p = "";
    for (let i = 1; i <= n; i++) {
        let c = lauxlib.luaL_checkinteger(L, i);
        lauxlib.luaL_argcheck(L, c >= 0 && c <= 255, "value out of range"); // Strings are 8-bit clean
        p += String.fromCharCode(c);
    }
    lapi.lua_pushstring(L, p);
    return 1;
};

const writer = function(L, b, size, B) {
    assert(Array.isArray(b));
    B.push(...b.slice(0, size));
    return 0;
};

const str_dump = function(L) {
    let b = [];
    let strip = lapi.lua_toboolean(L, 2);
    lauxlib.luaL_checktype(L, 1, CT.LUA_TFUNCTION);
    lapi.lua_settop(L, 1);
    if (lapi.lua_dump(L, writer, b, strip) !== 0)
        return lauxlib.luaL_error(L, "unable to dump given function");
    L.stack[L.top++] = new lobject.TValue(CT.LUA_TLNGSTR, b); // We don't want lua > js > lua string conversion here
    return 1;
};

const SIZELENMOD = luaconf.LUA_NUMBER_FRMLEN.length;

const L_NBFD = 16; // TODO: arbitrary

// See: http://croquetweak.blogspot.fr/2014/08/deconstructing-floats-frexp-and-ldexp.html
const frexp = function(value) {
    if (value === 0) return [value, 0];
    var data = new DataView(new ArrayBuffer(8));
    data.setFloat64(0, value);
    var bits = (data.getUint32(0) >>> 20) & 0x7FF;
    if (bits === 0) { // denormal
        data.setFloat64(0, value * Math.pow(2, 64));  // exp + 64
        bits = ((data.getUint32(0) >>> 20) & 0x7FF) - 64;
    }
    var exponent = bits - 1022;
    var mantissa = ldexp(value, -exponent);
    return [mantissa, exponent];
};

const ldexp = function(mantissa, exponent) {
    var steps = Math.min(3, Math.ceil(Math.abs(exponent) / 1023));
    var result = mantissa;
    for (var i = 0; i < steps; i++)
        result *= Math.pow(2, Math.floor((exponent + i) / steps));
    return result;
};

/*
** Add integer part of 'x' to buffer and return new 'x'
*/
const adddigit = function(buff, n, x) {
    let d = Math.floor(x)|0;  /* get integer part from 'x' */
    buff[n] = d < 10 ? d + '0'.charCodeAt(0) : d - 10 + 'a'.charCodeAt(0);  /* add to buffer */
    return x - d;  /* return what is left */
};

const num2straux = function(buff, x) {
    /* if 'inf' or 'NaN', format it like '%g' */
    if (x === Infinity || isNaN(x))
        return sprintf(luaconf.LUA_NUMBER_FMT, x).split('').map(e => e.charCodeAt(0));
    else if (x === 0) {  /* can be -0... */
        /* create "0" or "-0" followed by exponent */
        return sprintf(luaconf.LUA_NUMBER_FMT + "x0p+0", x).split('').map(e => e.charCodeAt(0));
    } else {
        let fe = frexp(x);  /* 'x' fraction and exponent */
        let m = fe[0];
        let e = fe[1];
        let n = 0;  /* character count */
        if (m < 0) {  /* is number negative? */
            buff[n++] = '-'.charCodeAt(0);  /* add signal */
            m = -m;  /* make it positive */
        }
        buff[n++] = '0'.charCodeAt(0);
        buff[n++] = 'x'.charCodeAt(0);  /* add "0x" */
        m = adddigit(buff, n++, m * (1 << L_NBFD));  /* add first digit */
        e -= L_NBFD;  /* this digit goes before the radix point */
        if (m > 0) {  /* more digits? */
            buff[n++] = luaconf.lua_getlocaledecpoint().charCodeAt(0);   /* add radix point */
            do {  /* add as many digits as needed */
                m = adddigit(buff, n++, m * 16);
            } while (m > 0);
        }
        let exp = sprintf("p%+d", e).split('').map(e => e.charCodeAt(0));
        return buff.slice(0, n + 1).concat(exp).concat(buff.slice(n));
    }
};

const lua_number2strx = function(L, buff, fmt, x) {
    let n = num2straux(buff, x);
    if (fmt[SIZELENMOD] === 'A'.charCodeAt(0)) {
        for (let i = 0; i < n; i++)
            buff[i] = String.fromCharCode(buff[i]).toUpperCase().charCodeAt(0);
    } else if (fmt[SIZELENMOD] !== 'a'.charCodeAt(0))
        lauxlib.luaL_error(L, "modifiers for format '%a'/'%A' not implemented");
    return n;
};

/*
** Maximum size of each formatted item. This maximum size is produced
** by format('%.99f', -maxfloat), and is equal to 99 + 3 ('-', '.',
** and '\0') + number of decimal digits to represent maxfloat (which
** is maximum exponent + 1). (99+3+1 then rounded to 120 for "extra
** expenses", such as locale-dependent stuff)
*/
const MAX_ITEM   = 120;// TODO: + l_mathlim(MAX_10_EXP);


/* valid flags in a format specification */
const FLAGS      = ["-", "+", " ", "#", "0"].map(e => e.charCodeAt(0));

/*
** maximum size of each format specification (such as "%-099.99d")
*/
const MAX_FORMAT = 32;

const isdigit = e => "0".charCodeAt(0) <= e && e <= "9".charCodeAt(0);

const iscntrl = e => (0x00 <= e && e <= 0x1f) || e === 0x7f;

const addquoted = function(b, s) {
    lauxlib.luaL_addchar(b, '"');
    let len = s.length;
    while (len--) {
        if (s[0] === '"'.charCodeAt(0) || s[0] === '\\'.charCodeAt(0) || s[0] === '\n'.charCodeAt(0)) {
            lauxlib.luaL_addchar(b, '\\');
            lauxlib.luaL_addchar(b, String.fromCharCode(s[0]));
        } else if (iscntrl(s[0])) {
            let buff = [];
            if (!isdigit(s[1]))
                buff = sprintf("\\%d", s[0]).split('').map(e => e.charCodeAt(0));
            else
                buff = sprintf("\\%03d", s[0]).split('').map(e => e.charCodeAt(0));
            lauxlib.luaL_addstring(b, buff);
        } else
            lauxlib.luaL_addchar(b, String.fromCharCode(s[0]));
        s = s.slice(1);
    }
    lauxlib.luaL_addchar(b, '"');
};

/*
** Ensures the 'buff' string uses a dot as the radix character.
*/
const checkdp = function(buff) {
    if (buff.indexOf('.') < 0) {  /* no dot? */
        let point = luaconf.lua_getlocaledecpoint().charCodeAt(0);  /* try locale point */
        let ppoint = buff.indexOf(point);
        if (ppoint) point[ppoint] = '.';  /* change it to a dot */
    }
};

const addliteral = function(L, b, arg) {
    switch(lapi.lua_type(L, arg)) {
        case CT.LUA_TSTRING: {
            let s = L.stack[lapi.index2addr_(L, arg)].value;
            addquoted(b, s, s.length);
            break;
        }
        case CT.LUA_TNUMBER: {
            let buff = lauxlib.luaL_prepbuffsize(b, MAX_ITEM);
            if (!lapi.lua_isinteger(L, arg)) {  /* float? */
                let n = lapi.lua_tonumber(L, arg);  /* write as hexa ('%a') */
                buff.b += lapi.lua_number2strx(L, buff.b, `%${luaconf.LUA_INTEGER_FRMLEN}a`, n);
                checkdp(buff.b);  /* ensure it uses a dot */
            } else {  /* integers */
                let n = lapi.lua_tointeger(L, arg);
                let format = (n === Number.MIN_SAFE_INTEGER) ? `0x%${luaconf.LUA_INTEGER_FRMLEN}x` : luaconf.LUA_INTEGER_FMT;
                buff.b += sprintf(format, n|0);
            }
            break;
        }
        case CT.LUA_TNIL: case CT.LUA_TBOOLEAN: {
            lauxlib.luaL_tolstring(L, arg);
            lauxlib.luaL_addvalue(b);
            break;
        }
        default: {
            lauxlib.luaL_argerror(L, arg, "value has no literal form");
        }
    }
};

const scanformat = function(L, strfrmt, form) {
    let p = strfrmt;
    while (p[0] !== 0 && FLAGS.indexOf(p[0]) >= 0) p = p.slice(1);  /* skip flags */
    if (strfrmt.length - p.length >= FLAGS.length)
        lauxlib.luaL_error(L, "invalid format (repeated flags)");
    if (isdigit(p[0])) p = p.slice(1);  /* skip width */
    if (isdigit(p[0])) p = p.slice(1);  /* (2 digits at most) */
    if (p[0] === '.'.charCodeAt(0)) {
        p = p.slice(1);
        if (isdigit(p[0])) p = p.slice(1);  /* skip precision */
        if (isdigit(p[0])) p = p.slice(1);  /* (2 digits at most) */
    }
    if (isdigit(p[0]))
        lauxlib.luaL_error(L, "invalid format (width or precision too long)");
    form[0] = "%".charCodeAt(0);
    for (let i = 0; i < strfrmt.length - p.length + 1; i++)
        form[i + 1] = strfrmt[i];
    // form[strfrmt.length - p.length + 2] = 0;
    return {
        form: form,
        p: p
    };
};

/*
** add length modifier into formats
*/
const addlenmod = function(form, lenmod) {
    let l = form.length;
    let lm = lenmod.length;
    let spec = form[l - 1];
    for (let i = 0; i < lenmod.length; i++)
        form[i + l - 1] = lenmod[i];
    form[l + lm - 1] = spec;
    // form[l + lm] = 0;
    return form;
};

const str_format = function(L) {
    let top = lapi.lua_gettop(L);
    let arg = 1;
    let strfrmt = lauxlib.luaL_checkstring(L, arg);
    strfrmt = L.stack[lapi.index2addr_(L, 1)].value;
    let b = new lauxlib.luaL_Buffer(L);

    while (strfrmt.length > 0) {
        if (strfrmt[0] !== L_ESC) {
            lauxlib.luaL_addchar(b, String.fromCharCode(strfrmt[0]));
            strfrmt = strfrmt.slice(1);
        } else if ((strfrmt = strfrmt.slice(1))[0] === L_ESC) {
            lauxlib.luaL_addchar(b, String.fromCharCode(strfrmt[0]));
            strfrmt = strfrmt.slice(1);
        } else { /* format item */
            let form = [];  /* to store the format ('%...') */
            let buff = lauxlib.luaL_prepbuffsize(b, MAX_ITEM);  /* to put formatted item */
            if (++arg > top)
                lauxlib.luaL_argerror(L, arg, "no value");
            let f = scanformat(L, strfrmt, form);
            strfrmt = f.p;
            form = f.form;
            switch (String.fromCharCode(strfrmt[0])) {
                case 'c': {
                    strfrmt = strfrmt.slice(1);
                    buff.b += sprintf(String.fromCharCode(...form), lauxlib.luaL_checkinteger(L, arg));
                    break;
                }
                case 'd': case 'i':
                case 'o': case 'u': case 'x': case 'X': {
                    strfrmt = strfrmt.slice(1);
                    let n = lauxlib.luaL_checkinteger(L, arg);
                    form = addlenmod(form, luaconf.LUA_INTEGER_FRMLEN.split('').map(e => e.charCodeAt(0)));
                    buff.b += sprintf(String.fromCharCode(...form), n|0);
                    break;
                }
                case 'a': case 'A': {
                    strfrmt = strfrmt.slice(1);
                    form = addlenmod(form, luaconf.LUA_INTEGER_FRMLEN.split('').map(e => e.charCodeAt(0)));
                    buff.b += lua_number2strx(L, buff.b, form, lauxlib.luaL_checknumber(L, arg));
                    break;
                }
                case 'e': case 'E': case 'f':
                case 'g': case 'G': {
                    strfrmt = strfrmt.slice(1);
                    let n = lauxlib.luaL_checknumber(L, arg);
                    form = addlenmod(form, luaconf.LUA_INTEGER_FRMLEN.split('').map(e => e.charCodeAt(0)));
                    buff.b += sprintf(String.fromCharCode(...form), n);
                    break;
                }
                case 'q': {
                    strfrmt = strfrmt.slice(1);
                    addliteral(L, b, arg);
                    break;
                }
                case 's': {
                    strfrmt = strfrmt.slice(1);
                    let str = lauxlib.luaL_tolstring(L, arg);
                    let  s = L.stack[lapi.index2addr_(L, arg)].value;
                    if (form[2] === '\0')  /* no modifiers? */
                        lauxlib.luaL_addvalue(b);  /* keep entire string */
                    else {
                        lauxlib.luaL_argcheck(L, s.length === str.length, arg, "string contains zeros");
                        if (form.indexOf('.') < 0 && s.length >= 100) {
                            /* no precision and string is too long to be formatted */
                            lauxlib.luaL_addvalue(b);  /* keep entire string */
                        } else {  /* format the string into 'buff' */
                            buff.b += sprintf(String.fromCharCode(...form), s);
                            lapi.lua_pop(L, 1);  /* remove result from 'luaL_tolstring' */
                        }
                    }
                    break;
                }
                default: {  /* also treat cases 'pnLlh' */
                    return lauxlib.luaL_error(L, `invalid option '%${strfrmt[0]}'`);
                }
            }
        }
    }

    lauxlib.luaL_pushresult(b);
    return 1;
};

/* value used for padding */
const LUAL_PACKPADBYTE = 0x00;

/* maximum size for the binary representation of an integer */
const MAXINTSIZE = 16;

const SZINT = 8; // Size of lua_Integer

/* number of bits in a character */
const NB = 8;

/* mask for one character (NB 1's) */
const MC = ((1 << NB) - 1);

const MAXALIGN = 8;

/*
** information to pack/unpack stuff
*/
class Header {
    constructor(L) {
        this.L = L;
        this.islittle = true;
        this.maxalign = 1;
    }
}

/*
** options for pack/unpack
*/
const KOption = {
    Kint:       0, /* signed integers */
    Kuint:      1, /* unsigned integers */
    Kfloat:     2, /* floating-point numbers */
    Kchar:      3, /* fixed-length strings */
    Kstring:    4, /* strings with prefixed length */
    Kzstr:      5, /* zero-terminated strings */
    Kpadding:   6, /* padding */
    Kpaddalign: 7, /* padding for alignment */
    Knop:       8  /* no-op (configuration or spaces) */
};

const digit = function(c) {
    return '0'.charCodeAt(0) <= c.charCodeAt(0) && c.charCodeAt(0) <= '9'.charCodeAt(0);
};

const getnum = function(fmt, df) {
    if (!digit(fmt.s[0]))  /* no number? */
        return df;  /* return default value */
    else {
        let a = 0;
        do {
            a = a * 10 + (fmt.s[0].charCodeAt(0) - '0'.charCodeAt(0));
            fmt.s = fmt.s.slice(1);
        } while (digit(fmt.s[0]) && a <= (MAXSIZE - 9)/10);
        return a;
    }
};

/*
** Read an integer numeral and raises an error if it is larger
** than the maximum size for integers.
*/
const getnumlimit = function(h, fmt, df) {
    let sz = getnum(fmt, df);
    if (sz > MAXINTSIZE || sz <= 0)
        lauxlib.luaL_error(h.L, `integral size (${sz}) out of limits [1,${MAXINTSIZE}]`);
    return sz;
};

/*
** Read and classify next option. 'size' is filled with option's size.
*/
const getoption = function(h, fmt) {
    let r = {
        opt: NaN,
        size: NaN
    };

    r.opt = fmt.s[0];
    fmt.s = fmt.s.slice(1);
    r.size = 0;  /* default */
    switch (r.opt) {
        case 'b': r.size = 1; r.opt = KOption.Kint;   return r; // sizeof(char): 1
        case 'B': r.size = 1; r.opt = KOption.Kuint;  return r;
        case 'h': r.size = 2; r.opt = KOption.Kint;   return r; // sizeof(short): 2
        case 'H': r.size = 2; r.opt = KOption.Kuint;  return r;
        case 'l': r.size = 8; r.opt = KOption.Kint;   return r; // sizeof(long): 8
        case 'L': r.size = 8; r.opt = KOption.Kuint;  return r;
        case 'j': r.size = 8; r.opt = KOption.Kint;   return r; // sizeof(lua_Integer): 8
        case 'J': r.size = 8; r.opt = KOption.Kuint;  return r;
        case 'T': r.size = 8; r.opt = KOption.Kuint;  return r; // sizeof(size_t): 8
        case 'f': r.size = 4; r.opt = KOption.Kfloat; return r; // sizeof(float): 4
        case 'd': r.size = 8; r.opt = KOption.Kfloat; return r; // sizeof(double): 8
        case 'n': r.size = 8; r.opt = KOption.Kfloat; return r; // sizeof(lua_Number): 8
        case 'i': r.size = getnumlimit(h, fmt, 4); r.opt = KOption.Kint;    return r; // sizeof(int): 4
        case 'I': r.size = getnumlimit(h, fmt, 4); r.opt = KOption.Kuint;   return r;
        case 's': r.size = getnumlimit(h, fmt, 8); r.opt = KOption.Kstring; return r;
        case 'c': {
            r.size = getnum(fmt, -1);
            if (r.size === -1)
                lauxlib.luaL_error(h.L, "missing size for format option 'c'");
            r.opt = KOption.Kchar;
            return r;
        }
        case 'z':             r.opt = KOption.Kzstr;      return r;
        case 'x': r.size = 1; r.opt = KOption.Kpadding;   return r;
        case 'X':             r.opt = KOption.Kpaddalign; return r;
        case ' ': break;
        case '<': h.islittle = true; break;
        case '>': h.islittle = false; break;
        case '=': h.islittle = true; break;
        case '!': h.maxalign = getnumlimit(h, fmt, MAXALIGN); break;
        default: lauxlib.luaL_error(h.L, `invalid format option '${r.opt}'`);
    }

    r.opt = KOption.Knop;
    return r;
};

/*
** Read, classify, and fill other details about the next option.
** 'psize' is filled with option's size, 'notoalign' with its
** alignment requirements.
** Local variable 'size' gets the size to be aligned. (Kpadal option
** always gets its full alignment, other options are limited by
** the maximum alignment ('maxalign'). Kchar option needs no alignment
** despite its size.
*/
const getdetails = function(h, totalsize, fmt) {
    let r = {
        opt: NaN,
        size: NaN,
        ntoalign: NaN
    };

    let opt = getoption(h, fmt);
    r.size = opt.size;
    r.opt = opt.opt;
    let align = r.size;  /* usually, alignment follows size */
    if (r.opt === KOption.Kpaddalign) {  /* 'X' gets alignment from following option */
        if (fmt.s[0] === 0)
            lauxlib.luaL_argerror(h.L, 1, "invalid next option for option 'X'");
        else {
            let o = getoption(h, fmt);
            align = o.size;
            o = o.opt;
            if (o === KOption.Kchar || align === 0)
                lauxlib.luaL_argerror(h.L, 1, "invalid next option for option 'X'");
        }
    }
    if (align <= 1 || r.opt === KOption.Kchar)  /* need no alignment? */
        r.ntoalign = 0;
    else {
        if (align > h.maxalign)  /* enforce maximum alignment */
            align = h.maxalign;
        if ((align & (align -1)) !== 0)  /* is 'align' not a power of 2? */
            lauxlib.luaL_argerror(h.L, 1, "format asks for alignment not power of 2");
        r.ntoalign = (align - (totalsize & (align - 1))) & (align - 1);
    }
    return r;
};

/*
** Pack integer 'n' with 'size' bytes and 'islittle' endianness.
** The final 'if' handles the case when 'size' is larger than
** the size of a Lua integer, correcting the extra sign-extension
** bytes if necessary (by default they would be zeros).
*/
const packint = function(b, n, islittle, size, neg) {
    let buff = new Array(size);

    buff[islittle ? 0 :  size - 1] = n & MC;  /* first byte */
    for (let i = 1; i < size; i++) {
        n >>= NB;
        buff[islittle ? i : size - 1 - i] = n & MC;
    }
    if (neg && size > SZINT) {  /* negative number need sign extension? */
        for (let i = SZINT; i < size; i++)  /* correct extra bytes */
            buff[islittle ? i : size - 1 - i] = MC;
    }
    b.push(...buff);  /* add result to buffer */
};

const packnum = function(b, n, islittle, size) {
    let dv = new DataView(new ArrayBuffer(size));
    dv.setFloat64(0, n, islittle);

    for (let i = 0; i < 8; i++)
        b.push(dv.getUint8(i, islittle));
};

const str_pack = function(L) {
    let b = [];
    let h = new Header(L);
    let fmt = lauxlib.luaL_checkstring(L, 1).split('');  /* format string */
    fmt.push('\0'); // Add \0 to avoid overflow
    fmt = {
        s: fmt,
        off: 0
    };
    let arg = 1;  /* current argument to pack */
    let totalsize = 0;  /* accumulate total size of result */
    lapi.lua_pushnil(L);  /* mark to separate arguments from string buffer */
    while (fmt.s.length - 1 > 0) {
        let details = getdetails(h, totalsize, fmt);
        let opt = details.opt;
        let size = details.size;
        let ntoalign = details.ntoalign;
        totalsize += ntoalign + size;
        while (ntoalign-- > 0)
            b.push(LUAL_PACKPADBYTE);  /* fill alignment */
        arg++;
        switch (opt) {
            case KOption.Kint: {  /* signed integers */
                let n = lauxlib.luaL_checkinteger(L, arg);
                if (size < SZINT) {  /* need overflow check? */
                    let lim = 1 << (size * 8) - 1;
                    lauxlib.luaL_argcheck(L, -lim <= n && n < lim, arg, "integer overflow");
                }
                packint(b, n, h.islittle, size, n < 0);
                break;
            }
            case KOption.Kuint: {  /* unsigned integers */
                let n = lauxlib.luaL_checkinteger(L, arg);
                if (size < SZINT)
                    lauxlib.luaL_argcheck(L, n < (1 << (size * NB)), arg, "unsigned overflow");
                packint(b, n, h.islittle, size, false);
                break;
            }
            case KOption.Kfloat: {  /* floating-point options */
                let n = lauxlib.luaL_checknumber(L, arg);  /* get argument */
                packnum(b, n, h.islittle, size);
                break;
            }
            case KOption.Kchar: {  /* fixed-size string */
                let s = lauxlib.luaL_checkstring(L, arg);
                s = L.stack[lapi.index2addr_(L, arg)];
                let len = s.value.length;
                lauxlib.luaL_argcheck(L, len <= size, arg, "string long than given size");
                b.push(...s.value);  /* add string */
                while (len++ < size)  /* pad extra space */
                    b.push(LUAL_PACKPADBYTE);
                break;
            }
            case KOption.Kstring: {  /* strings with length count */
                let s = lauxlib.luaL_checkstring(L, arg);
                s = L.stack[lapi.index2addr_(L, arg)].value;
                let len = s.value.length;
                lauxlib.luaL_argcheck(L, size >= NB || len < (1 << size * NB), arg, "string length does not fit in given size");
                packint(b, len, h.islittle, size, 0);  /* pack length */
                b.push(...s.value);
                totalsize += len;
                break;
            }
            case KOption.Kzstr: {  /* zero-terminated string */
                let s = lauxlib.luaL_checkstring(L, arg);
                s = L.stack[lapi.index2addr_(L, arg)].value;
                let len = s.value.length;
                lauxlib.luaL_argcheck(L, s.value.length === String.fromCharCode(...s.value).length, arg, "strings contains zeros");
                b.push(...s.value);
                b.push(0);  /* add zero at the end */
                totalsize += len + 1;
                break;
            }
            case KOption.Kpadding: b.push(LUAL_PACKPADBYTE);
            case KOption.Kpaddalign: case KOption.Knop:
                arg--;  /* undo increment */
                break;
        }
    }
    L.stack[L.top++] = new lobject.TValue(CT.LUA_TLNGSTR, b); // We don't want lua > js > lua string conversion here
    return 1;
};

const str_reverse = function(L) {
    lapi.lua_pushstring(L, lauxlib.luaL_checkstring(L, 1).split("").reverse().join(""));
    return 1;
};

const str_lower = function(L) {
    lapi.lua_pushstring(L, lauxlib.luaL_checkstring(L, 1).toLowerCase());
    return 1;
};

const str_upper = function(L) {
    lapi.lua_pushstring(L, lauxlib.luaL_checkstring(L, 1).toUpperCase());
    return 1;
};

const str_rep = function(L) {
    let s = lauxlib.luaL_checkstring(L, 1);
    let n = lauxlib.luaL_checkinteger(L, 2);
    let sep = lauxlib.luaL_optstring(L, 3, "");

    lapi.lua_pushstring(L, (s + sep).repeat(n - 1) + s);
    return 1;
};

const str_byte = function(L) {
    let s = lauxlib.luaL_checkstring(L, 1);
    s = L.stack[lapi.index2addr_(L, 1)].value;
    let l = s.length;
    let posi = posrelat(lauxlib.luaL_optinteger(L, 2, 1), l);
    let pose = posrelat(lauxlib.luaL_optinteger(L, 3, posi), l);

    if (posi < 1) posi = 1;
    if (pose > l) pose = l;
    if (posi > pose) return 0;  /* empty interval; return no values */
    if (pose - posi >= Number.MAX_SAFE_INTEGER)  /* arithmetic overflow? */
        return lauxlib.luaL_error(L, "string slice too long");

    let n = (pose - posi) + 1;
    lauxlib.luaL_checkstack(L, n, "string slice too long");
    for (let i = 0; i < n; i++)
        lapi.lua_pushinteger(L, s[posi + i - 1]);
    return n;
};

const str_packsize = function(L) {
    let h = new Header(L);
    let fmt = lauxlib.luaL_checkstring(L, 1).split('');
    fmt.push('\0'); // Add \0 to avoid overflow
    fmt = {
        s: fmt,
        off: 0
    };
    let totalsize = 0;  /* accumulate total size of result */
    while (fmt.s.length - 1 > 0) {
        let details = getdetails(h, totalsize, fmt);
        let opt = details.opt;
        let size = details.size;
        let ntoalign = details.ntoalign;
        size += ntoalign;  /* total space used by option */
        lauxlib.luaL_argcheck(L, totalsize <= MAXSIZE - size - 1, "format result too large");
        totalsize += size;
        switch (opt) {
            case KOption.Kstring:  /* strings with length count */
            case KOption.Kzstr:    /* zero-terminated string */
                lauxlib.luaL_argerror(L, 1, "variable-length format");
            default:  break;
        }
    }
    lapi.lua_pushinteger(L, totalsize);
    return 1;
};

/*
** Unpack an integer with 'size' bytes and 'islittle' endianness.
** If size is smaller than the size of a Lua integer and integer
** is signed, must do sign extension (propagating the sign to the
** higher bits); if size is larger than the size of a Lua integer,
** it must check the unread bytes to see whether they do not cause an
** overflow.
*/
const unpackint = function(L, str, islittle, size, issigned) {
    let res = 0;
    let limit = size <= SZINT ? size : SZINT;
    for (let i = limit - 1; i >= 0; i--) {
        res <<= NB;
        res |= str[islittle ? i : size - 1 - i];
    }
    if (size < SZINT) {  /* real size smaller than lua_Integer? */
        if (issigned) {  /* needs sign extension? */
            let mask = 1 << (size * NB - 1);
            res = ((res ^ mask) - mask);  /* do sign extension */
        }
    } else if (size > SZINT) {  /* must check unread bytes */
        let mask = issigned || res >= 0 ? 0 : MC;
        for (let i = limit; i < size; i++) {
            if (str[islittle ? i : size - 1 - i] !== mask)
                lauxlib.luaL_error(L, `${size}-byte integer does not fit into Lua Integer`);
        }
    }
    return res;
};

const unpacknum = function(L, b, islittle, size) {
    assert(b.length >= size);

    let dv = new DataView(new ArrayBuffer(size));
    b.forEach((e, i) => dv.setUint8(i, e, islittle));

    return dv.getFloat64(0, islittle);
};

const str_unpack = function(L) {
    let h = new Header(L);
    let fmt = lauxlib.luaL_checkstring(L, 1).split('');
    fmt.push('\0'); // Add \0 to avoid overflow
    fmt = {
        s: fmt,
        off: 0
    };
    let data = lauxlib.luaL_checkstring(L, 2);
    data = L.stack[lapi.index2addr_(L, 2)].value;
    let ld = data.length;
    let pos = posrelat(lauxlib.luaL_optinteger(L, 3, 1), ld) - 1;
    let n = 0;  /* number of results */
    lauxlib.luaL_argcheck(L, pos <= ld, 3, "initial position out of string");
    while (fmt.s.length - 1 > 0) {
        let details = getdetails(h, pos, fmt);
        let opt = details.opt;
        let size = details.size;
        let ntoalign = details.ntoalign;
        if (/*ntoalign + size > ~pos ||*/ pos + ntoalign + size > ld)
            lauxlib.luaL_argerror(L, 2, "data string too short");
        pos += ntoalign;  /* skip alignment */
        /* stack space for item + next position */
        lauxlib.luaL_checkstack(L, 2, "too many results");
        n++;
        switch (opt) {
            case KOption.Kint:
            case KOption.Kuint: {
                let res = unpackint(L, data.slice(pos), h.islittle, size, opt === KOption.Kint);
                lapi.lua_pushinteger(L, res);
                break;
            }
            case KOption.Kfloat: {
                let res = unpacknum(L, data.slice(pos), h.islittle, size);
                lapi.lua_pushnumber(L, res);
                break;
            }
            case KOption.Kchar: {
                // lapi.lua_pushstring(L, data.slice(pos, pos + size));
                L.stack[L.top++] = new lobject.TValue(CT.LUA_TLNGSTR, data.slice(pos, pos + size));
                break;
            }
            case KOption.Kstring: {
                let len = unpackint(L, data.slice(pos), h.islittle, size, 0);
                lauxlib.luaL_argcheck(L, pos + len + size <= ld, 2, "data string too short");
                // lapi.lua_pushstring(L, data.slice(pos + size, pos + size + len));
                L.stack[L.top++] = new lobject.TValue(CT.LUA_TLNGSTR, data.slice(pos + size, pos + size + len));
                pos += len;  /* skip string */
                break;
            }
            case KOption.Kzstr: {
                let len = data.slice(pos).indexOf(0);
                // lapi.lua_pushstring(L, data.slice(pos, pos + len));
                L.stack[L.top++] = new lobject.TValue(CT.LUA_TLNGSTR, data.slice(pos, pos + len));
                pos += len + 1;  /* skip string plus final '\0' */
                break;
            }
            case KOption.Kpaddalign: case KOption.Kpadding: case KOption.Knop:
                n--;  /* undo increment */
                break;
        }
        pos += size;
    }
    lapi.lua_pushinteger(L, pos + 1);  /* next position */
    return n + 1;
};

const strlib = {
    "byte":     str_byte,
    "char":     str_char,
    "dump":     str_dump,
    "format":   str_format,
    "len":      str_len,
    "lower":    str_lower,
    "pack":     str_pack,
    "packsize": str_packsize,
    "rep":      str_rep,
    "reverse":  str_reverse,
    "sub":      str_sub,
    "unpack":   str_unpack,
    "upper":    str_upper
};

const createmetatable = function(L) {
    lapi.lua_createtable(L, 0, 1);  /* table to be metatable for strings */
    lapi.lua_pushliteral(L, "");  /* dummy string */
    lapi.lua_pushvalue(L, -2);  /* copy table */
    lapi.lua_setmetatable(L, -2);  /* set table as metatable for strings */
    lapi.lua_pop(L, 1);  /* pop dummy string */
    lapi.lua_pushvalue(L, -2);  /* get string library */
    lapi.lua_setfield(L, -2, "__index");  /* metatable.__index = string */
    lapi.lua_pop(L, 1);  /* pop metatable */  
};

const luaopen_string = function(L) {
    lauxlib.luaL_newlib(L, strlib);
    createmetatable(L);
    return 1;
};

module.exports.luaopen_string = luaopen_string;