Mercurial > hg > toybox
comparison www/code.html @ 432:01473712c9fe
Document that optflags is always an int (so 32 bit and 64 bit platforms behave the same).
| author | Rob Landley <rob@landley.net> |
|---|---|
| date | Mon, 06 Feb 2012 21:15:19 -0600 |
| parents | 2cbbd4c5eaaa |
| children | 8abb9e307d0c |
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| 431:87edfe8ae99e | 432:01473712c9fe |
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| 526 <p><b>long toys.optflags</b></p> | 526 <p><b>long toys.optflags</b></p> |
| 527 | 527 |
| 528 <p>Each option in the optflags string corresponds to a bit position in | 528 <p>Each option in the optflags string corresponds to a bit position in |
| 529 toys.optflags, with the same value as a corresponding binary digit. The | 529 toys.optflags, with the same value as a corresponding binary digit. The |
| 530 rightmost argument is (1<<0), the next to last is (1<<1) and so on. If | 530 rightmost argument is (1<<0), the next to last is (1<<1) and so on. If |
| 531 the option isn't encountered while parsing argv[], its bit remains 0. | 531 the option isn't encountered while parsing argv[], its bit remains 0.</p> |
| 532 (Since toys.optflags is a long, it's only guaranteed to store 32 bits.) | 532 |
| 533 For example, | 533 <p>For example, |
| 534 the optflags string "abcd" would parse the command line argument "-c" to set | 534 the optflags string "abcd" would parse the command line argument "-c" to set |
| 535 optflags to 2, "-a" would set optflags to 8, "-bd" would set optflags to | 535 optflags to 2, "-a" would set optflags to 8, "-bd" would set optflags to |
| 536 6 (I.E. 4|2), and "-a -c" would set optflags to 10 (2|8).</p> | 536 6 (I.E. 4|2), and "-a -c" would set optflags to 10 (2|8).</p> |
| 537 | 537 |
| 538 <p>Only letters are relevant to optflags, punctuation is skipped: in the | 538 <p>Only letters are relevant to optflags, punctuation is skipped: in the |
| 539 string "a*b:c#d", d=1, c=2, b=4, a=8. The punctuation after a letter | 539 string "a*b:c#d", d=1, c=2, b=4, a=8. The punctuation after a letter |
| 540 usually indicate that the option takes an argument.</p> | 540 usually indicate that the option takes an argument.</p> |
| 541 | |
| 542 <p>Since toys.optflags is an unsigned int, it only stores 32 bits. (Which is | |
| 543 the amount a long would have on 32-bit platforms anyway; 64 bit code on | |
| 544 32 bit platforms is too expensive to require in common code used by almost | |
| 545 all commands.) Bit positions beyond the 1<<31 aren't recorded, but | |
| 546 parsing higher options can still set global variables.</p> | |
| 541 | 547 |
| 542 <p><b>Automatically setting global variables from arguments (union this)</b></p> | 548 <p><b>Automatically setting global variables from arguments (union this)</b></p> |
| 543 | 549 |
| 544 <p>The following punctuation characters may be appended to an optflags | 550 <p>The following punctuation characters may be appended to an optflags |
| 545 argument letter, indicating the option takes an additional argument:</p> | 551 argument letter, indicating the option takes an additional argument:</p> |
| 574 with the rightmost saved in this[0]. Again using "a*b:c#d", "-c 42" would set | 580 with the rightmost saved in this[0]. Again using "a*b:c#d", "-c 42" would set |
| 575 this[0]=42; and "-b 42" would set this[1]="42"; each slot is left NULL if | 581 this[0]=42; and "-b 42" would set this[1]="42"; each slot is left NULL if |
| 576 the corresponding argument is not encountered.</p> | 582 the corresponding argument is not encountered.</p> |
| 577 | 583 |
| 578 <p>This behavior is useful because the LP64 standard ensures long and pointer | 584 <p>This behavior is useful because the LP64 standard ensures long and pointer |
| 579 are the same size, and C99 guarantees structure members will occur in memory | 585 are the same size. C99 guarantees structure members will occur in memory |
| 580 in the | 586 in the same order they're declared, and that padding won't be inserted between |
| 581 same order they're declared, and that padding won't be inserted between | |
| 582 consecutive variables of register size. Thus the first few entries can | 587 consecutive variables of register size. Thus the first few entries can |
| 583 be longs or pointers corresponding to the saved arguments.</p> | 588 be longs or pointers corresponding to the saved arguments.</p> |
| 584 | 589 |
| 585 <p><b>char *toys.optargs[]</b></p> | 590 <p><b>char *toys.optargs[]</b></p> |
| 586 | 591 |