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Overview
Comment: | Document [binary set] and clean up the binary manpage |
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Downloads: | Tarball | ZIP archive |
Timelines: | family | ancestors | descendants | both | tip-450 |
Files: | files | file ages | folders |
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b0371b4216ea6217ad97064faea7014a |
User & Date: | dkf 2019-06-14 21:15:58.956 |
Context
2019-06-15
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07:03 | Rewrote to do modifications in-place unless Tcl_Obj is shared. check-in: 5c1e5aa513 user: dkf tags: tip-450 | |
2019-06-14
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21:15 | Document [binary set] and clean up the binary manpage check-in: b0371b4216 user: dkf tags: tip-450 | |
20:30 | Fix the bug; set current end to end of input string so @* can go there. check-in: 9df20cff69 user: dkf tags: tip-450 | |
Changes
Changes to doc/binary.n.
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8 9 10 11 12 13 14 | .TH binary n 8.0 Tcl "Tcl Built-In Commands" .so man.macros .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME binary \- Insert and extract fields from binary strings .SH SYNOPSIS | < < > > > > | > > > < < | 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 | .TH binary n 8.0 Tcl "Tcl Built-In Commands" .so man.macros .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME binary \- Insert and extract fields from binary strings .SH SYNOPSIS \fBbinary decode \fIformat\fR ?\fI\-option value ...\fR? \fIdata\fR .br \fBbinary encode \fIformat\fR ?\fI\-option value ...\fR? \fIdata\fR .br \fBbinary format \fIformatString \fR?\fIarg arg ...\fR? .br \fBbinary scan \fIstring formatString \fR?\fIvarName varName ...\fR? .br .VS "8.7, TIP 450" \fBbinary set \fIvarName formatString \fR?\fIarg arg ...\fR? .VE "8.7, TIP 450" .BE .SH DESCRIPTION .PP This command provides facilities for manipulating binary data. The subcommand \fBbinary format\fR creates a binary string from normal Tcl values. For example, given the values 16 and 22, on a 32-bit architecture, it might produce an 8-byte binary string consisting of two 4-byte integers, one for each of the numbers. The subcommand \fBbinary scan\fR, does the opposite: it extracts data from a binary string and returns it as ordinary Tcl string values. .VS "8.7, TIP 450" The subcommand \fBbinary set\fR is similar to \fBbinary format\fR, except that it updates an existing binary string in a variable. .VE "8.7, TIP 450" The \fBbinary encode\fR and \fBbinary decode\fR subcommands convert binary data to or from string encodings such as base64 (used in MIME messages for example). .PP Note that other operations on binary data, such as taking a subsequence of it, getting its length, or reinterpreting it as a string in some encoding, are done by other Tcl commands (respectively \fBstring range\fR, \fBstring length\fR and \fBencoding convertfrom\fR in the example cases). A binary string in Tcl is merely one where all the characters it contains are in the range \eu0000\-\eu00FF. .SH "BINARY ENCODE AND DECODE" .PP When encoding binary data as a readable string, the starting binary data is passed to the \fBbinary encode\fR command, together with the name of the encoding to use and any encoding-specific options desired. Data which has been encoded can be converted back to binary form using \fBbinary decode\fR. The following formats and options are supported. .TP |
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124 125 126 127 128 129 130 | . Instructs the decoder to throw an error if it encounters unexpected whitespace characters. Otherwise it ignores them. .PP Note that neither the encoder nor the decoder handle the header and footer of the uuencode format. .RE | < | > > > > > > > | | > > > | > | 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 | . Instructs the decoder to throw an error if it encounters unexpected whitespace characters. Otherwise it ignores them. .PP Note that neither the encoder nor the decoder handle the header and footer of the uuencode format. .RE .SH "BINARY FORMAT AND BINARY SET" .PP The \fBbinary format\fR command generates a binary string whose layout is specified by the \fIformatString\fR and whose contents come from the additional arguments. The resulting binary value is returned. .PP .VS "8.7, TIP 450" The \fBbinary set\fR command reads an existing binary string stored in the variable \fIvarName\fR, modifies it according to the \fIformatString\fR using the contents from the additional arguments, and writes the result back. The result of the command is the empty string. .VE "8.7, TIP 450" .PP In both cases, \fIformatString\fR consists of a sequence of zero or more field specifiers separated by zero or more spaces. Each field specifier is a single type character followed by an optional flag character followed by an optional numeric \fIcount\fR. Most field specifiers consume one argument to obtain the value to be formatted. The type character specifies how the value is to be formatted. The \fIcount\fR typically indicates how many items of the specified type are taken from the value. If present, the \fIcount\fR is a non-negative decimal integer or .QW \fB*\fR , which normally indicates that all of the items in the value are to be used. If the number of arguments does not match the number of fields in the format string that consume arguments, then an error is generated. The flag character .QW \fBu\fR is ignored for \fBbinary format\fR and \fBbinary set\fR. .PP Here is a small example to clarify the relation between the field specifiers and the arguments: .PP .CS \fBbinary format\fR d3d {1.0 2.0 3.0 4.0} 0.1 .CE .PP The first argument is a list of four numbers, but because of the count of 3 for the associated field specifier, only the first three will be used. The second argument is associated with the second field |
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174 175 176 177 178 179 180 | the \fBencoding convertto\fR command should be used first to change the string into an external representation if this truncation is not desired (i.e. if the characters are not part of the ISO 8859\-1 character set.) If \fIarg\fR has fewer than \fIcount\fR bytes, then additional zero bytes are used to pad out the field. If \fIarg\fR is longer than the specified length, the extra characters will be ignored. If | > > | > > > > > > > > > > | > > > > > > > | > > > > > > | > > > > > > > > > > > > > > > > > | > > | > > > > | > | > > > > | > > > > | > > | > > > > > > > > > > | 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 | the \fBencoding convertto\fR command should be used first to change the string into an external representation if this truncation is not desired (i.e. if the characters are not part of the ISO 8859\-1 character set.) If \fIarg\fR has fewer than \fIcount\fR bytes, then additional zero bytes are used to pad out the field. If \fIarg\fR is longer than the specified length, the extra characters will be ignored. If \fIcount\fR is .QW \fB*\fR , then all of the bytes in \fIarg\fR will be formatted. If \fIcount\fR is omitted, then one character will be formatted. For example, .RS .PP .CS \fBbinary format\fR a7a*a alpha bravo charlie .CE .PP will return a string equivalent to \fBalpha\e000\e000bravoc\fR, .PP .CS \fBbinary format\fR a* [encoding convertto utf-8 \eu20ac] .CE .PP will return a string equivalent to \fB\e342\e202\e254\fR (which is the UTF-8 byte sequence for a Euro-currency character) and .PP .CS \fBbinary format\fR a* [encoding convertto iso8859-15 \eu20ac] .CE .PP will return a string equivalent to \fB\e244\fR (which is the ISO 8859\-15 byte sequence for a Euro-currency character). Contrast these last two with: .PP .CS \fBbinary format\fR a* \eu20ac .CE .PP which returns a string equivalent to \fB\e254\fR (i.e. \fB\exac\fR) by truncating the high-bits of the character, and which is probably not what is desired. .RE .IP \fBA\fR 5 This form is the same as \fBa\fR except that spaces are used for padding instead of nulls. For example, .RS .PP .CS \fBbinary format\fR A6A*A alpha bravo charlie .CE .PP will return \fBalpha bravoc\fR. .RE .IP \fBb\fR 5 Stores a string of \fIcount\fR binary digits in low-to-high order within each byte in the output string. \fIArg\fR must contain a sequence of \fB1\fR and \fB0\fR characters. The resulting bytes are emitted in first to last order with the bits being formatted in low-to-high order within each byte. If \fIarg\fR has fewer than \fIcount\fR digits, then zeros will be used for the remaining bits. If \fIarg\fR has more than the specified number of digits, the extra digits will be ignored. If \fIcount\fR is .QW \fB*\fR , then all of the digits in \fIarg\fR will be formatted. If \fIcount\fR is omitted, then one digit will be formatted. If the number of bits formatted does not end at a byte boundary, the remaining bits of the last byte will be zeros. For example, .RS .PP .CS \fBbinary format\fR b5b* 11100 111000011010 .CE .PP will return a string equivalent to \fB\ex07\ex87\ex05\fR. .RE .IP \fBB\fR 5 This form is the same as \fBb\fR except that the bits are stored in high-to-low order within each byte. For example, .RS .PP .CS \fBbinary format\fR B5B* 11100 111000011010 .CE .PP will return a string equivalent to \fB\exe0\exe1\exa0\fR. .RE .IP \fBH\fR 5 Stores a string of \fIcount\fR hexadecimal digits in high-to-low within each byte in the output string. \fIArg\fR must contain a sequence of characters in the set .QW 0123456789abcdefABCDEF . The resulting bytes are emitted in first to last order with the hex digits being formatted in high-to-low order within each byte. If \fIarg\fR has fewer than \fIcount\fR digits, then zeros will be used for the remaining digits. If \fIarg\fR has more than the specified number of digits, the extra digits will be ignored. If \fIcount\fR is .QW \fB*\fR , then all of the digits in \fIarg\fR will be formatted. If \fIcount\fR is omitted, then one digit will be formatted. If the number of digits formatted does not end at a byte boundary, the remaining bits of the last byte will be zeros. For example, .RS .PP .CS \fBbinary format\fR H3H*H2 ab DEF 987 .CE .PP will return a string equivalent to \fB\exab\ex00\exde\exf0\ex98\fR. .RE .IP \fBh\fR 5 This form is the same as \fBH\fR except that the digits are stored in low-to-high order within each byte. This is seldom required. For example, .RS .PP .CS \fBbinary format\fR h3h*h2 AB def 987 .CE .PP will return a string equivalent to \fB\exba\ex00\exed\ex0f\ex89\fR. .RE .IP \fBc\fR 5 Stores one or more 8-bit integer values in the output string. If no \fIcount\fR is specified, then \fIarg\fR must consist of an integer value. If \fIcount\fR is specified, \fIarg\fR must consist of a list containing at least that many integers. The low-order 8 bits of each integer are stored as a one-byte value at the cursor position. If \fIcount\fR is .QW \fB*\fR , then all of the integers in the list are formatted. If the number of elements in the list is greater than \fIcount\fR, then the extra elements are ignored. For example, .RS .PP .CS \fBbinary format\fR c3cc* {3 -3 128 1} 260 {2 5} .CE .PP will return a string equivalent to \fB\ex03\exfd\ex80\ex04\ex02\ex05\fR, whereas .PP .CS \fBbinary format\fR c {2 5} .CE .PP will generate an error. .RE .IP \fBs\fR 5 This form is the same as \fBc\fR except that it stores one or more 16-bit integers in little-endian byte order in the output string. The low-order 16-bits of each integer are stored as a two-byte value at the cursor position with the least significant byte stored first. For example, .RS .PP .CS \fBbinary format\fR s3 {3 -3 258 1} .CE .PP will return a string equivalent to \fB\ex03\ex00\exfd\exff\ex02\ex01\fR. .RE .IP \fBS\fR 5 This form is the same as \fBs\fR except that it stores one or more 16-bit integers in big-endian byte order in the output string. For example, .RS .PP .CS \fBbinary format\fR S3 {3 -3 258 1} .CE .PP will return a string equivalent to \fB\ex00\ex03\exff\exfd\ex01\ex02\fR. .RE .IP \fBt\fR 5 This form (mnemonically \fItiny\fR) is the same as \fBs\fR and \fBS\fR except that it stores the 16-bit integers in the output string in the native byte order of the machine where the Tcl script is running. To determine what the native byte order of the machine is, refer to the \fBbyteOrder\fR element of the \fBtcl_platform\fR array. .IP \fBi\fR 5 This form is the same as \fBc\fR except that it stores one or more 32-bit integers in little-endian byte order in the output string. The low-order 32-bits of each integer are stored as a four-byte value at the cursor position with the least significant byte stored first. For example, .RS .PP .CS \fBbinary format\fR i3 {3 -3 65536 1} .CE .PP will return a string equivalent to \fB\ex03\ex00\ex00\ex00\exfd\exff\exff\exff\ex00\ex00\ex01\ex00\fR .RE .IP \fBI\fR 5 This form is the same as \fBi\fR except that it stores one or more one or more 32-bit integers in big-endian byte order in the output string. For example, .RS .PP .CS \fBbinary format\fR I3 {3 -3 65536 1} .CE .PP will return a string equivalent to \fB\ex00\ex00\ex00\ex03\exff\exff\exff\exfd\ex00\ex01\ex00\ex00\fR .RE .IP \fBn\fR 5 This form (mnemonically \fInumber\fR or \fInormal\fR) is the same as \fBi\fR and \fBI\fR except that it stores the 32-bit integers in the output string in the native byte order of the machine where the Tcl script is running. To determine what the native byte order of the machine is, refer to the \fBbyteOrder\fR element of the \fBtcl_platform\fR array. .IP \fBw\fR 5 This form is the same as \fBc\fR except that it stores one or more 64-bit integers in little-endian byte order in the output string. The low-order 64-bits of each integer are stored as an eight-byte value at the cursor position with the least significant byte stored first. For example, .RS .PP .CS \fBbinary format\fR w 7810179016327718216 .CE .PP will return the string \fBHelloTcl\fR .RE .IP \fBW\fR 5 This form is the same as \fBw\fR except that it stores one or more one or more 64-bit integers in big-endian byte order in the output string. For example, .RS .PP .CS \fBbinary format\fR Wc 4785469626960341345 110 .CE .PP will return the string \fBBigEndian\fR .RE .IP \fBm\fR 5 This form (mnemonically the mirror of \fBw\fR) is the same as \fBw\fR and \fBW\fR except that it stores the 64-bit integers in the output string in the native byte order of the machine where the Tcl script is running. To determine what the native byte order of the machine is, refer to the \fBbyteOrder\fR element of the \fBtcl_platform\fR array. .IP \fBf\fR 5 This form is the same as \fBc\fR except that it stores one or more one or more single-precision floating point numbers in the machine's native representation in the output string. This representation is not portable across architectures, so it should not be used to communicate floating point numbers across the network. The size of a floating point number may vary across architectures, so the number of bytes that are generated may vary, but is 4 on common architectures that implement IEEE floating point representation. If the value overflows the machine's native representation, then the value of FLT_MAX as defined by the system will be used instead. Because Tcl uses double-precision floating point numbers internally, there may be some loss of precision in the conversion to single-precision. For example, on a Windows system running on an Intel Pentium processor, .RS .PP .CS \fBbinary format\fR f2 {1.6 3.4} .CE .PP will return a string equivalent to \fB\excd\excc\excc\ex3f\ex9a\ex99\ex59\ex40\fR. .RE .IP \fBr\fR 5 This form (mnemonically \fIreal\fR) is the same as \fBf\fR except that it stores the single-precision floating point numbers in little-endian order. This conversion only produces meaningful output when used on machines which use the IEEE floating point representation (very common, but not universal.) .IP \fBR\fR 5 This form is the same as \fBr\fR except that it stores the single-precision floating point numbers in big-endian order. .IP \fBd\fR 5 This form is the same as \fBf\fR except that it stores one or more one or more double-precision floating point numbers in the machine's native representation in the output string (these are usually 8 bytes wide on common architectures, i.e., those that use IEEE floating point representation). For example, on a Windows system running on an Intel Pentium processor, .RS .PP .CS \fBbinary format\fR d1 {1.6} .CE .PP will return a string equivalent to \fB\ex9a\ex99\ex99\ex99\ex99\ex99\exf9\ex3f\fR. .RE .IP \fBq\fR 5 This form (mnemonically the mirror of \fBd\fR) is the same as \fBd\fR except that it stores the double-precision floating point numbers in little-endian order. This conversion only produces meaningful output when used on machines which use the IEEE floating point representation (very common, but not universal.) .IP \fBQ\fR 5 This form is the same as \fBq\fR except that it stores the double-precision floating point numbers in big-endian order. .IP \fBx\fR 5 Stores \fIcount\fR null bytes in the output string. If \fIcount\fR is not specified, stores one null byte. If \fIcount\fR is .QW \fB*\fR , this generates an error. This type does not consume an argument. For example, .RS .PP .CS \fBbinary format\fR a3xa3x2a3 abc def ghi .CE .PP will return a string equivalent to \fBabc\e000def\e000\e000ghi\fR. .RE .IP \fBX\fR 5 Moves the cursor back \fIcount\fR bytes in the output string. If \fIcount\fR is .QW \fB*\fR or is larger than the current cursor position, then the cursor is positioned at location 0 so that the next byte stored will be the first byte in the result string. If \fIcount\fR is omitted then the cursor is moved back one byte. This type does not consume an argument. For example, .RS .PP .CS \fBbinary format\fR a3X*a3X2a3 abc def ghi .CE .PP will return \fBdghi\fR. .RE .IP \fB@\fR 5 Moves the cursor to the absolute location in the output string specified by \fIcount\fR. Position 0 refers to the first byte in the output string. If \fIcount\fR refers to a position beyond the last byte stored so far, then null bytes will be placed in the uninitialized locations and the cursor will be placed at the specified location. If \fIcount\fR is .QW \fB*\fR , then the cursor is moved to the current end of the output string. If \fIcount\fR is omitted, then an error will be generated. This type does not consume an argument. For example, .RS .PP .CS \fBbinary format\fR a5@2a1@*a3@10a1 abcde f ghi j .CE .PP will return \fBabfdeghi\e000\e000j\fR, and .VS "8.7, TIP 450" .PP .CS set x abc \fBbinary set\fR x c@*c 65 68 .CE .PP will update the variable \fIx\fR to \fBAbcD\fR (extending it by one byte from the value it was before). .VE "8.7, TIP 450" .RE .SH "BINARY SCAN" .PP The \fBbinary scan\fR command parses fields from a binary string, returning the number of conversions performed. \fIString\fR gives the input bytes to be parsed (one byte per character, and characters not representable as a byte have their high bits chopped) |
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485 486 487 488 489 490 491 | spaces. Each field specifier is a single type character followed by an optional flag character followed by an optional numeric \fIcount\fR. Most field specifiers consume one argument to obtain the variable into which the scanned values should be placed. The type character specifies how the binary data is to be interpreted. The \fIcount\fR typically indicates how many items of the specified type are taken from the data. If present, the | | > > | > | > | > | > | > | > | | > > > | | > | > | > | > | > | > | > | | > | > | > | > > | | > | > | > | > | > | > | > | > | < < < < < | > | > | | > | > | < < < < < | > | > | > | > | > | > | | > | > | < < < < < | > | > | > | > | > | > | | > | > | < | > | > | > | > > > | | > | > | > | > | > | > > > | | > | > > > | | > | > | > | > | 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 | spaces. Each field specifier is a single type character followed by an optional flag character followed by an optional numeric \fIcount\fR. Most field specifiers consume one argument to obtain the variable into which the scanned values should be placed. The type character specifies how the binary data is to be interpreted. The \fIcount\fR typically indicates how many items of the specified type are taken from the data. If present, the \fIcount\fR is a non-negative decimal integer or .QW \fB*\fR , which normally indicates that all of the remaining items in the data are to be used. If there are not enough bytes left after the current cursor position to satisfy the current field specifier, then the corresponding variable is left untouched and \fBbinary scan\fR returns immediately with the number of variables that were set. If there are not enough arguments for all of the fields in the format string that consume arguments, then an error is generated. The flag character .QW \fBu\fR may be given to cause some types to be read as unsigned values. The flag is accepted for all field types but is ignored for non-integer fields. .PP A similar example as with \fBbinary format\fR should explain the relation between field specifiers and arguments in case of the binary scan subcommand: .PP .CS \fBbinary scan\fR $bytes s3s first second .CE .PP This command (provided the binary string in the variable \fIbytes\fR is long enough) assigns a list of three integers to the variable \fIfirst\fR and assigns a single value to the variable \fIsecond\fR. If \fIbytes\fR contains fewer than 8 bytes (i.e. four 2-byte integers), no assignment to \fIsecond\fR will be made, and if \fIbytes\fR contains fewer than 6 bytes (i.e. three 2-byte integers), no assignment to \fIfirst\fR will be made. Hence: .PP .CS puts [\fBbinary scan\fR abcdefg s3s first second] puts $first puts $second .CE .PP will print (assuming neither variable is set previously): .PP .CS 1 25185 25699 26213 can't read "second": no such variable .CE .PP It is \fIimportant\fR to note that the \fBc\fR, \fBs\fR, and \fBS\fR (and \fBi\fR and \fBI\fR on 64bit systems) will be scanned into long data size values. In doing this, values that have their high bit set (0x80 for chars, 0x8000 for shorts, 0x80000000 for ints), will be sign extended. Thus the following will occur: .PP .CS set signShort [\fBbinary format\fR s1 0x8000] \fBbinary scan\fR $signShort s1 val; \fI# val == 0xFFFF8000\fR .CE .PP If you require unsigned values you can include the .QW \fBu\fR flag character following the field type. For example, to read an \fIunsigned\fR short value: .PP .CS set signShort [\fBbinary format\fR s1 0x8000] \fBbinary scan\fR $signShort su1 val; \fI# val == 0x00008000\fR .CE .PP Each type-count pair moves an imaginary cursor through the binary data, reading bytes from the current position. The cursor is initially at position 0 at the beginning of the data. The type may be any one of the following characters: .IP \fBa\fR 5 The data is a byte string of length \fIcount\fR. If \fIcount\fR is .QW \fB*\fR , then all of the remaining bytes in \fIstring\fR will be scanned into the variable. If \fIcount\fR is omitted, then one byte will be scanned. All bytes scanned will be interpreted as being characters in the range \eu0000-\eu00ff so the \fBencoding convertfrom\fR command will be needed if the string is not a binary string or a string encoded in ISO 8859\-1. For example, .RS .PP .CS \fBbinary scan\fR abcde\e000fghi a6a10 var1 var2 .CE .PP will return \fB1\fR with the string equivalent to \fBabcde\e000\fR stored in \fIvar1\fR and \fIvar2\fR left unmodified, and .PP .CS \fBbinary scan\fR \e342\e202\e254 a* var1 set var2 [encoding convertfrom utf-8 $var1] .CE .PP will store a Euro-currency character in \fIvar2\fR. .RE .IP \fBA\fR 5 This form is the same as \fBa\fR, except trailing blanks and nulls are stripped from the scanned value before it is stored in the variable. For example, .RS .PP .CS \fBbinary scan\fR "abc efghi \e000" A* var1 .CE .PP will return \fB1\fR with \fBabc efghi\fR stored in \fIvar1\fR. .RE .IP \fBb\fR 5 The data is turned into a string of \fIcount\fR binary digits in low-to-high order represented as a sequence of .QW 1 and .QW 0 characters. The data bytes are scanned in first to last order with the bits being taken in low-to-high order within each byte. Any extra bits in the last byte are ignored. If \fIcount\fR is .QW \fB*\fR , then all of the remaining bits in \fIstring\fR will be scanned. If \fIcount\fR is omitted, then one bit will be scanned. For example, .RS .PP .CS \fBbinary scan\fR \ex07\ex87\ex05 b5b* var1 var2 .CE .PP will return \fB2\fR with \fB11100\fR stored in \fIvar1\fR and \fB1110000110100000\fR stored in \fIvar2\fR. .RE .IP \fBB\fR 5 This form is the same as \fBb\fR, except the bits are taken in high-to-low order within each byte. For example, .RS .PP .CS \fBbinary scan\fR \ex70\ex87\ex05 B5B* var1 var2 .CE .PP will return \fB2\fR with \fB01110\fR stored in \fIvar1\fR and \fB1000011100000101\fR stored in \fIvar2\fR. .RE .IP \fBH\fR 5 The data is turned into a string of \fIcount\fR hexadecimal digits in high-to-low order represented as a sequence of characters in the set .QW 0123456789abcdef . The data bytes are scanned in first to last order with the hex digits being taken in high-to-low order within each byte. Any extra bits in the last byte are ignored. If \fIcount\fR is .QW \fB*\fR , then all of the remaining hex digits in \fIstring\fR will be scanned. If \fIcount\fR is omitted, then one hex digit will be scanned. For example, .RS .PP .CS \fBbinary scan\fR \ex07\exC6\ex05\ex1f\ex34 H3H* var1 var2 .CE .PP will return \fB2\fR with \fB07c\fR stored in \fIvar1\fR and \fB051f34\fR stored in \fIvar2\fR. .RE .IP \fBh\fR 5 This form is the same as \fBH\fR, except the digits are taken in reverse (low-to-high) order within each byte. For example, .RS .PP .CS \fBbinary scan\fR \ex07\ex86\ex05\ex12\ex34 h3h* var1 var2 .CE .PP will return \fB2\fR with \fB706\fR stored in \fIvar1\fR and \fB502143\fR stored in \fIvar2\fR. .PP Note that most code that wishes to parse the hexadecimal digits from multiple bytes in order should use the \fBH\fR format. .RE .IP \fBc\fR 5 The data is turned into \fIcount\fR 8-bit signed (or unsigned if \fBcu\fR is used instead of \fBc\fR) integers and stored in the corresponding variable as a list. If \fIcount\fR is .QW \fB*\fR , then all of the remaining bytes in \fIstring\fR will be scanned. If \fIcount\fR is omitted, then one 8-bit integer will be scanned. For example, .RS .PP .CS \fBbinary scan\fR \ex07\ex86\ex05 c2c* var1 var2 .CE .PP will return \fB2\fR with \fB7 -122\fR stored in \fIvar1\fR and \fB5\fR stored in \fIvar2\fR. .RE .IP \fBs\fR 5 The data is interpreted as \fIcount\fR 16-bit signed (or unsigned if \fBsu\fR is used instead of \fBs\fR) integers represented in little-endian byte order. The integers are stored in the corresponding variable as a list. If \fIcount\fR is .QW \fB*\fR , then all of the remaining bytes in \fIstring\fR will be scanned. If \fIcount\fR is omitted, then one 16-bit integer will be scanned. For example, .RS .PP .CS \fBbinary scan\fR \ex05\ex00\ex07\ex00\exf0\exff s2s* var1 var2 .CE .PP will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR stored in \fIvar2\fR. .RE .IP \fBS\fR 5 This form is the same as \fBs\fR except that the data is interpreted as \fIcount\fR 16-bit signed (or unsigned if \fBSu\fR is used instead of \fBS\fR) integers represented in big-endian byte order. For example, .RS .PP .CS \fBbinary scan\fR \ex00\ex05\ex00\ex07\exff\exf0 S2S* var1 var2 .CE .PP will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR stored in \fIvar2\fR. .RE .IP \fBt\fR 5 The data is interpreted as \fIcount\fR 16-bit signed (or unsigned if \fBtu\fR is used instead of \fBt\fR) integers represented in the native byte order of the machine running the Tcl script. It is otherwise identical to \fBs\fR and \fBS\fR. To determine what the native byte order of the machine is, refer to the \fBbyteOrder\fR element of the \fBtcl_platform\fR array. .IP \fBi\fR 5 The data is interpreted as \fIcount\fR 32-bit signed (or unsigned if \fBiu\fR is used instead of \fBi\fR) integers represented in little-endian byte order. The integers are stored in the corresponding variable as a list. If \fIcount\fR is .QW \fB*\fR , then all of the remaining bytes in \fIstring\fR will be scanned. If \fIcount\fR is omitted, then one 32-bit integer will be scanned. For example, .RS .PP .CS set str \ex05\ex00\ex00\ex00\ex07\ex00\ex00\ex00\exf0\exff\exff\exff \fBbinary scan\fR $str i2i* var1 var2 .CE .PP will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR stored in \fIvar2\fR. .RE .IP \fBI\fR 5 This form is the same as \fBI\fR except that the data is interpreted as \fIcount\fR 32-bit signed (or unsigned if \fBIu\fR is used instead of \fBI\fR) integers represented in big-endian byte order. For example, .RS .PP .CS set str \ex00\ex00\ex00\ex05\ex00\ex00\ex00\ex07\exff\exff\exff\exf0 \fBbinary scan\fR $str I2I* var1 var2 .CE .PP will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR stored in \fIvar2\fR. .RE .IP \fBn\fR 5 The data is interpreted as \fIcount\fR 32-bit signed (or unsigned if \fBnu\fR is used instead of \fBn\fR) integers represented in the native byte order of the machine running the Tcl script. It is otherwise identical to \fBi\fR and \fBI\fR. To determine what the native byte order of the machine is, refer to the \fBbyteOrder\fR element of the \fBtcl_platform\fR array. .IP \fBw\fR 5 The data is interpreted as \fIcount\fR 64-bit signed (or unsigned if \fBwu\fR is used instead of \fBw\fR) integers represented in little-endian byte order. The integers are stored in the corresponding variable as a list. If \fIcount\fR is .QW \fB*\fR , then all of the remaining bytes in \fIstring\fR will be scanned. If \fIcount\fR is omitted, then one 64-bit integer will be scanned. For example, .RS .PP .CS set str \ex05\ex00\ex00\ex00\ex07\ex00\ex00\ex00\exf0\exff\exff\exff \fBbinary scan\fR $str wi* var1 var2 .CE .PP will return \fB2\fR with \fB30064771077\fR stored in \fIvar1\fR and \fB\-16\fR stored in \fIvar2\fR. .RE .IP \fBW\fR 5 This form is the same as \fBw\fR except that the data is interpreted as \fIcount\fR 64-bit signed (or unsigned if \fBWu\fR is used instead of \fBw\fR) integers represented in big-endian byte order. For example, .RS .PP .CS set str \ex00\ex00\ex00\ex05\ex00\ex00\ex00\ex07\exff\exff\exff\exf0 \fBbinary scan\fR $str WI* var1 var2 .CE .PP will return \fB2\fR with \fB21474836487\fR stored in \fIvar1\fR and \fB\-16\fR stored in \fIvar2\fR. .RE .IP \fBm\fR 5 The data is interpreted as \fIcount\fR 64-bit signed (or unsigned if \fBmu\fR is used instead of \fBm\fR) integers represented in the native byte order of the machine running the Tcl script. It is otherwise identical to \fBw\fR and \fBW\fR. To determine what the native byte order of the machine is, refer to the \fBbyteOrder\fR element of the \fBtcl_platform\fR array. .IP \fBf\fR 5 The data is interpreted as \fIcount\fR single-precision floating point numbers in the machine's native representation. The floating point numbers are stored in the corresponding variable as a list. If \fIcount\fR is .QW \fB*\fR , then all of the remaining bytes in \fIstring\fR will be scanned. If \fIcount\fR is omitted, then one single-precision floating point number will be scanned. The size of a floating point number may vary across architectures, so the number of bytes that are scanned may vary; on most common architectures (i.e., those that use IEEE floating point representation) it is 4 bytes wide. If the data does not represent a valid floating point number, the resulting value is undefined and compiler dependent. For example, on a Windows system running on an Intel Pentium processor, .RS .PP .CS \fBbinary scan\fR \ex3f\excc\excc\excd f var1 .CE .PP will return \fB1\fR with \fB1.6000000238418579\fR stored in \fIvar1\fR. .RE .IP \fBr\fR 5 This form is the same as \fBf\fR except that the data is interpreted as \fIcount\fR single-precision floating point number in little-endian order. This conversion is not portable to the minority of systems not using IEEE floating point representations. .IP \fBR\fR 5 This form is the same as \fBf\fR except that the data is interpreted as \fIcount\fR single-precision floating point number in big-endian order. This conversion is not portable to the minority of systems not using IEEE floating point representations. .IP \fBd\fR 5 This form is the same as \fBf\fR except that the data is interpreted as \fIcount\fR double-precision floating point numbers in the machine's native representation (which is 8 bytes wide when IEEE floating point representation is used; this is the common case). For example, on a Windows system running on an Intel Pentium processor, .RS .PP .CS \fBbinary scan\fR \ex9a\ex99\ex99\ex99\ex99\ex99\exf9\ex3f d var1 .CE .PP will return \fB1\fR with \fB1.6000000000000001\fR stored in \fIvar1\fR. .RE .IP \fBq\fR 5 This form is the same as \fBd\fR except that the data is interpreted as \fIcount\fR double-precision floating point number in little-endian order. This conversion is not portable to the minority of systems not using IEEE floating point representations. .IP \fBQ\fR 5 This form is the same as \fBd\fR except that the data is interpreted as \fIcount\fR double-precision floating point number in big-endian order. This conversion is not portable to the minority of systems not using IEEE floating point representations. .IP \fBx\fR 5 Moves the cursor forward \fIcount\fR bytes in \fIstring\fR. If \fIcount\fR is .QW \fB*\fR or is larger than the number of bytes after the current cursor position, then the cursor is positioned after the last byte in \fIstring\fR. If \fIcount\fR is omitted, then the cursor is moved forward one byte. Note that this type does not consume an argument. For example, .RS .PP .CS \fBbinary scan\fR \ex01\ex02\ex03\ex04 x2H* var1 .CE .PP will return \fB1\fR with \fB0304\fR stored in \fIvar1\fR. .RE .IP \fBX\fR 5 Moves the cursor back \fIcount\fR bytes in \fIstring\fR. If \fIcount\fR is .QW \fB*\fR or is larger than the current cursor position, then the cursor is positioned at location 0 so that the next byte scanned will be the first byte in \fIstring\fR. If \fIcount\fR is omitted then the cursor is moved back one byte. Note that this type does not consume an argument. For example, .RS .PP .CS \fBbinary scan\fR \ex01\ex02\ex03\ex04 c2XH* var1 var2 .CE .PP will return \fB2\fR with \fB1 2\fR stored in \fIvar1\fR and \fB020304\fR stored in \fIvar2\fR. .RE .IP \fB@\fR 5 Moves the cursor to the absolute location in the data string specified by \fIcount\fR. Note that position 0 refers to the first byte in \fIstring\fR. If \fIcount\fR refers to a position beyond the end of \fIstring\fR, then the cursor is positioned after the last byte. If \fIcount\fR is omitted, then an error will be generated. For example, .RS .PP .CS \fBbinary scan\fR \ex01\ex02\ex03\ex04 c2@1H* var1 var2 .CE .PP will return \fB2\fR with \fB1 2\fR stored in \fIvar1\fR and \fB020304\fR stored in \fIvar2\fR. .RE .SH "PORTABILITY ISSUES" .PP The \fBr\fR, \fBR\fR, \fBq\fR and \fBQ\fR conversions will only work reliably for transferring data between computers which are all using |
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