diff options
Diffstat (limited to 'tcl/doc/binary.n')
| -rw-r--r-- | tcl/doc/binary.n | 532 |
1 files changed, 532 insertions, 0 deletions
diff --git a/tcl/doc/binary.n b/tcl/doc/binary.n new file mode 100644 index 00000000000..e03924688a8 --- /dev/null +++ b/tcl/doc/binary.n @@ -0,0 +1,532 @@ +'\" +'\" Copyright (c) 1997 by Sun Microsystems, Inc. +'\" +'\" See the file "license.terms" for information on usage and redistribution +'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. +'\" +'\" RCS: @(#) $Id$ +'\" +.so man.macros +.TH binary n 8.0 Tcl "Tcl Built-In Commands" +.BS +'\" Note: do not modify the .SH NAME line immediately below! +.SH NAME +binary \- Insert and extract fields from binary strings +.SH SYNOPSIS +\fBbinary format \fIformatString \fR?\fIarg arg ...\fR? +.br +\fBbinary scan \fIstring formatString \fR?\fIvarName varName ...\fR? +.BE + +.SH DESCRIPTION +.PP +This command provides facilities for manipulating binary data. The +first form, \fBbinary format\fR, creates a binary string from normal +Tcl values. For example, given the values 16 and 22, it might produce +an 8-byte binary string consisting of two 4-byte integers, one for +each of the numbers. The second form of the command, +\fBbinary scan\fR, does the opposite: it extracts data from a binary +string and returns it as ordinary Tcl string values. + +.SH "BINARY FORMAT" +.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 +The \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 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 \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. +.PP +Each type-count pair moves an imaginary cursor through the binary +data, storing bytes at the current position and advancing the cursor +to just after the last byte stored. 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 +Stores a character string of length \fIcount\fR in the output string. +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 \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 +.CS +\fBbinary format a7a*a alpha bravo charlie\fR +.CE +will return a string equivalent to \fBalpha\\000\\000bravoc\fR. +.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 +.CS +\fBbinary format A6A*A alpha bravo charlie\fR +.CE +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 \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 +.CS +\fBbinary format b5b* 11100 111000011010\fR +.CE +will return a string equivalent to \fB\\x07\\x87\\x05\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 +.CS +\fBbinary format B5B* 11100 111000011010\fR +.CE +will return a string equivalent to \fB\\xe0\\xe1\\xa0\fR. +.RE +.IP \fBh\fR 5 +Stores a string of \fIcount\fR hexadecimal digits in low-to-high +within each byte in the output string. \fIArg\fR must contain a +sequence of characters in the set ``0123456789abcdefABCDEF''. The +resulting bytes are emitted in first to last order with the hex digits +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 digits. If \fIarg\fR has more than the specified number of +digits, the extra digits will be ignored. If \fIcount\fR is +\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 +.CS +\fBbinary format h3h* AB def\fR +.CE +will return a string equivalent to \fB\\xba\\xed\\x0f\fR. +.RE +.IP \fBH\fR 5 +This form is the same as \fBh\fR except that the digits are stored in +high-to-low order within each byte. For example, +.RS +.CS +\fBbinary format H3H* ab DEF\fR +.CE +will return a string equivalent to \fB\\xab\\xde\\xf0\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; otherwise \fIarg\fR must consist of a list containing at least +\fIcount\fR integer elements. The low-order 8 bits of each integer +are stored as a one-byte value at the cursor position. If \fIcount\fR +is \fB*\fR, then all of the integers in the list are formatted. If +the number of elements in the list is fewer than \fIcount\fR, then an +error is generated. If the number of elements in the list is greater +than \fIcount\fR, then the extra elements are ignored. For example, +.RS +.CS +\fBbinary format c3cc* {3 -3 128 1} 257 {2 5}\fR +.CE +will return a string equivalent to +\fB\\x03\\xfd\\x80\\x01\\x02\\x05\fR, whereas +.CS +\fBbinary format c {2 5}\fR +.CE +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 +.CS +\fBbinary format s3 {3 -3 258 1}\fR +.CE +will return a string equivalent to +\fB\\x03\\x00\\xfd\\xff\\x02\\x01\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 +.CS +\fBbinary format S3 {3 -3 258 1}\fR +.CE +will return a string equivalent to +\fB\\x00\\x03\\xff\\xfd\\x01\\x02\fR. +.RE +.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 +.CS +\fBbinary format i3 {3 -3 65536 1}\fR +.CE +will return a string equivalent to +\fB\\x03\\x00\\x00\\x00\\xfd\\xff\\xff\\xff\\x00\\x00\\x10\\x00\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 +.CS +\fBbinary format I3 {3 -3 65536 1}\fR +.CE +will return a string equivalent to +\fB\\x00\\x00\\x00\\x03\\xff\\xff\\xff\\xfd\\x00\\x10\\x00\\x00\fR. +.RE +.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 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. 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 +.CS +\fBbinary format f2 {1.6 3.4}\fR +.CE +will return a string equivalent to +\fB\\xcd\\xcc\\xcc\\x3f\\x9a\\x99\\x59\\x40\fR. +.RE +.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 in the machine's native +representation in the output string. For example, on a +Windows system running on an Intel Pentium processor, +.RS +.CS +\fBbinary format d1 {1.6}\fR +.CE +will return a string equivalent to +\fB\\x9a\\x99\\x99\\x99\\x99\\x99\\xf9\\x3f\fR. +.RE +.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 \fB*\fR, +generates an error. This type does not consume an argument. For +example, +.RS +.CS +\fBbinary format a3xa3x2a3 abc def ghi\fR +.CE +will return a string equivalent to \fBabc\\000def\\000\\000ghi\fR. +.RE +.IP \fBX\fR 5 +Moves the cursor back \fIcount\fR bytes in the output string. If +\fIcount\fR is \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 +.CS +\fBbinary format a3X*a3X2a3 abc def ghi\fR +.CE +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 unitialized +locations and the cursor will be placed at the specified location. If +\fIcount\fR is \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 +.CS +\fBbinary format a5@2a1@*a3@10a1 abcde f ghi j\fR +.CE +will return \fBabfdeghi\\000\\000j\fR. +.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 to be parsed and \fIformatString\fR indicates how to parse it. +Each \fIvarName\fR gives the name of a variable; when a field is +scanned from \fIstring\fR the result is assigned to the corresponding +variable. +.PP +As with \fBbinary format\fR, the \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 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 \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. +.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 character string of length \fIcount\fR. If \fIcount\fR +is \fB*\fR, then all of the remaining bytes in \fIstring\fR will be +scanned into the variable. If \fIcount\fR is omitted, then one +character will be scanned. For example, +.RS +.CS +\fBbinary scan abcde\\000fghi a6a10 var1 var2\fR +.CE +will return \fB1\fR with the string equivalent to \fBabcde\\000\fR +stored in \fBvar1\fR and \fBvar2\fR left unmodified. +.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 +.CS +\fBbinary scan "abc efghi \\000" a* var1\fR +.CE +will return \fB1\fR with \fBabc efghi\fR stored in \fBvar1\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 ``1'' and ``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 \fB*\fR, then +all of the remaining bits in \fBstring\fR will be scanned. If +\fIcount\fR is omitted, then one bit will be scanned. For example, +.RS +.CS +\fBbinary scan \\x07\\x87\\x05 b5b* var1 var2\fR +.CE +will return \fB2\fR with \fB11100\fR stored in \fBvar1\fR and +\fB1110000110100000\fR stored in \fBvar2\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 +.CS +\fBbinary scan \\x70\\x87\\x05 b5b* var1 var2\fR +.CE +will return \fB2\fR with \fB01110\fR stored in \fBvar1\fR and +\fB1000011100000101\fR stored in \fBvar2\fR. +.RE +.IP \fBh\fR 5 +The data is turned into a string of \fIcount\fR hexadecimal digits in +low-to-high order represented as a sequence of characters in the set +``0123456789abcdef''. The data bytes are scanned in first to last +order with the hex digits being taken in low-to-high order within each +byte. Any extra bits in the last byte are ignored. If \fIcount\fR +is \fB*\fR, then all of the remaining hex digits in \fBstring\fR will be +scanned. If \fIcount\fR is omitted, then one hex digit will be +scanned. For example, +.RS +.CS +\fBbinary scan \\x07\\x86\\x05 h3h* var1 var2\fR +.CE +will return \fB2\fR with \fB706\fR stored in \fBvar1\fR and +\fB50\fR stored in \fBvar2\fR. +.RE +.IP \fBH\fR 5 +This form is the same as \fBh\fR, except the digits are taken in +low-to-high order within each byte. For example, +.RS +.CS +\fBbinary scan \\x07\\x86\\x05 H3H* var1 var2\fR +.CE +will return \fB2\fR with \fB078\fR stored in \fBvar1\fR and +\fB05\fR stored in \fBvar2\fR. +.RE +.IP \fBc\fR 5 +The data is turned into \fIcount\fR 8-bit signed integers and stored +in the corresponding variable as a list. If \fIcount\fR is \fB*\fR, +then all of the remaining bytes in \fBstring\fR will be scanned. If +\fIcount\fR is omitted, then one 8-bit integer will be scanned. For +example, +.RS +.CS +\fBbinary scan \\x07\\x86\\x05 c2c* var1 var2\fR +.CE +will return \fB2\fR with \fB7 -122\fR stored in \fBvar1\fR and \fB5\fR +stored in \fBvar2\fR. Note that the integers returned are signed, but +they can be converted to unsigned 8-bit quantities using an expression +like: +.CS +\fBexpr ( $num + 0x100 ) % 0x100\fR +.CE +.RE +.IP \fBs\fR 5 +The data is interpreted as \fIcount\fR 16-bit signed integers +represented in little-endian byte order. The integers are stored in +the corresponding variable as a list. If \fIcount\fR is \fB*\fR, then +all of the remaining bytes in \fBstring\fR will be scanned. If +\fIcount\fR is omitted, then one 16-bit integer will be scanned. For +example, +.RS +.CS +\fBbinary scan \\x05\\x00\\x07\\x00\\xf0\\xff s2s* var1 var2\fR +.CE +will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR +stored in \fBvar2\fR. Note that the integers returned are signed, but +they can be converted to unsigned 16-bit quantities using an expression +like: +.CS +\fBexpr ( $num + 0x10000 ) % 0x10000\fR +.CE +.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 integers represented in big-endian byte +order. For example, +.RS +.CS +\fBbinary scan \\x00\\x05\\x00\\x07\\xff\\xf0 S2S* var1 var2\fR +.CE +will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR +stored in \fBvar2\fR. +.RE +.IP \fBi\fR 5 +The data is interpreted as \fIcount\fR 32-bit signed integers +represented in little-endian byte order. The integers are stored in +the corresponding variable as a list. If \fIcount\fR is \fB*\fR, then +all of the remaining bytes in \fBstring\fR will be scanned. If +\fIcount\fR is omitted, then one 32-bit integer will be scanned. For +example, +.RS +.CS +\fBbinary scan \\x05\\x00\\x00\\x00\\x07\\x00\\x00\\x00\\xf0\\xff\\xff\\xff i2i* var1 var2\fR +.CE +will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR +stored in \fBvar2\fR. Note that the integers returned are signed and +cannot be represented by Tcl as unsigned values. +.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 integers represented in big-endian byte +order. For example, +.RS +.CS +\fBbinary \\x00\\x00\\x00\\x05\\x00\\x00\\x00\\x07\\xff\\xff\\xff\\xf0 I2I* var1 var2\fR +.CE +will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR +stored in \fBvar2\fR. +.RE +.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 \fB*\fR, then all of the remaining bytes in +\fBstring\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. 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 +.CS +\fBbinary scan \\x3f\\xcc\\xcc\\xcd f var1\fR +.CE +will return \fB1\fR with \fB1.6000000238418579\fR stored in +\fBvar1\fR. +.RE +.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. For example, on a Windows system +running on an Intel Pentium processor, +.RS +.CS +\fBbinary scan \\x9a\\x99\\x99\\x99\\x99\\x99\\xf9\\x3f d var1\fR +.CE +will return \fB1\fR with \fB1.6000000000000001\fR +stored in \fBvar1\fR. +.RE +.IP \fBx\fR 5 +Moves the cursor forward \fIcount\fR bytes in \fIstring\fR. If +\fIcount\fR is \fB*\fR or is larger than the number of bytes after the +current cursor 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 +.CS +\fBbinary scan \\x01\\x02\\x03\\x04 x2H* var1\fR +.CE +will return \fB1\fR with \fB0304\fR stored in \fBvar1\fR. +.RE +.IP \fBX\fR 5 +Moves the cursor back \fIcount\fR bytes in \fIstring\fR. If +\fIcount\fR is \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 +.CS +\fBbinary scan \\x01\\x02\\x03\\x04 c2XH* var1 var2\fR +.CE +will return \fB2\fR with \fB1 2\fR stored in \fBvar1\fR and \fB020304\fR +stored in \fBvar2\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 +.CS +\fBbinary scan \\x01\\x02\\x03\\x04 c2@1H* var1 var2\fR +.CE +will return \fB2\fR with \fB1 2\fR stored in \fBvar1\fR and \fB020304\fR +stored in \fBvar2\fR. +.RE + +.SH "PLATFORM ISSUES" +Sometimes it is desirable to format or scan integer values in the +native byte order for the machine. Refer to the \fBbyteOrder\fR +element of the \fBtcl_platform\fR array to decide which type character +to use when formatting or scanning integers. + +.SH "SEE ALSO" +format, scan, tclvars + +.SH KEYWORDS +binary, format, scan |