533 lines
20 KiB
Plaintext
533 lines
20 KiB
Plaintext
'\"
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'\" Copyright (c) 1997 by Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) binary.n 1.7 97/11/11 19:08:47
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'\"
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.so man.macros
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.TH binary n 8.0 Tcl "Tcl Built-In Commands"
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.BS
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'\" Note: do not modify the .SH NAME line immediately below!
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.SH NAME
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binary \- Insert and extract fields from binary strings
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.SH SYNOPSIS
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\fBbinary format \fIformatString \fR?\fIarg arg ...\fR?
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.br
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\fBbinary scan \fIstring formatString \fR?\fIvarName varName ...\fR?
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.BE
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.SH DESCRIPTION
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.PP
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This command provides facilities for manipulating binary data. The
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first form, \fBbinary format\fR, creates a binary string from normal
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Tcl values. For example, given the values 16 and 22, it might produce
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an 8-byte binary string consisting of two 4-byte integers, one for
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each of the numbers. The second form of the command,
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\fBbinary scan\fR, does the opposite: it extracts data from a binary
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string and returns it as ordinary Tcl string values.
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.SH "BINARY FORMAT"
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.PP
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The \fBbinary format\fR command generates a binary string whose layout
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is specified by the \fIformatString\fR and whose contents come from
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the additional arguments. The resulting binary value is returned.
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.PP
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The \fIformatString\fR consists of a sequence of zero or more field
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specifiers separated by zero or more spaces. Each field specifier is
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a single type character followed by an optional numeric \fIcount\fR.
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Most field specifiers consume one argument to obtain the value to be
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formatted. The type character specifies how the value is to be
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formatted. The \fIcount\fR typically indicates how many items of the
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specified type are taken from the value. If present, the \fIcount\fR
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is a non-negative decimal integer or \fB*\fR, which normally indicates
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that all of the items in the value are to be used. If the number of
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arguments does not match the number of fields in the format string
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that consume arguments, then an error is generated.
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.PP
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Each type-count pair moves an imaginary cursor through the binary
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data, storing bytes at the current position and advancing the cursor
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to just after the last byte stored. The cursor is initially at
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position 0 at the beginning of the data. The type may be any one of
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the following characters:
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.IP \fBa\fR 5
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Stores a character string of length \fIcount\fR in the output string.
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If \fIarg\fR has fewer than \fIcount\fR bytes, then additional zero
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bytes are used to pad out the field. If \fIarg\fR is longer than the
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specified length, the extra characters will be ignored. If
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\fIcount\fR is \fB*\fR, then all of the bytes in \fIarg\fR will be
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formatted. If \fIcount\fR is omitted, then one character will be
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formatted. For example,
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.RS
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.CS
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\fBbinary format a7a*a alpha bravo charlie\fR
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.CE
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will return a string equivalent to \fBalpha\\000\\000bravoc\fR.
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.RE
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.IP \fBA\fR 5
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This form is the same as \fBa\fR except that spaces are used for
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padding instead of nulls. For example,
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.RS
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.CS
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\fBbinary format A6A*A alpha bravo charlie\fR
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.CE
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will return \fBalpha bravoc\fR.
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.RE
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.IP \fBb\fR 5
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Stores a string of \fIcount\fR binary digits in low-to-high order
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within each byte in the output string. \fIArg\fR must contain a
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sequence of \fB1\fR and \fB0\fR characters. The resulting bytes are
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emitted in first to last order with the bits being formatted in
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low-to-high order within each byte. If \fIarg\fR has fewer than
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\fIcount\fR digits, then zeros will be used for the remaining bits.
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If \fIarg\fR has more than the specified number of digits, the extra
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digits will be ignored. If \fIcount\fR is \fB*\fR, then all of the
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digits in \fIarg\fR will be formatted. If \fIcount\fR is omitted,
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then one digit will be formatted. If the number of bits formatted
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does not end at a byte boundary, the remaining bits of the last byte
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will be zeros. For example,
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.RS
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.CS
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\fBbinary format b5b* 11100 111000011010\fR
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.CE
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will return a string equivalent to \fB\\x07\\x87\\x05\fR.
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.RE
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.IP \fBB\fR 5
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This form is the same as \fBb\fR except that the bits are stored in
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high-to-low order within each byte. For example,
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.RS
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.CS
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\fBbinary format B5B* 11100 111000011010\fR
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.CE
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will return a string equivalent to \fB\\xe0\\xe1\\xa0\fR.
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.RE
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.IP \fBh\fR 5
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Stores a string of \fIcount\fR hexadecimal digits in low-to-high
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within each byte in the output string. \fIArg\fR must contain a
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sequence of characters in the set ``0123456789abcdefABCDEF''. The
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resulting bytes are emitted in first to last order with the hex digits
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being formatted in low-to-high order within each byte. If \fIarg\fR
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has fewer than \fIcount\fR digits, then zeros will be used for the
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remaining digits. If \fIarg\fR has more than the specified number of
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digits, the extra digits will be ignored. If \fIcount\fR is
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\fB*\fR, then all of the digits in \fIarg\fR will be formatted. If
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\fIcount\fR is omitted, then one digit will be formatted. If the
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number of digits formatted does not end at a byte boundary, the
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remaining bits of the last byte will be zeros. For example,
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.RS
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.CS
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\fBbinary format h3h* AB def\fR
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.CE
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will return a string equivalent to \fB\\xba\\xed\\x0f\fR.
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.RE
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.IP \fBH\fR 5
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This form is the same as \fBh\fR except that the digits are stored in
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high-to-low order within each byte. For example,
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.RS
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.CS
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\fBbinary format H3H* ab DEF\fR
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.CE
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will return a string equivalent to \fB\\xab\\xde\\xf0\fR.
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.RE
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.IP \fBc\fR 5
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Stores one or more 8-bit integer values in the output string. If no
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\fIcount\fR is specified, then \fIarg\fR must consist of an integer
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value; otherwise \fIarg\fR must consist of a list containing at least
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\fIcount\fR integer elements. The low-order 8 bits of each integer
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are stored as a one-byte value at the cursor position. If \fIcount\fR
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is \fB*\fR, then all of the integers in the list are formatted. If
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the number of elements in the list is fewer than \fIcount\fR, then an
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error is generated. If the number of elements in the list is greater
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than \fIcount\fR, then the extra elements are ignored. For example,
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.RS
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.CS
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\fBbinary format c3cc* {3 -3 128 1} 257 {2 5}\fR
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.CE
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will return a string equivalent to
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\fB\\x03\\xfd\\x80\\x01\\x02\\x05\fR, whereas
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.CS
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\fBbinary format c {2 5}\fR
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.CE
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will generate an error.
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.RE
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.IP \fBs\fR 5
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This form is the same as \fBc\fR except that it stores one or more
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16-bit integers in little-endian byte order in the output string. The
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low-order 16-bits of each integer are stored as a two-byte value at
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the cursor position with the least significant byte stored first. For
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example,
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.RS
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.CS
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\fBbinary format s3 {3 -3 258 1}\fR
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.CE
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will return a string equivalent to
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\fB\\x03\\x00\\xfd\\xff\\x02\\x01\fR.
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.RE
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.IP \fBS\fR 5
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This form is the same as \fBs\fR except that it stores one or more
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16-bit integers in big-endian byte order in the output string. For
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example,
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.RS
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.CS
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\fBbinary format S3 {3 -3 258 1}\fR
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.CE
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will return a string equivalent to
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\fB\\x00\\x03\\xff\\xfd\\x01\\x02\fR.
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.RE
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.IP \fBi\fR 5
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This form is the same as \fBc\fR except that it stores one or more
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32-bit integers in little-endian byte order in the output string. The
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low-order 32-bits of each integer are stored as a four-byte value at
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the cursor position with the least significant byte stored first. For
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example,
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.RS
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.CS
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\fBbinary format i3 {3 -3 65536 1}\fR
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.CE
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will return a string equivalent to
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\fB\\x03\\x00\\x00\\x00\\xfd\\xff\\xff\\xff\\x00\\x00\\x10\\x00\fR.
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.RE
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.IP \fBI\fR 5
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This form is the same as \fBi\fR except that it stores one or more one
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or more 32-bit integers in big-endian byte order in the output string.
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For example,
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.RS
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.CS
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\fBbinary format I3 {3 -3 65536 1}\fR
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.CE
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will return a string equivalent to
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\fB\\x00\\x00\\x00\\x03\\xff\\xff\\xff\\xfd\\x00\\x10\\x00\\x00\fR.
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.RE
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.IP \fBf\fR 5
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This form is the same as \fBc\fR except that it stores one or more one
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or more single-precision floating in the machine's native
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representation in the output string. This representation is not
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portable across architectures, so it should not be used to communicate
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floating point numbers across the network. The size of a floating
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point number may vary across architectures, so the number of bytes
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that are generated may vary. If the value overflows the
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machine's native representation, then the value of FLT_MAX
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as defined by the system will be used instead. Because Tcl uses
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double-precision floating-point numbers internally, there may be some
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loss of precision in the conversion to single-precision. For example,
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on a Windows system running on an Intel Pentium processor,
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.RS
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.CS
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\fBbinary format f2 {1.6 3.4}\fR
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.CE
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will return a string equivalent to
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\fB\\xcd\\xcc\\xcc\\x3f\\x9a\\x99\\x59\\x40\fR.
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.RE
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.IP \fBd\fR 5
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This form is the same as \fBf\fR except that it stores one or more one
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or more double-precision floating in the machine's native
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representation in the output string. For example, on a
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Windows system running on an Intel Pentium processor,
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.RS
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.CS
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\fBbinary format d1 {1.6}\fR
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.CE
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will return a string equivalent to
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\fB\\x9a\\x99\\x99\\x99\\x99\\x99\\xf9\\x3f\fR.
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.RE
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.IP \fBx\fR 5
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Stores \fIcount\fR null bytes in the output string. If \fIcount\fR is
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not specified, stores one null byte. If \fIcount\fR is \fB*\fR,
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generates an error. This type does not consume an argument. For
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example,
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.RS
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.CS
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\fBbinary format a3xa3x2a3 abc def ghi\fR
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.CE
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will return a string equivalent to \fBabc\\000def\\000\\000ghi\fR.
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.RE
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.IP \fBX\fR 5
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Moves the cursor back \fIcount\fR bytes in the output string. If
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\fIcount\fR is \fB*\fR or is larger than the current cursor position,
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then the cursor is positioned at location 0 so that the next byte
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stored will be the first byte in the result string. If \fIcount\fR is
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omitted then the cursor is moved back one byte. This type does not
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consume an argument. For example,
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.RS
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.CS
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\fBbinary format a3X*a3X2a3 abc def ghi\fR
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.CE
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will return \fBdghi\fR.
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.RE
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.IP \fB@\fR 5
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Moves the cursor to the absolute location in the output string
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specified by \fIcount\fR. Position 0 refers to the first byte in the
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output string. If \fIcount\fR refers to a position beyond the last
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byte stored so far, then null bytes will be placed in the unitialized
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locations and the cursor will be placed at the specified location. If
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\fIcount\fR is \fB*\fR, then the cursor is moved to the current end of
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the output string. If \fIcount\fR is omitted, then an error will be
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generated. This type does not consume an argument. For example,
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.RS
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.CS
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\fBbinary format a5@2a1@*a3@10a1 abcde f ghi j\fR
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.CE
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will return \fBabfdeghi\\000\\000j\fR.
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.RE
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.SH "BINARY SCAN"
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.PP
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The \fBbinary scan\fR command parses fields from a binary string,
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returning the number of conversions performed. \fIString\fR gives the
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input to be parsed and \fIformatString\fR indicates how to parse it.
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Each \fIvarName\fR gives the name of a variable; when a field is
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scanned from \fIstring\fR the result is assigned to the corresponding
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variable.
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.PP
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As with \fBbinary format\fR, the \fIformatString\fR consists of a
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sequence of zero or more field specifiers separated by zero or more
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spaces. Each field specifier is a single type character followed by
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an optional numeric \fIcount\fR. Most field specifiers consume one
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argument to obtain the variable into which the scanned values should
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be placed. The type character specifies how the binary data is to be
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interpreted. The \fIcount\fR typically indicates how many items of
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the specified type are taken from the data. If present, the
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\fIcount\fR is a non-negative decimal integer or \fB*\fR, which
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normally indicates that all of the remaining items in the data are to
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be used. If there are not enough bytes left after the current cursor
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position to satisfy the current field specifier, then the
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corresponding variable is left untouched and \fBbinary scan\fR returns
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immediately with the number of variables that were set. If there are
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not enough arguments for all of the fields in the format string that
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consume arguments, then an error is generated.
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.PP
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Each type-count pair moves an imaginary cursor through the binary data,
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reading bytes from the current position. The cursor is initially
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at position 0 at the beginning of the data. The type may be any one of
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the following characters:
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.IP \fBa\fR 5
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The data is a character string of length \fIcount\fR. If \fIcount\fR
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is \fB*\fR, then all of the remaining bytes in \fIstring\fR will be
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scanned into the variable. If \fIcount\fR is omitted, then one
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character will be scanned. For example,
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.RS
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.CS
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\fBbinary scan abcde\\000fghi a6a10 var1 var2\fR
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.CE
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will return \fB1\fR with the string equivalent to \fBabcde\\000\fR
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stored in \fBvar1\fR and \fBvar2\fR left unmodified.
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.RE
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.IP \fBA\fR 5
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This form is the same as \fBa\fR, except trailing blanks and nulls are stripped from
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the scanned value before it is stored in the variable. For example,
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.RS
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.CS
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\fBbinary scan "abc efghi \\000" a* var1\fR
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.CE
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will return \fB1\fR with \fBabc efghi\fR stored in \fBvar1\fR.
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.RE
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.IP \fBb\fR 5
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The data is turned into a string of \fIcount\fR binary digits in
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low-to-high order represented as a sequence of ``1'' and ``0''
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characters. The data bytes are scanned in first to last order with
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the bits being taken in low-to-high order within each byte. Any extra
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bits in the last byte are ignored. If \fIcount\fR is \fB*\fR, then
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all of the remaining bits in \fBstring\fR will be scanned. If
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\fIcount\fR is omitted, then one bit will be scanned. For example,
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.RS
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.CS
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\fBbinary scan \\x07\\x87\\x05 b5b* var1 var2\fR
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.CE
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will return \fB2\fR with \fB11100\fR stored in \fBvar1\fR and
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\fB1110000110100000\fR stored in \fBvar2\fR.
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.RE
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.IP \fBB\fR 5
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This form is the same as \fBB\fR, except the bits are taken in
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high-to-low order within each byte. For example,
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.RS
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.CS
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\fBbinary scan \\x70\\x87\\x05 b5b* var1 var2\fR
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.CE
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will return \fB2\fR with \fB01110\fR stored in \fBvar1\fR and
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\fB1000011100000101\fR stored in \fBvar2\fR.
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.RE
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.IP \fBh\fR 5
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The data is turned into a string of \fIcount\fR hexadecimal digits in
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low-to-high order represented as a sequence of characters in the set
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``0123456789abcdef''. The data bytes are scanned in first to last
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order with the hex digits being taken in low-to-high order within each
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byte. Any extra bits in the last byte are ignored. If \fIcount\fR
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is \fB*\fR, then all of the remaining hex digits in \fBstring\fR will be
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scanned. If \fIcount\fR is omitted, then one hex digit will be
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scanned. For example,
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.RS
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.CS
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\fBbinary scan \\x07\\x86\\x05 h3h* var1 var2\fR
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.CE
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will return \fB2\fR with \fB706\fR stored in \fBvar1\fR and
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\fB50\fR stored in \fBvar2\fR.
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.RE
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.IP \fBH\fR 5
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This form is the same as \fBh\fR, except the digits are taken in
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low-to-high order within each byte. For example,
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.RS
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.CS
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\fBbinary scan \\x07\\x86\\x05 H3H* var1 var2\fR
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.CE
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will return \fB2\fR with \fB078\fR stored in \fBvar1\fR and
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\fB05\fR stored in \fBvar2\fR.
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.RE
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.IP \fBc\fR 5
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The data is turned into \fIcount\fR 8-bit signed integers and stored
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in the corresponding variable as a list. If \fIcount\fR is \fB*\fR,
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then all of the remaining bytes in \fBstring\fR will be scanned. If
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\fIcount\fR is omitted, then one 8-bit integer will be scanned. For
|
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example,
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.RS
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.CS
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\fBbinary scan \\x07\\x86\\x05 c2c* var1 var2\fR
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.CE
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will return \fB2\fR with \fB7 -122\fR stored in \fBvar1\fR and \fB5\fR
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stored in \fBvar2\fR. Note that the integers returned are signed, but
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they can be converted to unsigned 8-bit quantities using an expression
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like:
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.CS
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\fBexpr ( $num + 0x100 ) % 0x100\fR
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.CE
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.RE
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.IP \fBs\fR 5
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The data is interpreted as \fIcount\fR 16-bit signed integers
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represented in little-endian byte order. The integers are stored in
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the corresponding variable as a list. If \fIcount\fR is \fB*\fR, then
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all of the remaining bytes in \fBstring\fR will be scanned. If
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\fIcount\fR is omitted, then one 16-bit integer will be scanned. For
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example,
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.RS
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.CS
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\fBbinary scan \\x05\\x00\\x07\\x00\\xf0\\xff s2s* var1 var2\fR
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.CE
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will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR
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stored in \fBvar2\fR. Note that the integers returned are signed, but
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they can be converted to unsigned 16-bit quantities using an expression
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like:
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.CS
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\fBexpr ( $num + 0x10000 ) % 0x10000\fR
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.CE
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.RE
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.IP \fBS\fR 5
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This form is the same as \fBs\fR except that the data is interpreted
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as \fIcount\fR 16-bit signed integers represented in big-endian byte
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order. For example,
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.RS
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.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
|