diff options
Diffstat (limited to 'doc/binary.n')
| -rw-r--r-- | doc/binary.n | 489 |
1 files changed, 315 insertions, 174 deletions
diff --git a/doc/binary.n b/doc/binary.n index fbe1a8c..6b2150e 100644 --- a/doc/binary.n +++ b/doc/binary.n @@ -15,17 +15,15 @@ binary \- Insert and extract fields from binary strings .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, on a 32 bit +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 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 @@ -34,7 +32,8 @@ 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. +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 @@ -42,12 +41,13 @@ 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. +that consume arguments, then an error is generated. The flag character +is ignored for for \fBbinary format\fR. .PP Here is a small example to clarify the relation between the field specifiers and the arguments: .CS -\fBbinary format d3d {1.0 2.0 3.0 4.0} 0.1\fR +\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 @@ -62,13 +62,14 @@ 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. +Stores a byte string of length \fIcount\fR in the output string. Every character is taken as modulo 256 (i.e. the low byte of every character is used, and the high byte discarded) so when storing -character strings not wholly expressible using the characters \\u0000-\\u00ff, -the \fBencoding convertto\fR command should be used -first if this truncation is not desired (i.e. if the characters are -not part of the ISO 8859-1 character set.) +character strings not wholly expressible using the characters \eu0000-\eu00ff, +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 @@ -77,16 +78,33 @@ formatted. If \fIcount\fR is omitted, then one character will be formatted. For example, .RS .CS -\fBbinary format a7a*a alpha bravo charlie\fR +\fBbinary format\fR a7a*a alpha bravo charlie .CE -will return a string equivalent to \fBalpha\\000\\000bravoc\fR. +will return a string equivalent to \fBalpha\e000\e000bravoc\fR, +.CS +\fBbinary format\fR a* [encoding convertto utf-8 \eu20ac] +.CE +will return a string equivalent to \fB\e342\e202\e254\fR (which is the +UTF-8 byte sequence for a Euro-currency character) and +.CS +\fBbinary format\fR a* [encoding convertto iso8859-15 \eu20ac] +.CE +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: +.CS +\fBbinary format\fR a* \eu20ac +.CE +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 .CS -\fBbinary format A6A*A alpha bravo charlie\fR +\fBbinary format\fR A6A*A alpha bravo charlie .CE will return \fBalpha bravoc\fR. .RE @@ -105,25 +123,26 @@ 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 +\fBbinary format\fR b5b* 11100 111000011010 .CE -will return a string equivalent to \fB\\x07\\x87\\x05\fR. +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 .CS -\fBbinary format B5B* 11100 111000011010\fR +\fBbinary format\fR B5B* 11100 111000011010 .CE -will return a string equivalent to \fB\\xe0\\xe1\\xa0\fR. +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 low-to-high +.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 ``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 +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 @@ -133,37 +152,36 @@ 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 +\fBbinary format\fR H3H*H2 ab DEF 987 .CE -will return a string equivalent to \fB\\xba\\x00\\xed\\x0f\fR. +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 -high-to-low order within each byte. For example, +.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 .CS -\fBbinary format H3H* ab DEF\fR +\fBbinary format\fR h3h*h2 AB def 987 .CE -will return a string equivalent to \fB\\xab\\x00\\xde\\xf0\fR. +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; otherwise \fIarg\fR must consist of a list containing at least -\fIcount\fR integer elements. The low-order 8 bits of each 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 \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 +is \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 .CS -\fBbinary format c3cc* {3 -3 128 1} 260 {2 5}\fR +\fBbinary format\fR c3cc* {3 -3 128 1} 260 {2 5} .CE will return a string equivalent to -\fB\\x03\\xfd\\x80\\x04\\x02\\x05\fR, whereas +\fB\ex03\exfd\ex80\ex04\ex02\ex05\fR, whereas .CS -\fBbinary format c {2 5}\fR +\fBbinary format\fR c {2 5} .CE will generate an error. .RE @@ -175,10 +193,10 @@ the cursor position with the least significant byte stored first. For example, .RS .CS -\fBbinary format s3 {3 -3 258 1}\fR +\fBbinary format\fR s3 {3 -3 258 1} .CE will return a string equivalent to -\fB\\x03\\x00\\xfd\\xff\\x02\\x01\fR. +\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 @@ -186,11 +204,19 @@ This form is the same as \fBs\fR except that it stores one or more example, .RS .CS -\fBbinary format S3 {3 -3 258 1}\fR +\fBbinary format\fR S3 {3 -3 258 1} .CE will return a string equivalent to -\fB\\x00\\x03\\xff\\xfd\\x01\\x02\fR. -.RE +\fB\ex00\ex03\exff\exfd\ex01\ex02\fR. +.RE +.IP \fBt\fR 5 +.VS 8.5 +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. +.VE 8.5 .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 @@ -199,10 +225,10 @@ the cursor position with the least significant byte stored first. For example, .RS .CS -\fBbinary format i3 {3 -3 65536 1}\fR +\fBbinary format\fR i3 {3 -3 65536 1} .CE will return a string equivalent to -\fB\\x03\\x00\\x00\\x00\\xfd\\xff\\xff\\xff\\x00\\x00\\x01\\x00\fR +\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 @@ -210,13 +236,21 @@ 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 +\fBbinary format\fR I3 {3 -3 65536 1} .CE will return a string equivalent to -\fB\\x00\\x00\\x00\\x03\\xff\\xff\\xff\\xfd\\x00\\x01\\x00\\x00\fR -.RE +\fB\ex00\ex00\ex00\ex03\exff\exff\exff\exfd\ex00\ex01\ex00\ex00\fR +.RE +.IP \fBn\fR 5 +.VS 8.5 +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. +.VE 8.5 .IP \fBw\fR 5 -.VS 8.4 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 @@ -224,7 +258,7 @@ the cursor position with the least significant byte stored first. For example, .RS .CS -\fBbinary format w 7810179016327718216\fR +\fBbinary format\fR w 7810179016327718216 .CE will return the string \fBHelloTcl\fR .RE @@ -234,14 +268,22 @@ or more 64-bit integers in big-endian byte order in the output string. For example, .RS .CS -\fBbinary format Wc 4785469626960341345 110\fR +\fBbinary format\fR Wc 4785469626960341345 110 .CE will return the string \fBBigEndian\fR -.VE .RE +.IP \fBm\fR 5 +.VS 8.5 +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. +.VE 8.5 .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 +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 @@ -249,28 +291,54 @@ 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 +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 +\fBbinary format\fR f2 {1.6 3.4} .CE will return a string equivalent to -\fB\\xcd\\xcc\\xcc\\x3f\\x9a\\x99\\x59\\x40\fR. -.RE +\fB\excd\excc\excc\ex3f\ex9a\ex99\ex59\ex40\fR. +.RE +.IP \fBr\fR 5 +.VS 8.5 +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.) +.VE 8.5 +.IP \fBR\fR 5 +.VS 8.5 +This form is the same as \fBr\fR except that it stores the +single-precision floating point numbers in big-endian order. +.VE 8.5 .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 +or more double-precision floating point numbers 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 +\fBbinary format\fR d1 {1.6} .CE will return a string equivalent to -\fB\\x9a\\x99\\x99\\x99\\x99\\x99\\xf9\\x3f\fR. -.RE +\fB\ex9a\ex99\ex99\ex99\ex99\ex99\exf9\ex3f\fR. +.RE +.IP \fBq\fR 5 +.VS 8.5 +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.) +.VE 8.5 +.IP \fBQ\fR 5 +.VS 8.5 +This form is the same as \fBq\fR except that it stores the +double-precision floating point numbers in big-endian order. +.VE 8.5 .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, @@ -278,9 +346,9 @@ generates an error. This type does not consume an argument. For example, .RS .CS -\fBbinary format a3xa3x2a3 abc def ghi\fR +\fBbinary format\fR a3xa3x2a3 abc def ghi .CE -will return a string equivalent to \fBabc\\000def\\000\\000ghi\fR. +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 @@ -291,7 +359,7 @@ 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 +\fBbinary format\fR a3X*a3X2a3 abc def ghi .CE will return \fBdghi\fR. .RE @@ -306,16 +374,17 @@ 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 +\fBbinary format\fR a5@2a1@*a3@10a1 abcde f ghi j .CE -will return \fBabfdeghi\\000\\000j\fR. +will return \fBabfdeghi\e000\e000j\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. +input bytes to be parsed (one byte per character, and characters not +representable as a byte have their high bits chopped) +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. @@ -323,7 +392,8 @@ variable. 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 +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 @@ -335,13 +405,16 @@ 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. +consume arguments, then an error is generated. The flag character +.QW u +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: .CS -\fBbinary scan $bytes s3s first second\fR +\fBbinary scan\fR $bytes s3s first second .CE .PP This command (provided the binary string in the variable \fIbytes\fR @@ -352,31 +425,33 @@ 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: .CS -\fBputs [binary scan abcdefg s3s first second]\fR -\fBputs $first\fR -\fBputs $second\fR +puts [\fBbinary scan\fR abcdefg s3s first second] +puts $first +puts $second .CE will print (assuming neither variable is set previously): .CS -\fB1\fR -\fB25185 25699 26213\fR -\fIcan't read "second": no such variable\fR +1 +25185 25699 26213 +can't read "second": no such variable .CE .PP -It is \fBimportant\fR to note that the \fBc\fR, \fBs\fR, and \fBS\fR +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: .CS -\fBset signShort [binary format s1 0x8000]\fR -\fBbinary scan $signShort s1 val; \fI# val == 0xFFFF8000\fR +set signShort [\fBbinary format\fR s1 0x8000] +\fBbinary scan\fR $signShort s1 val; \fI# val == 0xFFFF8000\fR .CE -If you want to produce an unsigned value, then you can mask the return -value to the desired size. For example, to produce an unsigned short -value: +If you require unsigned values you can include the +.QW u +flag character following +the field type. For example, to read an unsigned short value: .CS -\fBset val [expr {$val & 0xFFFF}]; \fI# val == 0x8000\fR +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, @@ -384,116 +459,128 @@ 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 +The data is a byte 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. -All characters scanned will be interpreted as being in the -range \\u0000-\\u00ff so the \fBencoding convertfrom\fR command might be -needed if the string is not an ISO 8859\-1 string. +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 .CS -\fBbinary scan abcde\\000fghi a6a10 var1 var2\fR +\fBbinary scan\fR abcde\e000fghi a6a10 var1 var2 +.CE +will return \fB1\fR with the string equivalent to \fBabcde\e000\fR +stored in \fIvar1\fR and \fIvar2\fR left unmodified, and +.CS +\fBbinary scan\fR \e342\e202\e254 a* var1 +set var2 [encoding convertfrom utf-8 $var1] .CE -will return \fB1\fR with the string equivalent to \fBabcde\\000\fR -stored in \fBvar1\fR and \fBvar2\fR left unmodified. +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 .CS -\fBbinary scan "abc efghi \\000" A* var1\fR +\fBbinary scan\fR "abc efghi \e000" A* var1 .CE -will return \fB1\fR with \fBabc efghi\fR stored in \fBvar1\fR. +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 ``1'' and ``0'' +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 \fB*\fR, then -all of the remaining bits in \fBstring\fR will be scanned. If +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 .CS -\fBbinary scan \\x07\\x87\\x05 b5b* var1 var2\fR +\fBbinary scan\fR \ex07\ex87\ex05 b5b* var1 var2 .CE -will return \fB2\fR with \fB11100\fR stored in \fBvar1\fR and -\fB1110000110100000\fR stored in \fBvar2\fR. +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 .CS -\fBbinary scan \\x70\\x87\\x05 B5B* var1 var2\fR +\fBbinary scan\fR \ex70\ex87\ex05 B5B* var1 var2 .CE -will return \fB2\fR with \fB01110\fR stored in \fBvar1\fR and -\fB1000011100000101\fR stored in \fBvar2\fR. +will return \fB2\fR with \fB01110\fR stored in \fIvar1\fR and +\fB1000011100000101\fR stored in \fIvar2\fR. .RE -.IP \fBh\fR 5 +.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, +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 +\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 .CS -\fBbinary scan \\x07\\x86\\x05 h3h* var1 var2\fR +\fBbinary scan\fR \ex07\exC6\ex05\ex1f\ex34 H3H* var1 var2 .CE -will return \fB2\fR with \fB706\fR stored in \fBvar1\fR and -\fB50\fR stored in \fBvar2\fR. +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 -high-to-low order within each byte. For example, +.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 .CS -\fBbinary scan \\x07\\x86\\x05 H3H* var1 var2\fR +\fBbinary scan\fR \ex07\ex86\ex05\ex12\ex34 h3h* var1 var2 .CE -will return \fB2\fR with \fB078\fR stored in \fBvar1\fR and -\fB05\fR stored in \fBvar2\fR. +will return \fB2\fR with \fB706\fR stored in \fIvar1\fR and +\fB502143\fR stored in \fIvar2\fR. .RE +Note that most code that wishes to parse the hexadecimal digits from +multiple bytes in order should use the \fBH\fR format. .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 +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 .CS -\fBbinary scan \\x07\\x86\\x05 c2c* var1 var2\fR +\fBbinary scan\fR \ex07\ex86\ex05 c2c* var1 var2 .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 +will return \fB2\fR with \fB7 -122\fR stored in \fIvar1\fR and \fB5\fR +stored in \fIvar2\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 & 0xff }\fR +set num [expr { $num & 0xff }] .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 +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 .CS -\fBbinary scan \\x05\\x00\\x07\\x00\\xf0\\xff s2s* var1 var2\fR +\fBbinary scan\fR \ex05\ex00\ex07\ex00\exf0\exff s2s* var1 var2 .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 +will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR +stored in \fIvar2\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 & 0xffff }\fR +set num [expr { $num & 0xffff }] .CE .RE .IP \fBS\fR 5 @@ -502,28 +589,37 @@ 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 +\fBbinary scan\fR \ex00\ex05\ex00\ex07\exff\exf0 S2S* var1 var2 .CE -will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR -stored in \fBvar2\fR. +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 +.VS 8.5 +The data is interpreted as \fIcount\fR 16-bit signed 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. +.VE 8.5 .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 +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 .CS -\fBbinary scan \\x05\\x00\\x00\\x00\\x07\\x00\\x00\\x00\\xf0\\xff\\xff\\xff i2i* var1 var2\fR +set str \ex05\ex00\ex00\ex00\ex07\ex00\ex00\ex00\exf0\exff\exff\exff +\fBbinary scan\fR $str i2i* var1 var2 .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 +will return \fB2\fR with \fB5 7\fR stored in \fIvar1\fR and \fB\-16\fR +stored in \fIvar2\fR. Note that the integers returned are signed, but they can be converted to unsigned 32-bit quantities using an expression like: .CS -\fBexpr { $num & 0xffffffff }\fR +set num [expr { $num & 0xffffffff }] .CE .RE .IP \fBI\fR 5 @@ -532,25 +628,34 @@ as \fIcount\fR 32-bit signed integers represented in big-endian byte order. For example, .RS .CS -\fBbinary scan \\x00\\x00\\x00\\x05\\x00\\x00\\x00\\x07\\xff\\xff\\xff\\xf0 I2I* var1 var2\fR +set str \ex00\ex00\ex00\ex05\ex00\ex00\ex00\ex07\exff\exff\exff\exf0 +\fBbinary scan\fR $str I2I* var1 var2 .CE -will return \fB2\fR with \fB5 7\fR stored in \fBvar1\fR and \fB-16\fR -stored in \fBvar2\fR. +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 +.VS 8.5 +The data is interpreted as \fIcount\fR 32-bit signed 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. +.VE 8.5 .IP \fBw\fR 5 -.VS 8.4 The data is interpreted as \fIcount\fR 64-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 +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 .CS -\fBbinary scan \\x05\\x00\\x00\\x00\\x07\\x00\\x00\\x00\\xf0\\xff\\xff\\xff wi* var1 var2\fR +set str \ex05\ex00\ex00\ex00\ex07\ex00\ex00\ex00\exf0\exff\exff\exff +\fBbinary scan\fR $str wi* var1 var2 .CE -will return \fB2\fR with \fB30064771077\fR stored in \fBvar1\fR and -\fB-16\fR stored in \fBvar2\fR. Note that the integers returned are +will return \fB2\fR with \fB30064771077\fR stored in \fIvar1\fR and +\fB\-16\fR stored in \fIvar2\fR. Note that the integers returned are signed and cannot be represented by Tcl as unsigned values. .RE .IP \fBW\fR 5 @@ -559,18 +664,26 @@ as \fIcount\fR 64-bit signed integers represented in big-endian byte order. For example, .RS .CS -\fBbinary scan \\x00\\x00\\x00\\x05\\x00\\x00\\x00\\x07\\xff\\xff\\xff\\xf0 WI* var1 var2\fR +set str \ex00\ex00\ex00\ex05\ex00\ex00\ex00\ex07\exff\exff\exff\exf0 +\fBbinary scan\fR $str WI* var1 var2 .CE -will return \fB2\fR with \fB21474836487\fR stored in \fBvar1\fR and \fB-16\fR -stored in \fBvar2\fR. -.VE +will return \fB2\fR with \fB21474836487\fR stored in \fIvar1\fR and \fB\-16\fR +stored in \fIvar2\fR. .RE +.IP \fBm\fR 5 +.VS 8.5 +The data is interpreted as \fIcount\fR 64-bit signed 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. +.VE 8.5 .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 +\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. If the data does not represent a @@ -579,11 +692,25 @@ 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 +\fBbinary scan\fR \ex3f\excc\excc\excd f var1 .CE will return \fB1\fR with \fB1.6000000238418579\fR stored in -\fBvar1\fR. +\fIvar1\fR. .RE +.IP \fBr\fR 5 +.VS 8.5 +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. +.VE 8.5 +.IP \fBR\fR 5 +.VS 8.5 +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. +.VE 8.5 .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 @@ -591,23 +718,37 @@ 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 +\fBbinary scan\fR \ex9a\ex99\ex99\ex99\ex99\ex99\exf9\ex3f d var1 .CE will return \fB1\fR with \fB1.6000000000000001\fR -stored in \fBvar1\fR. -.RE +stored in \fIvar1\fR. +.RE +.IP \fBq\fR 5 +.VS 8.5 +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. +.VE 8.5 +.IP \fBQ\fR 5 +.VS 8.5 +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. +.VE 8.5 .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 +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 .CS -\fBbinary scan \\x01\\x02\\x03\\x04 x2H* var1\fR +\fBbinary scan\fR \ex01\ex02\ex03\ex04 x2H* var1 .CE -will return \fB1\fR with \fB0304\fR stored in \fBvar1\fR. +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 @@ -618,10 +759,10 @@ 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 +\fBbinary scan\fR \ex01\ex02\ex03\ex04 c2XH* var1 var2 .CE -will return \fB2\fR with \fB1 2\fR stored in \fBvar1\fR and \fB020304\fR -stored in \fBvar2\fR. +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 @@ -631,21 +772,23 @@ by \fIcount\fR. Note that position 0 refers to the first byte in \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 +\fBbinary scan\fR \ex01\ex02\ex03\ex04 c2@1H* var1 var2 .CE -will return \fB2\fR with \fB1 2\fR stored in \fBvar1\fR and \fB020304\fR -stored in \fBvar2\fR. +will return \fB2\fR with \fB1 2\fR stored in \fIvar1\fR and \fB020304\fR +stored in \fIvar2\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 "PORTABILITY ISSUES" +The \fBr\fR, \fBR\fR, \fBq\fR and \fBQ\fR conversions will only work +reliably for transferring data between computers which are all using +IEEE floating point representations. This is very common, but not +universal. To transfer floating-point numbers portably between all +architectures, use their textual representation (as produced by +\fBformat\fR) instead. .SH EXAMPLES This is a procedure to write a Tcl string to a binary-encoded channel as UTF-8 data preceded by a length word: .CS -proc writeString {channel string} { +proc \fIwriteString\fR {channel string} { set data [encoding convertto utf-8 $string] puts -nonewline [\fBbinary format\fR Ia* \e [string length $data] $data] @@ -653,9 +796,9 @@ proc writeString {channel string} { .CE .PP This procedure reads a string from a channel that was written by the -previously presented \fBwriteString\fR procedure: +previously presented \fIwriteString\fR procedure: .CS -proc readString {channel} { +proc \fIreadString\fR {channel} { if {![\fBbinary scan\fR [read $channel 4] I length]} { error "missing length" } @@ -663,9 +806,7 @@ proc readString {channel} { return [encoding convertfrom utf-8 $data] } .CE - .SH "SEE ALSO" format(n), scan(n), tclvars(n) - .SH KEYWORDS binary, format, scan |