binary - Insert and extract fields from binary strings

(Dissect and join binary data into/from tcl values)

    :   '''[binary format]''' ''formatString'' ?''arg arg ...''?

    :   '''[binary scan]''' ''string formatString'' ?''varName varName ...''?

http://purl.org/tcl/home/man/tcl8.4/TclCmd/binary.htm

----

This is the primary command to use when [Working with binary data].

For dealing with binary data on C level see also http://www.tcl.tk/man/tcl8.4/TclLib/ByteArrObj.htm

See [Binary representation of numbers] or [bitstrings] for examples of usage.

What are the issues when dealing with special values - 64 bits for instance?

----

See also:

   * [format]
   * [scan]

----
'''Examples'''

In a conversation in the Tcl'ers Chat about how to display the bits in a number [DKF] came up with this:
 binary scan [binary format I $value] B32 x; set x

[GPS]: I use the following string to/from hex conversion procedures to store files that may contain special characters that interfere with the OS filesystem in my [Grindweb] program:

 proc convert.string.to.hex str {
  binary scan $str H* hex
  return $hex
 }

 proc convert.hex.to.string hex {
  foreach c [split $hex ""] {
   if {![string is xdigit $c]} {
    return "#invalid $hex"
   }
  }
  binary format H* $hex
 }

----
Q. Is there a way to display the [ASCII] equivalent of characters in a string?

A.
 set chrs "abc"
 binary scan [encoding convertto ascii $chrs] c* x
 puts $x
 97 98 99

results in the translation of the characters to hex being assigned to $x.
If the characters are some encoding other than ASCII, just change the
'''ascii''' to the appropriate encoding name.

[DKF]: Also consider using [[[scan] $str %c]] for single characters where you want the [UNICODE] character number (which is the same as the ASCII one for ASCII characters, and the same as the ISO8859-1 codepoint too, since UNICODE is a superset of ISO8859-1 and that in turn is a superset of ASCII).
----
!!!!!!
[Tcl syntax help] -
%| [Category Command] | [Category Binary Data] |%
!!!!!!