base64.tcl

Linux下的MSN聊天程序源码

# base64.tcl --
#
# Encode/Decode base64 for a string
# Stephen Uhler / Brent Welch (c) 1997 Sun Microsystems
# The decoder was done for exmh by Chris Garrigues
#
# Copyright (c) 1998-2000 by Ajuba Solutions.
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
# 
# RCS: @(#) $Id: base64.tcl 3433 2004-12-03 15:51:40Z germinator2000 $

# Version 1.0   implemented Base64_Encode, Bae64_Decode
# Version 2.0   uses the base64 namespace
# Version 2.1   fixes various decode bugs and adds options to encode
# Version 2.2   is much faster, Tcl8.0 compatible
# Version 2.2.1 bugfixes
# Version 2.2.2 bugfixes

package require Tcl 8.2
namespace eval ::base64 {
    namespace export encode decode
}

if {![catch {package require Trf 2.0}]} {
    # Trf is available, so implement the functionality provided here
    # in terms of calls to Trf for speed.

    # ::base64::encode --
    #
    #	Base64 encode a given string.
    #
    # Arguments:
    #	args	?-maxlen maxlen? ?-wrapchar wrapchar? string
    #	
    #		If maxlen is 0, the output is not wrapped.
    #
    # Results:
    #	A Base64 encoded version of $string, wrapped at $maxlen characters
    #	by $wrapchar.
    
    proc ::base64::encode {args} {
	# Set the default wrapchar and maximum line length to match the output
	# of GNU uuencode 4.2.  Various RFC's allow for different wrapping 
	# characters and wraplengths, so these may be overridden by command line
	# options.
	set wrapchar "\n"
	set maxlen 60

	if { [llength $args] == 0 } {
	    error "wrong # args: should be \"[lindex [info level 0] 0]\
		    ?-maxlen maxlen? ?-wrapchar wrapchar? string\""
	}

	set optionStrings [list "-maxlen" "-wrapchar"]
	for {set i 0} {$i < [llength $args] - 1} {incr i} {
	    set arg [lindex $args $i]
	    set index [lsearch -glob $optionStrings "${arg}*"]
	    if { $index == -1 } {
		error "unknown option \"$arg\": must be -maxlen or -wrapchar"
	    }
	    incr i
	    if { $i >= [llength $args] - 1 } {
		error "value for \"$arg\" missing"
	    }
	    set val [lindex $args $i]

	    # The name of the variable to assign the value to is extracted
	    # from the list of known options, all of which have an
	    # associated variable of the same name as the option without
	    # a leading "-". The [string range] command is used to strip
	    # of the leading "-" from the name of the option.
	    #
	    # FRINK: nocheck
	    set [string range [lindex $optionStrings $index] 1 end] $val
	}
    
	# [string is] requires Tcl8.2; this works with 8.0 too
	if {[catch {expr {$maxlen % 2}}]} {
	    error "expected integer but got \"$maxlen\""
	}

	set string [lindex $args end]
	set result [::base64 -mode encode -- $string]
	set result [string map [list \n ""] $result]

	if {$maxlen > 0} {
	    set res ""
	    set edge [expr {$maxlen - 1}]
	    while {[string length $result] > $maxlen} {
		append res [string range $result 0 $edge]$wrapchar
		set result [string range $result $maxlen end]
	    }
	    if {[string length $result] > 0} {
		append res $result
	    }
	    set result $res
	}

	return $result
    }

    # ::base64::decode --
    #
    #	Base64 decode a given string.
    #
    # Arguments:
    #	string	The string to decode.  Characters not in the base64
    #		alphabet are ignored (e.g., newlines)
    #
    # Results:
    #	The decoded value.

    proc ::base64::decode {string} {
	::base64 -mode decode -- $string
    }

} else {
    # Without Trf use a pure tcl implementation

    namespace eval base64 {
	variable base64 {}
	variable base64_en {}

	# We create the auxiliary array base64_tmp, it will be unset later.

	set i 0
	foreach char {A B C D E F G H I J K L M N O P Q R S T U V W X Y Z \
		a b c d e f g h i j k l m n o p q r s t u v w x y z \
		0 1 2 3 4 5 6 7 8 9 + /} {
	    set base64_tmp($char) $i
	    lappend base64_en $char
	    incr i
	}

	#
	# Create base64 as list: to code for instance C<->3, specify
	# that [lindex $base64 67] be 3 (C is 67 in ascii); non-coded
	# ascii chars get a {}. we later use the fact that lindex on a
	# non-existing index returns {}, and that [expr {} < 0] is true
	#

	# the last ascii char is 'z'
	scan z %c len
	for {set i 0} {$i <= $len} {incr i} {
	    set char [format %c $i]
	    set val {}
	    if {[info exists base64_tmp($char)]} {
		set val $base64_tmp($char)
	    } else {
		set val {}
	    }
	    lappend base64 $val
	}

	# code the character "=" as -1; used to signal end of message
	scan = %c i
	set base64 [lreplace $base64 $i $i -1]

	# remove unneeded variables
	unset base64_tmp i char len val

	namespace export encode decode
    }

    # ::base64::encode --
    #
    #	Base64 encode a given string.
    #
    # Arguments:
    #	args	?-maxlen maxlen? ?-wrapchar wrapchar? string
    #	
    #		If maxlen is 0, the output is not wrapped.
    #
    # Results:
    #	A Base64 encoded version of $string, wrapped at $maxlen characters
    #	by $wrapchar.
    
    proc ::base64::encode {args} {
	set base64_en $::base64::base64_en
	
	# Set the default wrapchar and maximum line length to match the output
	# of GNU uuencode 4.2.  Various RFC's allow for different wrapping 
	# characters and wraplengths, so these may be overridden by command line
	# options.
	set wrapchar "\n"
	set maxlen 60

	if { [llength $args] == 0 } {
	    error "wrong # args: should be \"[lindex [info level 0] 0]\
		    ?-maxlen maxlen? ?-wrapchar wrapchar? string\""
	}

	set optionStrings [list "-maxlen" "-wrapchar"]
	for {set i 0} {$i < [llength $args] - 1} {incr i} {
	    set arg [lindex $args $i]
	    set index [lsearch -glob $optionStrings "${arg}*"]
	    if { $index == -1 } {
		error "unknown option \"$arg\": must be -maxlen or -wrapchar"
	    }
	    incr i
	    if { $i >= [llength $args] - 1 } {
		error "value for \"$arg\" missing"
	    }
	    set val [lindex $args $i]

	    # The name of the variable to assign the value to is extracted
	    # from the list of known options, all of which have an
	    # associated variable of the same name as the option without
	    # a leading "-". The [string range] command is used to strip
	    # of the leading "-" from the name of the option.
	    #
	    # FRINK: nocheck
	    set [string range [lindex $optionStrings $index] 1 end] $val
	}
    
	# [string is] requires Tcl8.2; this works with 8.0 too
	if {[catch {expr {$maxlen % 2}}]} {
	    error "expected integer but got \"$maxlen\""
	}

	set string [lindex $args end]

	set result {}
	set state 0
	set length 0


	# Process the input bytes 3-by-3

	binary scan $string c* X
	foreach {x y z} $X {
	    # Do the line length check before appending so that we don't get an
	    # extra newline if the output is a multiple of $maxlen chars long.
	    if {$maxlen && $length >= $maxlen} {
		append result $wrapchar
		set length 0
	    }
	
	    append result [lindex $base64_en [expr {($x >>2) & 0x3F}]] 
	    if {$y != {}} {
		append result [lindex $base64_en [expr {(($x << 4) & 0x30) | (($y >> 4) & 0xF)}]] 
		if {$z != {}} {
		    append result \
			    [lindex $base64_en [expr {(($y << 2) & 0x3C) | (($z >> 6) & 0x3)}]]
		    append result [lindex $base64_en [expr {($z & 0x3F)}]]
		} else {
		    set state 2
		    break
		}
	    } else {
		set state 1
		break
	    }
	    incr length 4
	}
	if {$state == 1} {
	    append result [lindex $base64_en [expr {(($x << 4) & 0x30)}]]== 
	} elseif {$state == 2} {
	    append result [lindex $base64_en [expr {(($y << 2) & 0x3C)}]]=  
	}
	return $result
    }

    # ::base64::decode --
    #
    #	Base64 decode a given string.
    #
    # Arguments:
    #	string	The string to decode.  Characters not in the base64
    #		alphabet are ignored (e.g., newlines)
    #
    # Results:
    #	The decoded value.

    proc ::base64::decode {string} {
	if {[string length $string] == 0} {return ""}

	set base64 $::base64::base64

	binary scan $string c* X
	foreach x $X {
	    set bits [lindex $base64 $x]
	    if {$bits >= 0} {
		if {[llength [lappend nums $bits]] == 4} {
		    foreach {v w z y} $nums break
		    set a [expr {($v << 2) | ($w >> 4)}]
		    set b [expr {(($w & 0xF) << 4) | ($z >> 2)}]
		    set c [expr {(($z & 0x3) << 6) | $y}]
		    append output [binary format ccc $a $b $c]
		    set nums {}
		}		
	    } elseif {$bits == -1} {
		# = indicates end of data.  Output whatever chars are left.
		# The encoding algorithm dictates that we can only have 1 or 2
		# padding characters.  If x=={}, we have 12 bits of input 
		# (enough for 1 8-bit output).  If x!={}, we have 18 bits of
		# input (enough for 2 8-bit outputs).
		
		foreach {v w z} $nums break
		set a [expr {($v << 2) | (($w & 0x30) >> 4)}]
		
		if {$z == {}} {
		    append output [binary format c $a ]
		} else {
		    set b [expr {(($w & 0xF) << 4) | (($z & 0x3C) >> 2)}]
		    append output [binary format cc $a $b]
		}		
		break
	    } else {
		# RFC 2045 says that line breaks and other characters not part
		# of the Base64 alphabet must be ignored, and that the decoder
		# can optionally emit a warning or reject the message.  We opt
		# not to do so, but to just ignore the character. 
		continue
	    }
	}
	return $output
    }
}

package provide base64 2.2.2