$Base64 Decode: Difference between revisions
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<span class="pageSubtitle">Convert from base 64 to byte string</span> | <span class="pageSubtitle">Convert from base 64 to byte string</span> | ||
<p class=" | <p class="warn"><b>Note: </b>Many $functions have been deprecated in favor of Object Oriented methods. The OO equivalent for the $Base64_Decode function is the [[Base64ToString (String function)]].</p> | ||
This function converts from a base 64 encoded string to the decoded byte string. It is identical to $Lstr_Base64_Decode with the (hopefully obvious) exception that it is not longstring capable. As such, $Lstr_Base64_Decode is recommended over <var>$Base64_Decode</var> as it is a more flexible version of the latter. | This function converts from a base 64 encoded string to the decoded byte string. It is identical to [[$Lstr_Base64_Decode|$Lstr_Base64_Decode]] with the (hopefully obvious) exception that it is not [[Longstrings|longstring]] capable. As such, $Lstr_Base64_Decode is recommended over <var>$Base64_Decode</var> as it is a more flexible version of the latter. | ||
The <var>$Base64_Decode</var> function accepts one argument and returns a string result whose base 64 encoding is that argument. | The <var>$Base64_Decode</var> function accepts one argument and returns a string result whose base 64 encoding is that argument. | ||
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The returned value is the base 64 decoding of the argument string. If the argument is not a valid base 64 encoding, the null string is returned. | The returned value is the base 64 decoding of the argument string. If the argument is not a valid base 64 encoding, the null string is returned. | ||
==Syntax== | ==Syntax== | ||
<p class="syntax">< | <p class="syntax"><span class="term">%DECODED</span> = <span class="literal">$Base64_Decode</span>(<span class="term">string</span>) | ||
< | |||
< | |||
</p> | </p> | ||
<p> | |||
<var class="term">%DECODED</var> is set to the base 64 decoding of string.</p> | |||
==Usage notes== | |||
Because the maximum length of the argument is 255 bytes, if you have a longer stream to decode, you can do it in pieces, where any piece is a multiple of 4 bytes long (3 bytes are evenly packed into 4 bytes of a base 64 encoding). For example, if you have a valid base 64 string which is the concatenation of items in a Sirius $list and you wish to print that string, possibly producing multiple lines of length 60, you can use the following approach: | Because the maximum length of the argument is 255 bytes, if you have a longer stream to decode, you can do it in pieces, where any piece is a multiple of 4 bytes long (3 bytes are evenly packed into 4 bytes of a base 64 encoding). For example, if you have a valid base 64 string which is the concatenation of items in a Sirius $list and you wish to print that string, possibly producing multiple lines of length 60, you can use the following approach: | ||
<p class="code"> %S = | <p class="code">%S = '' | ||
FOR %I FROM 1 TO $ListCnt(%L) | |||
%T = $ListInf(%L, %I) | |||
REPEAT WHILE $LEN(%S) + $LEN(%T) > 80 | |||
%X = 80 - $LEN(%S) | |||
%U = %S WITH $SUBSTR(%T, 1, %X) | |||
PRINT $Base64_Decode(%U) | |||
%T = $SUBSTR(%T, %X + 1) | |||
%S = '' | |||
END REPEAT | |||
%S = %S WITH %T | |||
END FOR | |||
PRINT $Base64_Decode(%S) | |||
</p> | </p> | ||
As of <var class="product">[[Sirius Mods]]</var> Version 6.8, you can do base 64 decoding of strings longer than 255 bytes using [[$Lstr_Base64_Decode]], but if, as in the example above, the intent is to break the result into smaller chunks, anyway, there probably wouldn't be a marked difference between using <var>$Base64_Decode</var> or its longstring equivalent. | As of <var class="product">[[Sirius Mods]]</var> Version 6.8, you can do base 64 decoding of strings longer than 255 bytes using [[$Lstr_Base64_Decode]], but if, as in the example above, the intent is to break the result into smaller chunks, anyway, there probably wouldn't be a marked difference between using <var>$Base64_Decode</var> or its longstring equivalent. | ||
You may wish to check for an invalid base 64 encoding by checking for the null string return value from $Base64_Decode. Of course, if it is possible that the argument is null, the null string is a valid returned value. If you need to check for errors, and the null string is a possible argument value, you can use an approach such as the following: | You may wish to check for an invalid base 64 encoding by checking for the null string return value from <var>$Base64_Decode</var>. Of course, if it is possible that the argument is null, the null string is a valid returned value. If you need to check for errors, and the null string is a possible argument value, you can use an approach such as the following: | ||
<p class="code"> %STR = $Base64_Decode(%IN) | <p class="code">%STR = $Base64_Decode(%IN) | ||
IF %STR EQ '' Then | |||
IF %IN NE '' THEN | |||
error code ... | |||
END IF | |||
END IF | |||
</p> | </p> | ||
[[$Base64_Encode]] is the inverse of $Base64_Decode. | [[$Base64_Encode]] is the inverse of <var>$Base64_Decode</var>. | ||
==Example== | |||
Given the argument of length 4: | |||
<p class="code">%JUNK = $Base64_Decode('ABCD') | |||
</p> | |||
%JUNK would be set to the byte string (of length 3) represented in hexadecimal as X'001083'. | |||
==Products authorizing {{PAGENAMEE}}== | |||
<ul class="smallAndTightList"> | <ul class="smallAndTightList"> | ||
<li>[[Sirius functions]]</li> | <li>[[List of $functions|Sirius functions]]</li> | ||
<li>[[Fast/Unload User Language Interface]]</li> | <li>[[Fast/Unload User Language Interface]]</li> | ||
<li>[[Janus Open Client]]</li> | <li>[[Media:JoclrNew.pdf|Janus Open Client]]</li> | ||
<li>[[Janus Open Server]]</li> | <li>[[Media:JosrvrNew.pdf|Janus Open Server]]</li> | ||
<li>[[Janus Sockets]]</li> | <li>[[Janus Sockets]]</li> | ||
<li>[[Janus Web Server]]</li> | <li>[[Janus Web Server]]</li> | ||
<li> | <li>Japanese functions</li> | ||
<li>[[Sir2000 Field Migration Facility]]</li> | <li>[[Media:SirfieldNew.pdf|Sir2000 Field Migration Facility]]</li> | ||
</ul> | </ul> | ||
[[Category:$Functions|$Base64_Decode]] | [[Category:$Functions|$Base64_Decode]] | ||
Latest revision as of 22:51, 20 September 2018
Convert from base 64 to byte string
Note: Many $functions have been deprecated in favor of Object Oriented methods. The OO equivalent for the $Base64_Decode function is the Base64ToString (String function).
This function converts from a base 64 encoded string to the decoded byte string. It is identical to $Lstr_Base64_Decode with the (hopefully obvious) exception that it is not longstring capable. As such, $Lstr_Base64_Decode is recommended over $Base64_Decode as it is a more flexible version of the latter.
The $Base64_Decode function accepts one argument and returns a string result whose base 64 encoding is that argument.
The first argument is a string which is a base 64 encoding.
The returned value is the base 64 decoding of the argument string. If the argument is not a valid base 64 encoding, the null string is returned.
Syntax
%DECODED = $Base64_Decode(string)
%DECODED is set to the base 64 decoding of string.
Usage notes
Because the maximum length of the argument is 255 bytes, if you have a longer stream to decode, you can do it in pieces, where any piece is a multiple of 4 bytes long (3 bytes are evenly packed into 4 bytes of a base 64 encoding). For example, if you have a valid base 64 string which is the concatenation of items in a Sirius $list and you wish to print that string, possibly producing multiple lines of length 60, you can use the following approach:
%S = '' FOR %I FROM 1 TO $ListCnt(%L) %T = $ListInf(%L, %I) REPEAT WHILE $LEN(%S) + $LEN(%T) > 80 %X = 80 - $LEN(%S) %U = %S WITH $SUBSTR(%T, 1, %X) PRINT $Base64_Decode(%U) %T = $SUBSTR(%T, %X + 1) %S = '' END REPEAT %S = %S WITH %T END FOR PRINT $Base64_Decode(%S)
As of Sirius Mods Version 6.8, you can do base 64 decoding of strings longer than 255 bytes using $Lstr_Base64_Decode, but if, as in the example above, the intent is to break the result into smaller chunks, anyway, there probably wouldn't be a marked difference between using $Base64_Decode or its longstring equivalent.
You may wish to check for an invalid base 64 encoding by checking for the null string return value from $Base64_Decode. Of course, if it is possible that the argument is null, the null string is a valid returned value. If you need to check for errors, and the null string is a possible argument value, you can use an approach such as the following:
%STR = $Base64_Decode(%IN) IF %STR EQ '' Then IF %IN NE '' THEN error code ... END IF END IF
$Base64_Encode is the inverse of $Base64_Decode.
Example
Given the argument of length 4:
%JUNK = $Base64_Decode('ABCD')
%JUNK would be set to the byte string (of length 3) represented in hexadecimal as X'001083'.