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<table width="100%" summary="page for base64 {RCurl}"><tr><td>base64 {RCurl}</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>Encode/Decode base64 content</h2>

<h3>Description</h3>

<p>These functions encode and decode strings using base64 representations.
<code>base64</code> can be used as  a single entry point with an argument to 
encode or decode. The other two functions perform the specific action.
</p>

<h3>Usage</h3>

<pre>
base64(txt, encode = !inherits(txt, "base64"), mode = "character")
</pre>

<h3>Arguments</h3>

<table summary="R argblock">
<tr valign="top"><td><code>txt</code></td>
<td>
<p>character string to encode or decode</p>
</td></tr>
<tr valign="top"><td><code>encode</code></td>
<td>
<p>logical value indicating whether the desired action is to encode or decode the object.
If <code>txt</code> has (S3) class <code>base64</code>, the default is to decode this.
</p>
</td></tr>
<tr valign="top"><td><code>mode</code></td>
<td>
<p>a character string which is either &quot;raw&quot; or &quot;character&quot;.
This controls the type of vector that is returned.
If this is &quot;raw&quot;, a raw vector is created.  Otherwise, a character
vector of length 1 is returned and its element is the text version
of the original data given in <code>txt</code>.
</p>
</td></tr>
</table>

<h3>Details</h3>

<p>This calls the routines in libcurl. These are not
declared in the curl header files. So the support
may need to be handled carefully on some platforms,
e.g. Microsoft Windows.
</p>

<h3>Value</h3>

<p>If encode is <code>TRUE</code>, a character vector
with a class named <code>base64</code>.
If decode is <code>TRUE</code>, a simple string.
</p>

<p>This is currently not vectorized.
</p>
<p>We might extend this to work with raw objects.
</p>

<h3>Author(s)</h3>

<p>Duncan Temple Lang</p>

<h3>References</h3>

<p>libcurl - <a href="http://curl.haxx.se">http://curl.haxx.se</a>
Wikipedia's explanation of base 64 encoding - <a href="http://en.wikipedia.org/wiki/Base64">http://en.wikipedia.org/wiki/Base64</a>
</p>

<h3>Examples</h3>

<pre>
    # encode and then decode a simple string.
  txt = "Some simple text for base 64 to handle"
  x = base64(txt)
  base64(x)

# encode to a raw vector
  x = base64("Simple text", TRUE, "raw")

# decode to a character string.
  ans = base64Decode(x)
  ans == txt
    # decoded to a raw format.
  ans = base64Decode(x, "raw")

# Binary data
#  f = paste(R.home(), "doc", "html", "logo.jpg", sep = .Platform$file.sep)
  f = system.file("examples", "logo.jpg", package = "RCurl")
  img = readBin(f, "raw", file.info(f)[1, "size"])
  b64 = base64Encode(img, "raw")
  back = base64Decode(b64, "raw")
  identical(img, back)

# alternatively, we can encode to a string and then decode back again
   # to raw and see that we preserve the date.
 
  enc = base64Encode(img, "character")
  dec = base64Decode(enc, "raw")
  identical(img, dec)

# The following would be the sort of computation we could do if we
   # could have in-memory raw connections.
   # We would save() some objects to such an in-memory binary/raw connection
   # and then encode the resulting raw vector into a character vector.
   # Then we can insert that into a message, e.g. an email message or
   # an XML document and when we receive it in a different R session
   # we would get the string and reverse the encoding from the string to
   # a raw vector
   # In the absence of that in-memory connection  facility in save(),
   # we can use a file.
  
  x = 1:10

# save two objects - a function and a vector
  f = paste(tempfile(), "rda", sep = ".")
  save(base64, x, file = f)

# now read the results back from that file as a raw vector
  data = readBin(f, "raw", file.info(f)[1,"size"])

# base64 encode it
  txt = base64Encode(data, "character")

if(require(XML)) {
    tt = xmlTree("r:data", namespaces = c(r = "http://www.r-project.org"))
    tt$addNode(newXMLTextNode(txt))
    out = saveXML(tt)

doc = xmlRoot(xmlTreeParse(out, asText = TRUE))
    rda = base64Decode(xmlValue(doc), "raw")
    f = tempfile()
    writeBin(rda, f)
    e = new.env()
    load(f, e)
    objects(e)
  }

# we'd like to be able to do
   #  con = rawConnection(raw(), 'r+')
   #  save(base64, x, file = con)
   #  txt = base64Encode(rawConnectionValue(con), "character")
   # ... write and read xml stuff
   #  val = xmlValue(doc)
   #  rda = base64Decode(val, "raw")
   #  e = new.env()
   #  input = rawConnection(o, "r")
   #  load(input, e)
</pre>

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