[#BloombergLP-bdlde-Base64Decoder-convert-0e]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlde.adoc[bdlde]::xref:BloombergLP/bdlde/Base64Decoder.adoc[Base64Decoder]::convert
:relfileprefix: ../../../
:mrdocs:

Decode Base64 characters from `[begin, end)]` into `out` with limits.

== Synopsis

Declared in `<bdlde_base64decoder.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class OUTPUT_ITERATOR,
    class INPUT_ITERATOR>
int
convert(
    OUTPUT_ITERATOR out,
    int* numOut,
    int* numIn,
    INPUT_ITERATOR begin,
    INPUT_ITERATOR end,
    int maxNumOut = ‐1);
----

== Description

Decode the sequence of input characters starting at the specified `begin` position up to, but not including, the specified `end` position, writing any resulting output characters to the specified `out` buffer. Optionally specify the `maxNumOut` limit on the number of bytes to output; if `maxNumOut` is negative, no limit is imposed. If the `maxNumOut` limit is reached, no further input will be consumed. Load into the (optionally) specified `numOut` and `numIn` the number of output bytes produced and input bytes consumed, respectively. Return a non‐negative value on success, ‐1 on an input error, and ‐2 if the `endConvert` method has already been called without an intervening `resetState` call. A return status of ‐1 indicates that the data at `begin` + `numIn` constitutes an irrecoverably undecodable input sequence (i.e., the data cannot be extended to form any valid encoding). A positive return status indicates the number of valid processed output bytes retained by this decoder and not written to `out` because `maxNumOut` has been reached; these bytes are available for output if this method is called with appropriate input. Note that it is recommended that after all calls to `convert` are finished, the `endConvert` method be called to complete the decoding of any unprocessed input characters that do not complete a 3‐byte sequence.

== Specializations

[cols="1,4"]
|===
| Name| Description
| xref:BloombergLP/bdlde/Base64Decoder/convert-0c.adoc[`convert<char*, char const*>`] 
| Decode Base64 input for `char *` / `const char *` iterators.
| xref:BloombergLP/bdlde/Base64Decoder/convert-01.adoc[`convert<unsigned char*, unsigned char const*>`] 
| Decode Base64 input for `unsigned char *` iterators.
|===


== Return Value

non‐negative value on success (positive count of retained output bytes if `maxNumOut` was reached), ‐1 on input error, and ‐2 if `endConvert` has already been called without an intervening `resetState`

== Parameters

[cols="1,4"]
|===
| Name| Description
| *out*
| destination for decoded output bytes
| *numOut*
| if non‐null, receives the number of bytes written
| *numIn*
| if non‐null, receives the number of input bytes consumed
| *begin*
| beginning of the Base64 input range
| *end*
| end of the Base64 input range (exclusive)
| *maxNumOut*
| maximum bytes to write; negative means no limit
|===


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