__vic/doc/en/base64.h.xml

<chapter xml:id="base64.h">
<title><tt>__vic/base64.h</tt></title>

<p>Base64 encoder and decoder.</p>


<chapter xml:id="base64">
<title><tt>base64</tt></title>

<p>A class used as a namespace. Contains only types, constants and static
functions. No objects of this class are supposed to be created.</p>

</chapter>


<chapter xml:id="base64--bad_format">
<title><tt>base64::bad_format</tt></title>

<code-block lang="C++">
struct base64::bad_format : public std::exception {};
</code-block>

<p>Abstract base exception class.</p>

</chapter>


<chapter xml:id="base64--bad_digit">
<title><tt>base64::bad_digit</tt></title>

<code-block lang="C++">
struct base64::bad_digit : public base64::bad_format
{
    const char *what() const noexcept;
};
</code-block>

<p>Exception class thrown by <xref to="base64--decode"/> when the input sequence
contains character that is not a valid Base64 digit.</p>

</chapter>


<chapter xml:id="base64--bad_length">
<title><tt>base64::bad_length</tt></title>

<code-block lang="C++">
struct base64::bad_length : public base64::bad_format
{
    const char *what() const noexcept;
};
</code-block>

<p>Exception class thrown by <xref to="base64--decode"/> when the input sequence
length is not a multiple of 4.</p>

</chapter>


<chapter xml:id="base64--status">
<title><tt>base64::status</tt></title>

<code-block lang="C++">
enum class base64::status
{
    ok,
    invalid_length,
    invalid_digit
};
using base64::status_t = base64::status; // for C++98
</code-block>

<p>Input sequence parsing outcome status codes returned by
<xref to="base64--try_decode"/>.</p>

</chapter>


<chapter xml:id="base64--encode">
<title><tt>base64::encode()</tt></title>

<code-block lang="C++"><![CDATA[
// Bytes -> Text
template<class ByteReader, class CharWriter>
void base64::encode(ByteReader reader, CharWriter writer);
]]></code-block>

<p>Encodes bytes from <tt>reader</tt> and writes the resulting characters to
<tt>writer</tt>.</p>

<p><tt>ByteReader</tt> has to model <tt>Reader&lt;unsigned char></tt> concept.
See <xref to="readers"/>.</p>

<p><tt>CharWriter</tt> has to model <tt>Writer&lt;char></tt> concept.
See <xref to="writers"/>.</p>

<section><title>Example</title>
<code-block lang="C++"><![CDATA[
#include<__vic/readers/string.h>
#include<__vic/writers/string.h>

using bytes = std::string;
using bytes_reader = __vic::string_reader;

std::string encode_base64(const bytes &s)
{
    std::string res;
    res.reserve(__vic::base64::encoded_length(s.length()));
    __vic::base64::encode(bytes_reader(s), __vic::string_writer(res));
    return res;
}
]]></code-block>
</section>

</chapter>


<chapter xml:id="base64--decode">
<title><tt>base64::decode()</tt></title>

<code-block lang="C++"><![CDATA[
// Text -> Bytes
template<class CharReader, class ByteWriter>
void base64::decode(CharReader reader, ByteWriter writer);
]]></code-block>

<p>Decodes characters form <tt>reader</tt> and writes the resulting bytes to
<tt>writer</tt>. Exception derived from <xref to="base64--bad_format"/> is
thrown if the input sequence has invalid Base64 format.</p>

<p><tt>CharReader</tt> has to model <tt>Reader&lt;char></tt> concept.
See <xref to="readers"/>.</p>

<p><tt>ByteWriter</tt> has to model <tt>Writer&lt;unsigned char></tt> concept.
See <xref to="writers"/>.</p>

<section><title>Example</title>
<code-block lang="C++"><![CDATA[
#include<__vic/readers/string.h>
#include<__vic/writers/string.h>

using bytes = std::string;
using bytes_writer = __vic::string_writer;

bytes decode_base64(const std::string &s)
{
    bytes res;
    res.reserve(__vic::base64::max_decoded_length(s.length()));
    __vic::base64::decode(__vic::string_reader(s), bytes_writer(res));
    return res;
}
]]></code-block>
</section>

</chapter>


<chapter xml:id="base64--try_decode">
<title><tt>base64::try_decode()</tt></title>

<code-block lang="C++"><![CDATA[
// Text -> Bytes
template<class CharReader, class ByteWriter>
base64::status_t base64::try_decode(CharReader reader, ByteWriter writer);
]]></code-block>

<p>Same as <xref to="base64--decode"/> but returns <xref to="base64--status"/>
different from <tt>base64::status::ok</tt> in case of invalid input sequence
instead of throwing exception.</p>

</chapter>


<chapter xml:id="base64--encoded_length">
<title><tt>base64::encoded_length()</tt></title>

<code-block lang="C++">
constexpr size_t base64::encoded_length(size_t orig_len);
</code-block>

<p>Calculates the length of encoded sequence of characters using the original
length of the bytes sequence.</p>

</chapter>


<chapter xml:id="base64--max_decoded_length">
<title><tt>base64::max_decoded_length()</tt></title>

<code-block lang="C++">
constexpr size_t base64::max_decoded_length(size_t orig_len);
</code-block>

<p>Estimates the maximum length of decoded sequence of bytes using the original
length of the characters sequence. The actual value depends on trailing
<tt>'='</tt> in the encoded value.</p>

</chapter>


</chapter>