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// file : butl/base64.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#include <butl/base64>
#include <cstddef> // size_t
#include <istream>
#include <ostream>
#include <iterator> // {istreambuf, ostreambuf, back_insert}_iterator
#include <stdexcept> // invalid_argument
using namespace std;
namespace butl
{
static const char* codes =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
// base64-encode the data in the iterator range [i, e). Write the encoded
// data starting at the iterator position o.
//
template <typename I, typename O>
static void
base64_encode (I& i, const I& e, O& o)
{
const size_t un (65); // Non-existing index of the codes string.
for (size_t n (0); i != e; ++n)
{
if (n && n % 19 == 0)
*o++ = '\n'; // Split into lines, like the base64 utility does.
char c (*i++);
size_t i1 ((c >> 2) & 0x3F);
size_t i2 ((c << 4) & 0x30);
size_t i3 (un);
if (i != e)
{
c = *i++;
i2 |= (c >> 4) & 0xF;
i3 = (c << 2) & 0x3C;
}
size_t i4 (un);
if (i != e)
{
c = *i++;
i3 |= (c >> 6) & 0x3;
i4 = c & 0x3F;
}
*o++ = codes[i1];
*o++ = codes[i2];
*o++ = i3 == un ? '=' : codes[i3];
*o++ = i4 == un ? '=' : codes[i4];
}
}
static char
index (char c)
{
switch (c)
{
case '/': return 63;
case '+': return 62;
default:
{
if (c >= 'A' && c <= 'Z')
return c - 'A';
else if (c >= 'a' && c <= 'z')
return c - 'a' + 26;
else if (c >= '0' && c <= '9')
return c - '0' + 52;
else
throw invalid_argument ("invalid input");
}
}
}
// base64-decode the data in the iterator range [i, e). Write the decoded
// data starting at the iterator position o. Throw invalid_argument if the
// input data is invalid.
//
template <typename I, typename O>
static void
base64_decode (I& i, const I& e, O& o)
{
auto bad = []() {throw invalid_argument ("invalid input");};
auto next = [&i, &e, &bad]() -> char
{
if (i == e)
bad ();
return *i++;
};
while (i != e)
{
char c (next ());
if (c == '\n') // @@ Should we check for '\r' as well ?
continue;
char i1 = index (c);
char i2 = index (next ());
*o++ = (i1 << 2) | (i2 >> 4);
c = next ();
if (c == '=')
{
if (next () != '=' || i != e)
bad ();
}
else
{
char i3 = index (c);
*o++ = (i2 << 4) | (i3 >> 2);
c = next ();
if (c == '=')
{
if (i != e)
bad ();
}
else
*o++ = (i3 << 6) | index (c);
}
}
}
string
base64_encode (istream& is)
{
if (!is.good ())
throw invalid_argument ("bad stream");
string r;
istreambuf_iterator<char> i (is);
back_insert_iterator<string> o (r);
base64_encode (i, istreambuf_iterator<char> (), o);
is.setstate (istream::eofbit);
return r;
}
void
base64_encode (ostream& os, istream& is)
{
if (!os.good () || !is.good ())
throw invalid_argument ("bad stream");
istreambuf_iterator<char> i (is);
ostreambuf_iterator<char> o (os);
base64_encode (i, istreambuf_iterator<char> (), o);
if (o.failed ())
os.setstate (istream::badbit);
is.setstate (istream::eofbit);
}
string
base64_encode (const vector<char>& v)
{
string r;
back_insert_iterator<string> o (r);
auto i (v.begin ());
base64_encode (i, v.end (), o);
return r;
}
void
base64_decode (ostream& os, istream& is)
{
if (!os.good () || !is.good ())
throw invalid_argument ("bad stream");
istreambuf_iterator<char> i (is);
ostreambuf_iterator<char> o (os);
base64_decode (i, istreambuf_iterator<char> (), o);
if (o.failed ())
os.setstate (istream::badbit);
is.setstate (istream::eofbit);
}
void
base64_decode (ostream& os, const string& s)
{
if (!os.good ())
throw invalid_argument ("bad stream");
ostreambuf_iterator<char> o (os);
auto i (s.cbegin ());
base64_decode (i, s.cend (), o);
if (o.failed ())
os.setstate (istream::badbit);
}
vector<char>
base64_decode (const string& s)
{
vector<char> r;
back_insert_iterator<vector<char>> o (r);
auto i (s.cbegin ());
base64_decode (i, s.cend (), o);
return r;
}
}
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