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Refactor base64 decoding to use a lookup table (#364)
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* Refactor base64 decoding to use a lookup table

* Refactor base64 decoding to use a lookup table - clang format adaptions
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@ItsAMeMarcel
ItsAMeMarcel authored Nov 17, 2024
1 parent 6dd190d commit 59cdb43
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Showing 2 changed files with 87 additions and 16 deletions.
67 changes: 57 additions & 10 deletions include/jwt-cpp/base.h
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,22 @@ namespace jwt {
'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'}};
return data;
}
static const std::array<int8_t, 256>& rdata() {
static constexpr std::array<int8_t, 256> rdata{{
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
}};
return rdata;
}
static const std::string& fill() {
static const std::string fill{"="};
return fill;
Expand All @@ -61,6 +77,22 @@ namespace jwt {
'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_'}};
return data;
}
static const std::array<int8_t, 256>& rdata() {
static constexpr std::array<int8_t, 256> rdata{{
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63,
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
}};
return rdata;
}
static const std::string& fill() {
static const std::string fill{"%3d"};
return fill;
Expand All @@ -82,18 +114,33 @@ namespace jwt {
'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '_'}};
return data;
}
static const std::array<int8_t, 256>& rdata() {
static constexpr std::array<int8_t, 256> rdata{{
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63,
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
}};
return rdata;
}
static const std::vector<std::string>& fill() {
static const std::vector<std::string> fill{"%3D", "%3d"};
return fill;
}
};
} // namespace helper

inline uint32_t index(const std::array<char, 64>& alphabet, char symbol) {
auto itr = std::find_if(alphabet.cbegin(), alphabet.cend(), [symbol](char c) { return c == symbol; });
if (itr == alphabet.cend()) { throw std::runtime_error("Invalid input: not within alphabet"); }

return static_cast<uint32_t>(std::distance(alphabet.cbegin(), itr));
inline uint32_t index(const std::array<int8_t, 256>& rdata, char symbol) {
auto index = rdata[static_cast<unsigned char>(symbol)];
if (index <= -1) { throw std::runtime_error("Invalid input: not within alphabet"); }
return static_cast<uint32_t>(index);
}
} // namespace alphabet

Expand Down Expand Up @@ -178,7 +225,7 @@ namespace jwt {
return res;
}

inline std::string decode(const std::string& base, const std::array<char, 64>& alphabet,
inline std::string decode(const std::string& base, const std::array<int8_t, 256>& rdata,
const std::vector<std::string>& fill) {
const auto pad = count_padding(base, fill);
if (pad.count > 2) throw std::runtime_error("Invalid input: too much fill");
Expand All @@ -190,7 +237,7 @@ namespace jwt {
std::string res;
res.reserve(out_size);

auto get_sextet = [&](size_t offset) { return alphabet::index(alphabet, base[offset]); };
auto get_sextet = [&](size_t offset) { return alphabet::index(rdata, base[offset]); };

size_t fast_size = size - size % 4;
for (size_t i = 0; i < fast_size;) {
Expand Down Expand Up @@ -224,9 +271,9 @@ namespace jwt {
return res;
}

inline std::string decode(const std::string& base, const std::array<char, 64>& alphabet,
inline std::string decode(const std::string& base, const std::array<int8_t, 256>& rdata,
const std::string& fill) {
return decode(base, alphabet, std::vector<std::string>{fill});
return decode(base, rdata, std::vector<std::string>{fill});
}

inline std::string pad(const std::string& base, const std::string& fill) {
Expand Down Expand Up @@ -273,7 +320,7 @@ namespace jwt {
*/
template<typename T>
std::string decode(const std::string& base) {
return details::decode(base, T::data(), T::fill());
return details::decode(base, T::rdata(), T::fill());
}
/**
* \brief Generic base64 padding
Expand Down
36 changes: 30 additions & 6 deletions tests/BaseTest.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2,15 +2,39 @@
#include <gtest/gtest.h>

TEST(BaseTest, Base64Index) {
ASSERT_EQ(0, jwt::alphabet::index(jwt::alphabet::base64::data(), 'A'));
ASSERT_EQ(32, jwt::alphabet::index(jwt::alphabet::base64::data(), 'g'));
ASSERT_EQ(62, jwt::alphabet::index(jwt::alphabet::base64::data(), '+'));
ASSERT_EQ(0, jwt::alphabet::index(jwt::alphabet::base64::rdata(), 'A'));
ASSERT_EQ(32, jwt::alphabet::index(jwt::alphabet::base64::rdata(), 'g'));
ASSERT_EQ(62, jwt::alphabet::index(jwt::alphabet::base64::rdata(), '+'));

std::size_t index = 0;
for (auto c : jwt::alphabet::base64::data()) {
ASSERT_EQ(index, jwt::alphabet::index(jwt::alphabet::base64::rdata(), c));
index++;
}

std::size_t noBaseCharCount = 0;
for (std::size_t i = 0; i < jwt::alphabet::base64::rdata().size(); i++) {
if (jwt::alphabet::base64::rdata().at(i) == -1) { noBaseCharCount++; }
}
ASSERT_EQ(jwt::alphabet::base64::rdata().size() - jwt::alphabet::base64::data().size(), noBaseCharCount);
}

TEST(BaseTest, Base64URLIndex) {
ASSERT_EQ(0, jwt::alphabet::index(jwt::alphabet::base64url::data(), 'A'));
ASSERT_EQ(32, jwt::alphabet::index(jwt::alphabet::base64url::data(), 'g'));
ASSERT_EQ(62, jwt::alphabet::index(jwt::alphabet::base64url::data(), '-'));
ASSERT_EQ(0, jwt::alphabet::index(jwt::alphabet::base64url::rdata(), 'A'));
ASSERT_EQ(32, jwt::alphabet::index(jwt::alphabet::base64url::rdata(), 'g'));
ASSERT_EQ(62, jwt::alphabet::index(jwt::alphabet::base64url::rdata(), '-'));

std::size_t index = 0;
for (auto c : jwt::alphabet::base64url::data()) {
ASSERT_EQ(index, jwt::alphabet::index(jwt::alphabet::base64url::rdata(), c));
index++;
}

std::size_t noBaseCharCount = 0;
for (std::size_t i = 0; i < jwt::alphabet::base64url::rdata().size(); i++) {
if (jwt::alphabet::base64url::rdata().at(i) == -1) { noBaseCharCount++; }
}
ASSERT_EQ(jwt::alphabet::base64url::rdata().size() - jwt::alphabet::base64url::data().size(), noBaseCharCount);
}

TEST(BaseTest, BaseDetailsCountPadding) {
Expand Down

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