incremental
diff --git a/src/base64.cpp b/src/base64.cpp
new file mode 100644
index 0000000..2592887
--- /dev/null
+++ b/src/base64.cpp
@@ -0,0 +1,138 @@
+#include <base64.hpp>
+#include <cassert>
+
+namespace base64
+{
+bool base64_encode(const gsl::cstring_span<> &input, std::string &output)
+{
+ static const char encoding_data[] =
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+ unsigned int input_length = input.size();
+
+ // allocate space for output string
+ output.clear();
+ output.reserve(((input_length + 2) / 3) * 4);
+
+ // for each 3-bytes sequence from the input, extract 4 6-bits sequences and
+ // encode using
+ // encoding_data lookup table.
+ // if input do not contains enough chars to complete 3-byte sequence,use pad
+ // char '='
+ for (unsigned int i = 0; i < input_length; i++) {
+ int base64code0 = 0;
+ int base64code1 = 0;
+ int base64code2 = 0;
+ int base64code3 = 0;
+
+ base64code0 = (input[i] >> 2) & 0x3f; // 1-byte 6 bits
+ output += encoding_data[base64code0];
+ base64code1 = (input[i] << 4) & 0x3f; // 1-byte 2 bits +
+
+ if (++i < input_length) {
+ base64code1 |= (input[i] >> 4) & 0x0f; // 2-byte 4 bits
+ output += encoding_data[base64code1];
+ base64code2 = (input[i] << 2) & 0x3f; // 2-byte 4 bits +
+
+ if (++i < input_length) {
+ base64code2 |= (input[i] >> 6) & 0x03; // 3-byte 2 bits
+ base64code3 = input[i] & 0x3f; // 3-byte 6 bits
+ output += encoding_data[base64code2];
+ output += encoding_data[base64code3];
+ } else {
+ output += encoding_data[base64code2];
+ output += '=';
+ }
+ } else {
+ output += encoding_data[base64code1];
+ output += '=';
+ output += '=';
+ }
+ }
+
+ return true;
+}
+
+
+bool base64_decode(const gsl::cstring_span<> &input, std::string &output)
+{
+ static const char nop = -1;
+ static const char decoding_data[] = {
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, 62, nop,
+ nop, nop, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, nop, nop,
+ nop, nop, nop, nop, nop, 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, nop, nop, nop, nop, nop, nop, 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, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop, nop,
+ nop};
+
+ unsigned int input_length = input.size();
+
+ // allocate space for output string
+ output.clear();
+ output.reserve(((input_length + 2) / 3) * 4);
+
+ // for each 4-bytes sequence from the input, extract 4 6-bits sequences by
+ // droping first two bits
+ // and regenerate into 3 8-bits sequence
+
+ for (unsigned int i = 0; i < input_length; i++) {
+ char base64code0;
+ char base64code1;
+ char base64code2 = 0; // initialized to 0 to suppress warnings
+ char base64code3;
+
+ base64code0 = decoding_data[static_cast<int>(input[i])];
+ if (base64code0 == nop) // non base64 character
+ return false;
+ if (!(++i < input_length)) // we need at least two input bytes for first
+ // byte output
+ return false;
+ base64code1 = decoding_data[static_cast<int>(input[i])];
+ if (base64code1 == nop) // non base64 character
+ return false;
+
+ output += ((base64code0 << 2) | ((base64code1 >> 4) & 0x3));
+
+ if (++i < input_length) {
+ char c = input[i];
+ if (c == '=') { // padding , end of input
+ assert((base64code1 & 0x0f) == 0);
+ return true;
+ }
+ base64code2 = decoding_data[static_cast<int>(input[i])];
+ if (base64code2 == nop) // non base64 character
+ return false;
+
+ output += ((base64code1 << 4) & 0xf0) | ((base64code2 >> 2) & 0x0f);
+ }
+
+ if (++i < input_length) {
+ char c = input[i];
+ if (c == '=') { // padding , end of input
+ assert((base64code2 & 0x03) == 0);
+ return true;
+ }
+ base64code3 = decoding_data[static_cast<int>(input[i])];
+ if (base64code3 == nop) // non base64 character
+ return false;
+
+ output += (((base64code2 << 6) & 0xc0) | base64code3);
+ }
+ }
+
+ return true;
+}
+
+}
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