cpputils/include/cpputils/base32encoder.h at master · nlitsme/cpputils · GitHub

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#pragma once

#include <tuple>

#include <vector>

#include <string>

#include <stdexcept>

#include <cstdint>

// encode a 5 byte chunk into 8 characters

template<typename P, typename S>

P base32_encode_chunk(P chunk, P last, S enc)

{

static const char*b32ToChar= "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567=";

P p = chunk;

auto b = *p++;

int c[8] = { (b&0xF8)>>3, (b&0x07)<<2, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20 };

if (p < last) {

b = *p++;

c[1] |= (b&0xc0)>>6;

c[2] = (b&0x3e)>>1;

c[3] = (b&1)<<4;

if (p < last) {

b = *p++;

c[3] |= (b&0xf0)>>4;

c[4] = (b&0x0f)<<1;

if (p < last) {

b = *p++;

c[4] |= (b&0x80)>>7;

c[5] = (b&0x7c)>>2;

c[6] = (b&0x03)<<3;

if (p < last) {

b = *p++;

c[6] |= (b&0xe0)>>5;

c[7] = (b&0x1f);

}

for (int i=0 ; i<8 ; i++)

*enc++= b32ToChar[c[i]];

return p;

}

template<typename P, typename S>

std::tuple<P, S> base32_encode(P ifirst, P ilast, S ofirst, S olast)

{

P p = ifirst;

S o = ofirst;

while (p < ilast && o+8 <= olast)

{

p = base32_encode_chunk(p, ilast, o);

o += 8;

}

return { p, o };

}

// -1 : invalid b32

// -2 : b32 terminator

// -3 : whitespace

// >=0: valid b32

static const int char2b32[]= {

// 1 2 3 4 5 6 7 8 9 a b c d e f

-1,-1,-1,-1,-1,-1,-1,-1,-1,-3,-3,-1,-3,-3,-1,-1, // 0

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 1

-3,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 2

-1,-1,26,27,28,29,30,31,-1,-1,-1,-1,-1,-2,-1,-1, // 3

-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14, // 4

15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1, // 5

-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14, // 4

15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1, // 5

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 8

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // 9

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // a

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // b

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // c

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // d

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // e

-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, // f

};

template<typename S, typename P>

std::tuple<S, P, bool> base32_decode(S ifirst, S ilast, P ofirst, P olast)

{

S p = ifirst;

P o = ofirst;

uint8_t b = 0;

int i = 0;

while (p < ilast && o < olast)

{

auto c = *p++;

int cv = char2b32[(uint8_t)c];

if (cv==-2) {

// '=' is always a proper base32 ending

i = 0;

break;

}

else if (cv==-3) {

// skip whitespace

continue;

}

else if (cv==-1) {

// invalid character.

return { p, o, false };

}

// 00000111 11222223 33334444 45555566 66677777

switch(i)

{

case 0: b = cv<<3; i=1; break;

case 1: b |= cv>>2; *o++ = b; b = cv<<6; i=2; break;

case 2: b |= cv<<1; i=3; break;

case 3: b |= cv>>4; *o++ = b; b = cv<<4; i=4; break;

case 4: b |= cv>>1; *o++ = b; b = cv<<7; i=5; break;

case 5: b |= cv<<2; i=6; break;

case 6: b |= cv>>3; *o++ = b; b = cv<<5; i=7; break;

case 7: b |= cv; *o++ = b; i = 0; break;

}

// skip trailing '='

while (p < ilast && *p == '=')

p++;

return { p, o, i==0 };

}

template<typename S>

std::vector<uint8_t> base32_decode(const S& txt)

{

std::vector<uint8_t> data(((txt.size()+7)/8)*5);

auto [p, o, ok] = base32_decode(txt.begin(), txt.end(), data.begin(), data.end());

if (!ok)

throw std::runtime_error("base32_decode");

// todo: check if all data was decoded.

data.erase(o, data.end());

return data;

}

template<typename P>

std::string base32_encode(const P& data)

{

std::string txt(((data.size()+4)/5)*8, char(0));

auto [p, o] = base32_encode(data.begin(), data.end(), txt.begin(), txt.end());

// todo: check if all data was encoded.

txt.erase(o, txt.end());

return txt;

}

cpputils/include/cpputils/base32encoder.h at master · nlitsme/cpputils · GitHub

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