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/*
Copyright (C) 2024-2025 Selwin van Dijk
This file is part of signalbackup-tools.
signalbackup-tools is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
signalbackup-tools is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with signalbackup-tools. If not, see <https://www.gnu.org/licenses/>.
*/
#include "signalbackup.ih"
void SignalBackup::HTMLwriteCallLinkDiv(std::ofstream &htmloutput, int indent, std::string const &url, std::string const &title,
std::string const &description) const
{
// get avatar color
/*
the first byte of the root key is used to get a random color, the root key
as found in the url is the binary key in base16 encoding.
See: https://github.com/signalapp/ringrtc/blob/9eec8cf6795899e0e0f6a17d4e902c160cc96f00/src/rust/src/lite/call_links/root_key.rs#L147-L155
And: https://github.com/signalapp/ringrtc/blob/9eec8cf6795899e0e0f6a17d4e902c160cc96f00/src/rust/src/lite/call_links/base16.rs#L87-L145
It looks complicated, but basically each pair of letters from the alphabet, represents one 8-bit number
const ALPHABET: &[u8; 16] = b"bcdfghkmnpqrstxz";
1st letter > b c d f g h k m n p q r s t x z
2nd letter v
b 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
c 16 17 18 ....
d
[...]
t
x ... 235 236 237 238 239
z 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255
*/
std::string color = "E3E3FE"; // random default
if (url.size() > STRLEN("https://signal.link/call/#key=") + 2)
{
auto consonant_base16_decode = [](char first, char second) -> int32_t
{
int high = -1;
int low = -1;
switch (first)
{
case 'b':
high = 0;
break;
case 'c':
high = 16;
break;
case 'd':
high = 32;
break;
case 'f':
high = 48;
break;
case 'g':
high = 64;
break;
case 'h':
high = 80;
break;
case 'k':
high = 96;
break;
case 'm':
high = 112;
break;
case 'n':
high = 128;
break;
case 'p':
high = 144;
break;
case 'q':
high = 160;
break;
case 'r':
high = 176;
break;
case 's':
high = 192;
break;
case 't':
high = 208;
break;
case 'x':
high = 224;
break;
case 'z':
high = 240;
break;
}
switch (second)
{
case 'b':
low = 0;
break;
case 'c':
low = 1;
break;
case 'd':
low = 2;
break;
case 'f':
low = 3;
break;
case 'g':
low = 4;
break;
case 'h':
low = 5;
break;
case 'k':
low = 6;
break;
case 'm':
low = 7;
break;
case 'n':
low = 8;
break;
case 'p':
low = 9;
break;
case 'q':
low = 10;
break;
case 'r':
low = 11;
break;
case 's':
low = 12;
break;
case 't':
low = 13;
break;
case 'x':
low = 14;
break;
case 'z':
low = 15;
break;
}
if (high < 0 || low < 0) [[unlikely]]
return -1;
return high + low;
};
/*
// old version, the switch lookup is faster...
auto consonant_base16_decode = [](char first, char second) -> int32_t
{
char constexpr alphabet[16] = {'b', 'c', 'd', 'f', 'g', 'h', 'k', 'm', 'n', 'p', 'q', 'r', 's', 't', 'x', 'z'};
int high = -1;
int low = -1;
for (unsigned int i = 0; i < 16; ++i)
{
if (high < 0 && alphabet[i] == first)
{
high = i;
if (low >= 0)
break;
}
if (low < 0 && alphabet[i] == second)
{
low = i;
if (high >= 0)
break;
}
}
if (high < 0 || low < 0) [[unlikely]]
return -1;
return (high << 4) + low;
};
*/
int32_t index = consonant_base16_decode(url[STRLEN("https://signal.link/call/#key=")],
url[STRLEN("https://signal.link/call/#key=") + 1]);
//std::cout << (index % 12) << std::endl;
if (index > 0) [[likely]]
color = s_html_random_colors[index % s_html_random_colors.size()].second;
}
htmloutput << std::string(indent, ' ') << "<div class=\"call-link\">\n";
htmloutput << std::string(indent, ' ') << " <div class=\"call-link-avatar-container\" style=\"background-color: #" << color << ";\">\n";
htmloutput << std::string(indent, ' ') << " <div class=\"call-link-avatar\"></div>\n";
htmloutput << std::string(indent, ' ') << " </div>\n";
htmloutput << std::string(indent, ' ') << " <div class=\"call-link-info\">\n";
htmloutput << std::string(indent, ' ') << " <span class=\"call-link-title\">"
<< (!title.empty() ? HTMLescapeString(title) : "Signal call") << "</span>\n";
htmloutput << std::string(indent, ' ') << " <pre>"
<< (!description.empty() ? HTMLescapeString(description) : "Use this link to join a Signal Call") << "</pre>\n";
htmloutput << std::string(indent, ' ') << " </div>\n";
htmloutput << std::string(indent, ' ') << "</div>\n";
}
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