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LookupServer: Move parse_dns_name() -> DNSName::parse()

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While at it, refactor it slightly.
This commit is contained in:
Sergey Bugaev 2021-02-14 15:10:39 +03:00 • committed by Andreas Kling
parent ae1e82fd2f
commit 42bc5f2cc1
3 changed files with 41 additions and 35 deletions
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33
Userland/Services/LookupServer/DNSName.cpp
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@ -1,4 +1,5 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Sergey Bugaev <bugaevc@serenityos.org>
* All rights reserved.
*
@ -36,4 +37,36 @@ DNSName::DNSName(const String& name)
m_name = name;
}
DNSName DNSName::parse(const u8* data, size_t& offset, size_t max_offset, size_t recursion_level)
{
if (recursion_level > 4)
return DNSName({});
StringBuilder builder;
while (true) {
if (offset >= max_offset)
return DNSName({});
u8 b = data[offset++];
if (b == '\0') {
// This terminates the name.
return builder.to_string();
} else if ((b & 0xc0) == 0xc0) {
// The two bytes tell us the offset when to continue from.
if (offset >= max_offset)
return DNSName({});
size_t dummy = (b & 0x3f) << 8 | data[offset++];
auto rest_of_name = parse(data, dummy, max_offset, recursion_level + 1);
builder.append(rest_of_name.as_string());
return builder.to_string();
} else {
// This is the length of a part.
if (offset + b >= max_offset)
return DNSName({});
builder.append((const char*)&data[offset], (size_t)b);
builder.append('.');
offset += b;
}
}
}
}