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utils: support negative lexnums

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We use "lexnums" to efficiently/sortably store numbers >= 0; let's
support negative numbers as well (albeit not very optimal in size yet)
This commit is contained in:
Dirk-Jan C. Binnema
2026-07-23 11:05:08 +03:00
committed by Seth Ladygo
parent 51a2bc5f60
commit a03fd48551
3 changed files with 52 additions and 9 deletions
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23
lib/utils/mu-utils.cc
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@ -1,5 +1,5 @@
/*
** Copyright (C) 2017-2022 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
** Copyright (C) 2017-2026 Dirk-Jan C. Binnema <djcb@djcbsoftware.nl>
**
** This library is free software; you can redistribute it and/or
** modify it under the terms of the GNU Lesser General Public License
@ -581,17 +581,30 @@ std::string
Mu::to_lexnum(int64_t val)
{
char buf[18]; /* 1 byte prefix + hex + \0 */
buf[0] = 'f' + ::snprintf(buf + 1, sizeof(buf) - 1, "%" PRIx64, val);
const auto len = ::snprintf(buf + 1, sizeof(buf) - 1, "%" PRIx64,
static_cast<uint64_t>(val));
/* an uppercase prefix marks a negative value (see mu-utils.hh);
* uppercase sorts before lowercase, so negative values sort before
* the positive ones. */
buf[0] = (val < 0 ? 'F' : 'f') + len;
return buf;
}
int64_t
Mu::from_lexnum(const std::string& str)
{
int64_t val{};
std::from_chars(str.c_str() + 1, str.c_str() + str.size(), val, 16);
uint64_t val{};
if (str.empty())
return 0;
return val;
const auto res = std::from_chars(str.c_str() + 1,
str.c_str() + str.size(), val, 16);
if (res.ec != std::errc{})
return 0;
/* negative values are the two's-complement representation, so
* simply cast back. */
return static_cast<int64_t>(val);
}
bool