Waybar/include/util/format.hpp

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#pragma once
#include <fmt/format.h>
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class pow_format {
public:
pow_format(long long val, std::string&& unit, bool binary = false):
val_(val), unit_(unit), binary_(binary) { };
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long long val_;
std::string unit_;
bool binary_;
};
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namespace fmt {
template <>
struct formatter<pow_format> {
char spec = 0;
int width = 0;
template <typename ParseContext>
constexpr auto parse(ParseContext& ctx) -> decltype (ctx.begin()) {
auto it = ctx.begin(), end = ctx.end();
if (it != end && *it == ':') ++it;
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if (it && (*it == '>' || *it == '<' || *it == '=')) {
spec = *it;
++it;
}
if (it == end || *it == '}') return it;
if ('0' <= *it && *it <= '9') {
// We ignore it for now, but keep it for compatibility with
// existing configs where the format for pow_format'ed numbers was
// 'string' and specifications such as {:>9} were valid.
// The rationale for ignoring it is that the only reason to specify
// an alignment and a with is to get a fixed width bar, and ">" is
// sufficient in this implementation.
width = parse_nonnegative_int(it, end, ctx);
}
return it;
}
template<class FormatContext>
auto format(const pow_format& s, FormatContext &ctx) -> decltype (ctx.out()) {
const char* units[] = { "", "k", "M", "G", "T", "P", nullptr};
auto base = s.binary_ ? 1024ull : 1000ll;
auto fraction = (double) s.val_;
int pow;
for (pow = 0; units[pow+1] != nullptr && fraction / base >= 1; ++pow) {
fraction /= base;
}
auto max_width = 4 // coeff in {:.3g} format
+ 1 // prefix from units array
+ s.binary_ // for the 'i' in GiB.
+ s.unit_.length();
const char * format;
std::string string;
switch (spec) {
case '>':
return format_to(ctx.out(), "{:>{}}", fmt::format("{}", s), max_width);
case '<':
return format_to(ctx.out(), "{:<{}}", fmt::format("{}", s), max_width);
case '=':
format = "{coefficient:<4.3g}{padding}{prefix}{unit}";
break;
case 0:
default:
format = "{coefficient:.3g}{prefix}{unit}";
break;
}
return format_to(ctx.out(), format
, fmt::arg("coefficient", fraction)
, fmt::arg("prefix", std::string() + units[pow] + ((s.binary_ && pow) ? "i" : ""))
, fmt::arg("unit", s.unit_)
, fmt::arg("padding", pow ? "" : s.binary_ ? " " : " ")
);
}
};
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}