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Bitpack integral prefixes
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@vitaut
vitaut committed Mar 12, 2021
1 parent cdf877d commit af56753
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Showing 2 changed files with 43 additions and 42 deletions.
1 change: 1 addition & 0 deletions include/fmt/format-inl.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1066,6 +1066,7 @@ template <typename T> const char basic_data<T>::signs[] = {0, '-', '+', ' '};

#if __cplusplus < 201703L
template <typename T> constexpr const char basic_data<T>::hex_digits[];
template <typename T> constexpr const unsigned basic_data<T>::prefixes[];
template <typename T> constexpr const char basic_data<T>::left_padding_shifts[];
template <typename T>
constexpr const char basic_data<T>::right_padding_shifts[];
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84 changes: 42 additions & 42 deletions include/fmt/format.h
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Original file line number Diff line number Diff line change
Expand Up @@ -982,8 +982,10 @@ template <typename T = void> struct FMT_EXTERN_TEMPLATE_API basic_data {
static const char reset_color[5];
static const wchar_t wreset_color[5];
static const char signs[];
static constexpr const char left_padding_shifts[5] = {31, 31, 0, 1, 0};
static constexpr const char right_padding_shifts[5] = {0, 31, 0, 1, 0};
static constexpr const unsigned prefixes[] = {0, 0, 0x1000000u | '+',
0x1000000u | ' '};
static constexpr const char left_padding_shifts[] = {31, 31, 0, 1, 0};
static constexpr const char right_padding_shifts[] = {0, 31, 0, 1, 0};

// DEPRECATED! These are for ABI compatibility.
static const uint32_t zero_or_powers_of_10_32[];
Expand Down Expand Up @@ -1662,17 +1664,17 @@ template <typename Char> struct write_int_data {
size_t size;
size_t padding;

FMT_CONSTEXPR write_int_data(int num_digits, string_view prefix,
FMT_CONSTEXPR write_int_data(int num_digits, unsigned prefix,
const basic_format_specs<Char>& specs)
: size(prefix.size() + to_unsigned(num_digits)), padding(0) {
: size((prefix >> 24) + to_unsigned(num_digits)), padding(0) {
if (specs.align == align::numeric) {
auto width = to_unsigned(specs.width);
if (width > size) {
padding = width - size;
size = width;
}
} else if (specs.precision > num_digits) {
size = prefix.size() + to_unsigned(specs.precision);
size = (prefix >> 24) + to_unsigned(specs.precision);
padding = to_unsigned(specs.precision - num_digits);
}
}
Expand All @@ -1681,29 +1683,32 @@ template <typename Char> struct write_int_data {
// Writes an integer in the format
// <left-padding><prefix><numeric-padding><digits><right-padding>
// where <digits> are written by write_digits(it).
// prefix contains chars in three lower bytes and the size in the fourth byte.
template <typename OutputIt, typename Char, typename W>
FMT_CONSTEXPR FMT_INLINE OutputIt
write_int(OutputIt out, int num_digits, string_view prefix,
write_int(OutputIt out, int num_digits, unsigned prefix,
const basic_format_specs<Char>& specs, W write_digits) {
// Slightly faster check for specs.width == 0 && specs.precision == -1.
if ((specs.width | (specs.precision + 1)) == 0) {
auto it = reserve(out, to_unsigned(num_digits) + prefix.size());
if (prefix.size() != 0)
it = copy_str<Char>(prefix.begin(), prefix.end(), it);
auto it = reserve(out, to_unsigned(num_digits) + (prefix >> 24));
if (prefix != 0) {
for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
*it++ = static_cast<Char>(p & 0xff);
}
return base_iterator(out, write_digits(it));
}
auto data = write_int_data<Char>(num_digits, prefix, specs);
return write_padded<align::right>(
out, specs, data.size, [=](reserve_iterator<OutputIt> it) {
if (prefix.size() != 0)
it = copy_str<Char>(prefix.begin(), prefix.end(), it);
for (unsigned p = prefix & 0xffffff; p != 0; p >>= 8)
*it++ = static_cast<Char>(p & 0xff);
it = detail::fill_n(it, data.padding, static_cast<Char>('0'));
return write_digits(it);
});
}

template <typename OutputIt, typename UInt, typename Char>
FMT_CONSTEXPR OutputIt write_dec(OutputIt out, UInt value, string_view prefix,
FMT_CONSTEXPR OutputIt write_dec(OutputIt out, UInt value, unsigned prefix,
const basic_format_specs<Char>& specs) {
auto num_digits = count_digits(value);
return write_int(out, num_digits, prefix, specs,
Expand All @@ -1713,7 +1718,7 @@ FMT_CONSTEXPR OutputIt write_dec(OutputIt out, UInt value, string_view prefix,
}

template <typename OutputIt, typename UInt, typename Char>
OutputIt write_int_localized(OutputIt out, UInt value, string_view prefix,
OutputIt write_int_localized(OutputIt out, UInt value, unsigned prefix,
const basic_format_specs<Char>& specs,
locale_ref loc) {
static_assert(std::is_same<uint64_or_128_t<UInt>, UInt>::value, "");
Expand All @@ -1735,7 +1740,7 @@ OutputIt write_int_localized(OutputIt out, UInt value, string_view prefix,
char digits[40];
format_decimal(digits, value, num_digits);
basic_memory_buffer<Char> buffer;
size += static_cast<int>(prefix.size());
if (prefix != 0) ++size;
const auto usize = to_unsigned(size);
buffer.resize(usize);
basic_string_view<Char> s(&sep, sep_size);
Expand All @@ -1757,59 +1762,55 @@ OutputIt write_int_localized(OutputIt out, UInt value, string_view prefix,
p -= s.size();
}
*p-- = static_cast<Char>(*digits);
if (prefix.size() != 0) *p = static_cast<Char>(prefix[0]);
if (prefix != 0) *p = static_cast<Char>(prefix);
auto data = buffer.data();
return write_padded<align::right>(
out, specs, usize, usize, [=](reserve_iterator<OutputIt> it) {
return copy_str<Char>(data, data + size, it);
});
}

FMT_CONSTEXPR inline void prefix_append(unsigned& prefix, unsigned value) {
prefix |= prefix != 0 ? value << 8 : value;
prefix += (1u + (value > 0xff ? 1 : 0)) << 24;
}

template <typename OutputIt, typename T, typename Char>
FMT_CONSTEXPR OutputIt write_int(OutputIt out, T value,
const basic_format_specs<Char>& specs,
locale_ref loc) {
char prefix[4] = {};
auto prefix_size = 0u;
auto prefix = 0u;
auto abs_value = static_cast<uint32_or_64_or_128_t<T>>(value);
if (is_negative(value)) {
prefix[0] = '-';
++prefix_size;
prefix = 0x01000000 | '-';
abs_value = 0 - abs_value;
} else if (specs.sign != sign::none && specs.sign != sign::minus) {
prefix[0] = specs.sign == sign::plus ? '+' : ' ';
++prefix_size;
} else {
prefix = data::prefixes[specs.sign];
}
auto utype = static_cast<unsigned>(specs.type);
switch (specs.type) {
case 0:
case 'd':
return specs.localized
? write_int_localized(out,
static_cast<uint64_or_128_t<T>>(abs_value),
{prefix, prefix_size}, specs, loc)
: write_dec(out, abs_value, {prefix, prefix_size}, specs);
prefix, specs, loc)
: write_dec(out, abs_value, prefix, specs);
case 'x':
case 'X': {
if (specs.alt) {
prefix[prefix_size++] = '0';
prefix[prefix_size++] = specs.type;
}
if (specs.alt) prefix_append(prefix, (utype << 8) | '0');
bool upper = specs.type != 'x';
int num_digits = count_digits<4>(abs_value);
return write_int(out, num_digits, {prefix, prefix_size}, specs,
[=](reserve_iterator<OutputIt> it) {
return format_uint<4, Char>(it, abs_value, num_digits,
upper);
});
return write_int(
out, num_digits, prefix, specs, [=](reserve_iterator<OutputIt> it) {
return format_uint<4, Char>(it, abs_value, num_digits, upper);
});
}
case 'b':
case 'B': {
if (specs.alt) {
prefix[prefix_size++] = '0';
prefix[prefix_size++] = static_cast<char>(specs.type);
}
if (specs.alt) prefix_append(prefix, (utype << 8) | '0');
int num_digits = count_digits<1>(abs_value);
return write_int(out, num_digits, {prefix, prefix_size}, specs,
return write_int(out, num_digits, prefix, specs,
[=](reserve_iterator<OutputIt> it) {
return format_uint<1, Char>(it, abs_value, num_digits);
});
Expand All @@ -1819,17 +1820,16 @@ FMT_CONSTEXPR OutputIt write_int(OutputIt out, T value,
if (specs.alt && specs.precision <= num_digits && abs_value != 0) {
// Octal prefix '0' is counted as a digit, so only add it if precision
// is not greater than the number of digits.
prefix[prefix_size++] = '0';
prefix_append(prefix, '0');
}
return write_int(out, num_digits, {prefix, prefix_size}, specs,
return write_int(out, num_digits, prefix, specs,
[=](reserve_iterator<OutputIt> it) {
return format_uint<3, Char>(it, abs_value, num_digits);
});
}
#ifdef FMT_DEPRECATED_N_SPECIFIER
case 'n':
return write_int_localized(out, abs_value, {prefix, prefix_size}, specs,
loc);
return write_int_localized(out, abs_value, prefix, specs, loc);
#endif
case 'c':
return write_char(out, static_cast<Char>(abs_value), specs);
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