ios based formatting of floats (no heap alloc and basic locale awareness)
parent
602aa7f182
commit
81ccca0e52
131
ostd/format.hh
131
ostd/format.hh
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@ -9,9 +9,12 @@
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#include <stdio.h>
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#include <stdlib.h>
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#include <ctype.h>
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#include <cmath>
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#include <utility>
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#include <stdexcept>
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#include <locale>
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#include <ios>
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#include "ostd/algorithm.hh"
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#include "ostd/string.hh"
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@ -476,28 +479,6 @@ private:
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for (int w = p_width - int(n); --w >= 0; writer.put(c));
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}
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template<typename R>
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void build_spec(R &out, string_range spec) const {
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out.put('%');
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if (p_flags & FMT_FLAG_DASH ) {
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out.put('-');
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}
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if (p_flags & FMT_FLAG_ZERO ) {
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out.put('0');
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}
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if (p_flags & FMT_FLAG_SPACE) {
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out.put(' ');
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}
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if (p_flags & FMT_FLAG_PLUS ) {
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out.put('+');
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}
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if (p_flags & FMT_FLAG_HASH ) {
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out.put('#');
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}
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range_put_all(out, string_range{"*.*"});
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range_put_all(out, spec);
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}
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/* string base writer */
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template<typename R>
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void write_str(R &writer, bool escape, string_range val) const {
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@ -627,52 +608,52 @@ private:
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}
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/* floating point */
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template<typename R, typename T, bool Long = std::is_same_v<T, ldouble>>
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template<typename R, typename T>
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void write_float(R &writer, T val) const {
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char buf[16], rbuf[128];
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char fmtspec[Long + 1];
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fmtspec[Long] = spec();
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byte specn = detail::fmt_specs[spec() - 65];
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char isp = spec();
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byte specn = detail::fmt_specs[isp - 65];
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if (specn != 1 && specn != 7) {
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throw format_error{"cannot format floats with the given spec"};
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}
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if (specn == 7) {
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fmtspec[Long] = 'g';
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}
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if (Long) {
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fmtspec[0] = 'L';
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}
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auto bufr = iter(buf);
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build_spec(bufr, fmtspec);
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bufr.put('\0');
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int ret = snprintf(
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rbuf, sizeof(rbuf), buf, width(),
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has_precision() ? precision() : 6, val
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/* null streambuf because it's only used to read flags etc */
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std::ios st{nullptr};
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st.width(width());
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st.precision(has_precision() ? precision() : 6);
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typename std::ios_base::fmtflags fl = 0;
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if (!(isp & 32)) {
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fl |= std::ios_base::uppercase;
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}
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/* equivalent of printf 'g' or 'G' by default */
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if ((isp | 32) == 'f') {
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fl |= std::ios_base::fixed;
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} else if ((isp | 32) == 'e') {
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fl |= std::ios_base::scientific;
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} else if ((isp | 32) == 'a') {
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fl |= std::ios_base::fixed | std::ios_base::scientific;
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}
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if (p_flags & FMT_FLAG_DASH) {
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fl |= std::ios_base::right;
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}
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if (p_flags & FMT_FLAG_PLUS) {
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fl |= std::ios_base::showpos;
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} else if ((p_flags & FMT_FLAG_SPACE) && !signbit(val)) {
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/* only if no sign is shown... num_put does not
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* support this so we have to do it on our own
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*/
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writer.put(' ');
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}
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if (p_flags & FMT_FLAG_HASH) {
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fl |= std::ios_base::showpoint;
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}
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st.flags(fl);
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fmt_num_put<R> nump;
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nump.put(
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fmt_out<R>{&writer}, st, (p_flags & FMT_FLAG_ZERO) ? '0' : ' ', val
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);
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if (ret < 0) {
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/* typically unreachable, build_spec creates valid format */
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throw format_error{"invalid float format"};
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}
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char *dbuf = nullptr;
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if (size_t(ret) >= sizeof(rbuf)) {
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/* this should typically never happen */
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dbuf = new char[ret + 1];
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ret = snprintf(
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dbuf, ret + 1, buf, width(),
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has_precision() ? precision() : 6, val
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);
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if (ret < 0) {
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/* see above */
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throw format_error{"invalid float format"};
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}
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range_put_all(writer, string_range{dbuf, dbuf + ret});
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delete[] dbuf;
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} else {
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range_put_all(writer, string_range{rbuf, rbuf + ret});
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}
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}
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template<typename R, typename T>
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@ -928,6 +909,32 @@ private:
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}
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}
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template<typename R>
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struct fmt_out {
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using iterator_category = std::output_iterator_tag;
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using value_type = char;
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using pointer = char *;
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using reference = char &;
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using difference_type = typename std::char_traits<char>::off_type;
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fmt_out &operator=(char c) {
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p_out->put(c);
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return *this;
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}
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fmt_out &operator*() { return *this; }
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fmt_out &operator++() { return *this; }
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fmt_out &operator++(int) { return *this; }
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R *p_out;
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};
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template<typename R>
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struct fmt_num_put final: std::num_put<char, fmt_out<R>> {
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fmt_num_put(size_t refs = 0): std::num_put<char, fmt_out<R>>(refs) {}
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~fmt_num_put() {}
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};
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string_range p_fmt;
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char p_buf[32];
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};
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