flang/runtime/edit-output.cpp

   1 //===-- runtime/edit-output.cpp -------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "edit-output.h"
  10 #include "emit-encoded.h"
  11 #include "utf.h"
  12 #include "flang/Common/uint128.h"
  13 #include <algorithm>
  14
  15 namespace Fortran::runtime::io {
  16
  17 // In output statement, add a space between numbers and characters.
  18 static void addSpaceBeforeCharacter(IoStatementState &io) {
  19   if (auto *list{io.get_if<ListDirectedStatementState<Direction::Output>>()}) {
  20     list->set_lastWasUndelimitedCharacter(false);
  21   }
  22 }
  23
  24 // B/O/Z output of arbitrarily sized data emits a binary/octal/hexadecimal
  25 // representation of what is interpreted to be a single unsigned integer value.
  26 // When used with character data, endianness is exposed.
  27 template <int LOG2_BASE>
  28 static bool EditBOZOutput(IoStatementState &io, const DataEdit &edit,
  29     const unsigned char *data0, std::size_t bytes) {
  30   addSpaceBeforeCharacter(io);
  31   int digits{static_cast<int>((bytes * 8) / LOG2_BASE)};
  32   int get{static_cast<int>(bytes * 8) - digits * LOG2_BASE};
  33   if (get > 0) {
  34     ++digits;
  35   } else {
  36     get = LOG2_BASE;
  37   }
  38   int shift{7};
  39   int increment{isHostLittleEndian ? -1 : 1};
  40   const unsigned char *data{data0 + (isHostLittleEndian ? bytes - 1 : 0)};
  41   int skippedZeroes{0};
  42   int digit{0};
  43   // The same algorithm is used to generate digits for real (below)
  44   // as well as for generating them only to skip leading zeroes (here).
  45   // Bits are copied one at a time from the source data.
  46   // TODO: Multiple bit copies for hexadecimal, where misalignment
  47   // is not possible; or for octal when all 3 bits come from the
  48   // same byte.
  49   while (bytes > 0) {
  50     if (get == 0) {
  51       if (digit != 0) {
  52         break; // first nonzero leading digit
  53       }
  54       ++skippedZeroes;
  55       get = LOG2_BASE;
  56     } else if (shift < 0) {
  57       data += increment;
  58       --bytes;
  59       shift = 7;
  60     } else {
  61       digit = 2 * digit + ((*data >> shift--) & 1);
  62       --get;
  63     }
  64   }
  65   // Emit leading spaces and zeroes; detect field overflow
  66   int leadingZeroes{0};
  67   int editWidth{edit.width.value_or(0)};
  68   int significant{digits - skippedZeroes};
  69   if (edit.digits && significant <= *edit.digits) { // Bw.m, Ow.m, Zw.m
  70     if (*edit.digits == 0 && bytes == 0) {
  71       editWidth = std::max(1, editWidth);
  72     } else {
  73       leadingZeroes = *edit.digits - significant;
  74     }
  75   } else if (bytes == 0) {
  76     leadingZeroes = 1;
  77   }
  78   int subTotal{leadingZeroes + significant};
  79   int leadingSpaces{std::max(0, editWidth - subTotal)};
  80   if (editWidth > 0 && leadingSpaces + subTotal > editWidth) {
  81     return EmitRepeated(io, '*', editWidth);
  82   }
  83   if (!(EmitRepeated(io, ' ', leadingSpaces) &&
  84           EmitRepeated(io, '0', leadingZeroes))) {
  85     return false;
  86   }
  87   // Emit remaining digits
  88   while (bytes > 0) {
  89     if (get == 0) {
  90       char ch{static_cast<char>(digit >= 10 ? 'A' + digit - 10 : '0' + digit)};
  91       if (!EmitAscii(io, &ch, 1)) {
  92         return false;
  93       }
  94       get = LOG2_BASE;
  95       digit = 0;
  96     } else if (shift < 0) {
  97       data += increment;
  98       --bytes;
  99       shift = 7;
 100     } else {
 101       digit = 2 * digit + ((*data >> shift--) & 1);
 102       --get;
 103     }
 104   }
 105   return true;
 106 }
 107
 108 template <int KIND>
 109 bool EditIntegerOutput(IoStatementState &io, const DataEdit &edit,
 110     common::HostSignedIntType<8 * KIND> n) {
 111   addSpaceBeforeCharacter(io);
 112   char buffer[130], *end{&buffer[sizeof buffer]}, *p{end};
 113   bool isNegative{n < 0};
 114   using Unsigned = common::HostUnsignedIntType<8 * KIND>;
 115   Unsigned un{static_cast<Unsigned>(n)};
 116   int signChars{0};
 117   switch (edit.descriptor) {
 118   case DataEdit::ListDirected:
 119   case 'G':
 120   case 'I':
 121     if (isNegative) {
 122       un = -un;
 123     }
 124     if (isNegative || (edit.modes.editingFlags & signPlus)) {
 125       signChars = 1; // '-' or '+'
 126     }
 127     while (un > 0) {
 128       auto quotient{un / 10u};
 129       *--p = '0' + static_cast<int>(un - Unsigned{10} * quotient);
 130       un = quotient;
 131     }
 132     break;
 133   case 'B':
 134     return EditBOZOutput<1>(
 135         io, edit, reinterpret_cast<const unsigned char *>(&n), KIND);
 136   case 'O':
 137     return EditBOZOutput<3>(
 138         io, edit, reinterpret_cast<const unsigned char *>(&n), KIND);
 139   case 'Z':
 140     return EditBOZOutput<4>(
 141         io, edit, reinterpret_cast<const unsigned char *>(&n), KIND);
 142   case 'L':
 143     return EditLogicalOutput(io, edit, *reinterpret_cast<const char *>(&n));
 144   case 'A': // legacy extension
 145     return EditCharacterOutput(
 146         io, edit, reinterpret_cast<char *>(&n), sizeof n);
 147   default:
 148     io.GetIoErrorHandler().SignalError(IostatErrorInFormat,
 149         "Data edit descriptor '%c' may not be used with an INTEGER data item",
 150         edit.descriptor);
 151     return false;
 152   }
 153
 154   int digits = end - p;
 155   int leadingZeroes{0};
 156   int editWidth{edit.width.value_or(0)};
 157   if (edit.descriptor == 'I' && edit.digits && digits <= *edit.digits) {
 158     // Only Iw.m can produce leading zeroes, not Gw.d (F'202X 13.7.5.2.2)
 159     if (*edit.digits == 0 && n == 0) {
 160       // Iw.0 with zero value: output field must be blank.  For I0.0
 161       // and a zero value, emit one blank character.
 162       signChars = 0; // in case of SP
 163       editWidth = std::max(1, editWidth);
 164     } else {
 165       leadingZeroes = *edit.digits - digits;
 166     }
 167   } else if (n == 0) {
 168     leadingZeroes = 1;
 169   }
 170   int subTotal{signChars + leadingZeroes + digits};
 171   int leadingSpaces{std::max(0, editWidth - subTotal)};
 172   if (editWidth > 0 && leadingSpaces + subTotal > editWidth) {
 173     return EmitRepeated(io, '*', editWidth);
 174   }
 175   if (edit.IsListDirected()) {
 176     int total{std::max(leadingSpaces, 1) + subTotal};
 177     if (io.GetConnectionState().NeedAdvance(static_cast<std::size_t>(total)) &&
 178         !io.AdvanceRecord()) {
 179       return false;
 180     }
 181     leadingSpaces = 1;
 182   }
 183   return EmitRepeated(io, ' ', leadingSpaces) &&
 184       EmitAscii(io, n < 0 ? "-" : "+", signChars) &&
 185       EmitRepeated(io, '0', leadingZeroes) && EmitAscii(io, p, digits);
 186 }
 187
 188 // Formats the exponent (see table 13.1 for all the cases)
 189 const char *RealOutputEditingBase::FormatExponent(
 190     int expo, const DataEdit &edit, int &length) {
 191   char *eEnd{&exponent_[sizeof exponent_]};
 192   char *exponent{eEnd};
 193   for (unsigned e{static_cast<unsigned>(std::abs(expo))}; e > 0;) {
 194     unsigned quotient{e / 10u};
 195     *--exponent = '0' + e - 10 * quotient;
 196     e = quotient;
 197   }
 198   bool overflow{false};
 199   if (edit.expoDigits) {
 200     if (int ed{*edit.expoDigits}) { // Ew.dEe with e > 0
 201       overflow = exponent + ed < eEnd;
 202       while (exponent > exponent_ + 2 /*E+*/ && exponent + ed > eEnd) {
 203         *--exponent = '0';
 204       }
 205     } else if (exponent == eEnd) {
 206       *--exponent = '0'; // Ew.dE0 with zero-valued exponent
 207     }
 208   } else if (edit.variation == 'X') {
 209     if (expo == 0) {
 210       *--exponent = '0'; // EX without Ee and zero-valued exponent
 211     }
 212   } else {
 213     // Ensure at least two exponent digits unless EX
 214     while (exponent + 2 > eEnd) {
 215       *--exponent = '0';
 216     }
 217   }
 218   *--exponent = expo < 0 ? '-' : '+';
 219   if (edit.variation == 'X') {
 220     *--exponent = 'P';
 221   } else if (edit.expoDigits || edit.IsListDirected() || exponent + 3 == eEnd) {
 222     *--exponent = edit.descriptor == 'D' ? 'D' : 'E'; // not 'G' or 'Q'
 223   }
 224   length = eEnd - exponent;
 225   return overflow ? nullptr : exponent;
 226 }
 227
 228 bool RealOutputEditingBase::EmitPrefix(
 229     const DataEdit &edit, std::size_t length, std::size_t width) {
 230   if (edit.IsListDirected()) {
 231     int prefixLength{edit.descriptor == DataEdit::ListDirectedRealPart ? 2
 232             : edit.descriptor == DataEdit::ListDirectedImaginaryPart   ? 0
 233                                                                        : 1};
 234     int suffixLength{edit.descriptor == DataEdit::ListDirectedRealPart ||
 235                 edit.descriptor == DataEdit::ListDirectedImaginaryPart
 236             ? 1
 237             : 0};
 238     length += prefixLength + suffixLength;
 239     ConnectionState &connection{io_.GetConnectionState()};
 240     return (!connection.NeedAdvance(length) || io_.AdvanceRecord()) &&
 241         EmitAscii(io_, " (", prefixLength);
 242   } else if (width > length) {
 243     return EmitRepeated(io_, ' ', width - length);
 244   } else {
 245     return true;
 246   }
 247 }
 248
 249 bool RealOutputEditingBase::EmitSuffix(const DataEdit &edit) {
 250   if (edit.descriptor == DataEdit::ListDirectedRealPart) {
 251     return EmitAscii(
 252         io_, edit.modes.editingFlags & decimalComma ? ";" : ",", 1);
 253   } else if (edit.descriptor == DataEdit::ListDirectedImaginaryPart) {
 254     return EmitAscii(io_, ")", 1);
 255   } else {
 256     return true;
 257   }
 258 }
 259
 260 template <int KIND>
 261 decimal::ConversionToDecimalResult RealOutputEditing<KIND>::ConvertToDecimal(
 262     int significantDigits, enum decimal::FortranRounding rounding, int flags) {
 263   auto converted{decimal::ConvertToDecimal<binaryPrecision>(buffer_,
 264       sizeof buffer_, static_cast<enum decimal::DecimalConversionFlags>(flags),
 265       significantDigits, rounding, x_)};
 266   if (!converted.str) { // overflow
 267     io_.GetIoErrorHandler().Crash(
 268         "RealOutputEditing::ConvertToDecimal: buffer size %zd was insufficient",
 269         sizeof buffer_);
 270   }
 271   return converted;
 272 }
 273
 274 static bool IsInfOrNaN(const char *p, int length) {
 275   if (!p || length < 1) {
 276     return false;
 277   }
 278   if (*p == '-' || *p == '+') {
 279     if (length == 1) {
 280       return false;
 281     }
 282     ++p;
 283   }
 284   return *p == 'I' || *p == 'N';
 285 }
 286
 287 // 13.7.2.3.3 in F'2018
 288 template <int KIND>
 289 bool RealOutputEditing<KIND>::EditEorDOutput(const DataEdit &edit) {
 290   addSpaceBeforeCharacter(io_);
 291   int editDigits{edit.digits.value_or(0)}; // 'd' field
 292   int editWidth{edit.width.value_or(0)}; // 'w' field
 293   int significantDigits{editDigits};
 294   int flags{0};
 295   if (edit.modes.editingFlags & signPlus) {
 296     flags |= decimal::AlwaysSign;
 297   }
 298   int scale{edit.modes.scale}; // 'kP' value
 299   if (editWidth == 0) { // "the processor selects the field width"
 300     if (edit.digits.has_value()) { // E0.d
 301       if (editDigits == 0 && scale <= 0) { // E0.0
 302         significantDigits = 1;
 303       }
 304     } else { // E0
 305       flags |= decimal::Minimize;
 306       significantDigits =
 307           sizeof buffer_ - 5; // sign, NUL, + 3 extra for EN scaling
 308     }
 309   }
 310   bool isEN{edit.variation == 'N'};
 311   bool isES{edit.variation == 'S'};
 312   int zeroesAfterPoint{0};
 313   if (isEN) {
 314     scale = IsZero() ? 1 : 3;
 315     significantDigits += scale;
 316   } else if (isES) {
 317     scale = 1;
 318     ++significantDigits;
 319   } else if (scale < 0) {
 320     if (scale <= -editDigits) {
 321       io_.GetIoErrorHandler().SignalError(IostatBadScaleFactor,
 322           "Scale factor (kP) %d cannot be less than -d (%d)", scale,
 323           -editDigits);
 324       return false;
 325     }
 326     zeroesAfterPoint = -scale;
 327     significantDigits = std::max(0, significantDigits - zeroesAfterPoint);
 328   } else if (scale > 0) {
 329     if (scale >= editDigits + 2) {
 330       io_.GetIoErrorHandler().SignalError(IostatBadScaleFactor,
 331           "Scale factor (kP) %d cannot be greater than d+2 (%d)", scale,
 332           editDigits + 2);
 333       return false;
 334     }
 335     ++significantDigits;
 336     scale = std::min(scale, significantDigits + 1);
 337   }
 338   // In EN editing, multiple attempts may be necessary, so this is a loop.
 339   while (true) {
 340     decimal::ConversionToDecimalResult converted{
 341         ConvertToDecimal(significantDigits, edit.modes.round, flags)};
 342     if (IsInfOrNaN(converted.str, static_cast<int>(converted.length))) {
 343       return editWidth > 0 &&
 344               converted.length > static_cast<std::size_t>(editWidth)
 345           ? EmitRepeated(io_, '*', editWidth)
 346           : EmitPrefix(edit, converted.length, editWidth) &&
 347               EmitAscii(io_, converted.str, converted.length) &&
 348               EmitSuffix(edit);
 349     }
 350     if (!IsZero()) {
 351       converted.decimalExponent -= scale;
 352     }
 353     if (isEN) {
 354       // EN mode: we need an effective exponent field that is
 355       // a multiple of three.
 356       if (int modulus{converted.decimalExponent % 3}; modulus != 0) {
 357         if (significantDigits > 1) {
 358           --significantDigits;
 359           --scale;
 360           continue;
 361         }
 362         // Rounded nines up to a 1.
 363         scale += modulus;
 364         converted.decimalExponent -= modulus;
 365       }
 366       if (scale > 3) {
 367         int adjust{3 * (scale / 3)};
 368         scale -= adjust;
 369         converted.decimalExponent += adjust;
 370       } else if (scale < 1) {
 371         int adjust{3 - 3 * (scale / 3)};
 372         scale += adjust;
 373         converted.decimalExponent -= adjust;
 374       }
 375       significantDigits = editDigits + scale;
 376     }
 377     // Format the exponent (see table 13.1 for all the cases)
 378     int expoLength{0};
 379     const char *exponent{
 380         FormatExponent(converted.decimalExponent, edit, expoLength)};
 381     int signLength{*converted.str == '-' || *converted.str == '+' ? 1 : 0};
 382     int convertedDigits{static_cast<int>(converted.length) - signLength};
 383     int zeroesBeforePoint{std::max(0, scale - convertedDigits)};
 384     int digitsBeforePoint{std::max(0, scale - zeroesBeforePoint)};
 385     int digitsAfterPoint{convertedDigits - digitsBeforePoint};
 386     int trailingZeroes{flags & decimal::Minimize
 387             ? 0
 388             : std::max(0,
 389                   significantDigits - (convertedDigits + zeroesBeforePoint))};
 390     int totalLength{signLength + digitsBeforePoint + zeroesBeforePoint +
 391         1 /*'.'*/ + zeroesAfterPoint + digitsAfterPoint + trailingZeroes +
 392         expoLength};
 393     int width{editWidth > 0 ? editWidth : totalLength};
 394     if (totalLength > width || !exponent) {
 395       return EmitRepeated(io_, '*', width);
 396     }
 397     if (totalLength < width && digitsBeforePoint == 0 &&
 398         zeroesBeforePoint == 0) {
 399       zeroesBeforePoint = 1;
 400       ++totalLength;
 401     }
 402     if (totalLength < width && editWidth == 0) {
 403       width = totalLength;
 404     }
 405     return EmitPrefix(edit, totalLength, width) &&
 406         EmitAscii(io_, converted.str, signLength + digitsBeforePoint) &&
 407         EmitRepeated(io_, '0', zeroesBeforePoint) &&
 408         EmitAscii(io_, edit.modes.editingFlags & decimalComma ? "," : ".", 1) &&
 409         EmitRepeated(io_, '0', zeroesAfterPoint) &&
 410         EmitAscii(io_, converted.str + signLength + digitsBeforePoint,
 411             digitsAfterPoint) &&
 412         EmitRepeated(io_, '0', trailingZeroes) &&
 413         EmitAscii(io_, exponent, expoLength) && EmitSuffix(edit);
 414   }
 415 }
 416
 417 // 13.7.2.3.2 in F'2018
 418 template <int KIND>
 419 bool RealOutputEditing<KIND>::EditFOutput(const DataEdit &edit) {
 420   addSpaceBeforeCharacter(io_);
 421   int fracDigits{edit.digits.value_or(0)}; // 'd' field
 422   const int editWidth{edit.width.value_or(0)}; // 'w' field
 423   enum decimal::FortranRounding rounding{edit.modes.round};
 424   int flags{0};
 425   if (edit.modes.editingFlags & signPlus) {
 426     flags |= decimal::AlwaysSign;
 427   }
 428   if (editWidth == 0) { // "the processor selects the field width"
 429     if (!edit.digits.has_value()) { // F0
 430       flags |= decimal::Minimize;
 431       fracDigits = sizeof buffer_ - 2; // sign & NUL
 432     }
 433   }
 434   // Multiple conversions may be needed to get the right number of
 435   // effective rounded fractional digits.
 436   int extraDigits{0};
 437   bool canIncrease{true};
 438   while (true) {
 439     decimal::ConversionToDecimalResult converted{
 440         ConvertToDecimal(extraDigits + fracDigits, rounding, flags)};
 441     if (IsInfOrNaN(converted.str, static_cast<int>(converted.length))) {
 442       return editWidth > 0 &&
 443               converted.length > static_cast<std::size_t>(editWidth)
 444           ? EmitRepeated(io_, '*', editWidth)
 445           : EmitPrefix(edit, converted.length, editWidth) &&
 446               EmitAscii(io_, converted.str, converted.length) &&
 447               EmitSuffix(edit);
 448     }
 449     int expo{converted.decimalExponent + edit.modes.scale /*kP*/};
 450     int signLength{*converted.str == '-' || *converted.str == '+' ? 1 : 0};
 451     int convertedDigits{static_cast<int>(converted.length) - signLength};
 452     if (IsZero()) { // don't treat converted "0" as significant digit
 453       expo = 0;
 454       convertedDigits = 0;
 455     }
 456     int trailingOnes{0};
 457     if (expo > extraDigits && extraDigits >= 0 && canIncrease) {
 458       extraDigits = expo;
 459       if (!edit.digits.has_value()) { // F0
 460         fracDigits = sizeof buffer_ - extraDigits - 2; // sign & NUL
 461       }
 462       canIncrease = false; // only once
 463       continue;
 464     } else if (expo == -fracDigits && convertedDigits > 0) {
 465       if ((rounding == decimal::FortranRounding::RoundUp &&
 466               *converted.str != '-') ||
 467           (rounding == decimal::FortranRounding::RoundDown &&
 468               *converted.str == '-') ||
 469           (rounding == decimal::FortranRounding::RoundToZero &&
 470               rounding != edit.modes.round && // it changed below
 471               converted.str[signLength] >= '5')) {
 472         // Round up/down to a scaled 1
 473         ++expo;
 474         convertedDigits = 0;
 475         trailingOnes = 1;
 476       } else if (rounding != decimal::FortranRounding::RoundToZero) {
 477         // Convert again with truncation so first digit can be checked
 478         // on the next iteration by the code above
 479         rounding = decimal::FortranRounding::RoundToZero;
 480         continue;
 481       } else {
 482         // Value rounds down to zero
 483         expo = 0;
 484         convertedDigits = 0;
 485       }
 486     } else if (expo < extraDigits && extraDigits > -fracDigits) {
 487       extraDigits = std::max(expo, -fracDigits);
 488       continue;
 489     }
 490     int digitsBeforePoint{std::max(0, std::min(expo, convertedDigits))};
 491     int zeroesBeforePoint{std::max(0, expo - digitsBeforePoint)};
 492     int zeroesAfterPoint{std::min(fracDigits, std::max(0, -expo))};
 493     int digitsAfterPoint{convertedDigits - digitsBeforePoint};
 494     int trailingZeroes{flags & decimal::Minimize
 495             ? 0
 496             : std::max(0,
 497                   fracDigits -
 498                       (zeroesAfterPoint + digitsAfterPoint + trailingOnes))};
 499     if (digitsBeforePoint + zeroesBeforePoint + zeroesAfterPoint +
 500             digitsAfterPoint + trailingOnes + trailingZeroes ==
 501         0) {
 502       zeroesBeforePoint = 1; // "." -> "0."
 503     }
 504     int totalLength{signLength + digitsBeforePoint + zeroesBeforePoint +
 505         1 /*'.'*/ + zeroesAfterPoint + digitsAfterPoint + trailingOnes +
 506         trailingZeroes};
 507     int width{editWidth > 0 ? editWidth : totalLength};
 508     if (totalLength > width) {
 509       return EmitRepeated(io_, '*', width);
 510     }
 511     if (totalLength < width && digitsBeforePoint + zeroesBeforePoint == 0) {
 512       zeroesBeforePoint = 1;
 513       ++totalLength;
 514     }
 515     return EmitPrefix(edit, totalLength, width) &&
 516         EmitAscii(io_, converted.str, signLength + digitsBeforePoint) &&
 517         EmitRepeated(io_, '0', zeroesBeforePoint) &&
 518         EmitAscii(io_, edit.modes.editingFlags & decimalComma ? "," : ".", 1) &&
 519         EmitRepeated(io_, '0', zeroesAfterPoint) &&
 520         EmitAscii(io_, converted.str + signLength + digitsBeforePoint,
 521             digitsAfterPoint) &&
 522         EmitRepeated(io_, '1', trailingOnes) &&
 523         EmitRepeated(io_, '0', trailingZeroes) &&
 524         EmitRepeated(io_, ' ', trailingBlanks_) && EmitSuffix(edit);
 525   }
 526 }
 527
 528 // 13.7.5.2.3 in F'2018
 529 template <int KIND>
 530 DataEdit RealOutputEditing<KIND>::EditForGOutput(DataEdit edit) {
 531   edit.descriptor = 'E';
 532   int editWidth{edit.width.value_or(0)};
 533   int significantDigits{
 534       edit.digits.value_or(BinaryFloatingPoint::decimalPrecision)}; // 'd'
 535   if (editWidth > 0 && significantDigits == 0) {
 536     return edit; // Gw.0Ee -> Ew.0Ee for w > 0
 537   }
 538   int flags{0};
 539   if (edit.modes.editingFlags & signPlus) {
 540     flags |= decimal::AlwaysSign;
 541   }
 542   decimal::ConversionToDecimalResult converted{
 543       ConvertToDecimal(significantDigits, edit.modes.round, flags)};
 544   if (IsInfOrNaN(converted.str, static_cast<int>(converted.length))) {
 545     return edit; // Inf/Nan -> Ew.d (same as Fw.d)
 546   }
 547   int expo{IsZero() ? 1 : converted.decimalExponent}; // 's'
 548   if (expo < 0 || expo > significantDigits) {
 549     if (editWidth == 0 && !edit.expoDigits) { // G0.d -> G0.dE0
 550       edit.expoDigits = 0;
 551     }
 552     return edit; // Ew.dEe
 553   }
 554   edit.descriptor = 'F';
 555   edit.modes.scale = 0; // kP is ignored for G when no exponent field
 556   trailingBlanks_ = 0;
 557   if (editWidth > 0) {
 558     int expoDigits{edit.expoDigits.value_or(0)};
 559     trailingBlanks_ = expoDigits > 0 ? expoDigits + 2 : 4; // 'n'
 560     *edit.width = std::max(0, editWidth - trailingBlanks_);
 561   }
 562   if (edit.digits.has_value()) {
 563     *edit.digits = std::max(0, *edit.digits - expo);
 564   }
 565   return edit;
 566 }
 567
 568 // 13.10.4 in F'2018
 569 template <int KIND>
 570 bool RealOutputEditing<KIND>::EditListDirectedOutput(const DataEdit &edit) {
 571   decimal::ConversionToDecimalResult converted{
 572       ConvertToDecimal(1, edit.modes.round)};
 573   if (IsInfOrNaN(converted.str, static_cast<int>(converted.length))) {
 574     return EditEorDOutput(edit);
 575   }
 576   int expo{converted.decimalExponent};
 577   // The decimal precision of 16-bit floating-point types is very low,
 578   // so use a reasonable cap of 6 to allow more values to be emitted
 579   // with Fw.d editing.
 580   static constexpr int maxExpo{
 581       std::max(6, BinaryFloatingPoint::decimalPrecision)};
 582   if (expo < 0 || expo > maxExpo) {
 583     DataEdit copy{edit};
 584     copy.modes.scale = 1; // 1P
 585     return EditEorDOutput(copy);
 586   }
 587   return EditFOutput(edit);
 588 }
 589
 590 // 13.7.2.3.6 in F'2023
 591 // The specification for hexadecimal output, unfortunately for implementors,
 592 // leaves as "implementation dependent" the choice of how to emit values
 593 // with multiple hexadecimal output possibilities that are numerically
 594 // equivalent.  The one working implementation of EX output that I can find
 595 // apparently chooses to frame the nybbles from most to least significant,
 596 // rather than trying to minimize the magnitude of the binary exponent.
 597 // E.g., 2. is edited into 0X8.0P-2 rather than 0X2.0P0.  This implementation
 598 // follows that precedent so as to avoid a gratuitous incompatibility.
 599 template <int KIND>
 600 auto RealOutputEditing<KIND>::ConvertToHexadecimal(
 601     int significantDigits, enum decimal::FortranRounding rounding, int flags)
 602     -> ConvertToHexadecimalResult {
 603   if (x_.IsNaN() || x_.IsInfinite()) {
 604     auto converted{ConvertToDecimal(significantDigits, rounding, flags)};
 605     return {converted.str, static_cast<int>(converted.length), 0};
 606   }
 607   x_.RoundToBits(4 * significantDigits, rounding);
 608   if (x_.IsInfinite()) { // rounded away to +/-Inf
 609     auto converted{ConvertToDecimal(significantDigits, rounding, flags)};
 610     return {converted.str, static_cast<int>(converted.length), 0};
 611   }
 612   int len{0};
 613   if (x_.IsNegative()) {
 614     buffer_[len++] = '-';
 615   } else if (flags & decimal::AlwaysSign) {
 616     buffer_[len++] = '+';
 617   }
 618   auto fraction{x_.Fraction()};
 619   if (fraction == 0) {
 620     buffer_[len++] = '0';
 621     return {buffer_, len, 0};
 622   } else {
 623     // Ensure that the MSB is set.
 624     int expo{x_.UnbiasedExponent() - 3};
 625     while (!(fraction >> (x_.binaryPrecision - 1))) {
 626       fraction <<= 1;
 627       --expo;
 628     }
 629     // This is initially the right shift count needed to bring the
 630     // most-significant hexadecimal digit's bits into the LSBs.
 631     // x_.binaryPrecision is constant, so / can be used for readability.
 632     int shift{x_.binaryPrecision - 4};
 633     typename BinaryFloatingPoint::RawType one{1};
 634     auto remaining{(one << shift) - one};
 635     for (int digits{0}; digits < significantDigits; ++digits) {
 636       if ((flags & decimal::Minimize) && !(fraction & remaining)) {
 637         break;
 638       }
 639       int hexDigit{0};
 640       if (shift >= 0) {
 641         hexDigit = int(fraction >> shift) & 0xf;
 642       } else if (shift >= -3) {
 643         hexDigit = int(fraction << -shift) & 0xf;
 644       }
 645       if (hexDigit >= 10) {
 646         buffer_[len++] = 'A' + hexDigit - 10;
 647       } else {
 648         buffer_[len++] = '0' + hexDigit;
 649       }
 650       shift -= 4;
 651       remaining >>= 4;
 652     }
 653     return {buffer_, len, expo};
 654   }
 655 }
 656
 657 template <int KIND>
 658 bool RealOutputEditing<KIND>::EditEXOutput(const DataEdit &edit) {
 659   addSpaceBeforeCharacter(io_);
 660   int editDigits{edit.digits.value_or(0)}; // 'd' field
 661   int significantDigits{editDigits + 1};
 662   int flags{0};
 663   if (edit.modes.editingFlags & signPlus) {
 664     flags |= decimal::AlwaysSign;
 665   }
 666   int editWidth{edit.width.value_or(0)}; // 'w' field
 667   if (editWidth == 0 && !edit.digits) { // EX0 (no .d)
 668     flags |= decimal::Minimize;
 669     significantDigits = 28; // enough for 128-bit F.P.
 670   }
 671   auto converted{
 672       ConvertToHexadecimal(significantDigits, edit.modes.round, flags)};
 673   if (IsInfOrNaN(converted.str, converted.length)) {
 674     return editWidth > 0 && converted.length > editWidth
 675         ? EmitRepeated(io_, '*', editWidth)
 676         : (editWidth <= converted.length ||
 677               EmitRepeated(io_, ' ', editWidth - converted.length)) &&
 678             EmitAscii(io_, converted.str, converted.length);
 679   }
 680   int signLength{converted.length > 0 &&
 681               (converted.str[0] == '-' || converted.str[0] == '+')
 682           ? 1
 683           : 0};
 684   int convertedDigits{converted.length - signLength};
 685   int expoLength{0};
 686   const char *exponent{FormatExponent(converted.exponent, edit, expoLength)};
 687   int trailingZeroes{flags & decimal::Minimize
 688           ? 0
 689           : std::max(0, significantDigits - convertedDigits)};
 690   int totalLength{converted.length + trailingZeroes + expoLength + 3 /*0X.*/};
 691   int width{editWidth > 0 ? editWidth : totalLength};
 692   return totalLength > width || !exponent
 693       ? EmitRepeated(io_, '*', width)
 694       : EmitRepeated(io_, ' ', width - totalLength) &&
 695           EmitAscii(io_, converted.str, signLength) &&
 696           EmitAscii(io_, "0X", 2) &&
 697           EmitAscii(io_, converted.str + signLength, 1) &&
 698           EmitAscii(
 699               io_, edit.modes.editingFlags & decimalComma ? "," : ".", 1) &&
 700           EmitAscii(io_, converted.str + signLength + 1,
 701               converted.length - (signLength + 1)) &&
 702           EmitRepeated(io_, '0', trailingZeroes) &&
 703           EmitAscii(io_, exponent, expoLength);
 704 }
 705
 706 template <int KIND> bool RealOutputEditing<KIND>::Edit(const DataEdit &edit) {
 707   switch (edit.descriptor) {
 708   case 'D':
 709     return EditEorDOutput(edit);
 710   case 'E':
 711     if (edit.variation == 'X') {
 712       return EditEXOutput(edit);
 713     } else {
 714       return EditEorDOutput(edit);
 715     }
 716   case 'F':
 717     return EditFOutput(edit);
 718   case 'B':
 719     return EditBOZOutput<1>(io_, edit,
 720         reinterpret_cast<const unsigned char *>(&x_),
 721         common::BitsForBinaryPrecision(common::PrecisionOfRealKind(KIND)) >> 3);
 722   case 'O':
 723     return EditBOZOutput<3>(io_, edit,
 724         reinterpret_cast<const unsigned char *>(&x_),
 725         common::BitsForBinaryPrecision(common::PrecisionOfRealKind(KIND)) >> 3);
 726   case 'Z':
 727     return EditBOZOutput<4>(io_, edit,
 728         reinterpret_cast<const unsigned char *>(&x_),
 729         common::BitsForBinaryPrecision(common::PrecisionOfRealKind(KIND)) >> 3);
 730   case 'G':
 731     return Edit(EditForGOutput(edit));
 732   case 'L':
 733     return EditLogicalOutput(io_, edit, *reinterpret_cast<const char *>(&x_));
 734   case 'A': // legacy extension
 735     return EditCharacterOutput(
 736         io_, edit, reinterpret_cast<char *>(&x_), sizeof x_);
 737   default:
 738     if (edit.IsListDirected()) {
 739       return EditListDirectedOutput(edit);
 740     }
 741     io_.GetIoErrorHandler().SignalError(IostatErrorInFormat,
 742         "Data edit descriptor '%c' may not be used with a REAL data item",
 743         edit.descriptor);
 744     return false;
 745   }
 746   return false;
 747 }
 748
 749 bool ListDirectedLogicalOutput(IoStatementState &io,
 750     ListDirectedStatementState<Direction::Output> &list, bool truth) {
 751   return list.EmitLeadingSpaceOrAdvance(io) &&
 752       EmitAscii(io, truth ? "T" : "F", 1);
 753 }
 754
 755 bool EditLogicalOutput(IoStatementState &io, const DataEdit &edit, bool truth) {
 756   switch (edit.descriptor) {
 757   case 'L':
 758   case 'G':
 759     return EmitRepeated(io, ' ', std::max(0, edit.width.value_or(1) - 1)) &&
 760         EmitAscii(io, truth ? "T" : "F", 1);
 761   case 'B':
 762     return EditBOZOutput<1>(io, edit,
 763         reinterpret_cast<const unsigned char *>(&truth), sizeof truth);
 764   case 'O':
 765     return EditBOZOutput<3>(io, edit,
 766         reinterpret_cast<const unsigned char *>(&truth), sizeof truth);
 767   case 'Z':
 768     return EditBOZOutput<4>(io, edit,
 769         reinterpret_cast<const unsigned char *>(&truth), sizeof truth);
 770   default:
 771     io.GetIoErrorHandler().SignalError(IostatErrorInFormat,
 772         "Data edit descriptor '%c' may not be used with a LOGICAL data item",
 773         edit.descriptor);
 774     return false;
 775   }
 776 }
 777
 778 template <typename CHAR>
 779 bool ListDirectedCharacterOutput(IoStatementState &io,
 780     ListDirectedStatementState<Direction::Output> &list, const CHAR *x,
 781     std::size_t length) {
 782   bool ok{true};
 783   MutableModes &modes{io.mutableModes()};
 784   ConnectionState &connection{io.GetConnectionState()};
 785   if (modes.delim) {
 786     ok = ok && list.EmitLeadingSpaceOrAdvance(io);
 787     // Value is delimited with ' or " marks, and interior
 788     // instances of that character are doubled.
 789     auto EmitOne{[&](CHAR ch) {
 790       if (connection.NeedAdvance(1)) {
 791         ok = ok && io.AdvanceRecord();
 792       }
 793       ok = ok && EmitEncoded(io, &ch, 1);
 794     }};
 795     EmitOne(modes.delim);
 796     for (std::size_t j{0}; j < length; ++j) {
 797       // Doubled delimiters must be put on the same record
 798       // in order to be acceptable as list-directed or NAMELIST
 799       // input; however, this requirement is not always possible
 800       // when the records have a fixed length, as is the case with
 801       // internal output.  The standard is silent on what should
 802       // happen, and no two extant Fortran implementations do
 803       // the same thing when tested with this case.
 804       // This runtime splits the doubled delimiters across
 805       // two records for lack of a better alternative.
 806       if (x[j] == static_cast<CHAR>(modes.delim)) {
 807         EmitOne(x[j]);
 808       }
 809       EmitOne(x[j]);
 810     }
 811     EmitOne(modes.delim);
 812   } else {
 813     // Undelimited list-directed output
 814     ok = ok && list.EmitLeadingSpaceOrAdvance(io, length > 0 ? 1 : 0, true);
 815     std::size_t put{0};
 816     std::size_t oneAtATime{
 817         connection.useUTF8<CHAR>() || connection.internalIoCharKind > 1
 818             ? 1
 819             : length};
 820     while (ok && put < length) {
 821       if (std::size_t chunk{std::min<std::size_t>(
 822               std::min<std::size_t>(length - put, oneAtATime),
 823               connection.RemainingSpaceInRecord())}) {
 824         ok = EmitEncoded(io, x + put, chunk);
 825         put += chunk;
 826       } else {
 827         ok = io.AdvanceRecord() && EmitAscii(io, " ", 1);
 828       }
 829     }
 830     list.set_lastWasUndelimitedCharacter(true);
 831   }
 832   return ok;
 833 }
 834
 835 template <typename CHAR>
 836 bool EditCharacterOutput(IoStatementState &io, const DataEdit &edit,
 837     const CHAR *x, std::size_t length) {
 838   int len{static_cast<int>(length)};
 839   int width{edit.width.value_or(len)};
 840   switch (edit.descriptor) {
 841   case 'A':
 842     break;
 843   case 'G':
 844     if (width == 0) {
 845       width = len;
 846     }
 847     break;
 848   case 'B':
 849     return EditBOZOutput<1>(io, edit,
 850         reinterpret_cast<const unsigned char *>(x), sizeof(CHAR) * length);
 851   case 'O':
 852     return EditBOZOutput<3>(io, edit,
 853         reinterpret_cast<const unsigned char *>(x), sizeof(CHAR) * length);
 854   case 'Z':
 855     return EditBOZOutput<4>(io, edit,
 856         reinterpret_cast<const unsigned char *>(x), sizeof(CHAR) * length);
 857   case 'L':
 858     return EditLogicalOutput(io, edit, *reinterpret_cast<const char *>(x));
 859   default:
 860     io.GetIoErrorHandler().SignalError(IostatErrorInFormat,
 861         "Data edit descriptor '%c' may not be used with a CHARACTER data item",
 862         edit.descriptor);
 863     return false;
 864   }
 865   return EmitRepeated(io, ' ', std::max(0, width - len)) &&
 866       EmitEncoded(io, x, std::min(width, len));
 867 }
 868
 869 template bool EditIntegerOutput<1>(
 870     IoStatementState &, const DataEdit &, std::int8_t);
 871 template bool EditIntegerOutput<2>(
 872     IoStatementState &, const DataEdit &, std::int16_t);
 873 template bool EditIntegerOutput<4>(
 874     IoStatementState &, const DataEdit &, std::int32_t);
 875 template bool EditIntegerOutput<8>(
 876     IoStatementState &, const DataEdit &, std::int64_t);
 877 template bool EditIntegerOutput<16>(
 878     IoStatementState &, const DataEdit &, common::int128_t);
 879
 880 template class RealOutputEditing<2>;
 881 template class RealOutputEditing<3>;
 882 template class RealOutputEditing<4>;
 883 template class RealOutputEditing<8>;
 884 template class RealOutputEditing<10>;
 885 // TODO: double/double
 886 template class RealOutputEditing<16>;
 887
 888 template bool ListDirectedCharacterOutput(IoStatementState &,
 889     ListDirectedStatementState<Direction::Output> &, const char *,
 890     std::size_t chars);
 891 template bool ListDirectedCharacterOutput(IoStatementState &,
 892     ListDirectedStatementState<Direction::Output> &, const char16_t *,
 893     std::size_t chars);
 894 template bool ListDirectedCharacterOutput(IoStatementState &,
 895     ListDirectedStatementState<Direction::Output> &, const char32_t *,
 896     std::size_t chars);
 897
 898 template bool EditCharacterOutput(
 899     IoStatementState &, const DataEdit &, const char *, std::size_t chars);
 900 template bool EditCharacterOutput(
 901     IoStatementState &, const DataEdit &, const char16_t *, std::size_t chars);
 902 template bool EditCharacterOutput(
 903     IoStatementState &, const DataEdit &, const char32_t *, std::size_t chars);
 904
 905 } // namespace Fortran::runtime::io