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      1 //===--- FormatToken.cpp - Format C++ code --------------------------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 ///
     10 /// \file
     11 /// \brief This file implements specific functions of \c FormatTokens and their
     12 /// roles.
     13 ///
     14 //===----------------------------------------------------------------------===//
     15 
     16 #include "FormatToken.h"
     17 #include "ContinuationIndenter.h"
     18 #include "clang/Format/Format.h"
     19 #include "llvm/ADT/SmallVector.h"
     20 #include "llvm/Support/Debug.h"
     21 
     22 namespace clang {
     23 namespace format {
     24 
     25 // FIXME: This is copy&pasted from Sema. Put it in a common place and remove
     26 // duplication.
     27 bool FormatToken::isSimpleTypeSpecifier() const {
     28   switch (Tok.getKind()) {
     29   case tok::kw_short:
     30   case tok::kw_long:
     31   case tok::kw___int64:
     32   case tok::kw___int128:
     33   case tok::kw_signed:
     34   case tok::kw_unsigned:
     35   case tok::kw_void:
     36   case tok::kw_char:
     37   case tok::kw_int:
     38   case tok::kw_half:
     39   case tok::kw_float:
     40   case tok::kw_double:
     41   case tok::kw_wchar_t:
     42   case tok::kw_bool:
     43   case tok::kw___underlying_type:
     44   case tok::annot_typename:
     45   case tok::kw_char16_t:
     46   case tok::kw_char32_t:
     47   case tok::kw_typeof:
     48   case tok::kw_decltype:
     49     return true;
     50   default:
     51     return false;
     52   }
     53 }
     54 
     55 TokenRole::~TokenRole() {}
     56 
     57 void TokenRole::precomputeFormattingInfos(const FormatToken *Token) {}
     58 
     59 unsigned CommaSeparatedList::formatAfterToken(LineState &State,
     60                                               ContinuationIndenter *Indenter,
     61                                               bool DryRun) {
     62   if (!State.NextToken->Previous || !State.NextToken->Previous->Previous)
     63     return 0;
     64 
     65   // Ensure that we start on the opening brace.
     66   const FormatToken *LBrace = State.NextToken->Previous->Previous;
     67   if (LBrace->isNot(tok::l_brace) || LBrace->BlockKind == BK_Block ||
     68       LBrace->Type == TT_DictLiteral ||
     69       LBrace->Next->Type == TT_DesignatedInitializerPeriod)
     70     return 0;
     71 
     72   // Calculate the number of code points we have to format this list. As the
     73   // first token is already placed, we have to subtract it.
     74   unsigned RemainingCodePoints =
     75       Style.ColumnLimit - State.Column + State.NextToken->Previous->ColumnWidth;
     76 
     77   // Find the best ColumnFormat, i.e. the best number of columns to use.
     78   const ColumnFormat *Format = getColumnFormat(RemainingCodePoints);
     79   // If no ColumnFormat can be used, the braced list would generally be
     80   // bin-packed. Add a severe penalty to this so that column layouts are
     81   // preferred if possible.
     82   if (!Format)
     83     return 10000;
     84 
     85   // Format the entire list.
     86   unsigned Penalty = 0;
     87   unsigned Column = 0;
     88   unsigned Item = 0;
     89   while (State.NextToken != LBrace->MatchingParen) {
     90     bool NewLine = false;
     91     unsigned ExtraSpaces = 0;
     92 
     93     // If the previous token was one of our commas, we are now on the next item.
     94     if (Item < Commas.size() && State.NextToken->Previous == Commas[Item]) {
     95       if (!State.NextToken->isTrailingComment()) {
     96         ExtraSpaces += Format->ColumnSizes[Column] - ItemLengths[Item];
     97         ++Column;
     98       }
     99       ++Item;
    100     }
    101 
    102     if (Column == Format->Columns || State.NextToken->MustBreakBefore) {
    103       Column = 0;
    104       NewLine = true;
    105     }
    106 
    107     // Place token using the continuation indenter and store the penalty.
    108     Penalty += Indenter->addTokenToState(State, NewLine, DryRun, ExtraSpaces);
    109   }
    110   return Penalty;
    111 }
    112 
    113 unsigned CommaSeparatedList::formatFromToken(LineState &State,
    114                                              ContinuationIndenter *Indenter,
    115                                              bool DryRun) {
    116   if (HasNestedBracedList)
    117     State.Stack.back().AvoidBinPacking = true;
    118   return 0;
    119 }
    120 
    121 // Returns the lengths in code points between Begin and End (both included),
    122 // assuming that the entire sequence is put on a single line.
    123 static unsigned CodePointsBetween(const FormatToken *Begin,
    124                                   const FormatToken *End) {
    125   assert(End->TotalLength >= Begin->TotalLength);
    126   return End->TotalLength - Begin->TotalLength + Begin->ColumnWidth;
    127 }
    128 
    129 void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
    130   // FIXME: At some point we might want to do this for other lists, too.
    131   if (!Token->MatchingParen || Token->isNot(tok::l_brace))
    132     return;
    133 
    134   // In C++11 braced list style, we should not format in columns unless we allow
    135   // bin-packing of function parameters.
    136   if (Style.Cpp11BracedListStyle && !Style.BinPackParameters)
    137     return;
    138 
    139   FormatToken *ItemBegin = Token->Next;
    140   SmallVector<bool, 8> MustBreakBeforeItem;
    141 
    142   // The lengths of an item if it is put at the end of the line. This includes
    143   // trailing comments which are otherwise ignored for column alignment.
    144   SmallVector<unsigned, 8> EndOfLineItemLength;
    145 
    146   for (unsigned i = 0, e = Commas.size() + 1; i != e; ++i) {
    147     // Skip comments on their own line.
    148     while (ItemBegin->HasUnescapedNewline && ItemBegin->isTrailingComment())
    149       ItemBegin = ItemBegin->Next;
    150 
    151     MustBreakBeforeItem.push_back(ItemBegin->MustBreakBefore);
    152     if (ItemBegin->is(tok::l_brace))
    153       HasNestedBracedList = true;
    154     const FormatToken *ItemEnd = nullptr;
    155     if (i == Commas.size()) {
    156       ItemEnd = Token->MatchingParen;
    157       const FormatToken *NonCommentEnd = ItemEnd->getPreviousNonComment();
    158       ItemLengths.push_back(CodePointsBetween(ItemBegin, NonCommentEnd));
    159       if (Style.Cpp11BracedListStyle) {
    160         // In Cpp11 braced list style, the } and possibly other subsequent
    161         // tokens will need to stay on a line with the last element.
    162         while (ItemEnd->Next && !ItemEnd->Next->CanBreakBefore)
    163           ItemEnd = ItemEnd->Next;
    164       } else {
    165         // In other braced lists styles, the "}" can be wrapped to the new line.
    166         ItemEnd = Token->MatchingParen->Previous;
    167       }
    168     } else {
    169       ItemEnd = Commas[i];
    170       // The comma is counted as part of the item when calculating the length.
    171       ItemLengths.push_back(CodePointsBetween(ItemBegin, ItemEnd));
    172       // Consume trailing comments so the are included in EndOfLineItemLength.
    173       if (ItemEnd->Next && !ItemEnd->Next->HasUnescapedNewline &&
    174           ItemEnd->Next->isTrailingComment())
    175         ItemEnd = ItemEnd->Next;
    176     }
    177     EndOfLineItemLength.push_back(CodePointsBetween(ItemBegin, ItemEnd));
    178     // If there is a trailing comma in the list, the next item will start at the
    179     // closing brace. Don't create an extra item for this.
    180     if (ItemEnd->getNextNonComment() == Token->MatchingParen)
    181       break;
    182     ItemBegin = ItemEnd->Next;
    183   }
    184 
    185   // If this doesn't have a nested list, we require at least 6 elements in order
    186   // create a column layout. If it has a nested list, column layout ensures one
    187   // list element per line.
    188   if (HasNestedBracedList || Commas.size() < 5 || Token->NestingLevel != 0)
    189     return;
    190 
    191   // We can never place more than ColumnLimit / 3 items in a row (because of the
    192   // spaces and the comma).
    193   for (unsigned Columns = 1; Columns <= Style.ColumnLimit / 3; ++Columns) {
    194     ColumnFormat Format;
    195     Format.Columns = Columns;
    196     Format.ColumnSizes.resize(Columns);
    197     Format.LineCount = 1;
    198     bool HasRowWithSufficientColumns = false;
    199     unsigned Column = 0;
    200     for (unsigned i = 0, e = ItemLengths.size(); i != e; ++i) {
    201       assert(i < MustBreakBeforeItem.size());
    202       if (MustBreakBeforeItem[i] || Column == Columns) {
    203         ++Format.LineCount;
    204         Column = 0;
    205       }
    206       if (Column == Columns - 1)
    207         HasRowWithSufficientColumns = true;
    208       unsigned length =
    209           (Column == Columns - 1) ? EndOfLineItemLength[i] : ItemLengths[i];
    210       Format.ColumnSizes[Column] = std::max(Format.ColumnSizes[Column], length);
    211       ++Column;
    212     }
    213     // If all rows are terminated early (e.g. by trailing comments), we don't
    214     // need to look further.
    215     if (!HasRowWithSufficientColumns)
    216       break;
    217     Format.TotalWidth = Columns - 1; // Width of the N-1 spaces.
    218     for (unsigned i = 0; i < Columns; ++i) {
    219       Format.TotalWidth += Format.ColumnSizes[i];
    220     }
    221 
    222     // Ignore layouts that are bound to violate the column limit.
    223     if (Format.TotalWidth > Style.ColumnLimit)
    224       continue;
    225 
    226     Formats.push_back(Format);
    227   }
    228 }
    229 
    230 const CommaSeparatedList::ColumnFormat *
    231 CommaSeparatedList::getColumnFormat(unsigned RemainingCharacters) const {
    232   const ColumnFormat *BestFormat = nullptr;
    233   for (SmallVector<ColumnFormat, 4>::const_reverse_iterator
    234            I = Formats.rbegin(),
    235            E = Formats.rend();
    236        I != E; ++I) {
    237     if (I->TotalWidth <= RemainingCharacters) {
    238       if (BestFormat && I->LineCount > BestFormat->LineCount)
    239         break;
    240       BestFormat = &*I;
    241     }
    242   }
    243   return BestFormat;
    244 }
    245 
    246 } // namespace format
    247 } // namespace clang
    248