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 TokenRole::~TokenRole() {}
26 
27 void TokenRole::precomputeFormattingInfos(const FormatToken *Token) {}
28 
29 unsigned CommaSeparatedList::format(LineState &State,
30                                     ContinuationIndenter *Indenter,
31                                     bool DryRun) {
32   if (!State.NextToken->Previous || !State.NextToken->Previous->Previous ||
33       Commas.size() <= 2)
34     return 0;
35 
36   // Ensure that we start on the opening brace.
37   const FormatToken *LBrace = State.NextToken->Previous->Previous;
38   if (LBrace->isNot(tok::l_brace) ||
39       LBrace->BlockKind == BK_Block ||
40       LBrace->Next->Type == TT_DesignatedInitializerPeriod)
41     return 0;
42 
43   // Calculate the number of code points we have to format this list. As the
44   // first token is already placed, we have to subtract it.
45   unsigned RemainingCodePoints = Style.ColumnLimit - State.Column +
46                                  State.NextToken->Previous->ColumnWidth;
47 
48   // Find the best ColumnFormat, i.e. the best number of columns to use.
49   const ColumnFormat *Format = getColumnFormat(RemainingCodePoints);
50   if (!Format)
51     return 0;
52 
53   // Format the entire list.
54   unsigned Penalty = 0;
55   unsigned Column = 0;
56   unsigned Item = 0;
57   while (State.NextToken != LBrace->MatchingParen) {
58     bool NewLine = false;
59     unsigned ExtraSpaces = 0;
60 
61     // If the previous token was one of our commas, we are now on the next item.
62     if (Item < Commas.size() && State.NextToken->Previous == Commas[Item]) {
63       if (!State.NextToken->isTrailingComment()) {
64         ExtraSpaces += Format->ColumnSizes[Column] - ItemLengths[Item];
65         ++Column;
66       }
67       ++Item;
68     }
69 
70     if (Column == Format->Columns || State.NextToken->MustBreakBefore) {
71       Column = 0;
72       NewLine = true;
73     }
74 
75     // Place token using the continuation indenter and store the penalty.
76     Penalty += Indenter->addTokenToState(State, NewLine, DryRun, ExtraSpaces);
77   }
78   return Penalty;
79 }
80 
81 // Returns the lengths in code points between Begin and End (both included),
82 // assuming that the entire sequence is put on a single line.
83 static unsigned CodePointsBetween(const FormatToken *Begin,
84                                   const FormatToken *End) {
85   assert(End->TotalLength >= Begin->TotalLength);
86   return End->TotalLength - Begin->TotalLength + Begin->ColumnWidth;
87 }
88 
89 void CommaSeparatedList::precomputeFormattingInfos(const FormatToken *Token) {
90   // FIXME: At some point we might want to do this for other lists, too.
91   if (!Token->MatchingParen || Token->isNot(tok::l_brace))
92     return;
93 
94   FormatToken *ItemBegin = Token->Next;
95   SmallVector<bool, 8> MustBreakBeforeItem;
96 
97   // The lengths of an item if it is put at the end of the line. This includes
98   // trailing comments which are otherwise ignored for column alignment.
99   SmallVector<unsigned, 8> EndOfLineItemLength;
100 
101   for (unsigned i = 0, e = Commas.size() + 1; i != e; ++i) {
102     // Skip comments on their own line.
103     while (ItemBegin->HasUnescapedNewline && ItemBegin->isTrailingComment())
104       ItemBegin = ItemBegin->Next;
105 
106     MustBreakBeforeItem.push_back(ItemBegin->MustBreakBefore);
107     const FormatToken *ItemEnd = NULL;
108     if (i == Commas.size()) {
109       ItemEnd = Token->MatchingParen;
110       const FormatToken *NonCommentEnd = ItemEnd->getPreviousNonComment();
111       ItemLengths.push_back(CodePointsBetween(ItemBegin, NonCommentEnd));
112       if (Style.Cpp11BracedListStyle) {
113         // In Cpp11 braced list style, the } and possibly other subsequent
114         // tokens will need to stay on a line with the last element.
115         while (ItemEnd->Next && !ItemEnd->Next->CanBreakBefore)
116           ItemEnd = ItemEnd->Next;
117       } else {
118         // In other braced lists styles, the "}" can be wrapped to the new line.
119         ItemEnd = Token->MatchingParen->Previous;
120       }
121     } else {
122       ItemEnd = Commas[i];
123       // The comma is counted as part of the item when calculating the length.
124       ItemLengths.push_back(CodePointsBetween(ItemBegin, ItemEnd));
125       // Consume trailing comments so the are included in EndOfLineItemLength.
126       if (ItemEnd->Next && !ItemEnd->Next->HasUnescapedNewline &&
127           ItemEnd->Next->isTrailingComment())
128         ItemEnd = ItemEnd->Next;
129     }
130     EndOfLineItemLength.push_back(CodePointsBetween(ItemBegin, ItemEnd));
131     // If there is a trailing comma in the list, the next item will start at the
132     // closing brace. Don't create an extra item for this.
133     if (ItemEnd->getNextNonComment() == Token->MatchingParen)
134       break;
135     ItemBegin = ItemEnd->Next;
136   }
137 
138   // We can never place more than ColumnLimit / 3 items in a row (because of the
139   // spaces and the comma).
140   for (unsigned Columns = 1; Columns <= Style.ColumnLimit / 3; ++Columns) {
141     ColumnFormat Format;
142     Format.Columns = Columns;
143     Format.ColumnSizes.resize(Columns);
144     Format.LineCount = 0;
145     bool HasRowWithSufficientColumns = false;
146     unsigned Column = 0;
147     for (unsigned i = 0, e = ItemLengths.size(); i != e; ++i) {
148       if (MustBreakBeforeItem[i] || Column == Columns) {
149         ++Format.LineCount;
150         Column = 0;
151       }
152       if (Column == Columns - 1)
153         HasRowWithSufficientColumns = true;
154       unsigned length =
155           (Column == Columns - 1) ? EndOfLineItemLength[i] : ItemLengths[i];
156       Format.ColumnSizes[Column] =
157           std::max(Format.ColumnSizes[Column], length);
158       ++Column;
159     }
160     // If all rows are terminated early (e.g. by trailing comments), we don't
161     // need to look further.
162     if (!HasRowWithSufficientColumns)
163       break;
164     Format.TotalWidth = Columns - 1; // Width of the N-1 spaces.
165     for (unsigned i = 0; i < Columns; ++i) {
166       Format.TotalWidth += Format.ColumnSizes[i];
167     }
168 
169     // Ignore layouts that are bound to violate the column limit.
170     if (Format.TotalWidth > Style.ColumnLimit)
171       continue;
172 
173     Formats.push_back(Format);
174   }
175 }
176 
177 const CommaSeparatedList::ColumnFormat *
178 CommaSeparatedList::getColumnFormat(unsigned RemainingCharacters) const {
179   const ColumnFormat *BestFormat = NULL;
180   for (SmallVector<ColumnFormat, 4>::const_reverse_iterator
181            I = Formats.rbegin(),
182            E = Formats.rend();
183        I != E; ++I) {
184     if (I->TotalWidth <= RemainingCharacters) {
185       if (BestFormat && I->LineCount > BestFormat->LineCount)
186         break;
187       BestFormat = &*I;
188     }
189   }
190   return BestFormat;
191 }
192 
193 } // namespace format
194 } // namespace clang
195