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