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// Copyright 2017 The Effcee Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef EFFCEE_CURSOR_H
#define EFFCEE_CURSOR_H
#include <sstream>
#include <string>
#include "re2/stringpiece.h"
namespace effcee {
using StringPiece = re2::StringPiece;
// Represents a position in a StringPiece, while tracking line number.
class Cursor {
public:
explicit Cursor(StringPiece str)
: remaining_(str), line_num_(1) {}
StringPiece remaining() const { return remaining_; }
// Returns the current 1-based line number.
int line_num() const { return line_num_; }
// Returns true if the remaining text is empty.
bool Exhausted() const { return remaining_.empty(); }
// Returns a string piece from the current position until the end of the line
// or the end of input, up to and including the newline.
StringPiece RestOfLine() const {
const auto newline_pos = remaining_.find('\n');
return remaining_.substr(0, newline_pos + (newline_pos != StringPiece::npos));
}
// Advance |n| characters. Does not adjust line count. The next |n|
// characters should not contain newlines if line numbering is to remain
// up to date. Returns this object.
Cursor& Advance(size_t n) { remaining_.remove_prefix(n); return *this; }
// Advances the cursor by a line. If no text remains, then does nothing.
// Otherwise removes the first line (including newline) and increments the
// line count. If there is no newline then the remaining string becomes
// empty. Returns this object.
Cursor& AdvanceLine() {
if (remaining_.size()) {
Advance(RestOfLine().size());
++line_num_;
}
return *this;
}
private:
// The remaining text, after all previous advancements. References the
// original string storage.
StringPiece remaining_;
// The current 1-based line number.
int line_num_;
};
// Returns string containing a description of the line containing a given
// subtext, with a message, and a caret displaying the subtext position.
// Assumes subtext does not contain a newline.
inline std::string LineMessage(StringPiece text, StringPiece subtext,
StringPiece message) {
Cursor c(text);
StringPiece full_line = c.RestOfLine();
while (subtext.end() - full_line.end() > 0) {
c.AdvanceLine();
full_line = c.RestOfLine();
}
const char* full_line_newline =
full_line.find('\n') == StringPiece::npos ? "\n" : "";
const size_t column = subtext.begin() - full_line.begin();
std::ostringstream out;
out << ":" << c.line_num() << ":" << (1 + column) << ": " << message << "\n"
<< full_line << full_line_newline << std::string(column, ' ') << "^\n";
return out.str();
}
} // namespace effcee
#endif
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