printer.h

// Protocol Buffers - Google's data interchange format
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// Author: kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.
//
// Utility class for writing text to a ZeroCopyOutputStream.

#ifndef GOOGLE_PROTOBUF_IO_PRINTER_H__
#define GOOGLE_PROTOBUF_IO_PRINTER_H__


#include <map>
#include <string>
#include <vector>

#include <google/protobuf/stubs/common.h>
#include <google/protobuf/port_def.inc>

namespace google {
namespace protobuf {
namespace io {

class ZeroCopyOutputStream;  // zero_copy_stream.h

// Records annotations about a Printer's output.
class PROTOBUF_EXPORT AnnotationCollector {
 public:
  // Annotation is a offset range and a payload pair.
  typedef std::pair<std::pair<size_t, size_t>, std::string> Annotation;

  // Records that the bytes in file_path beginning with begin_offset and ending
  // before end_offset are associated with the SourceCodeInfo-style path.
  virtual void AddAnnotation(size_t begin_offset, size_t end_offset,
                             const std::string& file_path,
                             const std::vector<int>& path) = 0;

  // TODO(gerbens) I don't see why we need virtuals here. Just a vector of
  // range, payload pairs stored in a context should suffice.
  virtual void AddAnnotationNew(Annotation& a) {}

  virtual ~AnnotationCollector() {}
};

// Records annotations about a Printer's output to the given protocol buffer,
// assuming that the buffer has an ::Annotation message exposing path,
// source_file, begin and end fields.
template <typename AnnotationProto>
class AnnotationProtoCollector : public AnnotationCollector {
 public:
  // annotation_proto is the protocol buffer to which new Annotations should be
  // added. It is not owned by the AnnotationProtoCollector.
  explicit AnnotationProtoCollector(AnnotationProto* annotation_proto)
      : annotation_proto_(annotation_proto) {}

  // Override for AnnotationCollector::AddAnnotation.
  virtual void AddAnnotation(size_t begin_offset, size_t end_offset,
                             const std::string& file_path,
                             const std::vector<int>& path) {
    typename AnnotationProto::Annotation* annotation =
        annotation_proto_->add_annotation();
    for (int i = 0; i < path.size(); ++i) {
      annotation->add_path(path[i]);
    }
    annotation->set_source_file(file_path);
    annotation->set_begin(begin_offset);
    annotation->set_end(end_offset);
  }
  // Override for AnnotationCollector::AddAnnotation.
  virtual void AddAnnotationNew(Annotation& a) {
    auto* annotation = annotation_proto_->add_annotation();
    annotation->ParseFromString(a.second);
    annotation->set_begin(a.first.first);
    annotation->set_end(a.first.second);
  }

 private:
  // The protocol buffer to which new annotations should be added.
  AnnotationProto* const annotation_proto_;
};

// This simple utility class assists in code generation.  It basically
// allows the caller to define a set of variables and then output some
// text with variable substitutions.  Example usage:
//
//   Printer printer(output, '$');
//   map<string, string> vars;
//   vars["name"] = "Bob";
//   printer.Print(vars, "My name is $name$.");
//
// The above writes "My name is Bob." to the output stream.
//
// Printer aggressively enforces correct usage, crashing (with assert failures)
// in the case of undefined variables in debug builds. This helps greatly in
// debugging code which uses it.
//
// If a Printer is constructed with an AnnotationCollector, it will provide it
// with annotations that connect the Printer's output to paths that can identify
// various descriptors.  In the above example, if person_ is a descriptor that
// identifies Bob, we can associate the output string "My name is Bob." with
// a source path pointing to that descriptor with:
//
//   printer.Annotate("name", person_);
//
// The AnnotationCollector will be sent an annotation linking the output range
// covering "Bob" to the logical path provided by person_.  Tools may use
// this association to (for example) link "Bob" in the output back to the
// source file that defined the person_ descriptor identifying Bob.
//
// Annotate can only examine variables substituted during the last call to
// Print.  It is invalid to refer to a variable that was used multiple times
// in a single Print call.
//
// In full generality, one may specify a range of output text using a beginning
// substitution variable and an ending variable.  The resulting annotation will
// span from the first character of the substituted value for the beginning
// variable to the last character of the substituted value for the ending
// variable.  For example, the Annotate call above is equivalent to this one:
//
//   printer.Annotate("name", "name", person_);
//
// This is useful if multiple variables combine to form a single span of output
// that should be annotated with the same source path.  For example:
//
//   Printer printer(output, '$');
//   map<string, string> vars;
//   vars["first"] = "Alice";
//   vars["last"] = "Smith";
//   printer.Print(vars, "My name is $first$ $last$.");
//   printer.Annotate("first", "last", person_);
//
// This code would associate the span covering "Alice Smith" in the output with
// the person_ descriptor.
//
// Note that the beginning variable must come before (or overlap with, in the
// case of zero-sized substitution values) the ending variable.
//
// It is also sometimes useful to use variables with zero-sized values as
// markers.  This avoids issues with multiple references to the same variable
// and also allows annotation ranges to span literal text from the Print
// templates:
//
//   Printer printer(output, '$');
//   map<string, string> vars;
//   vars["foo"] = "bar";
//   vars["function"] = "call";
//   vars["mark"] = "";
//   printer.Print(vars, "$function$($foo$,$foo$)$mark$");
//   printer.Annotate("function", "mark", call_);
//
// This code associates the span covering "call(bar,bar)" in the output with the
// call_ descriptor.

class PROTOBUF_EXPORT Printer {
 public:
  // Create a printer that writes text to the given output stream.  Use the
  // given character as the delimiter for variables.
  Printer(ZeroCopyOutputStream* output, char variable_delimiter);

  // Create a printer that writes text to the given output stream.  Use the
  // given character as the delimiter for variables.  If annotation_collector
  // is not null, Printer will provide it with annotations about code written
  // to the stream.  annotation_collector is not owned by Printer.
  Printer(ZeroCopyOutputStream* output, char variable_delimiter,
          AnnotationCollector* annotation_collector);

  ~Printer();

  // Link a substitution variable emitted by the last call to Print to the
  // object described by descriptor.
  template <typename SomeDescriptor>
  void Annotate(const char* varname, const SomeDescriptor* descriptor) {
    Annotate(varname, varname, descriptor);
  }

  // Link the output range defined by the substitution variables as emitted by
  // the last call to Print to the object described by descriptor. The range
  // begins at begin_varname's value and ends after the last character of the
  // value substituted for end_varname.
  template <typename SomeDescriptor>
  void Annotate(const char* begin_varname, const char* end_varname,
                const SomeDescriptor* descriptor) {
    if (annotation_collector_ == NULL) {
      // Annotations aren't turned on for this Printer, so don't pay the cost
      // of building the location path.
      return;
    }
    std::vector<int> path;
    descriptor->GetLocationPath(&path);
    Annotate(begin_varname, end_varname, descriptor->file()->name(), path);
  }

  // Link a substitution variable emitted by the last call to Print to the file
  // with path file_name.
  void Annotate(const char* varname, const std::string& file_name) {
    Annotate(varname, varname, file_name);
  }

  // Link the output range defined by the substitution variables as emitted by
  // the last call to Print to the file with path file_name. The range begins
  // at begin_varname's value and ends after the last character of the value
  // substituted for end_varname.
  void Annotate(const char* begin_varname, const char* end_varname,
                const std::string& file_name) {
    if (annotation_collector_ == NULL) {
      // Annotations aren't turned on for this Printer.
      return;
    }
    std::vector<int> empty_path;
    Annotate(begin_varname, end_varname, file_name, empty_path);
  }

  // Print some text after applying variable substitutions.  If a particular
  // variable in the text is not defined, this will crash.  Variables to be
  // substituted are identified by their names surrounded by delimiter
  // characters (as given to the constructor).  The variable bindings are
  // defined by the given map.
  void Print(const std::map<std::string, std::string>& variables,
             const char* text);

  // Like the first Print(), except the substitutions are given as parameters.
  template <typename... Args>
  void Print(const char* text, const Args&... args) {
    std::map<std::string, std::string> vars;
    PrintInternal(&vars, text, args...);
  }

  // Indent text by two spaces.  After calling Indent(), two spaces will be
  // inserted at the beginning of each line of text.  Indent() may be called
  // multiple times to produce deeper indents.
  void Indent();

  // Reduces the current indent level by two spaces, or crashes if the indent
  // level is zero.
  void Outdent();

  // Write a string to the output buffer.
  // This method does not look for newlines to add indentation.
  void PrintRaw(const std::string& data);

  // Write a zero-delimited string to output buffer.
  // This method does not look for newlines to add indentation.
  void PrintRaw(const char* data);

  // Write some bytes to the output buffer.
  // This method does not look for newlines to add indentation.
  void WriteRaw(const char* data, int size);

  // FormatInternal is a helper function not meant to use directly, use
  // compiler::cpp::Formatter instead. This function is meant to support
  // formatting text using named variables (eq. "$foo$) from a lookup map (vars)
  // and variables directly supplied by arguments (eq "$1$" meaning first
  // argument which is the zero index element of args).
  void FormatInternal(const std::vector<std::string>& args,
                      const std::map<std::string, std::string>& vars,
                      const char* format);

  // True if any write to the underlying stream failed.  (We don't just
  // crash in this case because this is an I/O failure, not a programming
  // error.)
  bool failed() const { return failed_; }

 private:
  // Link the output range defined by the substitution variables as emitted by
  // the last call to Print to the object found at the SourceCodeInfo-style path
  // in a file with path file_path. The range begins at the start of
  // begin_varname's value and ends after the last character of the value
  // substituted for end_varname. Note that begin_varname and end_varname
  // may refer to the same variable.
  void Annotate(const char* begin_varname, const char* end_varname,
                const std::string& file_path, const std::vector<int>& path);

  // Base case
  void PrintInternal(std::map<std::string, std::string>* vars,
                     const char* text) {
    Print(*vars, text);
  }

  template <typename... Args>
  void PrintInternal(std::map<std::string, std::string>* vars, const char* text,
                     const char* key, const std::string& value,
                     const Args&... args) {
    (*vars)[key] = value;
    PrintInternal(vars, text, args...);
  }

  // Copy size worth of bytes from data to buffer_.
  void CopyToBuffer(const char* data, int size);

  void push_back(char c) {
    if (failed_) return;
    if (buffer_size_ == 0) {
      if (!Next()) return;
    }
    *buffer_++ = c;
    buffer_size_--;
    offset_++;
  }

  bool Next();

  inline void IndentIfAtStart();
  const char* WriteVariable(
      const std::vector<std::string>& args,
      const std::map<std::string, std::string>& vars, const char* format,
      int* arg_index,
      std::vector<AnnotationCollector::Annotation>* annotations);

  const char variable_delimiter_;

  ZeroCopyOutputStream* const output_;
  char* buffer_;
  int buffer_size_;
  // The current position, in bytes, in the output stream.  This is equivalent
  // to the total number of bytes that have been written so far.  This value is
  // used to calculate annotation ranges in the substitutions_ map below.
  size_t offset_;

  std::string indent_;
  bool at_start_of_line_;
  bool failed_;

  // A map from variable name to [start, end) offsets in the output buffer.
  // These refer to the offsets used for a variable after the last call to
  // Print.  If a variable was used more than once, the entry used in
  // this map is set to a negative-length span.  For singly-used variables, the
  // start offset is the beginning of the substitution; the end offset is the
  // last byte of the substitution plus one (such that (end - start) is the
  // length of the substituted string).
  std::map<std::string, std::pair<size_t, size_t> > substitutions_;

  // Keeps track of the keys in substitutions_ that need to be updated when
  // indents are inserted. These are keys that refer to the beginning of the
  // current line.
  std::vector<std::string> line_start_variables_;

  // Returns true and sets range to the substitution range in the output for
  // varname if varname was used once in the last call to Print. If varname
  // was not used, or if it was used multiple times, returns false (and
  // fails a debug assertion).
  bool GetSubstitutionRange(const char* varname,
                            std::pair<size_t, size_t>* range);

  // If non-null, annotation_collector_ is used to store annotations about
  // generated code.
  AnnotationCollector* const annotation_collector_;

  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Printer);
};

}  // namespace io
}  // namespace protobuf
}  // namespace google

#include <google/protobuf/port_undef.inc>

#endif  // GOOGLE_PROTOBUF_IO_PRINTER_H__