importer.h

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// Protocol Buffers - Google's data interchange format
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// https://developers.google.com/protocol-buffers/
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// Author: [email protected] (Kenton Varda)
// Based on original Protocol Buffers design by
// Sanjay Ghemawat, Jeff Dean, and others.
//
// This file is the public interface to the .proto file parser.

#ifndef GOOGLE_PROTOBUF_COMPILER_IMPORTER_H__
#define GOOGLE_PROTOBUF_COMPILER_IMPORTER_H__

#include <string>
#include <vector>
#include <set>
#include <utility>
#include <google/protobuf/descriptor.h>
#include <google/protobuf/descriptor_database.h>
#include <google/protobuf/compiler/parser.h>

namespace google {
namespace protobuf {

namespace io { class ZeroCopyInputStream; }

namespace compiler {

// Defined in this file.
class Importer;
class MultiFileErrorCollector;
class SourceTree;
class DiskSourceTree;

// TODO(kenton): Move all SourceTree stuff to a separate file?

// An implementation of DescriptorDatabase which loads files from a SourceTree
// and parses them.
//
// Note: This class is not thread-safe since it maintains a table of source
// code locations for error reporting. However, when a DescriptorPool wraps
// a DescriptorDatabase, it uses mutex locking to make sure only one method
// of the database is called at a time, even if the DescriptorPool is used
// from multiple threads. Therefore, there is only a problem if you create
// multiple DescriptorPools wrapping the same SourceTreeDescriptorDatabase
// and use them from multiple threads.
//
// Note: This class does not implement FindFileContainingSymbol() or
// FindFileContainingExtension(); these will always return false.
class LIBPROTOBUF_EXPORT SourceTreeDescriptorDatabase : public DescriptorDatabase {
 public:
 SourceTreeDescriptorDatabase(SourceTree* source_tree);
 ~SourceTreeDescriptorDatabase();

 // Instructs the SourceTreeDescriptorDatabase to report any parse errors
 // to the given MultiFileErrorCollector. This should be called before
 // parsing. error_collector must remain valid until either this method
 // is called again or the SourceTreeDescriptorDatabase is destroyed.
 void RecordErrorsTo(MultiFileErrorCollector* error_collector) {
 error_collector_ = error_collector;
 }

 // Gets a DescriptorPool::ErrorCollector which records errors to the
 // MultiFileErrorCollector specified with RecordErrorsTo(). This collector
 // has the ability to determine exact line and column numbers of errors
 // from the information given to it by the DescriptorPool.
 DescriptorPool::ErrorCollector* GetValidationErrorCollector() {
 using_validation_error_collector_ = true;
 return &validation_error_collector_;
 }

 // implements DescriptorDatabase -----------------------------------
 bool FindFileByName(const string& filename, FileDescriptorProto* output);
 bool FindFileContainingSymbol(const string& symbol_name,
 FileDescriptorProto* output);
 bool FindFileContainingExtension(const string& containing_type,
 int field_number,
 FileDescriptorProto* output);

 private:
 class SingleFileErrorCollector;

 SourceTree* source_tree_;
 MultiFileErrorCollector* error_collector_;

 class LIBPROTOBUF_EXPORT ValidationErrorCollector : public DescriptorPool::ErrorCollector {
 public:
 ValidationErrorCollector(SourceTreeDescriptorDatabase* owner);
 ~ValidationErrorCollector();

 // implements ErrorCollector ---------------------------------------
 void AddError(const string& filename,
 const string& element_name,
 const Message* descriptor,
 ErrorLocation location,
 const string& message);

 private:
 SourceTreeDescriptorDatabase* owner_;
 };
 friend class ValidationErrorCollector;

 bool using_validation_error_collector_;
 SourceLocationTable source_locations_;
 ValidationErrorCollector validation_error_collector_;
};

// Simple interface for parsing .proto files. This wraps the process
// of opening the file, parsing it with a Parser, recursively parsing all its
// imports, and then cross-linking the results to produce a FileDescriptor.
//
// This is really just a thin wrapper around SourceTreeDescriptorDatabase.
// You may find that SourceTreeDescriptorDatabase is more flexible.
//
// TODO(kenton): I feel like this class is not well-named.
class LIBPROTOBUF_EXPORT Importer {
 public:
 Importer(SourceTree* source_tree,
 MultiFileErrorCollector* error_collector);
 ~Importer();

 // Import the given file and build a FileDescriptor representing it. If
 // the file is already in the DescriptorPool, the existing FileDescriptor
 // will be returned. The FileDescriptor is property of the DescriptorPool,
 // and will remain valid until it is destroyed. If any errors occur, they
 // will be reported using the error collector and Import() will return NULL.
 //
 // A particular Importer object will only report errors for a particular
 // file once. All future attempts to import the same file will return NULL
 // without reporting any errors. The idea is that you might want to import
 // a lot of files without seeing the same errors over and over again. If
 // you want to see errors for the same files repeatedly, you can use a
 // separate Importer object to import each one (but use the same
 // DescriptorPool so that they can be cross-linked).
 const FileDescriptor* Import(const string& filename);

 // The DescriptorPool in which all imported FileDescriptors and their
 // contents are stored.
 inline const DescriptorPool* pool() const {
 return &pool_;
 }

 void AddUnusedImportTrackFile(const string& file_name);
 void ClearUnusedImportTrackFiles();

 private:
 SourceTreeDescriptorDatabase database_;
 DescriptorPool pool_;

 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Importer);
};

// If the importer encounters problems while trying to import the proto files,
// it reports them to a MultiFileErrorCollector.
class LIBPROTOBUF_EXPORT MultiFileErrorCollector {
 public:
 inline MultiFileErrorCollector() {}
 virtual ~MultiFileErrorCollector();

 // Line and column numbers are zero-based. A line number of -1 indicates
 // an error with the entire file (e.g. "not found").
 virtual void AddError(const string& filename, int line, int column,
 const string& message) = 0;

 private:
 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MultiFileErrorCollector);
};

// Abstract interface which represents a directory tree containing proto files.
// Used by the default implementation of Importer to resolve import statements
// Most users will probably want to use the DiskSourceTree implementation,
// below.
class LIBPROTOBUF_EXPORT SourceTree {
 public:
 inline SourceTree() {}
 virtual ~SourceTree();

 // Open the given file and return a stream that reads it, or NULL if not
 // found. The caller takes ownership of the returned object. The filename
 // must be a path relative to the root of the source tree and must not
 // contain "." or ".." components.
 virtual io::ZeroCopyInputStream* Open(const string& filename) = 0;

 // If Open() returns NULL, calling this method immediately will return an
 // description of the error.
 // Subclasses should implement this method and return a meaningful value for
 // better error reporting.
 // TODO(xiaofeng): change this to a pure virtual function.
 virtual string GetLastErrorMessage();

 private:
 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(SourceTree);
};

// An implementation of SourceTree which loads files from locations on disk.
// Multiple mappings can be set up to map locations in the DiskSourceTree to
// locations in the physical filesystem.
class LIBPROTOBUF_EXPORT DiskSourceTree : public SourceTree {
 public:
 DiskSourceTree();
 ~DiskSourceTree();

 // Map a path on disk to a location in the SourceTree. The path may be
 // either a file or a directory. If it is a directory, the entire tree
 // under it will be mapped to the given virtual location. To map a directory
 // to the root of the source tree, pass an empty string for virtual_path.
 //
 // If multiple mapped paths apply when opening a file, they will be searched
 // in order. For example, if you do:
 // MapPath("bar", "foo/bar");
 // MapPath("", "baz");
 // and then you do:
 // Open("bar/qux");
 // the DiskSourceTree will first try to open foo/bar/qux, then baz/bar/qux,
 // returning the first one that opens successfuly.
 //
 // disk_path may be an absolute path or relative to the current directory,
 // just like a path you'd pass to open().
 void MapPath(const string& virtual_path, const string& disk_path);

 // Return type for DiskFileToVirtualFile().
 enum DiskFileToVirtualFileResult {
 SUCCESS,
 SHADOWED,
 CANNOT_OPEN,
 NO_MAPPING
 };

 // Given a path to a file on disk, find a virtual path mapping to that
 // file. The first mapping created with MapPath() whose disk_path contains
 // the filename is used. However, that virtual path may not actually be
 // usable to open the given file. Possible return values are:
 // * SUCCESS: The mapping was found. *virtual_file is filled in so that
 // calling Open(*virtual_file) will open the file named by disk_file.
 // * SHADOWED: A mapping was found, but using Open() to open this virtual
 // path will end up returning some different file. This is because some
 // other mapping with a higher precedence also matches this virtual path
 // and maps it to a different file that exists on disk. *virtual_file
 // is filled in as it would be in the SUCCESS case. *shadowing_disk_file
 // is filled in with the disk path of the file which would be opened if
 // you were to call Open(*virtual_file).
 // * CANNOT_OPEN: The mapping was found and was not shadowed, but the
 // file specified cannot be opened. When this value is returned,
 // errno will indicate the reason the file cannot be opened. *virtual_file
 // will be set to the virtual path as in the SUCCESS case, even though
 // it is not useful.
 // * NO_MAPPING: Indicates that no mapping was found which contains this
 // file.
 DiskFileToVirtualFileResult
 DiskFileToVirtualFile(const string& disk_file,
 string* virtual_file,
 string* shadowing_disk_file);

 // Given a virtual path, find the path to the file on disk.
 // Return true and update disk_file with the on-disk path if the file exists.
 // Return false and leave disk_file untouched if the file doesn't exist.
 bool VirtualFileToDiskFile(const string& virtual_file, string* disk_file);

 // implements SourceTree -------------------------------------------
 virtual io::ZeroCopyInputStream* Open(const string& filename);

 virtual string GetLastErrorMessage();

 private:
 struct Mapping {
 string virtual_path;
 string disk_path;

 inline Mapping(const string& virtual_path_param,
 const string& disk_path_param)
 : virtual_path(virtual_path_param), disk_path(disk_path_param) {}
 };
 vector<Mapping> mappings_;
 string last_error_message_;

 // Like Open(), but returns the on-disk path in disk_file if disk_file is
 // non-NULL and the file could be successfully opened.
 io::ZeroCopyInputStream* OpenVirtualFile(const string& virtual_file,
 string* disk_file);

 // Like Open() but given the actual on-disk path.
 io::ZeroCopyInputStream* OpenDiskFile(const string& filename);

 GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DiskSourceTree);
};

} // namespace compiler
} // namespace protobuf

} // namespace google
#endif // GOOGLE_PROTOBUF_COMPILER_IMPORTER_H__