1// Protocol Buffers - Google's data interchange format
2// Copyright 2008 Google Inc.  All rights reserved.
3// https://developers.google.com/protocol-buffers/
4//
5// Redistribution and use in source and binary forms, with or without
6// modification, are permitted provided that the following conditions are
7// met:
8//
9//     * Redistributions of source code must retain the above copyright
10// notice, this list of conditions and the following disclaimer.
11//     * Redistributions in binary form must reproduce the above
12// copyright notice, this list of conditions and the following disclaimer
13// in the documentation and/or other materials provided with the
14// distribution.
15//     * Neither the name of Google Inc. nor the names of its
16// contributors may be used to endorse or promote products derived from
17// this software without specific prior written permission.
18//
19// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30
31// Author: kenton@google.com (Kenton Varda)
32//  Based on original Protocol Buffers design by
33//  Sanjay Ghemawat, Jeff Dean, and others.
34//
35// The messages in this file describe the definitions found in .proto files.
36// A valid .proto file can be translated directly to a FileDescriptorProto
37// without any other information (e.g. without reading its imports).
38
39
40
41package google.protobuf;
42option java_package = "com.google.protobuf";
43option java_outer_classname = "DescriptorProtos";
44
45// descriptor.proto must be optimized for speed because reflection-based
46// algorithms don't work during bootstrapping.
47option optimize_for = SPEED;
48
49// The protocol compiler can output a FileDescriptorSet containing the .proto
50// files it parses.
51message FileDescriptorSet {
52  repeated FileDescriptorProto file = 1;
53}
54
55// Describes a complete .proto file.
56message FileDescriptorProto {
57  optional string name = 1;       // file name, relative to root of source tree
58  optional string package = 2;    // e.g. "foo", "foo.bar", etc.
59
60  // Names of files imported by this file.
61  repeated string dependency = 3;
62  // Indexes of the public imported files in the dependency list above.
63  repeated int32 public_dependency = 10;
64  // Indexes of the weak imported files in the dependency list.
65  // For Google-internal migration only. Do not use.
66  repeated int32 weak_dependency = 11;
67
68  // All top-level definitions in this file.
69  repeated DescriptorProto message_type = 4;
70  repeated EnumDescriptorProto enum_type = 5;
71  repeated ServiceDescriptorProto service = 6;
72  repeated FieldDescriptorProto extension = 7;
73
74  optional FileOptions options = 8;
75
76  // This field contains optional information about the original source code.
77  // You may safely remove this entire field whithout harming runtime
78  // functionality of the descriptors -- the information is needed only by
79  // development tools.
80  optional SourceCodeInfo source_code_info = 9;
81}
82
83// Describes a message type.
84message DescriptorProto {
85  optional string name = 1;
86
87  repeated FieldDescriptorProto field = 2;
88  repeated FieldDescriptorProto extension = 6;
89
90  repeated DescriptorProto nested_type = 3;
91  repeated EnumDescriptorProto enum_type = 4;
92
93  message ExtensionRange {
94    optional int32 start = 1;
95    optional int32 end = 2;
96  }
97  repeated ExtensionRange extension_range = 5;
98
99  repeated OneofDescriptorProto oneof_decl = 8;
100
101  optional MessageOptions options = 7;
102}
103
104// Describes a field within a message.
105message FieldDescriptorProto {
106  enum Type {
107    // 0 is reserved for errors.
108    // Order is weird for historical reasons.
109    TYPE_DOUBLE         = 1;
110    TYPE_FLOAT          = 2;
111    // Not ZigZag encoded.  Negative numbers take 10 bytes.  Use TYPE_SINT64 if
112    // negative values are likely.
113    TYPE_INT64          = 3;
114    TYPE_UINT64         = 4;
115    // Not ZigZag encoded.  Negative numbers take 10 bytes.  Use TYPE_SINT32 if
116    // negative values are likely.
117    TYPE_INT32          = 5;
118    TYPE_FIXED64        = 6;
119    TYPE_FIXED32        = 7;
120    TYPE_BOOL           = 8;
121    TYPE_STRING         = 9;
122    TYPE_GROUP          = 10;  // Tag-delimited aggregate.
123    TYPE_MESSAGE        = 11;  // Length-delimited aggregate.
124
125    // New in version 2.
126    TYPE_BYTES          = 12;
127    TYPE_UINT32         = 13;
128    TYPE_ENUM           = 14;
129    TYPE_SFIXED32       = 15;
130    TYPE_SFIXED64       = 16;
131    TYPE_SINT32         = 17;  // Uses ZigZag encoding.
132    TYPE_SINT64         = 18;  // Uses ZigZag encoding.
133  };
134
135  enum Label {
136    // 0 is reserved for errors
137    LABEL_OPTIONAL      = 1;
138    LABEL_REQUIRED      = 2;
139    LABEL_REPEATED      = 3;
140    // TODO(sanjay): Should we add LABEL_MAP?
141  };
142
143  optional string name = 1;
144  optional int32 number = 3;
145  optional Label label = 4;
146
147  // If type_name is set, this need not be set.  If both this and type_name
148  // are set, this must be one of TYPE_ENUM, TYPE_MESSAGE or TYPE_GROUP.
149  optional Type type = 5;
150
151  // For message and enum types, this is the name of the type.  If the name
152  // starts with a '.', it is fully-qualified.  Otherwise, C++-like scoping
153  // rules are used to find the type (i.e. first the nested types within this
154  // message are searched, then within the parent, on up to the root
155  // namespace).
156  optional string type_name = 6;
157
158  // For extensions, this is the name of the type being extended.  It is
159  // resolved in the same manner as type_name.
160  optional string extendee = 2;
161
162  // For numeric types, contains the original text representation of the value.
163  // For booleans, "true" or "false".
164  // For strings, contains the default text contents (not escaped in any way).
165  // For bytes, contains the C escaped value.  All bytes >= 128 are escaped.
166  // TODO(kenton):  Base-64 encode?
167  optional string default_value = 7;
168
169  // If set, gives the index of a oneof in the containing type's oneof_decl
170  // list.  This field is a member of that oneof.  Extensions of a oneof should
171  // not set this since the oneof to which they belong will be inferred based
172  // on the extension range containing the extension's field number.
173  optional int32 oneof_index = 9;
174
175  optional FieldOptions options = 8;
176}
177
178// Describes a oneof.
179message OneofDescriptorProto {
180  optional string name = 1;
181}
182
183// Describes an enum type.
184message EnumDescriptorProto {
185  optional string name = 1;
186
187  repeated EnumValueDescriptorProto value = 2;
188
189  optional EnumOptions options = 3;
190}
191
192// Describes a value within an enum.
193message EnumValueDescriptorProto {
194  optional string name = 1;
195  optional int32 number = 2;
196
197  optional EnumValueOptions options = 3;
198}
199
200// Describes a service.
201message ServiceDescriptorProto {
202  optional string name = 1;
203  repeated MethodDescriptorProto method = 2;
204
205  optional ServiceOptions options = 3;
206}
207
208// Describes a method of a service.
209message MethodDescriptorProto {
210  optional string name = 1;
211
212  // Input and output type names.  These are resolved in the same way as
213  // FieldDescriptorProto.type_name, but must refer to a message type.
214  optional string input_type = 2;
215  optional string output_type = 3;
216
217  optional MethodOptions options = 4;
218}
219
220
221// ===================================================================
222// Options
223
224// Each of the definitions above may have "options" attached.  These are
225// just annotations which may cause code to be generated slightly differently
226// or may contain hints for code that manipulates protocol messages.
227//
228// Clients may define custom options as extensions of the *Options messages.
229// These extensions may not yet be known at parsing time, so the parser cannot
230// store the values in them.  Instead it stores them in a field in the *Options
231// message called uninterpreted_option. This field must have the same name
232// across all *Options messages. We then use this field to populate the
233// extensions when we build a descriptor, at which point all protos have been
234// parsed and so all extensions are known.
235//
236// Extension numbers for custom options may be chosen as follows:
237// * For options which will only be used within a single application or
238//   organization, or for experimental options, use field numbers 50000
239//   through 99999.  It is up to you to ensure that you do not use the
240//   same number for multiple options.
241// * For options which will be published and used publicly by multiple
242//   independent entities, e-mail protobuf-global-extension-registry@google.com
243//   to reserve extension numbers. Simply provide your project name (e.g.
244//   Object-C plugin) and your porject website (if available) -- there's no need
245//   to explain how you intend to use them. Usually you only need one extension
246//   number. You can declare multiple options with only one extension number by
247//   putting them in a sub-message. See the Custom Options section of the docs
248//   for examples:
249//   https://developers.google.com/protocol-buffers/docs/proto#options
250//   If this turns out to be popular, a web service will be set up
251//   to automatically assign option numbers.
252
253
254message FileOptions {
255
256  // Sets the Java package where classes generated from this .proto will be
257  // placed.  By default, the proto package is used, but this is often
258  // inappropriate because proto packages do not normally start with backwards
259  // domain names.
260  optional string java_package = 1;
261
262
263  // If set, all the classes from the .proto file are wrapped in a single
264  // outer class with the given name.  This applies to both Proto1
265  // (equivalent to the old "--one_java_file" option) and Proto2 (where
266  // a .proto always translates to a single class, but you may want to
267  // explicitly choose the class name).
268  optional string java_outer_classname = 8;
269
270  // If set true, then the Java code generator will generate a separate .java
271  // file for each top-level message, enum, and service defined in the .proto
272  // file.  Thus, these types will *not* be nested inside the outer class
273  // named by java_outer_classname.  However, the outer class will still be
274  // generated to contain the file's getDescriptor() method as well as any
275  // top-level extensions defined in the file.
276  optional bool java_multiple_files = 10 [default=false];
277
278  // If set true, then the Java code generator will generate equals() and
279  // hashCode() methods for all messages defined in the .proto file.
280  // - In the full runtime, this is purely a speed optimization, as the
281  // AbstractMessage base class includes reflection-based implementations of
282  // these methods.
283  //- In the lite runtime, setting this option changes the semantics of
284  // equals() and hashCode() to more closely match those of the full runtime;
285  // the generated methods compute their results based on field values rather
286  // than object identity. (Implementations should not assume that hashcodes
287  // will be consistent across runtimes or versions of the protocol compiler.)
288  optional bool java_generate_equals_and_hash = 20 [default=false];
289
290  // If set true, then the Java2 code generator will generate code that
291  // throws an exception whenever an attempt is made to assign a non-UTF-8
292  // byte sequence to a string field.
293  // Message reflection will do the same.
294  // However, an extension field still accepts non-UTF-8 byte sequences.
295  // This option has no effect on when used with the lite runtime.
296  optional bool java_string_check_utf8 = 27 [default=false];
297
298
299  // Generated classes can be optimized for speed or code size.
300  enum OptimizeMode {
301    SPEED = 1;        // Generate complete code for parsing, serialization,
302                      // etc.
303    CODE_SIZE = 2;    // Use ReflectionOps to implement these methods.
304    LITE_RUNTIME = 3; // Generate code using MessageLite and the lite runtime.
305  }
306  optional OptimizeMode optimize_for = 9 [default=SPEED];
307
308  // Sets the Go package where structs generated from this .proto will be
309  // placed.  There is no default.
310  optional string go_package = 11;
311
312
313
314  // Should generic services be generated in each language?  "Generic" services
315  // are not specific to any particular RPC system.  They are generated by the
316  // main code generators in each language (without additional plugins).
317  // Generic services were the only kind of service generation supported by
318  // early versions of proto2.
319  //
320  // Generic services are now considered deprecated in favor of using plugins
321  // that generate code specific to your particular RPC system.  Therefore,
322  // these default to false.  Old code which depends on generic services should
323  // explicitly set them to true.
324  optional bool cc_generic_services = 16 [default=false];
325  optional bool java_generic_services = 17 [default=false];
326  optional bool py_generic_services = 18 [default=false];
327
328  // Is this file deprecated?
329  // Depending on the target platform, this can emit Deprecated annotations
330  // for everything in the file, or it will be completely ignored; in the very
331  // least, this is a formalization for deprecating files.
332  optional bool deprecated = 23 [default=false];
333
334
335  // The parser stores options it doesn't recognize here. See above.
336  repeated UninterpretedOption uninterpreted_option = 999;
337
338  // Clients can define custom options in extensions of this message. See above.
339  extensions 1000 to max;
340}
341
342message MessageOptions {
343  // Set true to use the old proto1 MessageSet wire format for extensions.
344  // This is provided for backwards-compatibility with the MessageSet wire
345  // format.  You should not use this for any other reason:  It's less
346  // efficient, has fewer features, and is more complicated.
347  //
348  // The message must be defined exactly as follows:
349  //   message Foo {
350  //     option message_set_wire_format = true;
351  //     extensions 4 to max;
352  //   }
353  // Note that the message cannot have any defined fields; MessageSets only
354  // have extensions.
355  //
356  // All extensions of your type must be singular messages; e.g. they cannot
357  // be int32s, enums, or repeated messages.
358  //
359  // Because this is an option, the above two restrictions are not enforced by
360  // the protocol compiler.
361  optional bool message_set_wire_format = 1 [default=false];
362
363  // Disables the generation of the standard "descriptor()" accessor, which can
364  // conflict with a field of the same name.  This is meant to make migration
365  // from proto1 easier; new code should avoid fields named "descriptor".
366  optional bool no_standard_descriptor_accessor = 2 [default=false];
367
368  // Is this message deprecated?
369  // Depending on the target platform, this can emit Deprecated annotations
370  // for the message, or it will be completely ignored; in the very least,
371  // this is a formalization for deprecating messages.
372  optional bool deprecated = 3 [default=false];
373
374  // The parser stores options it doesn't recognize here. See above.
375  repeated UninterpretedOption uninterpreted_option = 999;
376
377  // Clients can define custom options in extensions of this message. See above.
378  extensions 1000 to max;
379}
380
381message FieldOptions {
382  // The ctype option instructs the C++ code generator to use a different
383  // representation of the field than it normally would.  See the specific
384  // options below.  This option is not yet implemented in the open source
385  // release -- sorry, we'll try to include it in a future version!
386  optional CType ctype = 1 [default = STRING];
387  enum CType {
388    // Default mode.
389    STRING = 0;
390
391    CORD = 1;
392
393    STRING_PIECE = 2;
394  }
395  // The packed option can be enabled for repeated primitive fields to enable
396  // a more efficient representation on the wire. Rather than repeatedly
397  // writing the tag and type for each element, the entire array is encoded as
398  // a single length-delimited blob.
399  optional bool packed = 2;
400
401
402
403  // Should this field be parsed lazily?  Lazy applies only to message-type
404  // fields.  It means that when the outer message is initially parsed, the
405  // inner message's contents will not be parsed but instead stored in encoded
406  // form.  The inner message will actually be parsed when it is first accessed.
407  //
408  // This is only a hint.  Implementations are free to choose whether to use
409  // eager or lazy parsing regardless of the value of this option.  However,
410  // setting this option true suggests that the protocol author believes that
411  // using lazy parsing on this field is worth the additional bookkeeping
412  // overhead typically needed to implement it.
413  //
414  // This option does not affect the public interface of any generated code;
415  // all method signatures remain the same.  Furthermore, thread-safety of the
416  // interface is not affected by this option; const methods remain safe to
417  // call from multiple threads concurrently, while non-const methods continue
418  // to require exclusive access.
419  //
420  //
421  // Note that implementations may choose not to check required fields within
422  // a lazy sub-message.  That is, calling IsInitialized() on the outher message
423  // may return true even if the inner message has missing required fields.
424  // This is necessary because otherwise the inner message would have to be
425  // parsed in order to perform the check, defeating the purpose of lazy
426  // parsing.  An implementation which chooses not to check required fields
427  // must be consistent about it.  That is, for any particular sub-message, the
428  // implementation must either *always* check its required fields, or *never*
429  // check its required fields, regardless of whether or not the message has
430  // been parsed.
431  optional bool lazy = 5 [default=false];
432
433  // Is this field deprecated?
434  // Depending on the target platform, this can emit Deprecated annotations
435  // for accessors, or it will be completely ignored; in the very least, this
436  // is a formalization for deprecating fields.
437  optional bool deprecated = 3 [default=false];
438
439  // EXPERIMENTAL.  DO NOT USE.
440  // For "map" fields, the name of the field in the enclosed type that
441  // is the key for this map.  For example, suppose we have:
442  //   message Item {
443  //     required string name = 1;
444  //     required string value = 2;
445  //   }
446  //   message Config {
447  //     repeated Item items = 1 [experimental_map_key="name"];
448  //   }
449  // In this situation, the map key for Item will be set to "name".
450  // TODO: Fully-implement this, then remove the "experimental_" prefix.
451  optional string experimental_map_key = 9;
452
453  // For Google-internal migration only. Do not use.
454  optional bool weak = 10 [default=false];
455
456
457
458  // The parser stores options it doesn't recognize here. See above.
459  repeated UninterpretedOption uninterpreted_option = 999;
460
461  // Clients can define custom options in extensions of this message. See above.
462  extensions 1000 to max;
463}
464
465message EnumOptions {
466
467  // Set this option to true to allow mapping different tag names to the same
468  // value.
469  optional bool allow_alias = 2;
470
471  // Is this enum deprecated?
472  // Depending on the target platform, this can emit Deprecated annotations
473  // for the enum, or it will be completely ignored; in the very least, this
474  // is a formalization for deprecating enums.
475  optional bool deprecated = 3 [default=false];
476
477  // The parser stores options it doesn't recognize here. See above.
478  repeated UninterpretedOption uninterpreted_option = 999;
479
480  // Clients can define custom options in extensions of this message. See above.
481  extensions 1000 to max;
482}
483
484message EnumValueOptions {
485  // Is this enum value deprecated?
486  // Depending on the target platform, this can emit Deprecated annotations
487  // for the enum value, or it will be completely ignored; in the very least,
488  // this is a formalization for deprecating enum values.
489  optional bool deprecated = 1 [default=false];
490
491  // The parser stores options it doesn't recognize here. See above.
492  repeated UninterpretedOption uninterpreted_option = 999;
493
494  // Clients can define custom options in extensions of this message. See above.
495  extensions 1000 to max;
496}
497
498message ServiceOptions {
499
500  // Note:  Field numbers 1 through 32 are reserved for Google's internal RPC
501  //   framework.  We apologize for hoarding these numbers to ourselves, but
502  //   we were already using them long before we decided to release Protocol
503  //   Buffers.
504
505  // Is this service deprecated?
506  // Depending on the target platform, this can emit Deprecated annotations
507  // for the service, or it will be completely ignored; in the very least,
508  // this is a formalization for deprecating services.
509  optional bool deprecated = 33 [default=false];
510
511  // The parser stores options it doesn't recognize here. See above.
512  repeated UninterpretedOption uninterpreted_option = 999;
513
514  // Clients can define custom options in extensions of this message. See above.
515  extensions 1000 to max;
516}
517
518message MethodOptions {
519
520  // Note:  Field numbers 1 through 32 are reserved for Google's internal RPC
521  //   framework.  We apologize for hoarding these numbers to ourselves, but
522  //   we were already using them long before we decided to release Protocol
523  //   Buffers.
524
525  // Is this method deprecated?
526  // Depending on the target platform, this can emit Deprecated annotations
527  // for the method, or it will be completely ignored; in the very least,
528  // this is a formalization for deprecating methods.
529  optional bool deprecated = 33 [default=false];
530
531  // The parser stores options it doesn't recognize here. See above.
532  repeated UninterpretedOption uninterpreted_option = 999;
533
534  // Clients can define custom options in extensions of this message. See above.
535  extensions 1000 to max;
536}
537
538
539// A message representing a option the parser does not recognize. This only
540// appears in options protos created by the compiler::Parser class.
541// DescriptorPool resolves these when building Descriptor objects. Therefore,
542// options protos in descriptor objects (e.g. returned by Descriptor::options(),
543// or produced by Descriptor::CopyTo()) will never have UninterpretedOptions
544// in them.
545message UninterpretedOption {
546  // The name of the uninterpreted option.  Each string represents a segment in
547  // a dot-separated name.  is_extension is true iff a segment represents an
548  // extension (denoted with parentheses in options specs in .proto files).
549  // E.g.,{ ["foo", false], ["bar.baz", true], ["qux", false] } represents
550  // "foo.(bar.baz).qux".
551  message NamePart {
552    required string name_part = 1;
553    required bool is_extension = 2;
554  }
555  repeated NamePart name = 2;
556
557  // The value of the uninterpreted option, in whatever type the tokenizer
558  // identified it as during parsing. Exactly one of these should be set.
559  optional string identifier_value = 3;
560  optional uint64 positive_int_value = 4;
561  optional int64 negative_int_value = 5;
562  optional double double_value = 6;
563  optional bytes string_value = 7;
564  optional string aggregate_value = 8;
565}
566
567// ===================================================================
568// Optional source code info
569
570// Encapsulates information about the original source file from which a
571// FileDescriptorProto was generated.
572message SourceCodeInfo {
573  // A Location identifies a piece of source code in a .proto file which
574  // corresponds to a particular definition.  This information is intended
575  // to be useful to IDEs, code indexers, documentation generators, and similar
576  // tools.
577  //
578  // For example, say we have a file like:
579  //   message Foo {
580  //     optional string foo = 1;
581  //   }
582  // Let's look at just the field definition:
583  //   optional string foo = 1;
584  //   ^       ^^     ^^  ^  ^^^
585  //   a       bc     de  f  ghi
586  // We have the following locations:
587  //   span   path               represents
588  //   [a,i)  [ 4, 0, 2, 0 ]     The whole field definition.
589  //   [a,b)  [ 4, 0, 2, 0, 4 ]  The label (optional).
590  //   [c,d)  [ 4, 0, 2, 0, 5 ]  The type (string).
591  //   [e,f)  [ 4, 0, 2, 0, 1 ]  The name (foo).
592  //   [g,h)  [ 4, 0, 2, 0, 3 ]  The number (1).
593  //
594  // Notes:
595  // - A location may refer to a repeated field itself (i.e. not to any
596  //   particular index within it).  This is used whenever a set of elements are
597  //   logically enclosed in a single code segment.  For example, an entire
598  //   extend block (possibly containing multiple extension definitions) will
599  //   have an outer location whose path refers to the "extensions" repeated
600  //   field without an index.
601  // - Multiple locations may have the same path.  This happens when a single
602  //   logical declaration is spread out across multiple places.  The most
603  //   obvious example is the "extend" block again -- there may be multiple
604  //   extend blocks in the same scope, each of which will have the same path.
605  // - A location's span is not always a subset of its parent's span.  For
606  //   example, the "extendee" of an extension declaration appears at the
607  //   beginning of the "extend" block and is shared by all extensions within
608  //   the block.
609  // - Just because a location's span is a subset of some other location's span
610  //   does not mean that it is a descendent.  For example, a "group" defines
611  //   both a type and a field in a single declaration.  Thus, the locations
612  //   corresponding to the type and field and their components will overlap.
613  // - Code which tries to interpret locations should probably be designed to
614  //   ignore those that it doesn't understand, as more types of locations could
615  //   be recorded in the future.
616  repeated Location location = 1;
617  message Location {
618    // Identifies which part of the FileDescriptorProto was defined at this
619    // location.
620    //
621    // Each element is a field number or an index.  They form a path from
622    // the root FileDescriptorProto to the place where the definition.  For
623    // example, this path:
624    //   [ 4, 3, 2, 7, 1 ]
625    // refers to:
626    //   file.message_type(3)  // 4, 3
627    //       .field(7)         // 2, 7
628    //       .name()           // 1
629    // This is because FileDescriptorProto.message_type has field number 4:
630    //   repeated DescriptorProto message_type = 4;
631    // and DescriptorProto.field has field number 2:
632    //   repeated FieldDescriptorProto field = 2;
633    // and FieldDescriptorProto.name has field number 1:
634    //   optional string name = 1;
635    //
636    // Thus, the above path gives the location of a field name.  If we removed
637    // the last element:
638    //   [ 4, 3, 2, 7 ]
639    // this path refers to the whole field declaration (from the beginning
640    // of the label to the terminating semicolon).
641    repeated int32 path = 1 [packed=true];
642
643    // Always has exactly three or four elements: start line, start column,
644    // end line (optional, otherwise assumed same as start line), end column.
645    // These are packed into a single field for efficiency.  Note that line
646    // and column numbers are zero-based -- typically you will want to add
647    // 1 to each before displaying to a user.
648    repeated int32 span = 2 [packed=true];
649
650    // If this SourceCodeInfo represents a complete declaration, these are any
651    // comments appearing before and after the declaration which appear to be
652    // attached to the declaration.
653    //
654    // A series of line comments appearing on consecutive lines, with no other
655    // tokens appearing on those lines, will be treated as a single comment.
656    //
657    // Only the comment content is provided; comment markers (e.g. //) are
658    // stripped out.  For block comments, leading whitespace and an asterisk
659    // will be stripped from the beginning of each line other than the first.
660    // Newlines are included in the output.
661    //
662    // Examples:
663    //
664    //   optional int32 foo = 1;  // Comment attached to foo.
665    //   // Comment attached to bar.
666    //   optional int32 bar = 2;
667    //
668    //   optional string baz = 3;
669    //   // Comment attached to baz.
670    //   // Another line attached to baz.
671    //
672    //   // Comment attached to qux.
673    //   //
674    //   // Another line attached to qux.
675    //   optional double qux = 4;
676    //
677    //   optional string corge = 5;
678    //   /* Block comment attached
679    //    * to corge.  Leading asterisks
680    //    * will be removed. */
681    //   /* Block comment attached to
682    //    * grault. */
683    //   optional int32 grault = 6;
684    optional string leading_comments = 3;
685    optional string trailing_comments = 4;
686  }
687}
688