使用protobuf的生成器可以对proto文件进行解析后生成指定的目标语言代码.随着项目的不断扩大, 协议修改变的非常频繁, 因此每次重编变的异常耗时. 模仿C/C++编译器的时间戳检查生成机制,我给protobuf生成器添加了时间戳检查功能. 下面说下原理:
此功能不是必须的, 可以通过命令行指定—timestampfile FILE 来指定要生成的proto文件对应的时间戳
每次运行解析器时, 解析器通过命令行获取proto文件, 我们可以先读取之前保存的时间戳, 然后与这个文件的当前修改时间进行对比
如果时间戳不相等,说明文件已经被修改, 需要重新生成.之后更新时间戳文件即可.
下面是在protobuf的protoc工程里添加的代码:
command_line_interface.cc
void CommandLineInterface::ReadTimeStampFile( const string& timestampfile )
{
FILE* f = fopen( timestampfile.c_str(), "rb" );
if ( f == NULL )
return;
time_stamp_map_.clear( );
while( !feof( f ) )
{
size_t read = 0;
int strlen = 0;
read = fread( &strlen, 1 , sizeof strlen, f );
if ( read == 0 )
break;
std::string filename;
filename.resize( strlen );
read = fread( (void*)filename.data(), 1, sizeof(char) * strlen, f );
if ( read == 0 )
break;
__time64_t timestamp;
read = fread( ×tamp, 1, sizeof(timestamp), f );
if ( read == 0 )
break;
time_stamp_map_[filename] = timestamp;
}
fclose( f );
}
void CommandLineInterface::WriteTimeStampFile( const string& timestampfile )
{
FILE* f = fopen( timestampfile.c_str(), "wb" );
if ( f == NULL )
return;
for ( time_stamp_map::iterator it = time_stamp_map_.begin();
it != time_stamp_map_.end();
it++)
{
const std::string& filename = it->first;
__time64_t timestamp = it->second;
int strlen = filename.length();
fwrite( &strlen, 1, sizeof(strlen), f );
fwrite( (void*)filename.data(), 1, sizeof(char)*strlen, f );
fwrite( ×tamp, 1, sizeof( timestamp ), f );
}
fclose( f );
}
bool CommandLineInterface::NeedGenerate( const std::string& filename )
{
struct _stat buf;
if ( _stat( filename.c_str(), &buf ) != 0 )
{
// file error
return true;
}
time_stamp_map::iterator it = time_stamp_map_.find( filename );
if ( it != time_stamp_map_.end() )
{
__time64_t& timestamp = it->second;
if ( timestamp == buf.st_mtime )
return false;
}
// don't hold the time stamp or time stamp not match, generate it!
// save to map , then write time stamp
time_stamp_map_[filename] = buf.st_mtime;
return true;
}
void CommandLineInterface::CheckFileStamp( const string& timestampfile )
{
ReadTimeStampFile( timestampfile );
for (vector<string>::iterator it = input_files_.begin();
it != input_files_.end();) {
if ( !NeedGenerate( *it) )
{
it = input_files_.erase( it );
}
else
{
++it;
}
}
WriteTimeStampFile( timestampfile );
}
以上代码为核心逻辑, 之后在int CommandLineInterface::Run(int argc, const char* const argv[]) 函数中添加代码:
int CommandLineInterface::Run(int argc, const char* const argv[]) {
Clear();
if (!ParseArguments(argc, argv)) return 1;
// Set up the source tree.
DiskSourceTree source_tree;
for (int i = 0; i < proto_path_.size(); i++) {
source_tree.MapPath(proto_path_[i].first, proto_path_[i].second);
}
// Map input files to virtual paths if necessary.
if (!inputs_are_proto_path_relative_) {
if (!MakeInputsBeProtoPathRelative(&source_tree)) {
return 1;
}
}
// Allocate the Importer.
ErrorPrinter error_collector(error_format_, &source_tree);
Importer importer(&source_tree, &error_collector);
vector<const FileDescriptor*> parsed_files;
if ( time_stamp_filename_ != "" )
CheckFileStamp( time_stamp_filename_ );
加黑部分为添加的代码, 这里是检查时间戳的入口
同时,我们还需要添加命令行解析开关, 这里在
bool CommandLineInterface::InterpretArgument(const string& name,
const string& value) {
函数中,找到:
} else if (name == "--error_format") {
if (value == "gcc") {
error_format_ = ERROR_FORMAT_GCC;
} else if (value == "msvs") {
error_format_ = ERROR_FORMAT_MSVS;
} else {
cerr << "Unknown error format: " << value << endl;
return false;
}
}
else if ( name == "--timestampfile" ){
time_stamp_filename_ = value;
}
else if (name == "--plugin") {
if (plugin_prefix_.empty()) {
cerr << "This compiler does not support plugins." << endl;
return false;
}
加黑部分为解析开关
之后在头文件中添加声明代码:
// Time stamp function
void ReadTimeStampFile( const string& timestampfile );
void WriteTimeStampFile( const string& timestampfile );
bool NeedGenerate( const std::string& filename );
void CheckFileStamp( const string& timestampfile );
typedef std::map<std::string, __time64_t> time_stamp_map; // proto file name as key, timestamp as value
time_stamp_map time_stamp_map_;
string time_stamp_filename_;
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