如何挂钩加速系列化和放大器; iostreams的序列化和放大器; gzip压缩的目的是字符串? [英] How to hook up Boost serialization & iostreams to serialize & gzip an object to string?
问题描述
我一直在使用升压序列化库,这实际上是pretty不错,并让我做简单封装到我的序列化对象保存为字符串,像这样:
命名空间栏=的boost ::存档;
空间生物=的boost ::输入输出流;模板<类T>内联的std ::字符串saveString(常量T&放大器; O){
的std :: ostringstream OSS;
酒吧:: binary_oarchive OA(OSS);
OA<< O;
返回oss.str();
}
模板<类T>内嵌无效saveFile的(常量T&放大器; 0,为const char * FNAME){
的std :: OFS的ofstream(FNAME,性病::内部监督办公室::出来|的std :: IOS ::二进制|性病:: IOS :: TRUNC);
酒吧:: binary_oarchive OA(OFS);
OA<< O;
}
模板<类T>内嵌无效的loadFile(T&安培; 0,为const char * FNAME){
性病:: ifstream的IFS(FNAME,性病::内部监督办公室::在|的std :: IOS ::二进制);
断言(ifs.good()); // XXX捕捉如果找不到文件
酒吧:: binary_iarchive IA(IFS);
IA>> O;
}
问题是,我刚刚发现需要COM preSS我的序列化数据,也因此我期待在这样做,在升压::输入输出流过滤器。我想通了如何使用文件做成功:
模板<类T>内嵌无效saveGZFile(常量T&放大器; 0,为const char * FNAME){
的std :: OFS的ofstream(FNAME,性病::内部监督办公室::出来|的std :: IOS ::二进制|性病:: IOS :: TRUNC);
生物:: filtering_streambuf<生物::输出>出;
out.push(升压::输入输出流:: gzip_com pressor());
out.push(OFS);
酒吧:: binary_oarchive OA(出);
OA<< O;
}
模板<类T>内嵌无效loadGZFile(T&安培; 0,为const char * FNAME){
性病:: ifstream的IFS(FNAME,性病::内部监督办公室::在|的std :: IOS ::二进制);
断言(ifs.good()); // XXX捕捉如果找不到文件
生物:: filtering_streambuf<生物::输入>在;
in.push(生物:: gzip_decom pressor());
in.push(IFS);
酒吧:: binary_iarchive IA(中);
IA>> O;
}
但无法弄清楚如何正确保存到一个COM pressed字符串。问题是,我不冲洗过滤器的链条,但我已经试过弹出和同步,并似乎没有任何工作。这里是我的破code:
模板<类T>内联的std ::字符串saveGZString(常量T&放大器; O){
的std :: ostringstream OSS;
生物:: filtering_streambuf<生物::输出>出;
out.push(生物:: gzip_com pressor());
out.push(OSS);
酒吧:: binary_oarchive OA(出);
OA<< O;
// XXX out.pop()两次? out.strict_sync()? oss.flush()?
返回oss.str();
}
因此,一些数据卡在流缓冲的地方,我最后总是以com pressed数据AA几个完整的块(16K或32K),当我知道它应该是43K左右,考虑到(有效)输出我使用我的saveGZFile方法来获取。显然挂钩的关闭ofstream的刷新和正确,但挂接的ostringstream没有。
任何帮助吗? (这是我的第一个计算器的问题 - !帮帮我,伙计们,你是我唯一的希望)
解决方案
回到这个问题,我才意识到去年我一定是固定它的某个时候(因为我用saveGZString现在)
命名空间栏=的boost ::存档;
空间生物=的boost ::输入输出流;模板< typename的T>内联的std ::字符串saveGZString(常量T&放大器; O){
的std :: ostringstream OSS;
{
生物:: filtering_stream<生物::输出> F;
f.push(生物:: gzip_com pressor());
f.push(OSS);
酒吧:: binary_oarchive OA(F);
OA<< O;
} // gzip_com pressor刷新当f超出作用域
返回oss.str();
}
只是让整个链条超出范围和它的作品!整齐!这里是我的装载机的完整性:
模板< typename的T>内嵌无效loadGZString(T&安培O,常量标准::字符串&安培; S){
的std :: istringstream ISS(S);
生物:: filtering_stream<生物::输入> F;
f.push(生物:: gzip_decom pressor());
f.push(ISS);
酒吧:: binary_iarchive IA(F);
IA>> O;
}
I've been using the Boost serialization library, which is actually pretty nice, and lets me make simple wrappers to save my serializable objects to strings, like so:
namespace bar = boost::archive;
namespace bio = boost::iostreams;
template <class T> inline std::string saveString(const T & o) {
std::ostringstream oss;
bar::binary_oarchive oa(oss);
oa << o;
return oss.str();
}
template <class T> inline void saveFile(const T & o, const char* fname) {
std::ofstream ofs(fname, std::ios::out|std::ios::binary|std::ios::trunc);
bar::binary_oarchive oa(ofs);
oa << o;
}
template <class T> inline void loadFile(T & o, const char* fname) {
std::ifstream ifs(fname, std::ios::in|std::ios::binary);
assert(ifs.good()); // XXX catch if file not found
bar::binary_iarchive ia(ifs);
ia >> o;
}
The thing is, I just found the need to compress my serialized data, too, so I'm looking at doing that with the filters in boost::iostreams. I figured out how to do it successfully with files:
template <class T> inline void saveGZFile(const T & o, const char* fname) {
std::ofstream ofs(fname, std::ios::out|std::ios::binary|std::ios::trunc);
bio::filtering_streambuf<bio::output> out;
out.push(boost::iostreams::gzip_compressor());
out.push(ofs);
bar::binary_oarchive oa(out);
oa << o;
}
template <class T> inline void loadGZFile(T & o, const char* fname) {
std::ifstream ifs(fname, std::ios::in|std::ios::binary);
assert(ifs.good()); // XXX catch if file not found
bio::filtering_streambuf<bio::input> in;
in.push(bio::gzip_decompressor());
in.push(ifs);
bar::binary_iarchive ia(in);
ia >> o;
}
But can't figure out how to save correctly to a compressed string. The problem is that I'm not flushing the chain of filters, but I've tried popping and syncing and nothing seems to work. Here's my broken code:
template <class T> inline std::string saveGZString(const T & o) {
std::ostringstream oss;
bio::filtering_streambuf<bio::output> out;
out.push(bio::gzip_compressor());
out.push(oss);
bar::binary_oarchive oa(out);
oa << o;
// XXX out.pop() twice? out.strict_sync()?? oss.flush()??
return oss.str();
}
As a result some data gets stuck in the stream buffer somewhere, and I always end up with a a few complete blocks (16K or 32K) of compressed data when I know it should be 43K or so given the (valid) output I get from using my saveGZFile method. Apparently hooking up the ofstream closes and flushes properly, but hooking up the ostringstream doesn't.
Any help? (This is my first stackoverflow question — help me, guys, you're my only hope!)
Returning to this question, I realized I must've fixed it sometime last year (as I'm using saveGZString right now). Digging to see how I fixed it, it was pretty silly/simple:
namespace bar = boost::archive;
namespace bio = boost::iostreams;
template <typename T> inline std::string saveGZString(const T & o) {
std::ostringstream oss;
{
bio::filtering_stream<bio::output> f;
f.push(bio::gzip_compressor());
f.push(oss);
bar::binary_oarchive oa(f);
oa << o;
} // gzip_compressor flushes when f goes out of scope
return oss.str();
}
Just let the whole chain go out of scope and it works! Neat! Here's my loader for completeness:
template <typename T> inline void loadGZString(T & o, const std::string& s) {
std::istringstream iss(s);
bio::filtering_stream<bio::input> f;
f.push(bio::gzip_decompressor());
f.push(iss);
bar::binary_iarchive ia(f);
ia >> o;
}
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