Boost Iostreams zlib_error与自定义源 [英] Boost Iostreams zlib_error with Custom Source

问题描述

我尝试使用 zlib_decompressor 通过 istreambuf_iterator 解压缩数据。我找不到一个内置的方式使用输入迭代器作为流的输入（请指出一种方式，如果一个已经存在）所以我写了这个源：

  template< class cha_type，class iterator_type> 
 class IteratorSource {
 public：
 typedef cha_type char_type; 
 typedef boost :: iostreams :: source_tag category; 
 iterator_type&一世; 
 iterator_type eof; 
 
 IteratorSource（iterator_type& it，iterator_type end）：i（it），eof（end）{
} 
 
 std :: streamsize read（char * s ，std :: streamsize n）{
 for（int j = 0; j  if（i == eof）{
 std :: cout< ; 到达eof之后< j<< bytes\\\
; 
 return -1; 
} 
 char next = * i ++; 
 std :: cout<< 阅读<<下一个< \\\
; 
 * s ++ = next; 
} 
 return n; 
} 
}; 
  

并使用它：

  int main（）{
 std :: vector< char> data_back = {'\x78'，'\x9c'，'\x73'，'\x04'，'\x00'，'\x00'，'\x42'，'\x00' ，'\x42'}; 
 auto start = data_back.begin（）; 
 IteratorSource< char，decltype（data_back）:: iterator> data（start，data_back.end（））; 
 
 boost :: iostreams :: filtering_istreambuf def; 
 def.push（boost :: iostreams :: zlib_decompressor（））; 
 def.push（data）; 
 boost :: iostreams :: copy（def，std :: cout）; 
 return 0; 
} 
  

要提供此输出：

 阅读x 
阅读 
阅读s 
阅读
阅读
阅读
阅读B 
 Reading 
 Reading B 
在9个字节后达到eof 
在抛出boost :: exception_detail :: clone_impl< boost :: exception_detail :: error_info_injector< boost :: iostreams :: zlib_error> >'
 what（）：zlib错误
中止（转储核心）
  

解决方案

EDIT 为了回应澄清的问题（在下面的评论中），以下是我对原始示例，我的盒子上的 JustWorks™进行的小改动：

  #include< boost / iostreams / copy.hpp> 
 #include< boost / iostreams / filter / zlib.hpp> 
 #include< boost / iostreams / filtering_streambuf.hpp> 
 #include< iostream> 
 #include< sstream> 
 
 template< class cha_type，class iterator_type> 
 struct my_source {
 typedef cha_type char_type; 
 typedef boost :: iostreams :: source_tag category; 
 
 iterator_type&它; 
 iterator_type end; 
 
 my_source（iterator_type& it，iterator_type end = {}）：it（it），end（end）
 {} 
 
 std :: streamsize read char * s，std :: streamsize n）{
 std :: streamsize result = 0; 
 while（（it！= end）&& n--）{
 ++ result; 
 * s ++ = * it ++; 
} 
 return result; 
} 
}; 
 
 int main（）{
 std :: string const rawdata {'x'，'\234'，'\313'，'H'，'\315' '\311'，'\311'，'W'，'（'，'\317'，'/'，'\312'，'I'，'\341'，'\002 '，'\ 0'，'\ 036'，'r'，'\004'，'g'}; 
 std :: istringstream iss（rawdata，std :: ios :: binary）; 
 
 auto start = std :: istreambuf_iterator< char>（iss）; 
 my_source< char，decltype（start）> data（start）; 
 
 boost :: iostreams :: filtering_istreambuf def; 
 def.push（boost :: iostreams :: zlib_decompressor（））; 
 def.push（data）; 
 
 boost :: iostreams :: copy（def，std :: cout）; 
} 
  

> Live On Coliru

---

旧答案：

我认为您只能使用任何流stringstream：

  std :: istringstream iss（hello world\\\
）; 
 
 filtering_streambuf< ; input> def; 
 def.push（zlib_compressor（））; 
 def.push（iss）; 
 boost :: iostreams :: copy（def，std :: cout）; 
  

或解压缩：

  std :: string const rawdata {'x'，'\234'，'\313'，'H'，'\315'，'\311'，'\311 '，'W'，'（'，'\317'，'/'，'\312'，'I'，'\341'，'\002'，'\0' \\ 036'，'r'，'\004'，'g'}; 
 std :: istringstream iss（rawdata，std :: ios :: binary）; 
 
 filtering_streambuf< input> def; 
 def.push（zlib_decompressor（））; 
 def.push（iss）; 
 boost :: iostreams :: copy（def，std :: cout）; 
  

这是一个很好的八进制转义：这是bash给我的

  printf％q\\\
$（echo hello world | zlib-flate -compress）
  
 
 
 
，我很懒得保持这种方式）。
 
 
 
完整示例  Live on Coliru   
 
 
 
 
 
 
 或 Boost Iostreams接受流缓冲区，因此您可以等效
  def.push（* iss.rdbuf（））; 
  
 
I am trying to use a zlib_decompressor to decompress data through an istreambuf_iterator. I couldn't find an in built way to use an input iterator as input to a stream (please point out a way if one exists already) so I wrote this source: 
template <class cha_type, class iterator_type>
class IteratorSource {
    public:
        typedef cha_type char_type;
        typedef boost::iostreams::source_tag category;
        iterator_type& i;
        iterator_type eof;

        IteratorSource(iterator_type& it, iterator_type end) : i(it), eof(end) {
        }

        std::streamsize read(char* s, std::streamsize n) {
            for(int j = 0; j < n; j++) {
                if(i == eof) {
                    std::cout << "Reached eof after " << j << " bytes\n";
                    return -1;
                }
                char next = *i++;
                std::cout << "Reading " << next << "\n";
                *s++ = next;
            }
            return n;
        }
};
And used it like this:
int main() {       
    std::vector<char> data_back = {'\x78', '\x9c', '\x73', '\x04', '\x00', '\x00', '\x42', '\x00', '\x42'};
    auto start = data_back.begin();
    IteratorSource<char, decltype(data_back)::iterator> data(start, data_back.end());

    boost::iostreams::filtering_istreambuf def;
    def.push(boost::iostreams::zlib_decompressor());
    def.push(data);
    boost::iostreams::copy(def, std::cout);
    return 0;
}
To give this output:
Reading x
Reading �
Reading s
Reading 
Reading 
Reading 
Reading B
Reading 
Reading B
Reached eof after 9 bytes
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::iostreams::zlib_error> >'
  what():  zlib error
Aborted (core dumped)
I am not sure why this is producing an error because loading from a file works fine.
解决方案
EDIT In response to the clarified question (in the comments below), here's a trivial adaptation I did of your original sample, that JustWorks™ on my box:
#include <boost/iostreams/copy.hpp>
#include <boost/iostreams/filter/zlib.hpp>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <iostream>
#include <sstream>

template <class cha_type, class iterator_type>
struct my_source {
    typedef cha_type char_type;
    typedef boost::iostreams::source_tag category;

    iterator_type& it;
    iterator_type end;

    my_source(iterator_type& it, iterator_type end = {}) : it(it), end(end) 
    { }

    std::streamsize read(char* s, std::streamsize n) {
        std::streamsize result = 0;
        while ((it!=end) && n--) {
            ++result;
            *s++ = *it++;
        }
        return result;
    }
};

int main() {       
    std::string const rawdata {'x', '\234', '\313', 'H', '\315', '\311', '\311', 'W', '(', '\317', '/', '\312', 'I', '\341', '\002', '\0', '\036', 'r', '\004', 'g' };
    std::istringstream iss(rawdata, std::ios::binary);

    auto start = std::istreambuf_iterator<char>(iss);
    my_source<char, decltype(start)> data(start);

    boost::iostreams::filtering_istreambuf def;
    def.push(boost::iostreams::zlib_decompressor());
    def.push(data);

    boost::iostreams::copy(def, std::cout);
}
See it Live On Coliru



Old answer:

I think you can use just any stream, like stringstream:
std::istringstream iss("hello world\n");

filtering_streambuf<input> def;
def.push(zlib_compressor());
def.push(iss);
boost::iostreams::copy(def, std::cout);
or to decompress:
std::string const rawdata {'x', '\234', '\313', 'H', '\315', '\311', '\311', 'W', '(', '\317', '/', '\312', 'I', '\341', '\002', '\0', '\036', 'r', '\004', 'g' };
std::istringstream iss(rawdata, std::ios::binary);

filtering_streambuf<input> def;
def.push(zlib_decompressor());
def.push(iss);
boost::iostreams::copy(def, std::cout);
This works like a charm here. (Sorry for the octal escapes: it's what bash gave me
printf "%q\n" "$(echo hello world | zlib-flate -compress)"
and I'm lazy enough to keep it that way).

See full example Live on Coliru



Alternatively Boost Iostreams accepts a streambuffer, so you can equivalently
def.push(*iss.rdbuf());


                        
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