[iostreams] filtering streams in a chain are continually writing the same bytes
Perhaps someone can clarify that my use of multichar_output_filter is valid. When I debug this, even though my write method is returning 4 bytes for every write, the caller of my output filter keeps providing me the same four bytes after the first sequence of 4 bytes. This is boot version 1.62. Here is compiling code that illustrates: class fixed_size_output_filter : public boost::iostreams::multichar_output_filter { public: fixed_size_output_filter(std::streamsize size = 4) : mSize(size) {} template<typename Sink> std::streamsize write(Sink &sink, const char *s, std::streamsize n) { std::streamsize bytesAttempted = std::min(mSize, n); std::streamsize bytesActual = boost::iostreams::write(sink, s, bytesAttempted); return bytesActual; } private: std::streamsize mSize; }; BOOST_AUTO_TEST_CASE(FixedSizeOutputFilter) { #define BYTES 500 char sink_buffer[BYTES]; array_sink array_sink(sink_buffer, sizeof(sink_buffer)); std::streampos os_pos; { filtering_ostream os; os.push(fixed_size_output_filter()); os.push(array_sink); char buffer[BYTES]; for(char i = 0; i < sizeof(buffer); i++) buffer[i] = i; os.write(buffer, sizeof(buffer)); } for(char i = 0; i < sizeof(sink_buffer); i++) BOOST_CHECK(i == sink_buffer[i]); } The actual bytes that end up in the sink_buffer are as follows: 0, 1, 2, 3, 4, 5, 6, 7, 4, 5, 6, 7, 4, 5, 6, 7, 4, 5, 6, 7, ....uninitialized bytes follow through the rest of the buffer. It would appear that the indirect_streambuf in use by the filter chain is incorrectly flushing the bytes. Is my understanding of the library flawed? Does this appear to be a bug? Any help is greatly appreciated. -- Andrew Ames aames@tanzle.com
The problem appears to be in the code that calls setp inside the
indirect_streambuf. It seems to be using incorrect pointers.
Can someone confirm my thinking here?
I changed this function from this:
template
Perhaps someone can clarify that my use of multichar_output_filter is valid.
When I debug this, even though my write method is returning 4 bytes for every write, the caller of my output filter keeps providing me the same four bytes after the first sequence of 4 bytes.
This is boot version 1.62. Here is compiling code that illustrates:
class fixed_size_output_filter : public boost::iostreams::multichar_ output_filter { public:
fixed_size_output_filter(std::streamsize size = 4) : mSize(size) {}
template<typename Sink> std::streamsize write(Sink &sink, const char *s, std::streamsize n) { std::streamsize bytesAttempted = std::min(mSize, n); std::streamsize bytesActual = boost::iostreams::write(sink, s, bytesAttempted); return bytesActual; }
private:
std::streamsize mSize;
};
BOOST_AUTO_TEST_CASE(FixedSizeOutputFilter) { #define BYTES 500
char sink_buffer[BYTES]; array_sink array_sink(sink_buffer, sizeof(sink_buffer));
std::streampos os_pos; { filtering_ostream os; os.push(fixed_size_output_filter()); os.push(array_sink);
char buffer[BYTES]; for(char i = 0; i < sizeof(buffer); i++) buffer[i] = i;
os.write(buffer, sizeof(buffer)); }
for(char i = 0; i < sizeof(sink_buffer); i++) BOOST_CHECK(i == sink_buffer[i]); }
The actual bytes that end up in the sink_buffer are as follows:
0, 1, 2, 3, 4, 5, 6, 7, 4, 5, 6, 7, 4, 5, 6, 7, 4, 5, 6, 7, ....uninitialized bytes follow through the rest of the buffer.
It would appear that the indirect_streambuf in use by the filter chain is incorrectly flushing the bytes.
Is my understanding of the library flawed? Does this appear to be a bug? Any help is greatly appreciated.
-- Andrew Ames aames@tanzle.com
-- Andrew Ames aames@tanzle.com
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Andrew Ames