Unable to capture standard output of process using Boost.Process
- by Chris Kaminski
Currently am using Boost.Process from the Boost sandbox, and am having issues getting it to capture my standard output properly; wondering if someone can give me a second pair of eyeballs into what I might be doing wrong.
I'm trying to take thumbnails out of RAW camera images using DCRAW (latest version), and capture them for conversion to QT QImage's.
The process launch function:
namespace bf = ::boost::filesystem;
namespace bp = ::boost::process;
QImage DCRawInterface::convertRawImage(string path) {
// commandline: dcraw -e -c <srcfile> -> piped to stdout.
if ( bf::exists( path ) ) {
std::string exec = "bin\\dcraw.exe";
std::vector<std::string> args;
args.push_back("-v");
args.push_back("-c");
args.push_back("-e");
args.push_back(path);
bp::context ctx;
ctx.stdout_behavior = bp::capture_stream();
bp::child c = bp::launch(exec, args, ctx);
bp::pistream &is = c.get_stdout();
ofstream output("C:\\temp\\testcfk.jpg");
streamcopy(is, output);
}
return (NULL);
}
inline void streamcopy(std::istream& input, std::ostream& out) {
char buffer[4096];
int i = 0;
while (!input.eof() ) {
memset(buffer, 0, sizeof(buffer));
int bytes = input.readsome(buffer, sizeof buffer);
out.write(buffer, bytes);
i++;
}
}
Invoking the converter:
DCRawInterface DcRaw;
DcRaw.convertRawImage("test/CFK_2439.NEF");
The goal is to simply verify that I can copy the input stream to an output file.
Currently, if I comment out the following line:
args.push_back("-c");
then the thumbnail is written by DCRAW to the source directory with a name of CFK_2439.thumb.jpg, which proves to me that the process is getting invoked with the right arguments. What's not happening is connecting to the output pipe properly.
FWIW: I'm performing this test on Windows XP under Eclipse 3.5/Latest MingW (GCC 4.4).
