Simple command-line HTTP-only downloader using JNetLib

jnetlib_get.cpp

// DEPENDENCIES:
// WDL from https://cockos.com/wdl/
//
// BUILD INSTRUCTIONS:
// Windows:
// - SET WDL=path/to/WDL
// - cl /O2 /I%WDL% jnetlib_get.cpp %WDL%/WDL/jnetlib/httpget.cpp %WDL%/WDL/jnetlib/util.cpp %WDL%/WDL/jnetlib/connection.cpp %WDL%/WDL/jnetlib/asyncdns.cpp Ws2_32.lib
// - jnetlib_get.exe http://google.com/
//
// macOS & Linux
// - WDL=path/to/WDL; c++ -O2 -I$WDL jnetlib_get.cpp $WDL/WDL/jnetlib/{httpget,connection,util,asyncdns}.cpp -pthread -o jnetlib_get
// - ./jnetlib_get http://google.com/

#include <cstdio>
#include <string>

#ifdef _WIN32
#  include <windows.h>
#else
#  include <unistd.h>
  void Sleep(const int ms) { usleep(ms * 1000); }
#endif

#include <WDL/jnetlib/jnetlib.h>

class InitSocketLib {
public:
  InitSocketLib() { JNL::open_socketlib(); }
  ~InitSocketLib() { JNL::close_socketlib(); }
};

static void writeChunk(JNL_HTTPGet &agent, std::string *buffer)
{
  const size_t dataSize = agent.bytes_available();

  if(!dataSize)
    return; // nothing to do

  const size_t originalSize = buffer->size();

  buffer->resize(originalSize + dataSize);
  agent.get_bytes(&(*buffer)[originalSize], dataSize);
}

int main(int argc, char *argv[])
{
  if(argc != 2) {
    fprintf(stderr, "usage: %s [url]\n", argv[0]);
    return 1;
  }

  InitSocketLib raii;

  std::string contents;
  const int chunkSize = 1<<14; // default value from JNetLib

  JNL_HTTPGet agent(JNL_CONNECTION_AUTODNS, chunkSize);
  agent.addheader("Accept: */*");
  agent.addheader("User-Agent: jnetlib_get.cpp");
  agent.connect(argv[1]);

  // wait until the connection is closed
  while(agent.run() == 0) {
    if(agent.bytes_available() >= chunkSize)
      writeChunk(agent, &contents);

    Sleep(50);
  }

  const int status = agent.getreplycode();

  if(status == 200) {
    writeChunk(agent, &contents); // fetch the last (incomplete) chunk
    printf("%s", contents.c_str());
    return 0;
  }
  else {
    fprintf(stderr, "error: (%d) %s\n", status, agent.geterrorstr());
    return 1;
  }
}