X-Git-Url: https://git.dogcows.com/gitweb?p=chaz%2Fyoink;a=blobdiff_plain;f=src%2Fstlplus%2Fportability%2Fsubprocesses.cpp;fp=src%2Fstlplus%2Fportability%2Fsubprocesses.cpp;h=a8139c238468b8ff6665234fd56ce25d6eedcfeb;hp=0000000000000000000000000000000000000000;hb=6b0a0d0efafe34d48ab344fca3b479553bd4e62c;hpb=85783316365181491a3e3c0c63659972477cebba

diff --git a/src/stlplus/portability/subprocesses.cpp b/src/stlplus/portability/subprocesses.cpp
new file mode 100644
index 0000000..a8139c2
--- /dev/null
+++ b/src/stlplus/portability/subprocesses.cpp
@@ -0,0 +1,2077 @@
+////////////////////////////////////////////////////////////////////////////////
+
+//   Author:    Andy Rushton
+//   Copyright: (c) Southampton University 1999-2004
+//              (c) Andy Rushton           2004-2009
+//   License:   BSD License, see ../docs/license.html
+
+////////////////////////////////////////////////////////////////////////////////
+
+// Bug fix by Alistair Low: kill on Windows now kills grandchild processes as
+// well as the child process. This is done using jobs - which has to be
+// enabled by stating that the version of Windows is at least 5.0
+#if defined(_WIN32) || defined(_WIN32_WCE)
+#define _WIN32_WINNT 0x0500
+#endif
+
+#include "subprocesses.hpp"
+#include "file_system.hpp"
+#include "dprintf.hpp"
+#include <ctype.h>
+#include <string.h>
+#include <stdlib.h>
+
+#ifdef MSWINDOWS
+#else
+#include <signal.h>
+#include <errno.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <fcntl.h>
+#endif
+
+////////////////////////////////////////////////////////////////////////////////
+
+namespace stlplus
+{
+
+  ////////////////////////////////////////////////////////////////////////////////
+  // argument-vector related stuff
+
+  static void skip_white (const std::string& command, unsigned& i)
+  {
+    while(i < command.size() && isspace(command[i]))
+      i++;
+  }
+
+  // get_argument is the main function for breaking a string down into separate command arguments
+  // it mimics the way shells break down a command into an argv[] and unescapes the escaped characters on the way
+
+  static std::string get_argument (const std::string& command, unsigned& i)
+  {
+    std::string result;
+#ifdef MSWINDOWS
+
+  // as far as I know, there is only double-quoting and no escape character in DOS
+  // so, how do you include a double-quote in an argument???
+
+    bool dquote = false;
+    for ( ; i < command.size(); i++)
+    {
+      char ch = command[i];
+      if (!dquote && isspace(ch)) break;
+      if (dquote)
+      {
+        if (ch == '\"')
+          dquote = false;
+        else
+          result += ch;
+      }
+      else if (ch == '\"')
+        dquote = true;
+      else
+        result += ch;
+    }
+#else
+    bool squote = false;
+    bool dquote = false;
+    bool escaped = false;
+    for ( ; i < command.size(); i++)
+    {
+      char ch = command[i];
+      if (!squote && !dquote && !escaped && isspace(ch)) break;
+      if (escaped)
+      {
+        result += ch;
+        escaped = false;
+      }
+      else if (squote)
+      {
+        if (ch == '\'')
+          squote = false;
+        else
+          result += ch;
+      }
+      else if (ch == '\\')
+        escaped = true;
+      else if (dquote)
+      {
+        if (ch == '\"')
+          dquote = false;
+        else
+          result += ch;
+      }
+      else if (ch == '\'')
+        squote = true;
+      else if (ch == '\"')
+        dquote = true;
+      else
+        result += ch;
+    }
+#endif
+
+    return result;
+  }
+
+
+  // this function performs the reverse of the above on a single argument
+  // it escapes special characters and quotes the argument if necessary ready for shell interpretation
+
+  static std::string make_argument (const std::string& arg)
+  {
+    std::string result;
+    bool needs_quotes = false;
+
+    for (unsigned i = 0; i < arg.size(); i++)
+    {
+      switch (arg[i])
+      {
+        // set of characters requiring escapes
+#ifdef MSWINDOWS
+#else
+      case '\\': case '\'': case '\"': case '`': case '(': case ')': 
+      case '&': case '|': case '<': case '>': case '*': case '?': case '!':
+        result += '\\';
+        result += arg[i];
+        break;
+#endif
+        // set of whitespace characters that force quoting
+      case ' ':
+        result += arg[i];
+        needs_quotes = true;
+        break;
+      default:
+        result += arg[i];
+        break;
+      }
+    }
+
+    if (needs_quotes)
+    {
+      result.insert(result.begin(), '"');
+      result += '"';
+    }
+    return result;
+  }
+
+  static char* copy_string (const char* str)
+  {
+    char* result = new char[strlen(str)+1];
+    strcpy(result,str);
+    return result;
+  }
+
+  ////////////////////////////////////////////////////////////////////////////////
+
+  arg_vector::arg_vector (void)
+  {
+    m_argv = 0;
+  }
+
+  arg_vector::arg_vector (const arg_vector& a)
+  {
+    m_argv = 0;
+    *this = a;
+  }
+
+  arg_vector::arg_vector (char** a)
+  {
+    m_argv = 0;
+    *this = a;
+  }
+
+  arg_vector::arg_vector (const std::string& command)
+  {
+    m_argv = 0;
+    *this = command;
+  }
+
+  arg_vector::arg_vector (const char* command)
+  {
+    m_argv = 0;
+    *this = command;
+  }
+
+  arg_vector::~arg_vector (void)
+  {
+    clear();
+  }
+
+  arg_vector& arg_vector::operator = (const arg_vector& a)
+  {
+    return *this = a.m_argv;
+  }
+
+  arg_vector& arg_vector::operator = (char** argv)
+  {
+    clear();
+    for (unsigned i = 0; argv[i]; i++)
+      operator += (argv[i]);
+    return *this;
+  }
+
+  arg_vector& arg_vector::operator = (const std::string& command)
+  {
+    clear();
+    for (unsigned i = 0; i < command.size(); )
+    {
+      std::string argument = get_argument(command, i);
+      operator += (argument);
+      skip_white(command, i);
+    }
+    return *this;
+  }
+
+  arg_vector& arg_vector::operator = (const char* command)
+  {
+    return operator = (std::string(command));
+  }
+
+  arg_vector& arg_vector::operator += (const std::string& str)
+  {
+    insert(size(), str);
+    return *this;
+  }
+
+  arg_vector& arg_vector::operator -= (const std::string& str)
+  {
+    insert(0, str);
+    return *this;
+  }
+
+  void arg_vector::insert (unsigned index, const std::string& str) throw(std::out_of_range)
+  {
+    if (index > size()) throw std::out_of_range("arg_vector::insert");
+    // copy up to but not including index, then add the new argument, then copy the rest
+    char** new_argv = new char*[size()+2];
+    unsigned i = 0;
+    for ( ; i < index; i++)
+      new_argv[i] = copy_string(m_argv[i]);
+    new_argv[index] = copy_string(str.c_str());
+    for ( ; i < size(); i++)
+      new_argv[i+1] = copy_string(m_argv[i]);
+    new_argv[i+1] = 0;
+    clear();
+    m_argv = new_argv;
+  }
+
+  void arg_vector::clear (unsigned index) throw(std::out_of_range)
+  {
+    if (index >= size()) throw std::out_of_range("arg_vector::clear");
+    // copy up to index, skip it, then copy the rest
+    char** new_argv = new char*[size()];
+    unsigned i = 0;
+    for ( ; i < index; i++)
+      new_argv[i] = copy_string(m_argv[i]);
+    i++;
+    for ( ; i < size(); i++)
+      new_argv[i-1] = copy_string(m_argv[i]);
+    new_argv[i-1] = 0;
+    clear();
+    m_argv = new_argv;
+  }
+
+  void arg_vector::clear(void)
+  {
+    if (m_argv)
+    {
+      for (unsigned i = 0; m_argv[i]; i++)
+        delete[] m_argv[i];
+      delete[] m_argv;
+      m_argv = 0;
+    }
+  }
+
+  unsigned arg_vector::size (void) const
+  {
+    unsigned i = 0;
+    if (m_argv)
+      while (m_argv[i])
+        i++;
+    return i;
+  }
+
+  arg_vector::operator char** (void) const
+  {
+    return m_argv;
+  }
+
+  char** arg_vector::argv (void) const
+  {
+    return m_argv;
+  }
+
+  char* arg_vector::operator [] (unsigned index) const throw(std::out_of_range)
+  {
+    if (index >= size()) throw std::out_of_range("arg_vector::operator[]");
+    return m_argv[index];
+  }
+
+  char* arg_vector::argv0 (void) const throw(std::out_of_range)
+  {
+    return operator [] (0);
+  }
+
+  std::string arg_vector::image (void) const
+  {
+    std::string result;
+    for (unsigned i = 0; i < size(); i++)
+    {
+      if (i) result += ' ';
+      result += make_argument(m_argv[i]);
+    }
+    return result;
+  }
+
+  ////////////////////////////////////////////////////////////////////////////////
+  // environment-vector
+
+  // Windoze environment is a single string containing null-terminated
+  // name=value strings and the whole terminated by a null
+
+  // Unix environment is a null-terminated vector of pointers to null-terminated strings
+
+  ////////////////////////////////////////////////////////////////////////////////
+  // platform specifics
+
+#ifdef MSWINDOWS
+  // Windows utilities
+
+  // Windows environment variables are case-insensitive and I do comparisons by converting to lowercase
+  static std::string lowercase(const std::string& val)
+  {
+    std::string text = val;
+    for (unsigned i = 0; i < text.size(); i++)
+      text[i] = tolower(text[i]);
+    return text;
+  }
+
+  static unsigned envp_size(const char* envp)
+  {
+    unsigned size = 0;
+    while (envp[size] || (size > 0 && envp[size-1])) size++;
+    size++;
+    return size;
+  }
+
+  static void envp_extract(std::string& name, std::string& value, const char* envp, unsigned& envi)
+  {
+    name.erase();
+    value.erase();
+    if (!envp[envi]) return;
+    // some special variables start with '=' so ensure at least one character in the name
+    name += envp[envi++];
+    while(envp[envi] != '=')
+      name += envp[envi++];
+    envi++;
+    while(envp[envi])
+      value += envp[envi++];
+    envi++;
+  }
+
+  static void envp_append(const std::string& name, const std::string& value, char* envp, unsigned& envi)
+  {
+    for (unsigned i = 0; i < name.size(); i++)
+      envp[envi++] = name[i];
+    envp[envi++] = '=';
+    for (unsigned j = 0; j < value.size(); j++)
+      envp[envi++] = value[j];
+    envp[envi++] = '\0';
+    envp[envi] = '\0';
+  }
+
+  static char* envp_copy(const char* envp)
+  {
+    unsigned size = envp_size(envp);
+    char* result = new char[size];
+    result[0] = '\0';
+    unsigned i = 0;
+    unsigned j = 0;
+    while(envp[i])
+    {
+      std::string name;
+      std::string value;
+      envp_extract(name, value, envp, i);
+      envp_append(name, value, result, j);
+    }
+    return result;
+  }
+
+  static void envp_clear(char*& envp)
+  {
+    if (envp)
+    {
+      delete[] envp;
+      envp = 0;
+    }
+  }
+
+  static bool envp_equal(const std::string& left, const std::string& right)
+  {
+    return lowercase(left) == lowercase(right);
+  }
+
+  static bool envp_less(const std::string& left, const std::string& right)
+  {
+    return lowercase(left) < lowercase(right);
+  }
+
+#else
+  // Unix utilities
+
+  extern char** environ;
+
+  static unsigned envp_size(char* const* envp)
+  {
+    unsigned size = 0;
+    while(envp[size]) size++;
+    size++;
+    return size;
+  }
+
+  static void envp_extract(std::string& name, std::string& value, char* const* envp, unsigned& envi)
+  {
+    name = "";
+    value = "";
+    if (!envp[envi]) return;
+    unsigned i = 0;
+    while(envp[envi][i] != '=')
+      name += envp[envi][i++];
+    i++;
+    while(envp[envi][i])
+      value += envp[envi][i++];
+    envi++;
+  }
+
+  static void envp_append(const std::string& name, const std::string& value, char** envp, unsigned& envi)
+  {
+    std::string entry = name + "=" + value;
+    envp[envi] = copy_string(entry.c_str());
+    envi++;
+    envp[envi] = 0;
+  }
+
+  static char** envp_copy(char* const* envp)
+  {
+    unsigned size = envp_size(envp);
+    char** result = new char*[size];
+    unsigned i = 0;
+    unsigned j = 0;
+    while(envp[i])
+    {
+      std::string name;
+      std::string value;
+      envp_extract(name, value, envp, i);
+      envp_append(name, value, result, j);
+    }
+    return result;
+  }
+
+  static void envp_clear(char**& envp)
+  {
+    if (envp)
+    {
+      for (unsigned i = 0; envp[i]; i++)
+        delete[] envp[i];
+      delete[] envp;
+      envp = 0;
+    }
+  }
+
+  static bool envp_equal(const std::string& left, const std::string& right)
+  {
+    return left == right;
+  }
+
+  static bool envp_less(const std::string& left, const std::string& right)
+  {
+    return left < right;
+  }
+
+#endif
+  ////////////////////////////////////////////////////////////////////////////////
+
+  env_vector::env_vector(void)
+  {
+#ifdef MSWINDOWS
+    char* env = (char*)GetEnvironmentStringsA();
+    m_env = envp_copy(env);
+    FreeEnvironmentStringsA(env);
+#else
+    m_env = envp_copy(::environ);
+#endif
+  }
+
+  env_vector::env_vector (const env_vector& a)
+  {
+    m_env = 0;
+    *this = a;
+  }
+
+  env_vector::~env_vector (void)
+  {
+    clear();
+  }
+
+  env_vector& env_vector::operator = (const env_vector& a)
+  {
+    clear();
+    m_env = envp_copy(a.m_env);
+    return *this;
+  }
+
+  void env_vector::clear(void)
+  {
+    envp_clear(m_env);
+  }
+
+  void env_vector::add(const std::string& name, const std::string& value)
+  {
+    // the trick is to add the value in alphabetic order
+    // this is done by copying the existing environment string to a new
+    // string, inserting the new value when a name greater than it is found
+    unsigned size = envp_size(m_env);
+#ifdef MSWINDOWS
+    unsigned new_size = size + name.size() + value.size() + 2;
+    char* new_v = new char[new_size];
+    new_v[0] = '\0';
+#else
+    unsigned new_size = size + 1;
+    char** new_v = new char*[new_size];
+    new_v[0] = 0;
+#endif
+    // now extract each name=value pair and check the ordering
+    bool added = false;
+    unsigned i = 0;
+    unsigned j = 0;
+    while(m_env[i])
+    {
+      std::string current_name;
+      std::string current_value;
+      envp_extract(current_name, current_value, m_env, i);
+      if (envp_equal(name,current_name))
+      {
+        // replace an existing value
+        envp_append(name, value, new_v, j);
+      }
+      else if (!added && envp_less(name,current_name))
+      {
+        // add the new value first, then the existing one
+        envp_append(name, value, new_v, j);
+        envp_append(current_name, current_value, new_v, j);
+        added = true;
+      }
+      else
+      {
+        // just add the existing value
+        envp_append(current_name, current_value, new_v, j);
+      }
+    }
+    if (!added)
+      envp_append(name, value, new_v, j);
+    envp_clear(m_env);
+    m_env = new_v;
+  }
+
+
+  bool env_vector::remove (const std::string& name)
+  {
+    bool result = false;
+    // this is done by copying the existing environment string to a new string, but excluding the specified name
+    unsigned size = envp_size(m_env);
+#ifdef MSWINDOWS
+    char* new_v = new char[size];
+    new_v[0] = '\0';
+#else
+    char** new_v = new char*[size];
+    new_v[0] = 0;
+#endif
+    unsigned i = 0;
+    unsigned j = 0;
+    while(m_env[i])
+    {
+      std::string current_name;
+      std::string current_value;
+      envp_extract(current_name, current_value, m_env, i);
+      if (envp_equal(name,current_name))
+        result = true;
+      else
+        envp_append(current_name, current_value, new_v, j);
+    }
+    envp_clear(m_env);
+    m_env = new_v;
+    return result;
+  }
+
+  std::string env_vector::operator [] (const std::string& name) const
+  {
+    return get(name);
+  }
+
+  std::string env_vector::get (const std::string& name) const
+  {
+    unsigned i = 0;
+    while(m_env[i])
+    {
+      std::string current_name;
+      std::string current_value;
+      envp_extract(current_name, current_value, m_env, i);
+      if (envp_equal(name,current_name))
+        return current_value;
+    }
+    return std::string();
+  }
+
+  unsigned env_vector::size (void) const
+  {
+    unsigned i = 0;
+#ifdef MSWINDOWS
+    unsigned offset = 0;
+    while(m_env[offset])
+    {
+      std::string current_name;
+      std::string current_value;
+      envp_extract(current_name, current_value, m_env, offset);
+      i++;
+    }
+#else
+    while(m_env[i])
+      i++;
+#endif
+
+    return i;
+  }
+
+  std::pair<std::string,std::string> env_vector::operator [] (unsigned index) const throw(std::out_of_range)
+  {
+    return get(index);
+  }
+
+  std::pair<std::string,std::string> env_vector::get (unsigned index) const throw(std::out_of_range)
+  {
+    if (index >= size()) throw std::out_of_range("arg_vector::get");
+    unsigned j = 0;
+    for (unsigned i = 0; i < index; i++)
+    {
+      std::string current_name;
+      std::string current_value;
+      envp_extract(current_name, current_value, m_env, j);
+    }
+    std::string name;
+    std::string value;
+    envp_extract(name, value, m_env, j);
+    return std::make_pair(name,value);
+  }
+
+  ENVIRON_TYPE env_vector::envp (void) const
+  {
+    return m_env;
+  }
+
+  ////////////////////////////////////////////////////////////////////////////////
+  // Synchronous subprocess
+  // Win32 implementation mostly cribbed from MSDN examples and then made (much) more readable
+  // Unix implementation mostly from man pages and bitter experience
+  ////////////////////////////////////////////////////////////////////////////////
+
+#ifdef MSWINDOWS
+
+  subprocess::subprocess(void)
+  {
+    m_pid.hProcess = 0;
+    m_job = 0;
+    m_child_in = 0;
+    m_child_out = 0;
+    m_child_err = 0;
+    m_err = 0;
+    m_status = 0;
+  }
+
+#else
+
+  subprocess::subprocess(void)
+  {
+    m_pid = -1;
+    m_child_in = -1;
+    m_child_out = -1;
+    m_child_err = -1;
+    m_err = 0;
+    m_status = 0;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  subprocess::~subprocess(void)
+  {
+    if (m_pid.hProcess != 0)
+    {
+      close_stdin();
+      close_stdout();
+      close_stderr();
+      kill();
+      WaitForSingleObject(m_pid.hProcess, INFINITE);
+      CloseHandle(m_pid.hThread);
+      CloseHandle(m_pid.hProcess);
+      CloseHandle(m_job);
+    }
+  }
+
+#else
+
+  subprocess::~subprocess(void)
+  {
+    if (m_pid != -1)
+    {
+      close_stdin();
+      close_stdout();
+      close_stderr();
+      kill();
+      for (;;)
+      {
+        int wait_status = 0;
+        int wait_ret_val = waitpid(m_pid, &wait_status, 0);
+        if (wait_ret_val != -1 || errno != EINTR) break;
+      }
+    }
+  }
+
+#endif
+
+  void subprocess::add_variable(const std::string& name, const std::string& value)
+  {
+    m_env.add(name, value);
+  }
+
+  bool subprocess::remove_variable(const std::string& name)
+  {
+    return m_env.remove(name);
+  }
+
+#ifdef MSWINDOWS
+
+  bool subprocess::spawn(const std::string& path, const arg_vector& argv,
+                         bool connect_stdin, bool connect_stdout, bool connect_stderr)
+  {
+    bool result = true;
+    // first create the pipes to be used to connect to the child stdin/out/err
+    // If no pipes requested, then connect to the parent stdin/out/err
+    // for some reason you have to create a pipe handle, then duplicate it
+    // This is not well explained in MSDN but seems to work
+    PIPE_TYPE parent_stdin = 0;
+    if (!connect_stdin)
+      parent_stdin = GetStdHandle(STD_INPUT_HANDLE);
+    else
+    {
+      PIPE_TYPE tmp = 0;
+      SECURITY_ATTRIBUTES inherit_handles = {sizeof(SECURITY_ATTRIBUTES), 0, TRUE};
+      CreatePipe(&parent_stdin, &tmp, &inherit_handles, 0);
+      DuplicateHandle(GetCurrentProcess(), tmp, GetCurrentProcess(), &m_child_in, 0, FALSE, DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS);
+    }
+
+    PIPE_TYPE parent_stdout = 0;
+    if (!connect_stdout)
+      parent_stdout = GetStdHandle(STD_OUTPUT_HANDLE);
+    else
+    {
+      PIPE_TYPE tmp = 0;
+      SECURITY_ATTRIBUTES inherit_handles = {sizeof(SECURITY_ATTRIBUTES), 0, TRUE};
+      CreatePipe(&tmp, &parent_stdout, &inherit_handles, 0);
+      DuplicateHandle(GetCurrentProcess(), tmp, GetCurrentProcess(), &m_child_out, 0, FALSE, DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS);
+    }
+
+    PIPE_TYPE parent_stderr = 0;
+    if (!connect_stderr)
+      parent_stderr = GetStdHandle(STD_ERROR_HANDLE);
+    else
+    {
+      PIPE_TYPE tmp = 0;
+      SECURITY_ATTRIBUTES inherit_handles = {sizeof(SECURITY_ATTRIBUTES), 0, TRUE};
+      CreatePipe(&tmp, &parent_stderr, &inherit_handles, 0);
+      DuplicateHandle(GetCurrentProcess(), tmp, GetCurrentProcess(), &m_child_err, 0, FALSE, DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS);
+    }
+
+    // Now create the subprocess
+    // The horrible trick of creating a console window and hiding it seems to be required for the pipes to work
+    // Note that the child will inherit a copy of the pipe handles
+    STARTUPINFOA startup = {sizeof(STARTUPINFO),0,0,0,0,0,0,0,0,0,0,
+                            STARTF_USESTDHANDLES|STARTF_USESHOWWINDOW,SW_HIDE,0,0,
+                            parent_stdin,parent_stdout,parent_stderr};
+    bool created = CreateProcessA(path.c_str(),(char*)argv.image().c_str(),0,0,TRUE,CREATE_SUSPENDED,m_env.envp(),0,&startup,&m_pid) != 0;
+    // close the parent copy of the pipe handles so that the pipes will be closed when the child releases them
+    if (connect_stdin) CloseHandle(parent_stdin);
+    if (connect_stdout) CloseHandle(parent_stdout);
+    if (connect_stderr) CloseHandle(parent_stderr);
+    if (!created)
+    {
+      m_err = GetLastError();
+      close_stdin();
+      close_stdout();
+      close_stderr();
+      result = false;
+    }
+    else
+    {
+      m_job = CreateJobObject(NULL, NULL);
+      AssignProcessToJobObject(m_job, m_pid.hProcess);
+      ResumeThread(m_pid.hThread);
+
+      // The child process is now running so call the user's callback
+      // The convention is that the callback can return false, in which case this will kill the child (if its still running)
+      if (!callback())
+      {
+        result = false;
+        kill();
+      }
+      close_stdin();
+      close_stdout();
+      close_stderr();
+      // wait for the child to finish
+      // TODO - kill the child if a timeout happens
+      WaitForSingleObject(m_pid.hProcess, INFINITE);
+      DWORD exit_status = 0;
+      if (!GetExitCodeProcess(m_pid.hProcess, &exit_status))
+      {
+        m_err = GetLastError();
+        result = false;
+      }
+      else if (exit_status != 0)
+        result = false;
+      m_status = (int)exit_status;
+      CloseHandle(m_pid.hThread);
+      CloseHandle(m_pid.hProcess);
+      CloseHandle(m_job);
+    }
+    m_pid.hProcess = 0;
+    return result;
+  }
+
+#else
+
+  bool subprocess::spawn(const std::string& path, const arg_vector& argv,
+                         bool connect_stdin, bool connect_stdout, bool connect_stderr)
+  {
+    bool result = true;
+    // first create the pipes to be used to connect to the child stdin/out/err
+
+    int stdin_pipe [2] = {-1, -1};
+    if (connect_stdin)
+      pipe(stdin_pipe);
+
+    int stdout_pipe [2] = {-1, -1};
+    if (connect_stdout)
+      pipe(stdout_pipe);
+
+    int stderr_pipe [2] = {-1, -1};
+    if (connect_stderr)
+      pipe(stderr_pipe);
+
+    // now create the subprocess
+    // In Unix, this is done by forking (creating two copies of the parent), then overwriting the child copy using exec
+    m_pid = ::fork();
+    switch(m_pid)
+    {
+    case -1:   // failed to fork
+      m_err = errno;
+      if (connect_stdin)
+      {
+        ::close(stdin_pipe[0]);
+        ::close(stdin_pipe[1]);
+      }
+      if (connect_stdout)
+      {
+        ::close(stdout_pipe[0]);
+        ::close(stdout_pipe[1]);
+      }
+      if (connect_stderr)
+      {
+        ::close(stderr_pipe[0]);
+        ::close(stderr_pipe[1]);
+      }
+      result = false;
+      break;
+    case 0:  // in child;
+    {
+      // for each pipe, close the end of the duplicated pipe that is being used by the parent
+      // and connect the child's end of the pipe to the appropriate standard I/O device
+      if (connect_stdin)
+      {
+        ::close(stdin_pipe[1]);
+        dup2(stdin_pipe[0],STDIN_FILENO);
+      }
+      if (connect_stdout)
+      {
+        ::close(stdout_pipe[0]);
+        dup2(stdout_pipe[1],STDOUT_FILENO);
+      }
+      if (connect_stderr)
+      {
+        ::close(stderr_pipe[0]);
+        dup2(stderr_pipe[1],STDERR_FILENO);
+      }
+      execve(path.c_str(), argv.argv(), m_env.envp());
+      // will only ever get here if the exec() failed completely - *must* now exit the child process
+      // by using errno, the parent has some chance of diagnosing the cause of the problem
+      exit(errno);
+    }
+    break;
+    default:  // in parent
+    {
+      // for each pipe, close the end of the duplicated pipe that is being used by the child
+      // and connect the parent's end of the pipe to the class members so that they are visible to the parent() callback
+      if (connect_stdin)
+      {
+        ::close(stdin_pipe[0]);
+        m_child_in = stdin_pipe[1];
+      }
+      if (connect_stdout)
+      {
+        ::close(stdout_pipe[1]);
+        m_child_out = stdout_pipe[0];
+      }
+      if (connect_stderr)
+      {
+        ::close(stderr_pipe[1]);
+        m_child_err = stderr_pipe[0];
+      }
+      // call the user's callback
+      if (!callback())
+      {
+        result = false;
+        kill();
+      }
+      // close the pipes and wait for the child to finish
+      // wait exits on a signal which may be the child signalling its exit or may be an interrupt
+      close_stdin();
+      close_stdout();
+      close_stderr();
+      int wait_status = 0;
+      for (;;)
+      {
+        int wait_ret_val = waitpid(m_pid, &wait_status, 0);
+        if (wait_ret_val != -1 || errno != EINTR) break;
+      }
+      // establish whether an error occurred
+      if (WIFSIGNALED(wait_status))
+      {
+        // set_error(errno);
+        m_status = WTERMSIG(wait_status);
+        result = false;
+      }
+      else if (WIFEXITED(wait_status))
+      {
+        m_status = WEXITSTATUS(wait_status);
+        if (m_status != 0)
+          result = false;
+      }
+      m_pid = -1;
+    }
+    break;
+    }
+    return result;
+  }
+
+#endif
+
+  bool subprocess::spawn(const std::string& command_line,
+                                  bool connect_stdin, bool connect_stdout, bool connect_stderr)
+  {
+    arg_vector arguments = command_line;
+    if (arguments.size() == 0) return false;
+    std::string path = path_lookup(arguments.argv0());
+    if (path.empty()) return false;
+    return spawn(path, arguments, connect_stdin, connect_stdout, connect_stderr);
+  }
+
+  bool subprocess::callback(void)
+  {
+    return true;
+  }
+
+#ifdef MSWINDOWS
+
+  bool subprocess::kill (void)
+  {
+    if (!m_pid.hProcess) return false;
+    close_stdin();
+    close_stdout();
+    close_stderr();
+    if (!TerminateJobObject(m_job, (UINT)-1))
+    {
+      m_err = GetLastError();
+      return false;
+    }
+    return true;
+  }
+
+#else
+
+  bool subprocess::kill (void)
+  {
+    if (m_pid == -1) return false;
+    close_stdin();
+    close_stdout();
+    close_stderr();
+    if (::kill(m_pid, SIGINT) == -1)
+    {
+      m_err = errno;
+      return false;
+    }
+    return true;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  int subprocess::write_stdin (std::string& buffer)
+  {
+    if (m_child_in == 0) return -1;
+    // do a blocking write of the whole buffer
+    DWORD bytes = 0;
+    if (!WriteFile(m_child_in, buffer.c_str(), (DWORD)buffer.size(), &bytes, 0))
+    {
+      m_err = GetLastError();
+      close_stdin();
+      return -1;
+    }
+    // now discard that part of the buffer that was written
+    if (bytes > 0)
+      buffer.erase(0, bytes);
+    return bytes;
+  }
+
+#else
+
+  int subprocess::write_stdin (std::string& buffer)
+  {
+    if (m_child_in == -1) return -1;
+    // do a blocking write of the whole buffer
+    int bytes = write(m_child_in, buffer.c_str(), buffer.size());
+    if (bytes == -1)
+    {
+      m_err = errno;
+      close_stdin();
+      return -1;
+    }
+    // now discard that part of the buffer that was written
+    if (bytes > 0)
+      buffer.erase(0, bytes);
+    return bytes;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  int subprocess::read_stdout (std::string& buffer)
+  {
+    if (m_child_out == 0) return -1;
+    DWORD bytes = 0;
+    DWORD buffer_size = 256;
+    char* tmp = new char[buffer_size];
+    if (!ReadFile(m_child_out, tmp, buffer_size, &bytes, 0))
+    {
+      if (GetLastError() != ERROR_BROKEN_PIPE)
+        m_err = GetLastError();
+      close_stdout();
+      delete[] tmp;
+      return -1;
+    }
+    if (bytes == 0)
+    {
+      // EOF
+      close_stdout();
+      delete[] tmp;
+      return -1;
+    }
+    buffer.append(tmp, bytes);
+    delete[] tmp;
+    return (int)bytes;
+  }
+
+#else
+
+  int subprocess::read_stdout (std::string& buffer)
+  {
+    if (m_child_out == -1) return -1;
+    int buffer_size = 256;
+    char* tmp = new char[buffer_size];
+    int bytes = read(m_child_out, tmp, buffer_size);
+    if (bytes == -1)
+    {
+      m_err = errno;
+      close_stdout();
+      delete[] tmp;
+      return -1;
+    }
+    if (bytes == 0)
+    {
+      // EOF
+      close_stdout();
+      delete[] tmp;
+      return -1;
+    }
+    buffer.append(tmp, bytes);
+    delete[] tmp;
+    return bytes;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  int subprocess::read_stderr(std::string& buffer)
+  {
+    if (m_child_err == 0) return -1;
+    DWORD bytes = 0;
+    DWORD buffer_size = 256;
+    char* tmp = new char[buffer_size];
+    if (!ReadFile(m_child_err, tmp, buffer_size, &bytes, 0))
+    {
+      if (GetLastError() != ERROR_BROKEN_PIPE)
+        m_err = GetLastError();
+      close_stderr();
+      delete[] tmp;
+      return -1;
+    }
+    if (bytes == 0)
+    {
+      // EOF
+      close_stderr();
+      delete[] tmp;
+      return -1;
+    }
+    buffer.append(tmp, bytes);
+    delete[] tmp;
+    return (int)bytes;
+  }
+
+#else
+
+  int subprocess::read_stderr (std::string& buffer)
+  {
+    if (m_child_err == -1) return -1;
+    int buffer_size = 256;
+    char* tmp = new char[buffer_size];
+    int bytes = read(m_child_err, tmp, buffer_size);
+    if (bytes == -1)
+    {
+      m_err = errno;
+      close_stderr();
+      delete[] tmp;
+      return -1;
+    }
+    if (bytes == 0)
+    {
+      // EOF
+      close_stderr();
+      delete[] tmp;
+      return -1;
+    }
+    buffer.append(tmp, bytes);
+    delete[] tmp;
+    return bytes;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  void subprocess::close_stdin (void)
+  {
+    if (m_child_in)
+    {
+      CloseHandle(m_child_in);
+      m_child_in = 0;
+    }
+  }
+
+#else
+
+  void subprocess::close_stdin (void)
+  {
+    if (m_child_in != -1)
+    {
+      ::close(m_child_in);
+      m_child_in = -1;
+    }
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  void subprocess::close_stdout (void)
+  {
+    if (m_child_out)
+    {
+      CloseHandle(m_child_out);
+      m_child_out = 0;
+    }
+  }
+
+#else
+
+  void subprocess::close_stdout (void)
+  {
+    if (m_child_out != -1)
+    {
+      ::close(m_child_out);
+      m_child_out = -1;
+    }
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  void subprocess::close_stderr (void)
+  {
+    if (m_child_err)
+    {
+      CloseHandle(m_child_err);
+      m_child_err = 0;
+    }
+  }
+
+#else
+
+  void subprocess::close_stderr (void)
+  {
+    if (m_child_err != -1)
+    {
+      ::close(m_child_err);
+      m_child_err = -1;
+    }
+  }
+
+#endif
+
+  bool subprocess::error(void) const
+  {
+    return m_err != 0;
+  }
+
+  int subprocess::error_number(void) const
+  {
+    return m_err;
+  }
+
+#ifdef MSWINDOWS
+
+  std::string subprocess::error_text(void) const
+  {
+    if (m_err == 0) return std::string();
+    char* message;
+    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS,
+                  0,
+                  m_err,
+                  MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                  (LPTSTR)&message,
+                  0,0);
+    std::string result = message;
+    LocalFree(message);
+    // the error message is for some perverse reason newline terminated - remove this
+    if (result[result.size()-1] == '\n')
+      result.erase(result.end()-1);
+    if (result[result.size()-1] == '\r')
+      result.erase(result.end()-1);
+    return result;
+  }
+
+#else
+
+  std::string subprocess::error_text(void) const
+  {
+    if (m_err == 0) return std::string();
+    char* text = strerror(m_err);
+    if (text) return std::string(text);
+    return "error number " + dformat("%d",m_err);
+  }
+
+#endif
+
+  int subprocess::exit_status(void) const
+  {
+    return m_status;
+  }
+
+  ////////////////////////////////////////////////////////////////////////////////
+  // backtick subprocess and operations
+
+  backtick_subprocess::backtick_subprocess(void) : subprocess()
+  {
+  }
+
+  bool backtick_subprocess::callback(void)
+  {
+    for (;;)
+    {
+      std::string buffer;
+      int read_size = read_stdout(buffer);
+      if (read_size < 0) break;
+      m_text += buffer;
+    }
+    return !error();
+  }
+
+  bool backtick_subprocess::spawn(const std::string& path, const arg_vector& argv)
+  {
+    return subprocess::spawn(path, argv, false, true, false);
+  }
+
+  bool backtick_subprocess::spawn(const std::string& command_line)
+  {
+    return subprocess::spawn(command_line, false, true, false);
+  }
+
+  std::vector<std::string> backtick_subprocess::text(void) const
+  {
+    std::vector<std::string> result;
+    // convert the raw text into a vector of strings, each corresponding to a line
+    // in the process, strip out platform-specific line-endings
+    for (unsigned i = 0; i < m_text.size(); i++)
+    {
+      // handle any kind of line-ending - Dos, Unix or MacOS
+      switch(m_text[i])
+      {
+      case '\xd': // carriage-return - optionally followed by linefeed
+      {
+        // discard optional following linefeed
+        if ((i+1 < m_text.size()) && (m_text[i+1] == '\xa'))
+          i++;
+        // add a new line to the end of the vector
+        result.push_back(std::string());
+        break;
+      }
+      case '\xa': // linefeed
+      {
+        // add a new line to the end of the vector
+        result.push_back(std::string());
+        break;
+      }
+      default:
+      {
+        result.back() += m_text[i];
+        break;
+      }
+      }
+    }
+    // tidy up - if the last line ended with a newline, the vector will end with an empty string - discard this
+    if ((result.size()) > 0 && result.back().empty())
+      result.erase(result.end()-1);
+    return result;
+  }
+
+  std::vector<std::string> backtick(const std::string& path, const arg_vector& argv)
+  {
+    backtick_subprocess sub;
+    sub.spawn(path, argv);
+    return sub.text();
+  }
+
+  std::vector<std::string> backtick(const std::string& command_line)
+  {
+    backtick_subprocess sub;
+    sub.spawn(command_line);
+    return sub.text();
+  }
+
+  ////////////////////////////////////////////////////////////////////////////////
+  // Asynchronous subprocess
+
+#ifdef MSWINDOWS
+
+  async_subprocess::async_subprocess(void)
+  {
+    m_pid.hProcess = 0;
+    m_job = 0;
+    m_child_in = 0;
+    m_child_out = 0;
+    m_child_err = 0;
+    m_err = 0;
+    m_status = 0;
+  }
+
+#else
+
+  async_subprocess::async_subprocess(void)
+  {
+    m_pid = -1;
+    m_child_in = -1;
+    m_child_out = -1;
+    m_child_err = -1;
+    m_err = 0;
+    m_status = 0;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  async_subprocess::~async_subprocess(void)
+  {
+    if (m_pid.hProcess != 0)
+    {
+      close_stdin();
+      close_stdout();
+      close_stderr();
+      kill();
+      WaitForSingleObject(m_pid.hProcess, INFINITE);
+      CloseHandle(m_pid.hThread);
+      CloseHandle(m_pid.hProcess);
+      CloseHandle(m_job);
+    }
+  }
+
+#else
+
+  async_subprocess::~async_subprocess(void)
+  {
+    if (m_pid != -1)
+    {
+      close_stdin();
+      close_stdout();
+      close_stderr();
+      kill();
+      for (;;)
+      {
+        int wait_status = 0;
+        int wait_ret_val = waitpid(m_pid, &wait_status, 0);
+        if (wait_ret_val != -1 || errno != EINTR) break;
+      }
+    }
+  }
+
+#endif
+
+  void async_subprocess::set_error(int e)
+  {
+    m_err = e;
+  }
+
+  void async_subprocess::add_variable(const std::string& name, const std::string& value)
+  {
+    m_env.add(name, value);
+  }
+
+  bool async_subprocess::remove_variable(const std::string& name)
+  {
+    return m_env.remove(name);
+  }
+
+#ifdef MSWINDOWS
+
+  bool async_subprocess::spawn(const std::string& path, const arg_vector& argv,
+                                        bool connect_stdin, bool connect_stdout, bool connect_stderr)
+  {
+    bool result = true;
+    // first create the pipes to be used to connect to the child stdin/out/err
+    // If no pipes requested, then connect to the parent stdin/out/err
+    // for some reason you have to create a pipe handle, then duplicate it
+    // This is not well explained in MSDN but seems to work
+    PIPE_TYPE parent_stdin = 0;
+    if (!connect_stdin)
+      parent_stdin = GetStdHandle(STD_INPUT_HANDLE);
+    else
+    {
+      PIPE_TYPE tmp = 0;
+      SECURITY_ATTRIBUTES inherit_handles = {sizeof(SECURITY_ATTRIBUTES), 0, TRUE};
+      CreatePipe(&parent_stdin, &tmp, &inherit_handles, 0);
+      DuplicateHandle(GetCurrentProcess(), tmp, GetCurrentProcess(), &m_child_in, 0, FALSE, DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS);
+    }
+
+    PIPE_TYPE parent_stdout = 0;
+    if (!connect_stdout)
+      parent_stdout = GetStdHandle(STD_OUTPUT_HANDLE);
+    else
+    {
+      PIPE_TYPE tmp = 0;
+      SECURITY_ATTRIBUTES inherit_handles = {sizeof(SECURITY_ATTRIBUTES), 0, TRUE};
+      CreatePipe(&tmp, &parent_stdout, &inherit_handles, 0);
+      DuplicateHandle(GetCurrentProcess(), tmp, GetCurrentProcess(), &m_child_out, 0, FALSE, DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS);
+    }
+
+    PIPE_TYPE parent_stderr = 0;
+    if (!connect_stderr)
+      parent_stderr = GetStdHandle(STD_ERROR_HANDLE);
+    else
+    {
+      PIPE_TYPE tmp = 0;
+      SECURITY_ATTRIBUTES inherit_handles = {sizeof(SECURITY_ATTRIBUTES), 0, TRUE};
+      CreatePipe(&tmp, &parent_stderr, &inherit_handles, 0);
+      DuplicateHandle(GetCurrentProcess(), tmp, GetCurrentProcess(), &m_child_err, 0, FALSE, DUPLICATE_CLOSE_SOURCE | DUPLICATE_SAME_ACCESS);
+    }
+
+    // Now create the subprocess
+    // The horrible trick of creating a console window and hiding it seems to be required for the pipes to work
+    // Note that the child will inherit a copy of the pipe handles
+    STARTUPINFOA startup = {sizeof(STARTUPINFO),0,0,0,0,0,0,0,0,0,0,
+                            STARTF_USESTDHANDLES|STARTF_USESHOWWINDOW,SW_HIDE,0,0,
+                            parent_stdin,parent_stdout,parent_stderr};
+    bool created = CreateProcessA(path.c_str(),(char*)argv.image().c_str(),0,0,TRUE,CREATE_SUSPENDED,m_env.envp(),0,&startup,&m_pid) != 0;
+    // close the parent copy of the pipe handles so that the pipes will be closed when the child releases them
+    if (connect_stdin) CloseHandle(parent_stdin);
+    if (connect_stdout) CloseHandle(parent_stdout);
+    if (connect_stderr) CloseHandle(parent_stderr);
+    if (!created)
+    {
+      set_error(GetLastError());
+      close_stdin();
+      close_stdout();
+      close_stderr();
+      result = false;
+    }
+    else
+    {
+      m_job = CreateJobObject(NULL, NULL);
+      AssignProcessToJobObject(m_job, m_pid.hProcess);
+      ResumeThread(m_pid.hThread);
+    }
+    return result;
+  }
+
+#else
+
+  bool async_subprocess::spawn(const std::string& path, const arg_vector& argv,
+                               bool connect_stdin, bool connect_stdout, bool connect_stderr)
+  {
+    bool result = true;
+    // first create the pipes to be used to connect to the child stdin/out/err
+
+    int stdin_pipe [2] = {-1, -1};
+    if (connect_stdin)
+      pipe(stdin_pipe);
+
+    int stdout_pipe [2] = {-1, -1};
+    if (connect_stdout)
+      pipe(stdout_pipe);
+
+    int stderr_pipe [2] = {-1, -1};
+    if (connect_stderr)
+      pipe(stderr_pipe);
+
+    // now create the subprocess
+    // In Unix, this is done by forking (creating two copies of the parent), then overwriting the child copy using exec
+    m_pid = ::fork();
+    switch(m_pid)
+    {
+    case -1:   // failed to fork
+      set_error(errno);
+      if (connect_stdin)
+      {
+        ::close(stdin_pipe[0]);
+        ::close(stdin_pipe[1]);
+      }
+      if (connect_stdout)
+      {
+        ::close(stdout_pipe[0]);
+        ::close(stdout_pipe[1]);
+      }
+      if (connect_stderr)
+      {
+        ::close(stderr_pipe[0]);
+        ::close(stderr_pipe[1]);
+      }
+      result = false;
+      break;
+    case 0:  // in child;
+    {
+      // for each pipe, close the end of the duplicated pipe that is being used by the parent
+      // and connect the child's end of the pipe to the appropriate standard I/O device
+      if (connect_stdin)
+      {
+        ::close(stdin_pipe[1]);
+        dup2(stdin_pipe[0],STDIN_FILENO);
+      }
+      if (connect_stdout)
+      {
+        ::close(stdout_pipe[0]);
+        dup2(stdout_pipe[1],STDOUT_FILENO);
+      }
+      if (connect_stderr)
+      {
+        ::close(stderr_pipe[0]);
+        dup2(stderr_pipe[1],STDERR_FILENO);
+      }
+      execve(path.c_str(), argv.argv(), m_env.envp());
+      // will only ever get here if the exec() failed completely - *must* now exit the child process
+      // by using errno, the parent has some chance of diagnosing the cause of the problem
+      exit(errno);
+    }
+    break;
+    default:  // in parent
+    {
+      // for each pipe, close the end of the duplicated pipe that is being used by the child
+      // and connect the parent's end of the pipe to the class members so that they are visible to the parent() callback
+      if (connect_stdin)
+      {
+        ::close(stdin_pipe[0]);
+        m_child_in = stdin_pipe[1];
+        if (fcntl(m_child_in, F_SETFL, O_NONBLOCK) == -1)
+        {
+          set_error(errno);
+          result = false;
+        }
+      }
+      if (connect_stdout)
+      {
+        ::close(stdout_pipe[1]);
+        m_child_out = stdout_pipe[0];
+        if (fcntl(m_child_out, F_SETFL, O_NONBLOCK) == -1)
+        {
+          set_error(errno);
+          result = false;
+        }
+      }
+      if (connect_stderr)
+      {
+        ::close(stderr_pipe[1]);
+        m_child_err = stderr_pipe[0];
+        if (fcntl(m_child_err, F_SETFL, O_NONBLOCK) == -1)
+        {
+          set_error(errno);
+          result = false;
+        }
+      }
+    }
+    break;
+    }
+    return result;
+  }
+
+#endif
+
+  bool async_subprocess::spawn(const std::string& command_line,
+                               bool connect_stdin, bool connect_stdout, bool connect_stderr)
+  {
+    arg_vector arguments = command_line;
+    if (arguments.size() == 0) return false;
+    std::string path = path_lookup(arguments.argv0());
+    if (path.empty()) return false;
+    return spawn(path, arguments, connect_stdin, connect_stdout, connect_stderr);
+  }
+
+  bool async_subprocess::callback(void)
+  {
+    return true;
+  }
+
+#ifdef MSWINDOWS
+
+  bool async_subprocess::tick(void)
+  {
+    bool result = true;
+    if (!callback())
+      kill();
+    DWORD exit_status = 0;
+    if (!GetExitCodeProcess(m_pid.hProcess, &exit_status))
+    {
+      set_error(GetLastError());
+      result = false;
+    }
+    else if (exit_status != STILL_ACTIVE)
+    {
+      CloseHandle(m_pid.hThread);
+      CloseHandle(m_pid.hProcess);
+      CloseHandle(m_job);
+      m_pid.hProcess = 0;
+      result = false;
+    }
+    m_status = (int)exit_status;
+    return result;
+  }
+
+#else
+
+  bool async_subprocess::tick(void)
+  {
+    bool result = true;
+    if (!callback())
+      kill();
+    int wait_status = 0;
+    int wait_ret_val = waitpid(m_pid, &wait_status, WNOHANG);
+    if (wait_ret_val == -1 && errno != EINTR)
+    {
+      set_error(errno);
+      result = false;
+    }
+    else if (wait_ret_val != 0)
+    {
+      // the only states that indicate a terminated child are WIFSIGNALLED and WIFEXITED
+      if (WIFSIGNALED(wait_status))
+      {
+        // set_error(errno);
+        m_status = WTERMSIG(wait_status);
+        result = false;
+      }
+      else if (WIFEXITED(wait_status))
+      {
+        // child has exited
+        m_status = WEXITSTATUS(wait_status);
+        result = false;
+      }
+    }
+    if (!result)
+      m_pid = -1;
+    return result;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  bool async_subprocess::kill(void)
+  {
+    if (!m_pid.hProcess) return false;
+    close_stdin();
+    close_stdout();
+    close_stderr();
+    if (!TerminateJobObject(m_job, (UINT)-1))
+    {
+      set_error(GetLastError());
+      return false;
+    }
+    return true;
+  }
+
+#else
+
+  bool async_subprocess::kill(void)
+  {
+    if (m_pid == -1) return false;
+    close_stdin();
+    close_stdout();
+    close_stderr();
+    if (::kill(m_pid, SIGINT) == -1)
+    {
+      set_error(errno);
+      return false;
+    }
+    return true;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  int async_subprocess::write_stdin (std::string& buffer)
+  {
+    if (m_child_in == 0) return -1;
+    // there doesn't seem to be a way of doing non-blocking writes under Windoze
+    DWORD bytes = 0;
+    if (!WriteFile(m_child_in, buffer.c_str(), (DWORD)buffer.size(), &bytes, 0))
+    {
+      set_error(GetLastError());
+      close_stdin();
+      return -1;
+    }
+    // now discard that part of the buffer that was written
+    if (bytes > 0)
+      buffer.erase(0, bytes);
+    return (int)bytes;
+  }
+
+#else
+
+  int async_subprocess::write_stdin (std::string& buffer)
+  {
+    if (m_child_in == -1) return -1;
+    // relies on the pipe being non-blocking
+    // This does block under Windoze
+    int bytes = write(m_child_in, buffer.c_str(), buffer.size());
+    if (bytes == -1 && errno == EAGAIN)
+    {
+      // not ready
+      return 0;
+    }
+    if (bytes == -1)
+    {
+      // error on write - close the pipe and give up
+      set_error(errno);
+      close_stdin();
+      return -1;
+    }
+    // successful write
+    // now discard that part of the buffer that was written
+    if (bytes > 0)
+      buffer.erase(0, bytes);
+    return bytes;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  int async_subprocess::read_stdout (std::string& buffer)
+  {
+    if (m_child_out == 0) return -1;
+    // peek at the buffer to see how much data there is in the first place
+    DWORD buffer_size = 0;
+    if (!PeekNamedPipe(m_child_out, 0, 0, 0, &buffer_size, 0))
+    {
+      if (GetLastError() != ERROR_BROKEN_PIPE)
+        set_error(GetLastError());
+      close_stdout();
+      return -1;
+    }
+    if (buffer_size == 0) return 0;
+    DWORD bytes = 0;
+    char* tmp = new char[buffer_size];
+    if (!ReadFile(m_child_out, tmp, buffer_size, &bytes, 0))
+    {
+      set_error(GetLastError());
+      close_stdout();
+      delete[] tmp;
+      return -1;
+    }
+    if (bytes == 0)
+    {
+      // EOF
+      close_stdout();
+      delete[] tmp;
+      return -1;
+    }
+    buffer.append(tmp, bytes);
+    delete[] tmp;
+    return (int)bytes;
+  }
+
+#else
+
+  int async_subprocess::read_stdout (std::string& buffer)
+  {
+    if (m_child_out == -1) return -1;
+    // rely on the pipe being non-blocking
+    int buffer_size = 256;
+    char* tmp = new char[buffer_size];
+    int bytes = read(m_child_out, tmp, buffer_size);
+    if (bytes == -1 && errno == EAGAIN)
+    {
+      // not ready
+      delete[] tmp;
+      return 0;
+    }
+    if (bytes == -1)
+    {
+      // error
+      set_error(errno);
+      close_stdout();
+      delete[] tmp;
+      return -1;
+    }
+    if (bytes == 0)
+    {
+      // EOF
+      close_stdout();
+      delete[] tmp;
+      return -1;
+    }
+    // successful read
+    buffer.append(tmp, bytes);
+    delete[] tmp;
+    return bytes;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  int async_subprocess::read_stderr (std::string& buffer)
+  {
+    if (m_child_err == 0) return -1;
+    // peek at the buffer to see how much data there is in the first place
+    DWORD buffer_size = 0;
+    if (!PeekNamedPipe(m_child_err, 0, 0, 0, &buffer_size, 0))
+    {
+      if (GetLastError() != ERROR_BROKEN_PIPE)
+        set_error(GetLastError());
+      close_stderr();
+      return -1;
+    }
+    if (buffer_size == 0) return 0;
+    DWORD bytes = 0;
+    char* tmp = new char[buffer_size];
+    if (!ReadFile(m_child_err, tmp, buffer_size, &bytes, 0))
+    {
+      set_error(GetLastError());
+      close_stderr();
+      delete[] tmp;
+      return -1;
+    }
+    if (bytes == 0)
+    {
+      // EOF
+      close_stderr();
+      delete[] tmp;
+      return -1;
+    }
+    buffer.append(tmp, bytes);
+    delete[] tmp;
+    return (int)bytes;
+  }
+
+#else
+
+  int async_subprocess::read_stderr (std::string& buffer)
+  {
+    if (m_child_err == -1) return -1;
+    // rely on the pipe being non-blocking
+    int buffer_size = 256;
+    char* tmp = new char[buffer_size];
+    int bytes = read(m_child_err, tmp, buffer_size);
+    if (bytes == -1 && errno == EAGAIN)
+    {
+      // not ready
+      delete[] tmp;
+      return 0;
+    }
+    if (bytes == -1)
+    {
+      // error
+      set_error(errno);
+      close_stderr();
+      delete[] tmp;
+      return -1;
+    }
+    if (bytes == 0)
+    {
+      // EOF
+      close_stderr();
+      delete[] tmp;
+      return -1;
+    }
+    // successful read
+    buffer.append(tmp, bytes);
+    delete[] tmp;
+    return bytes;
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  void async_subprocess::close_stdin (void)
+  {
+    if (m_child_in)
+    {
+      CloseHandle(m_child_in);
+      m_child_in = 0;
+    }
+  }
+
+#else
+
+  void async_subprocess::close_stdin (void)
+  {
+    if (m_child_in != -1)
+    {
+      ::close(m_child_in);
+      m_child_in = -1;
+    }
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  void async_subprocess::close_stdout (void)
+  {
+    if (m_child_out)
+    {
+      CloseHandle(m_child_out);
+      m_child_out = 0;
+    }
+  }
+
+#else
+
+  void async_subprocess::close_stdout (void)
+  {
+    if (m_child_out != -1)
+    {
+      ::close(m_child_out);
+      m_child_out = -1;
+    }
+  }
+
+#endif
+
+#ifdef MSWINDOWS
+
+  void async_subprocess::close_stderr (void)
+  {
+    if (m_child_err)
+    {
+      CloseHandle(m_child_err);
+      m_child_err = 0;
+    }
+  }
+
+#else
+
+  void async_subprocess::close_stderr (void)
+  {
+    if (m_child_err != -1)
+    {
+      ::close(m_child_err);
+      m_child_err = -1;
+    }
+  }
+
+#endif
+
+  bool async_subprocess::error(void) const
+  {
+    return m_err != 0;
+  }
+
+  int async_subprocess::error_number(void) const
+  {
+    return m_err;
+  }
+
+#ifdef MSWINDOWS
+
+  std::string async_subprocess::error_text(void) const
+  {
+    if (m_err == 0) return std::string();
+    char* message;
+    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS,
+                  0,
+                  m_err,
+                  MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                  (LPTSTR)&message,
+                  0,0);
+    std::string result = message;
+    LocalFree(message);
+    // the error message is for some perverse reason newline terminated - remove this
+    if (result[result.size()-1] == '\n')
+      result.erase(result.end()-1);
+    if (result[result.size()-1] == '\r')
+      result.erase(result.end()-1);
+    return result;
+  }
+
+#else
+
+  std::string async_subprocess::error_text(void) const
+  {
+    if (m_err == 0) return std::string();
+    char* text = strerror(m_err);
+    if (text) return std::string(text);
+    return "error number " + dformat("%d",m_err);
+  }
+
+#endif
+
+  int async_subprocess::exit_status(void) const
+  {
+    return m_status;
+  }
+
+  ////////////////////////////////////////////////////////////////////////////////
+
+} // end namespace stlplus