* src/preproc/html/pre-html.cpp (write_upto_newline): Don't use

`(*t)->next' without testing validity of `*t'.
(usage): Make it more readable.


Make html device run under both MS-DOS and Win32.

* src/preproc/html/pre-html.cpp (MAY_FORK_CHILD_PROCESS,
MAY_SPAWN_ASYNCHRONOUS_CHILD): New macros to control whether
spawn or fork+exec has to be used, and whether parent must sleep
until the child process terminates.  Used in
`char_buffer::run_output_filter'.
(copyofstdoutfd): Removed.
(char_buffer): Replace `write_file_html' and `write_file_troff'
member functions with `emit_troff_output' and `run_output_filter'.
The latter
(DEVICE_FORMAT, HTML_OUTPUT_FILTER, IMAGE_OUTPUT_FILTER): New
macros.
(replaceFd): Replaced with...
(set_redirection): New auxiliary function.
(waitForChild): Replaced with...
(save_and_redirect): New auxiliary function for.

(char_buffer::do_html, char_buffer::do_image): Simplified, using new
functions.

1 files changed, 633 insertions, 476 deletions

diff --git a/src/preproc/html/pre-html.cpp b/src/preproc/html/pre-html.cpp
index ee3c28e5..0fa925e5 100644
--- a/src/preproc/html/pre-html.cpp
+++ b/src/preproc/html/pre-html.cpp
@@ -39,36 +39,79 @@ Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
 #include <errno.h>
 #include <sys/types.h>
 #ifdef HAVE_UNISTD_H
-#include <unistd.h>
+# include <unistd.h>
 #endif
 
 #ifdef _POSIX_VERSION
-#include <sys/wait.h>
-#define PID_T pid_t
+# include <sys/wait.h>
+# define PID_T pid_t
 #else /* not _POSIX_VERSION */
-#define PID_T int
+# define PID_T int
 #endif /* not _POSIX_VERSION */
 
 #include <stdarg.h>
 
 #include "nonposix.h"
 
+/* Establish some definitions to facilitate discrimination between
+   differing runtime environments. */
+
+#undef __tmpfile
+#undef MAY_FORK_CHILD_PROCESS
+#undef MAY_SPAWN_ASYNCHRONOUS_CHILD
+
+#if defined(__MSDOS__) || defined(_WIN32)
+/* Most MS-DOS and Win32 environments will be missing the `fork' capability
+   (some like Cygwin have it, but it is best avoided). */
+# define MAY_FORK_CHILD_PROCESS 0
+
+/* On these systems, we use `spawn...', instead of `fork' ... `exec...'. */
+# include <process.h>	// for `spawn...'
+# include <fcntl.h>	// for attributes of pipes
+
+# if defined(__CYGWIN__) || defined(_UWIN) || defined(__MINGW32__)
+/* These Win32 implementations allow parent and `spawn...'ed child to
+   multitask asynchronously. */
+#  define MAY_SPAWN_ASYNCHRONOUS_CHILD 1
+# else
+/* Others may adopt MS-DOS behaviour where parent must sleep,
+   from `spawn...' until child terminates. */
+#  define MAY_SPAWN_ASYNCHRONOUS_CHILD 0
+# endif /* not defined __CYGWIN__, _UWIN, or __MINGW32__ */
+
+/* MS-DOS and Win32 will probably not have `/tmp' on all disk drives,
+   but we can normally expect to be able to use `c:/temp' for temporary
+   files. */
+# define __tmpfile "c:/temp/"
+
+#else /* not __MSDOS__ or _WIN32 */
+
+/* For non-Microsoft environments assume UNIX conventions,
+   so `fork' is required and child processes are asynchronous */
+# define MAY_FORK_CHILD_PROCESS 1
+# define MAY_SPAWN_ASYNCHRONOUS_CHILD 1
+
+/* We can also usually rely on being able to use `/tmp' for temporary
+   file storage. */
+# define __tmpfile "/tmp/"
+#endif /* not __MSDOS__ or _WIN32 */
+
 extern "C" const char *Version_string;
 
 #include "pre-html.h"
 #include "pushback.h"
 #include "html-strings.h"
 
-#define DEFAULT_LINE_LENGTH        7   // inches wide
-#define DEFAULT_IMAGE_RES        100   // number of pixels per inch resolution
-#define IMAGE_BOARDER_PIXELS       0
-#define INLINE_LEADER_CHAR      '\\'
+#define DEFAULT_LINE_LENGTH 7	// inches wide
+#define DEFAULT_IMAGE_RES 100	// number of pixels per inch resolution
+#define IMAGE_BOARDER_PIXELS 0
+#define INLINE_LEADER_CHAR '\\'
 
 // Don't use colour names here!  Otherwise there is a dependency on
 // a file called `rgb.txt' which maps names to colours.
-#define TRANSPARENT  "-background rgb:f/f/f -transparent rgb:f/f/f"
-#define MIN_ALPHA_BITS             0
-#define MAX_ALPHA_BITS             4
+#define TRANSPARENT "-background rgb:f/f/f -transparent rgb:f/f/f"
+#define MIN_ALPHA_BITS 0
+#define MAX_ALPHA_BITS 4
 
 #define PAGE_TEMPLATE_SHORT "pg"
 #define PAGE_TEMPLATE_LONG "-page-"
@@ -78,46 +121,55 @@ extern "C" const char *Version_string;
 #define REGION_TEMPLATE_LONG "-regions-"
 
 #if 0
-#   define  DEBUGGING
+# define DEBUGGING
 #endif
 
 #if !defined(TRUE)
-#   define TRUE (1==1)
+# define TRUE (1==1)
 #endif
 #if !defined(FALSE)
-#   define FALSE (1==0)
+# define FALSE (1==0)
 #endif
 
-typedef enum {CENTERED, LEFT, RIGHT, INLINE} IMAGE_ALIGNMENT;
-
-static int   postscriptRes    =-1;              // postscript resolution, dots per inch
-static int   stdoutfd         = 1;              // output file descriptor - normally 1 but might move
-                                                // -1 means closed
-static int   copyofstdoutfd   =-1;              // a copy of stdout, so we can restore stdout when
-                                                // writing to post-html
-static char *psFileName       = NULL;           // name of postscript file
-static char *psPageName       = NULL;           // name of file containing postscript current page
-static char *regionFileName   = NULL;           // name of file containing all image regions
-static char *imagePageName    = NULL;           // name of bitmap image containing current page
+typedef enum {
+  CENTERED, LEFT, RIGHT, INLINE
+} IMAGE_ALIGNMENT;
+
+static int postscriptRes = -1;		// postscript resolution,
+					// dots per inch
+static int stdoutfd = 1;		// output file descriptor -
+					// normally 1 but might move
+					// -1 means closed
+static char *psFileName = NULL;		// name of postscript file
+static char *psPageName = NULL;		// name of file containing
+					// postscript current page
+static char *regionFileName = NULL;	// name of file containing all
+					// image regions
+static char *imagePageName = NULL;	// name of bitmap image containing
+					// current page
 static const char *image_device = "pnmraw";
-static int   image_res        = DEFAULT_IMAGE_RES;
-static int   vertical_offset  = 0;
-static char *image_template   = NULL;           // image template filename
-static char *macroset_template= NULL;           // image template passed to troff by -D
-static int   troff_arg        = 0;              // troff arg index
-static char *image_dir        = NULL;           // user specified image directory
-static int   textAlphaBits    = MAX_ALPHA_BITS;
-static int   graphicAlphaBits = MAX_ALPHA_BITS;
-static char *antiAlias        = NULL;           // antialias arguments we pass to gs.
-static int   show_progress    = FALSE;          // should we display page numbers as they are processed?
-static int   currentPageNo    = -1;             // current image page number
+static int image_res = DEFAULT_IMAGE_RES;
+static int vertical_offset = 0;
+static char *image_template = NULL;	// image template filename
+static char *macroset_template= NULL;	// image template passed to troff
+					// by -D
+static int troff_arg = 0;		// troff arg index
+static char *image_dir = NULL;		// user specified image directory
+static int textAlphaBits = MAX_ALPHA_BITS;
+static int graphicAlphaBits = MAX_ALPHA_BITS;
+static char *antiAlias = NULL;		// antialias arguments we pass to gs
+static int show_progress = FALSE;	// should we display page numbers as
+					// they are processed?
+static int currentPageNo = -1;		// current image page number
 #if defined(DEBUGGING)
-static int   debug          = FALSE;
-static char *troffFileName  = NULL;             // output of pre-html output which is sent to troff -Tps
-static char *htmlFileName   = NULL;             // output of pre-html output which is sent to troff -Thtml
+static int debug = FALSE;
+static char *troffFileName = NULL;	// output of pre-html output which
+					// is sent to troff -Tps
+static char *htmlFileName = NULL;	// output of pre-html output which
+					// is sent to troff -Thtml
 #endif
 
-static char *linebuf = NULL;                    // for scanning devps/DESC
+static char *linebuf = NULL;		// for scanning devps/DESC
 static int linebufsize = 0;
 
 const char *const FONT_ENV_VAR = "GROFF_FONT_PATH";
@@ -125,31 +177,30 @@ static search_path font_path(FONT_ENV_VAR, FONTPATH, 0, 0);
 
 
 /*
- *  Images are generated via postscript, gs and the pnm utilities.
+ *  Images are generated via postscript, gs, and the pnm utilities.
  */
+#define IMAGE_DEVICE "-Tps"
 
-#define IMAGE_DEVICE    "-Tps"
 
-/*
- *  prototypes
- */
 static int do_file(const char *filename);
 
+
 /*
- *  sys_fatal - writes a fatal error message.
- *  Taken from src/roff/groff/pipeline.c.
+ *  sys_fatal - Write a fatal error message.
+ *              Taken from src/roff/groff/pipeline.c.
  */
 
-void sys_fatal (const char *s)
+void sys_fatal(const char *s)
 {
   fatal("%1: %2", s, strerror(errno));
 }
 
 /*
- *  get_line - copies a line (w/o newline) from a file to the global line buffer
+ *  get_line - Copy a line (w/o newline) from a file to the
+ *             global line buffer.
  */
 
-int get_line (FILE *f)
+int get_line(FILE *f)
 {
   if (f == 0)
     return 0;
@@ -190,10 +241,10 @@ int get_line (FILE *f)
 }
 
 /*
- *  get_resolution - returns the postscript resolution from devps/DESC
+ *  get_resolution - Return the postscript resolution from devps/DESC.
  */
 
-static unsigned int get_resolution (void)
+static unsigned int get_resolution(void)
 {
   char *pathp;
   FILE *f;
@@ -214,7 +265,7 @@ static unsigned int get_resolution (void)
 }
 
 /*
- *  html_system - a wrapper for system()
+ *  html_system - A wrapper for system().
  */
 
 void html_system(const char *s, int redirect_stdout)
@@ -244,29 +295,28 @@ void html_system(const char *s, int redirect_stdout)
 }
 
 /*
- *  make_message - taken from man printf(3), creates a string via malloc
- *                 and places the result of the va args into string.
- *                 Finally the new string is returned.
+ *  make_message - Create a string via malloc and place the result of the
+ *                 va args into string.  Finally the new string is returned.
+ *                 Taken from man page of printf(3).
  */
 
-char *
-make_message (const char *fmt, ...)
+char *make_message(const char *fmt, ...)
 {
   /* Guess we need no more than 100 bytes. */
   int n, size = 100;
   char *p;
   char *np;
   va_list ap;
-  if ((p = (char *)malloc (size)) == NULL)
+  if ((p = (char *)malloc(size)) == NULL)
     return NULL;
   while (1) {
     /* Try to print in the allocated space. */
     va_start(ap, fmt);
-    n = vsnprintf (p, size, fmt, ap);
+    n = vsnprintf(p, size, fmt, ap);
     va_end(ap);
     /* If that worked, return the string. */
     if (n > -1 && n < size) {
-      if (size > n+1) {
+      if (size > n + 1) {
 	np = strsave(p);
 	free(p);
 	return np;
@@ -274,15 +324,15 @@ make_message (const char *fmt, ...)
       return p;
     }
     /* Else try again with more space. */
-    if (n > -1)    /* glibc 2.1 */
-      size = n+1; /* precisely what is needed */
-    else           /* glibc 2.0 */
-      size *= 2;  /* twice the old size */
-    if ((np = (char *)realloc (p, size)) == NULL) {
-      free(p);  /* realloc failed, free old, p. */
+    if (n > -1)		/* glibc 2.1 */
+      size = n + 1;	/* precisely what is needed */
+    else		/* glibc 2.0 */
+      size *= 2;	/* twice the old size */
+    if ((np = (char *)realloc(p, size)) == NULL) {
+      free(p);		/* realloc failed, free old, p. */
       return NULL;
     }
-    p = np;  /* use realloc'ed, p */
+    p = np;		/* use realloc'ed, p */
   }
 }
 
@@ -292,15 +342,15 @@ make_message (const char *fmt, ...)
 
 struct char_block {
   enum { SIZE = 256 };
-  char          buffer[SIZE];
-  int           used;
-  char_block   *next;
+  char buffer[SIZE];
+  int used;
+  char_block *next;
 
   char_block();
 };
 
 /*
- *  char_block - constructor, sets the, used, and, next, fields to zero.
+ *  char_block - Constructor.  Set the, used, and, next, fields to zero.
  */
 
 char_block::char_block()
@@ -314,22 +364,22 @@ class char_buffer {
 public:
   char_buffer();
   ~char_buffer();
-  int  read_file(FILE *fp);
-  int  do_html(int argc, char *argv[]);
-  int  do_image(int argc, char *argv[]);
-  void write_file_html(void);
-  void write_file_troff(void);
-  void write_upto_newline (char_block **t, int *i, int is_html);
-  int  can_see(char_block **t, int *i, const char *string);
-  int  skip_spaces(char_block **t, int *i);
+  int read_file(FILE *fp);
+  int do_html(int argc, char *argv[]);
+  int do_image(int argc, char *argv[]);
+  void emit_troff_output(int device_format_selector);
+  void write_upto_newline(char_block **t, int *i, int is_html);
+  int can_see(char_block **t, int *i, const char *string);
+  int skip_spaces(char_block **t, int *i);
   void skip_until_newline(char_block **t, int *i);
 private:
   char_block *head;
   char_block *tail;
+  int run_output_filter(int device_format_selector, int argc, char *argv[]);
 };
 
 /*
- *  char_buffer - constructor
+ *  char_buffer - Constructor.
  */
 
 char_buffer::char_buffer()
@@ -338,7 +388,7 @@ char_buffer::char_buffer()
 }
 
 /*
- *  char_buffer - deconstructor, throws aways the whole buffer list.
+ *  char_buffer - Destructor.  Throw away the whole buffer list.
  */
 
 char_buffer::~char_buffer()
@@ -351,70 +401,69 @@ char_buffer::~char_buffer()
 }
 
 /*
- *  read_file - read in a complete file, fp, placing the contents inside char_blocks.
+ *  read_file - Read in a complete file, fp, placing the contents inside
+ *              char_blocks.
  */
 
-int char_buffer::read_file (FILE *fp)
+int char_buffer::read_file(FILE *fp)
 {
   int n;
-
-  while (! feof(fp)) {
+  while (!feof(fp)) {
     if (tail == NULL) {
       tail = new char_block;
       head = tail;
-    } else {
+    }
+    else {
       if (tail->used == char_block::SIZE) {
 	tail->next = new char_block;
-	tail       = tail->next;
+	tail = tail->next;
       }
     }
-    // at this point we have a tail which is ready for the next SIZE bytes of the file
-
+    // at this point we have a tail which is ready for the next SIZE
+    // bytes of the file
     n = fread(tail->buffer, sizeof(char), char_block::SIZE-tail->used, fp);
-    if (n <= 0) {
+    if (n <= 0)
       // error
-      return( 0 );
-    } else {
-      tail->used += n*sizeof(char);
-    }
+      return 0;
+    else
+      tail->used += n * sizeof(char);
   }
-  return( 1 );
+  return 1;
 }
 
 /*
- *  writeNbytes - writes n bytes to stdout.
+ *  writeNbytes - Write n bytes to stdout.
  */
 
-static void writeNbytes (const char *s, int l)
+static void writeNbytes(const char *s, int l)
 {
-  int n=0;
+  int n = 0;
   int r;
 
-  while (n<l) {
-    r = write(stdoutfd, s, l-n);
-    if (r<0) {
+  while (n < l) {
+    r = write(stdoutfd, s, l - n);
+    if (r < 0)
       sys_fatal("write");
-    }
     n += r;
     s += r;
   }
 }
 
 /*
- *  writeString - writes a string to stdout.
+ *  writeString - Write a string to stdout.
  */
 
-static void writeString (const char *s)
+static void writeString(const char *s)
 {
   writeNbytes(s, strlen(s));
 }
 
 /*
- *  makeFileName - creates the image filename template
+ *  makeFileName - Create the image filename template
  *                 and the macroset image template.
  */
 
-static void makeFileName (void)
+static void makeFileName(void)
 {
   if ((image_dir != NULL) && (strchr(image_dir, '%') != NULL)) {
     error("cannot use a `%%' within the image directory name");
@@ -426,23 +475,26 @@ static void makeFileName (void)
     exit(1);
   }
 
-  if (image_dir == NULL) {
+  if (image_dir == NULL)
     image_dir = "";
-  } else if ((strlen(image_dir)>0) && (image_dir[strlen(image_dir)-1] != '/')) {
+  else if (strlen(image_dir) > 0
+	   && image_dir[strlen(image_dir) - 1] != '/') {
     image_dir = make_message("%s/", image_dir);
     if (image_dir == NULL)
       sys_fatal("make_message");
   }
-  
+
   if (image_template == NULL)
-    macroset_template = make_message("%sgrohtml-%d", image_dir, (int)getpid());
+    macroset_template = make_message("%sgrohtml-%d", image_dir,
+				     (int)getpid());
   else
     macroset_template = make_message("%s%s", image_dir, image_template);
 
   if (macroset_template == NULL)
     sys_fatal("make_message");
 
-  image_template = (char *)malloc(strlen("-%d")+strlen(macroset_template)+1);
+  image_template =
+    (char *)malloc(strlen("-%d") + strlen(macroset_template) + 1);
   if (image_template == NULL)
     sys_fatal("malloc");
   strcpy(image_template, macroset_template);
@@ -450,10 +502,10 @@ static void makeFileName (void)
 }
 
 /*
- *  setupAntiAlias - sets up the antialias string, used when we call gs.
+ *  setupAntiAlias - Set up the antialias string, used when we call gs.
  */
 
-static void setupAntiAlias (void)
+static void setupAntiAlias(void)
 {
   if (textAlphaBits == 0 && graphicAlphaBits == 0)
     antiAlias = make_message(" ");
@@ -467,23 +519,24 @@ static void setupAntiAlias (void)
 }
 
 /*
- *  checkImageDir - checks to see whether the image directory is available.
+ *  checkImageDir - Check whether the image directory is available.
  */
 
-static void checkImageDir (void)
+static void checkImageDir(void)
 {
-  if ((image_dir != NULL) && (strcmp(image_dir, "") != 0))
-    if (! ((mkdir(image_dir, 0777) == 0) || (errno == EEXIST))) {
+  if (image_dir != NULL && strcmp(image_dir, "") != 0)
+    if (!(mkdir(image_dir, 0777) == 0 || errno == EEXIST)) {
       error("cannot create directory `%1'", image_dir);
       exit(1);
     }
 }
 
 /*
- *  write_end_image - ends the image. It writes out the image extents if we are using -Tps.
+ *  write_end_image - End the image.  Write out the image extents if we
+ *                    are using -Tps.
  */
 
-static void write_end_image (int is_html)
+static void write_end_image(int is_html)
 {
   /*
    *  if we are producing html then these
@@ -501,18 +554,17 @@ static void write_end_image (int is_html)
 }
 
 /*
- *  write_start_image - writes the troff which will:
+ *  write_start_image - Write troff code which will:
  *
  *                      (i)  disable html output for the following image
  *                      (ii) reset the max/min x/y registers during postscript
  *                           rendering.
  */
 
-static void write_start_image (IMAGE_ALIGNMENT pos, int is_html)
+static void write_start_image(IMAGE_ALIGNMENT pos, int is_html)
 {
   writeString("\\O[5");
   switch (pos) {
-
   case INLINE:
     writeString("i");
     break;
@@ -527,7 +579,8 @@ static void write_start_image (IMAGE_ALIGNMENT pos, int is_html)
     writeString("c");
     break;
   }
-  writeString(image_template); writeString(".png]");
+  writeString(image_template);
+  writeString(".png]");
   if (is_html)
     writeString("\\O[0]\\O[3]");
   else
@@ -536,24 +589,25 @@ static void write_start_image (IMAGE_ALIGNMENT pos, int is_html)
 }
 
 /*
- *  write_upto_newline - writes the contents of the buffer until a newline is seen.
- *                       It checks for HTML_IMAGE_INLINE_BEGIN and HTML_IMAGE_INLINE_END
- *                       and if they are present it processes them.
+ *  write_upto_newline - Write the contents of the buffer until a newline
+ *                       is seen.  Check for HTML_IMAGE_INLINE_BEGIN and
+ *                       HTML_IMAGE_INLINE_END; process them if they are
+ *                       present.
  */
 
-void char_buffer::write_upto_newline (char_block **t, int *i, int is_html)
+void char_buffer::write_upto_newline(char_block **t, int *i, int is_html)
 {
-  int j=*i;
+  int j = *i;
 
   if (*t) {
-    while ((j < (*t)->used) && ((*t)->buffer[j] != '\n') &&
-	   ((*t)->buffer[j] != INLINE_LEADER_CHAR)) {
+    while (j < (*t)->used
+	   && (*t)->buffer[j] != '\n'
+	   && (*t)->buffer[j] != INLINE_LEADER_CHAR)
       j++;
-    }
-    if ((j < (*t)->used) && ((*t)->buffer[j] == '\n')) {
+    if (j < (*t)->used
+	&& (*t)->buffer[j] == '\n')
       j++;
-    }
-    writeNbytes((*t)->buffer+(*i), j-(*i));
+    writeNbytes((*t)->buffer + (*i), j - (*i));
     if ((*t)->buffer[j] == INLINE_LEADER_CHAR) {
       if (can_see(t, &j, HTML_IMAGE_INLINE_BEGIN))
 	write_start_image(INLINE, is_html);
@@ -563,208 +617,222 @@ void char_buffer::write_upto_newline (char_block **t, int *i, int is_html)
 	if (j < (*t)->used) {
 	  *i = j;
 	  j++;
-	  writeNbytes((*t)->buffer+(*i), j-(*i));
+	  writeNbytes((*t)->buffer + (*i), j - (*i));
 	}
       }
     }
     if (j == (*t)->used) {
       *i = 0;
-      if ((*t)->buffer[j-1] == '\n') {
-	*t = (*t)->next;
-      } else {
-	*t = (*t)->next;
+      *t = (*t)->next;
+      if (*t && (*t)->buffer[j - 1] != '\n')
 	write_upto_newline(t, i, is_html);
-      }
-    } else {
+    }
+    else
       // newline was seen
       *i = j;
-    }
   }
 }
 
 /*
- *  can_see - returns TRUE if we can see string in t->buffer[i] onwards
+ *  can_see - Return TRUE if we can see string in t->buffer[i] onwards.
  */
 
-int char_buffer::can_see (char_block **t, int *i, const char *string)
+int char_buffer::can_see(char_block **t, int *i, const char *string)
 {
-  int j         = 0;
-  int l         = strlen(string);
-  int k         = *i;
+  int j = 0;
+  int l = strlen(string);
+  int k = *i;
   char_block *s = *t;
 
   while (s) {
-    while ((k<s->used) && (j<l) && (s->buffer[k] == string[j])) {
+    while (k < s->used && j < l && s->buffer[k] == string[j]) {
       j++;
       k++;
     }
     if (j == l) {
       *i = k;
       *t = s;
-      return( TRUE );
-    } else if ((k<s->used) && (s->buffer[k] != string[j])) {
-      return( FALSE );
+      return TRUE;
     }
+    else if (k < s->used && s->buffer[k] != string[j])
+      return( FALSE );
     s = s->next;
     k = 0;
   }
-  return( FALSE );
+  return FALSE;
 }
 
 /*
- *  skip_spaces - returns TRUE if we have not run out of data.
- *                It also consumes spaces.
+ *  skip_spaces - Return TRUE if we have not run out of data.
+ *                Consume spaces also.
  */
 
 int char_buffer::skip_spaces(char_block **t, int *i)
 {
   char_block *s = *t;
-  int k         = *i;
+  int k = *i;
 
   while (s) {
-    while ((k<s->used) && (isspace(s->buffer[k]))) {
+    while (k < s->used && isspace(s->buffer[k]))
       k++;
-    }
     if (k == s->used) {
       k = 0;
       s = s->next;
-    } else {
+    }
+    else {
       *i = k;
-      return( TRUE );
+      return TRUE;
     }
   }
-  return( FALSE );
+  return FALSE;
 }
 
 /*
- *  skip_until_newline - skips all characters until a newline is seen.
+ *  skip_until_newline - Skip all characters until a newline is seen.
  *                       The newline is not consumed.
  */
 
-void char_buffer::skip_until_newline (char_block **t, int *i)
+void char_buffer::skip_until_newline(char_block **t, int *i)
 {
-  int j=*i;
+  int j = *i;
 
   if (*t) {
-    while ((j < (*t)->used) && ((*t)->buffer[j] != '\n')) {
+    while (j < (*t)->used && (*t)->buffer[j] != '\n')
       j++;
-    }
     if (j == (*t)->used) {
       *i = 0;
       *t = (*t)->next;
       skip_until_newline(t, i);
-    } else {
+    }
+    else
       // newline was seen
       *i = j;
-    }
   }
 }
 
+#define DEVICE_FORMAT(filter) (filter == HTML_OUTPUT_FILTER)
+#define HTML_OUTPUT_FILTER 0
+#define IMAGE_OUTPUT_FILTER 1
+
 /*
- *  write_file_troff - writes the buffer to stdout (troff).
+ *  emit_troff_output - Write formatted buffer content to the troff
+ *                      post-processor data pipeline.
  */
 
-void char_buffer::write_file_troff (void)
+void char_buffer::emit_troff_output(int device_format_selector)
 {
-  char_block *t=head;
-  int         i=0;
+  // Handle output for BOTH html and image device formats
+  // if `device_format_selector' is passed as
+  //
+  //   HTML_FORMAT(HTML_OUTPUT_FILTER)
+  //     Buffer data is written to the output stream
+  //     with template image names translated to actual image names.
+  //
+  //   HTML_FORMAT(IMAGE_OUTPUT_FILTER)
+  //     Buffer data is written to the output stream
+  //     with no translation, for image file creation in the post-processor.
+
+  int index = 0;
+  char_block *element = head;
+
+  while (element != NULL)
+    write_upto_newline(&element, &index, device_format_selector);
 
-  if (t != NULL) {
-    do {
-      write_upto_newline(&t, &i, FALSE);
-    } while (t != NULL);
-  }
+#if 0
   if (close(stdoutfd) < 0)
-    sys_fatal("close");
+    sys_fatal ("close");
 
   // now we grab fd=1 so that the next pipe cannot use fd=1
   if (stdoutfd == 1) {
-    if (dup(2) != stdoutfd) {
-      sys_fatal("dup failed to use fd=1");
-    }
+    if (dup(2) != stdoutfd)
+      sys_fatal ("dup failed to use fd=1");
   }
+#endif /* 0 */
 }
 
 /*
- *  the image class remembers the position of all images in the postscript file
- *  and assigns names for each image.
+ *  The image class remembers the position of all images in the
+ *  postscript file and assigns names for each image.
  */
 
 struct imageItem {
-  imageItem  *next;
-  int         X1;
-  int         Y1;
-  int         X2;
-  int         Y2;
-  char       *imageName;
-  int         resolution;
-  int         maxx;
-  int         pageNo;
-
-  imageItem (int x1, int y1, int x2, int y2, int page, int res, int max_width, char *name);
-  ~imageItem ();
+  imageItem *next;
+  int X1;
+  int Y1;
+  int X2;
+  int Y2;
+  char *imageName;
+  int resolution;
+  int maxx;
+  int pageNo;
+
+  imageItem(int x1, int y1, int x2, int y2,
+	    int page, int res, int max_width, char *name);
+  ~imageItem();
 };
 
 /*
- *  imageItem - constructor
+ *  imageItem - Constructor.
  */
 
-imageItem::imageItem (int x1, int y1, int x2, int y2, int page, int res, int max_width, char *name)
+imageItem::imageItem(int x1, int y1, int x2, int y2,
+		     int page, int res, int max_width, char *name)
 {
-  X1         = x1;
-  Y1         = y1;
-  X2         = x2;
-  Y2         = y2;
-  pageNo     = page;
+  X1 = x1;
+  Y1 = y1;
+  X2 = x2;
+  Y2 = y2;
+  pageNo = page;
   resolution = res;
-  maxx       = max_width;
-  imageName  = name;
-  next       = NULL;
+  maxx = max_width;
+  imageName = name;
+  next = NULL;
 }
 
 /*
- *  imageItem - deconstructor
+ *  imageItem - Destructor.
  */
 
-imageItem::~imageItem ()
+imageItem::~imageItem()
 {
   if (imageName)
     free(imageName);
 }
 
 /*
- *  imageList - class containing a list of imageItems.
+ *  imageList - A class containing a list of imageItems.
  */
 
 class imageList {
 private:
   imageItem *head;
   imageItem *tail;
-  int        count;
+  int count;
 public:
   imageList();
   ~imageList();
-  void  add(int x1, int y1, int x2, int y2, int page, int res, int maxx, char *name);
-  void  createImages (void);
-  int   createPage (int pageno);
-  void  createImage (imageItem *i);
-  int   getMaxX (int pageno);
+  void add(int x1, int y1, int x2, int y2,
+	   int page, int res, int maxx, char *name);
+  void createImages(void);
+  int createPage(int pageno);
+  void createImage(imageItem *i);
+  int getMaxX(int pageno);
 };
 
 /*
- *  imageList - constructor.
+ *  imageList - Constructor.
  */
 
-imageList::imageList ()
-  : head(0), tail(0), count(0)
+imageList::imageList()
+: head(0), tail(0), count(0)
 {
 }
 
 /*
- *  imageList - deconstructor.
+ *  imageList - Destructor.
  */
 
-imageList::~imageList ()
+imageList::~imageList()
 {
   while (head != NULL) {
     imageItem *i = head;
@@ -774,10 +842,10 @@ imageList::~imageList ()
 }
 
 /*
- *  createPage - creates one image of, page pageno, from the postscript file.
+ *  createPage - Create one image of, page pageno, from the postscript file.
  */
 
-int imageList::createPage (int pageno)
+int imageList::createPage(int pageno)
 {
   char *s;
 
@@ -786,8 +854,9 @@ int imageList::createPage (int pageno)
 
   if (currentPageNo >= 1) {
     /*
-     *  we need to unlink the files which change each time a new page is processed.
-     *  The final unlink is done by xtmpfile when pre-grohtml exits.
+     *  We need to unlink the files which change each time a new page is
+     *  processed.  The final unlink is done by xtmpfile when pre-grohtml
+     *  exits.
      */
     unlink(imagePageName);
     unlink(psPageName);
@@ -815,7 +884,7 @@ int imageList::createPage (int pageno)
   }
 #endif
   html_system(s, 1);
-  
+
   s = make_message("echo showpage | "
 		   "gs%s -q -dBATCH -dSAFER "
 		   "-dDEVICEHEIGHTPOINTS=792 "
@@ -844,39 +913,38 @@ int imageList::createPage (int pageno)
 }
 
 /*
- *  min - returns the minimum of two numbers.
+ *  min - Return the minimum of two numbers.
  */
 
-int min (int x, int y)
+int min(int x, int y)
 {
-  if (x < y) {
-    return( x );
-  } else {
-    return( y );
-  }
+  if (x < y)
+    return x;
+  else
+    return y;
 }
 
 /*
- *  max - returns the maximum of two numbers.
+ *  max - Return the maximum of two numbers.
  */
 
-int max (int x, int y)
+int max(int x, int y)
 {
-  if (x > y) {
-    return( x );
-  } else {
-    return( y );
-  }
+  if (x > y)
+    return x;
+  else
+    return y;
 }
 
 /*
- *  getMaxX - returns the largest right hand position for any image on, pageno
+ *  getMaxX - Return the largest right-hand position for any image
+ *            on, pageno.
  */
 
-int imageList::getMaxX (int pageno)
+int imageList::getMaxX(int pageno)
 {
   imageItem *h = head;
-  int x        = postscriptRes * DEFAULT_LINE_LENGTH;
+  int x = postscriptRes * DEFAULT_LINE_LENGTH;
 
   while (h != NULL) {
     if (h->pageNo == pageno)
@@ -887,21 +955,30 @@ int imageList::getMaxX (int pageno)
 }
 
 /*
- *  createImage - generates a minimal png file from the set of page images.
+ *  createImage - Generate a minimal png file from the set of page images.
  */
 
-void imageList::createImage (imageItem *i)
+void imageList::createImage(imageItem *i)
 {
   if (i->X1 != -1) {
     char *s;
-    int  x1 = max(min(i->X1, i->X2)*image_res/postscriptRes-1*IMAGE_BOARDER_PIXELS, 0);
-    int  y1 = max((image_res*vertical_offset/72)+min(i->Y1, i->Y2)*image_res/postscriptRes-IMAGE_BOARDER_PIXELS, 0);
-    int  x2 = max(i->X1, i->X2)*image_res/postscriptRes+1*IMAGE_BOARDER_PIXELS;
-    int  y2 = (image_res*vertical_offset/72)+(max(i->Y1, i->Y2)*image_res/postscriptRes)+1+IMAGE_BOARDER_PIXELS;
+    int x1 = max(min(i->X1, i->X2) * image_res / postscriptRes
+		   - IMAGE_BOARDER_PIXELS,
+		 0);
+    int y1 = max(image_res * vertical_offset / 72
+		   + min(i->Y1, i->Y2) * image_res / postscriptRes
+		   - IMAGE_BOARDER_PIXELS,
+		 0);
+    int x2 = max(i->X1, i->X2) * image_res / postscriptRes
+	     + IMAGE_BOARDER_PIXELS;
+    int y2 = image_res * vertical_offset / 72
+	     + max(i->Y1, i->Y2) * image_res / postscriptRes
+	     + 1 + IMAGE_BOARDER_PIXELS;
     if (createPage(i->pageNo) == 0) {
-      s = make_message("pnmcut%s %d %d %d %d < %s | pnmcrop -quiet | pnmtopng%s %s > %s \n",
+      s = make_message("pnmcut%s %d %d %d %d < %s "
+		       "| pnmcrop -quiet | pnmtopng%s %s > %s\n",
 		       EXE_EXT,
-		       x1, y1, x2-x1+1, y2-y1+1,
+		       x1, y1, x2 - x1 + 1, y2 - y1 + 1,
 		       imagePageName,
 		       EXE_EXT,
 		       TRANSPARENT,
@@ -917,12 +994,14 @@ void imageList::createImage (imageItem *i)
 #endif
       html_system(s, 0);
       free(s);
-    } else {
+    }
+    else {
       fprintf(stderr, "failed to generate image of page %d\n", i->pageNo);
       fflush(stderr);
     }
 #if defined(DEBUGGING)
-  } else {
+  }
+  else {
     if (debug) {
       fprintf(stderr, "ignoring image as x1 coord is -1\n");
       fflush(stderr);
@@ -932,27 +1011,30 @@ void imageList::createImage (imageItem *i)
 }
 
 /*
- *  add - an image description to the imageList.
+ *  add - Add an image description to the imageList.
  */
 
-void imageList::add (int x1, int y1, int x2, int y2, int page, int res, int maxx, char *name)
+void imageList::add(int x1, int y1, int x2, int y2,
+		    int page, int res, int maxx, char *name)
 {
   imageItem *i = new imageItem(x1, y1, x2, y2, page, res, maxx, name);
 
   if (head == NULL) {
     head = i;
     tail = i;
-  } else {
+  }
+  else {
     tail->next = i;
     tail = i;
   }
 }
 
 /*
- *  createImages - foreach image descriptor on the imageList, create the actual image.
+ *  createImages - For each image descriptor on the imageList,
+ *                 create the actual image.
  */
 
-void imageList::createImages (void)
+void imageList::createImages(void)
 {
   imageItem *h = head;
 
@@ -962,72 +1044,42 @@ void imageList::createImages (void)
   }
 }
 
-static imageList listOfImages;  // list of images defined by the region file.
-
-/*
- *  write_file_html - writes the buffer to stdout (troff).
- *                    It writes out the file replacing template image names with
- *                    actual image names.
- */
-
-void char_buffer::write_file_html (void)
-{
-  char_block *t=head;
-  int         i=0;
-
-  if (t != NULL) {
-    do {
-      write_upto_newline(&t, &i, TRUE);
-    } while (t != NULL);
-  }
-  if (close(stdoutfd) < 0)
-    sys_fatal("close");
-
-  // now we grab fd=1 so that the next pipe cannot use fd=1
-  if (stdoutfd == 1) {
-    if (dup(2) != stdoutfd) {
-      sys_fatal("dup failed to use fd=1");
-    }
-  }
-}
+static imageList listOfImages;	// List of images defined by the region file.
 
 /*
- *  generateImages - parses the region file and generates images
- *                   from the postscript file. The region file
- *                   contains the x1,y1  x2,y2 extents of each
+ *  generateImages - Parse the region file and generate images
+ *                   from the postscript file.  The region file
+ *                   contains the x1,y1--x2,y2 extents of each
  *                   image.
  */
 
-static void generateImages (char *regionFileName)
+static void generateImages(char *regionFileName)
 {
   pushBackBuffer *f=new pushBackBuffer(regionFileName);
 
   while (f->putPB(f->getPB()) != eof) {
     if (f->isString("grohtml-info:page")) {
-      int page   = f->readInt();
-      int x1     = f->readInt();
-      int y1     = f->readInt();
-      int x2     = f->readInt();
-      int y2     = f->readInt();
-      int maxx   = f->readInt();
+      int page = f->readInt();
+      int x1 = f->readInt();
+      int y1 = f->readInt();
+      int x2 = f->readInt();
+      int y2 = f->readInt();
+      int maxx = f->readInt();
       char *name = f->readString();
-      int res    = postscriptRes;
+      int res = postscriptRes;
       listOfImages.add(x1, y1, x2, y2, page, res, maxx, name);
-      while ((f->putPB(f->getPB()) != '\n') &&
-	     (f->putPB(f->getPB()) != eof)) {
+      while (f->putPB(f->getPB()) != '\n'
+	     && f->putPB(f->getPB()) != eof)
 	(void)f->getPB();
-      }
-      if (f->putPB(f->getPB()) == '\n') {
+      if (f->putPB(f->getPB()) == '\n')
 	(void)f->getPB();
-      }
-    } else {
-      /*
-       *  write any error messages out to the user
-       */
+    }
+    else {
+      /* Write any error messages out to the user. */
       fputc(f->getPB(), stderr);
     }
   }
-  
+
   listOfImages.createImages();
   if (show_progress) {
     fprintf(stderr, "done\n");
@@ -1037,84 +1089,97 @@ static void generateImages (char *regionFileName)
 }
 
 /*
- *  replaceFd - replace a file descriptor, was, with, willbe.
+ *  set_redirection - Set up I/O Redirection for handle, was, to refer to
+ *                    stream on handle, willbe.
  */
 
-static void replaceFd (int was, int willbe)
+static void set_redirection(int was, int willbe)
 {
-  int dupres;
-
+  // Nothing to do if `was' and `willbe' already have same handle.
   if (was != willbe) {
-    if (close(was)<0) {
-      sys_fatal("close");
-    }
-    dupres = dup(willbe);
-    if (dupres != was) {
-      sys_fatal("dup");
-      fprintf(stderr, "trying to replace fd=%d with %d dup used %d\n", was, willbe, dupres);
-      if (willbe == 1) {
-	fprintf(stderr, "likely that stdout should be opened before %d\n", was);
-      }
-      exit(1);
+    // Otherwise attempt the specified redirection.
+    if (dup2 (willbe, was) < 0) {
+      // Redirection failed, so issue diagnostic and bail out.
+      fprintf(stderr, "failed to replace fd=%d with %d\n", was, willbe);
+      if (willbe == STDOUT_FILENO)
+	fprintf(stderr,
+		"likely that stdout should be opened before %d\n", was);
+      sys_fatal("dup2");
     }
-    if (close(willbe) < 0) {
+
+    // When redirection has been successfully completed assume redundant
+    // handle `willbe' is no longer required, so close it.
+    if (close(willbe) < 0)
+      // Issue diagnostic if `close' fails.
       sys_fatal("close");
-    }
   }
 }
 
 /*
- *  waitForChild - waits for child, pid, to exit.
+ *  save_and_redirect - Get duplicate handle for stream, was, then
+ *                      redirect, was, to refer to, willbe.
  */
 
-static void waitForChild (PID_T pid)
+static int save_and_redirect(int was, int willbe)
 {
-  PID_T waitpd;
-  int   status;
+  if (was == willbe)
+    // No redirection specified so don't do anything but silently bailing out.
+    return (was);
+
+  // Proceeding with redirection so first save and verify our duplicate
+  // handle for `was'.
+  int saved = dup(was);
+  if (saved < 0) {
+    fprintf(stderr, "unable to get duplicate handle for %d\n", was);
+    sys_fatal("dup");
+  }
 
-  waitpd = WAIT(&status, pid, _WAIT_CHILD);
-  if (waitpd != pid)
-    sys_fatal("wait");
+  // Duplicate handle safely established so complete redirection.
+  set_redirection(was, willbe);
+
+  // Finally return the saved duplicate descriptor for the
+  // original `was' stream.
+  return saved;
 }
 
 /*
- *  alterDeviceTo - if toImage is set then the arg list is altered to include
+ *  alterDeviceTo - If, toImage, is set
+ *                     the argument list is altered to include
  *                     IMAGE_DEVICE and we invoke groff rather than troff.
- *                  else 
- *                     set -Thtml and groff
+ *                  Else
+ *                     set -Thtml and groff.
  */
 
-static void alterDeviceTo (int argc, char *argv[], int toImage)
+static void alterDeviceTo(int argc, char *argv[], int toImage)
 {
-  int i=0;
+  int i = 0;
 
   if (toImage) {
     while (i < argc) {
-      if (strcmp(argv[i], "-Thtml") == 0) {
+      if (strcmp(argv[i], "-Thtml") == 0)
 	argv[i] = IMAGE_DEVICE;
-      }
       i++;
     }
-    argv[troff_arg] = "groff";  /* rather than troff */
-  } else {
+    argv[troff_arg] = "groff";	/* rather than troff */
+  }
+  else {
     while (i < argc) {
-      if (strcmp(argv[i], IMAGE_DEVICE) == 0) {
+      if (strcmp(argv[i], IMAGE_DEVICE) == 0)
 	argv[i] = "-Thtml";
-      }
       i++;
     }
-    argv[troff_arg] = "groff";   /* use groff -Z */
+    argv[troff_arg] = "groff";	/* use groff -Z */
   }
 }
 
 /*
- *  addZ - appends -Z onto the command list for groff.
+ *  addZ - Append -Z onto the command list for groff.
  */
 
-char **addZ (int argc, char *argv[])
+char **addZ(int argc, char *argv[])
 {
-  char **new_argv = (char **)malloc((argc+2)*sizeof(char *));
-  int    i=0;
+  char **new_argv = (char **)malloc((argc + 2) * sizeof(char *));
+  int i = 0;
 
   if (new_argv == NULL)
     sys_fatal("malloc");
@@ -1124,8 +1189,8 @@ char **addZ (int argc, char *argv[])
     i++;
   }
   new_argv[i] = "-Z";
-  while (i<argc) {
-    new_argv[i+1] = argv[i];
+  while (i < argc) {
+    new_argv[i + 1] = argv[i];
     i++;
   }
   argc++;
@@ -1134,18 +1199,19 @@ char **addZ (int argc, char *argv[])
 }
 
 /*
- *  addRegDef - appends a defined register or string onto the command list for troff.
+ *  addRegDef - Append a defined register or string onto the command
+ *              list for troff.
  */
 
-char **addRegDef (int argc, char *argv[], const char *numReg)
+char **addRegDef(int argc, char *argv[], const char *numReg)
 {
-  char **new_argv = (char **)malloc((argc+2)*sizeof(char *));
-  int    i=0;
+  char **new_argv = (char **)malloc((argc + 2) * sizeof(char *));
+  int i = 0;
 
   if (new_argv == NULL)
     sys_fatal("malloc");
 
-  while (i<argc) {
+  while (i < argc) {
     new_argv[i] = argv[i];
     i++;
   }
@@ -1156,94 +1222,192 @@ char **addRegDef (int argc, char *argv[], const char *numReg)
 }
 
 /*
- *  dump_args - display the argument list.
+ *  dump_args - Display the argument list.
  */
 
-void dump_args (int argc, char *argv[])
+void dump_args(int argc, char *argv[])
 {
   fprintf(stderr, "  %d arguments:", argc);
-  for (int i=0; i<argc; i++)
+  for (int i = 0; i < argc; i++)
     fprintf(stderr, " %s", argv[i]);
   fprintf(stderr, "\n");
 }
 
+int char_buffer::run_output_filter(int filter, int argc, char **argv)
+{
+  int pipedes[2];
+  PID_T child_pid;
+  int status;
+
+  if (pipe(pipedes) < 0)
+    sys_fatal("pipe");
+
+#if MAY_FORK_CHILD_PROCESS
+  // This is the UNIX process model.  To invoke our post-processor,
+  // we must `fork' the current process.
+
+  if ((child_pid = fork()) < 0)
+    sys_fatal("fork");
+
+  else if (child_pid == 0) {
+    // This is the child process fork.  We redirect its `stdin' stream
+    // to read data emerging from our pipe.  There is no point in saving,
+    // since we won't be able to restore later!
+
+    set_redirection(STDIN_FILENO, pipedes[0]);
+
+    // The parent process will be writing this data so we should release
+    // the child's writeable handle on the pipe.
+
+    if (close(pipedes[1]) < 0)
+      sys_fatal("close");
+
+    // The IMAGE_OUTPUT_FILTER needs special output redirection...
+
+    if (filter == IMAGE_OUTPUT_FILTER) {
+      // with BOTH `stdout' AND `stderr' diverted to files.
+
+      set_redirection(STDOUT_FILENO,
+		      creat(psFileName, S_IWUSR | S_IRUSR));
+      set_redirection(STDERR_FILENO,
+		      creat(regionFileName, S_IWUSR | S_IRUSR));
+    }
+
+    // Now we are ready to launch the output filter.
+
+    execvp(argv[0], argv);
+
+    // If we get to here then the `exec...' request for the output filter
+    // failed.  Diagnose it and bail out.
+
+    error("couldn't exec %1: %2", argv[0], strerror(errno), ((char *)0));
+    fflush(stderr);	// just in case error() didn't
+    exit(1);
+  }
+
+  else {
+    // This is the parent process fork.  We will be writing data to the
+    // filter pipeline but we can close our handle on the output end of
+    // the pipe so we don't block the output data stream.
+
+    if (close(pipedes[0]) < 0)
+      sys_fatal("close");
+
+    // Now we redirect the `stdout' stream to the inlet end of the pipe.
+    // Push out the appropiately formatted data to the filter.
+
+    pipedes[1] = save_and_redirect(STDOUT_FILENO, pipedes[1]);
+    emit_troff_output(DEVICE_FORMAT(filter));
+
+    // After emitting all the data we close our connection to the inlet
+    // end of the pipe so the child process will detect end of data.
+
+    set_redirection(STDOUT_FILENO, pipedes[1]);
+
+    // Finally we must wait for the child process to complete.
+
+    if (WAIT(&status, &child_pid, _WAIT_CHILD) != child_pid)
+      sys_fatal("wait");
+  }
+
+#elif MAY_SPAWN_ASYNCHRONOUS_CHILD
+
+  // This should be ok for most Win32 systems and is preferred to `fork'
+  // for starting child processes under Cygwin.
+
+  // Before we start the post-processor we bind its inherited `stdin'
+  // stream to the readable end of our pipe, saving our own `stdin' stream
+  // in `pipedes[0]'.
+
+  pipedes[0] = save_and_redirect(STDIN_FILENO, pipedes[0]);
+
+  int saved_stdout = dup(STDOUT_FILENO);
+  int saved_stderr = STDERR_FILENO;
+
+  // The IMAGE_OUTPUT_FILTER needs special output redirection...
+
+  if (filter == IMAGE_OUTPUT_FILTER) {
+    // with BOTH `stdout' AND `stderr' diverted to files while saving a
+    // duplicate handle for `stderr'.
+
+    set_redirection(STDOUT_FILENO, creat(psFileName, S_IWUSR | S_IRUSR));
+    saved_stderr =
+      save_and_redirect(STDERR_FILENO,
+			creat(regionFileName, S_IWUSR | S_IRUSR));
+  }
+
+  // We then use an asynchronous spawn request to start the post-processor.
+
+  if ((child_pid = spawnvp(_P_NOWAIT, argv[0], argv)) < 0) {
+    // Should the spawn request fail we issue a diagnostic and bail out.
+
+    error("cannot spawn %1: %2", argv[0], strerror(errno), ((char *)0));
+    exit(1);
+  }
+
+  // Once the post-processor has been started we revert our `stdin'
+  // to its original saved source which also closes the readable handle
+  // for the pipe.
+
+  set_redirection(STDIN_FILENO, pipedes[0]);
+
+  set_redirection(STDERR_FILENO, saved_stderr);
+  set_redirection(STDOUT_FILENO, pipedes[1]);
+  emit_troff_output(DEVICE_FORMAT(filter));
+
+  set_redirection(STDOUT_FILENO, saved_stdout);
+
+  if (WAIT(&status, child_pid, _WAIT_CHILD) != child_pid)
+    sys_fatal("wait");
+
+#endif /* MAY_FORK_CHILD_PROCESS or MAY_SPAWN_ASYNCHRONOUS_CHILD */
+
+  return 0;
+}
+
 /*
- *  do_html - sets the troff number htmlflip and
- *            writes out the buffer to troff -Thtml
+ *  do_html - Set the troff number htmlflip and
+ *            write out the buffer to troff -Thtml.
  */
 
 int char_buffer::do_html(int argc, char *argv[])
 {
-  int pdes[2];
-  PID_T pid;
   string s;
 
   alterDeviceTo(argc, argv, 0);
-  argv += troff_arg;   // skip all arguments up to groff
+  argv += troff_arg;		// skip all arguments up to groff
   argc -= troff_arg;
   argv = addZ(argc, argv);
   argc++;
 
   s = "-dwww-image-template=";
-  s += macroset_template;   // do not combine these statements otherwise they will not work
-  s += '\0';                // the trailing '\0' is ignored
+  s += macroset_template;	// do not combine these statements,
+				// otherwise they will not work
+  s += '\0';                	// the trailing `\0' is ignored
   argv = addRegDef(argc, argv, s.contents());
   argc++;
 
-  if (pipe(pdes) < 0)
-    sys_fatal("pipe");
-
-  pid = fork();
-  if (pid < 0)
-    sys_fatal("fork");
-
-  if (pid == 0) {
-    // child
-    replaceFd(0, pdes[0]);
-    // close end we are not using
-    if (close(pdes[1])<0)
-      sys_fatal("close");
-    replaceFd(1, copyofstdoutfd); // and restore stdout
-
-    execvp(argv[0], argv);
-    error("couldn't exec %1: %2", argv[0], strerror(errno), (char *)0);
-    fflush(stderr);		/* just in case error() doesn't */
-    exit(1);
-  } else {
-    // parent
-
 #if defined(DEBUGGING)
-    /*
-     *  slight security risk so only enabled if compiled with defined(DEBUGGING)
-     */
-    if (debug) {
-      replaceFd(1, creat(htmlFileName, S_IWUSR|S_IRUSR));
-      write_file_html();
-    }
+  // slight security risk so only enabled if compiled with defined(DEBUGGING)
+  if (debug) {
+    set_redirection(STDOUT_FILENO, creat(htmlFileName, S_IWUSR | S_IRUSR));
+    emit_troff_output(DEVICE_FORMAT(HTML_OUTPUT_FILTER));
+  }
 #endif
-    replaceFd(1, pdes[1]);
-    // close end we are not using
-    if (close(pdes[0])<0)
-      sys_fatal("close");
 
-    write_file_html();
-    waitForChild(pid);
-  }
-  return 0;
+  return run_output_filter(HTML_OUTPUT_FILTER, argc, argv);
 }
 
 /*
- *  do_image - writes out the buffer to troff -Tps
+ *  do_image - Write out the buffer to troff -Tps.
  */
 
 int char_buffer::do_image(int argc, char *argv[])
 {
-  PID_T pid;
-  int pdes[2];
   string s;
 
   alterDeviceTo(argc, argv, 1);
-  argv += troff_arg;   // skip all arguments up to troff/groff
+  argv += troff_arg;		// skip all arguments up to troff/groff
   argc -= troff_arg;
   argv = addRegDef(argc, argv, "-rps4html=1");
   argc++;
@@ -1258,69 +1422,50 @@ int char_buffer::do_image(int argc, char *argv[])
   argv = addRegDef(argc, argv, "-P-pletter");
   argc++;
 
-  if (pipe(pdes) < 0)
-    sys_fatal("pipe");
-
-  pid = fork();
-  if (pid == 0) {
-    // child
-
-    int psFd     = creat(psFileName,     S_IWUSR|S_IRUSR);
-    int regionFd = creat(regionFileName, S_IWUSR|S_IRUSR);
-
-    replaceFd(1, psFd);
-    replaceFd(0, pdes[0]);
-    replaceFd(2, regionFd);
-
-    // close end we are not using
-    if (close(pdes[1])<0)
-      sys_fatal("close");
-
-    execvp(argv[0], argv);
-    error("couldn't exec %1: %2", argv[0], strerror(errno), (char *)0);
-    fflush(stderr);		/* just in case error() doesn't */
-    exit(1);
-  } else {
-    // parent
-
 #if defined(DEBUGGING)
-    /*
-     *  slight security risk so only enabled if compiled with defined(DEBUGGING)
-     */
-    if (debug) {
-      replaceFd(1, creat(troffFileName, S_IWUSR|S_IRUSR));
-      write_file_troff();
-    }
-#endif
-    replaceFd(1, pdes[1]);
-    write_file_troff();
-    waitForChild(pid);
+  // slight security risk so only enabled if compiled with defined(DEBUGGING)
+  if (debug) {
+    set_redirection(STDOUT_FILENO, creat(troffFileName, S_IWUSR | S_IRUSR));
+    emit_troff_output(DEVICE_FORMAT(IMAGE_OUTPUT_FILTER));
   }
-  return 0;
+#endif
+
+  return run_output_filter(IMAGE_OUTPUT_FILTER, argc, argv);
 }
 
 static char_buffer inputFile;
 
-
 /*
- *  usage - emit usage arguments.
+ *  usage - Emit usage arguments.
  */
 
-void usage(FILE *stream)
+static void usage(FILE *stream)
 {
-  fprintf(stream, "usage: %s troffname [-Iimage_name] [-Dimage_directory] [-P-o vertical_image_offset] [-P-i image_resolution] [troff flags] [files]\n", program_name);
-  fprintf(stream, "    vertical_image_offset (default %d/72 of an inch)\n", vertical_offset);
-  fprintf(stream, "    image_resolution (default %d) pixels per inch\n", image_res);
-  fprintf(stream, "    image_name is the name of the stem for all images (default is grohtml-<pid>)\n");
-  fprintf(stream, "    place all png files into image_directory\n");
+  fprintf(stream,
+	  "usage: %s troffname [-Iimage_name] [-Dimage_directory]\n"
+	  "       [-P-o vertical_image_offset] [-P-i image_resolution]\n"
+	  "       [troff flags] [files]\n",
+	  program_name);
+  fprintf(stream,
+	  "    vertical_image_offset (default %d/72 of an inch)\n",
+	  vertical_offset);
+  fprintf(stream,
+	  "    image_resolution (default %d) pixels per inch\n",
+	  image_res);
+  fprintf(stream,
+	  "    image_name is the name of the stem for all images\n"
+	  "    (default is grohtml-<pid>)\n");
+  fprintf(stream,
+	  "    place all png files into image_directory\n");
 }
 
 /*
- *  scanArguments - scans for all arguments including -P-i, -P-o, -P-D and -P-I. It returns
- *                  the argument index of the first non option.
+ *  scanArguments - Scan for all arguments including -P-i, -P-o, -P-D,
+ *                  and -P-I.  Return the argument index of the first
+ *                  non-option.
  */
 
-int scanArguments (int argc, char **argv)
+static int scanArguments(int argc, char **argv)
 {
   const char *command_prefix = getenv("GROFF_COMMAND_PREFIX");
   if (!command_prefix)
@@ -1334,21 +1479,24 @@ int scanArguments (int argc, char **argv)
     { "version", no_argument, 0, 'v' },
     { NULL, 0, 0, 0 }
   };
-  while ((c = getopt_long(argc, argv, "+a:g:o:i:I:j:D:F:vbdhlrnp", long_options, NULL))
+  while ((c = getopt_long(argc, argv,
+			  "+a:g:o:i:I:j:D:F:vbdhlrnp", long_options, NULL))
 	 != EOF)
     switch(c) {
     case 'v':
       printf("GNU pre-grohtml (groff) version %s\n", Version_string);
       exit(0);
     case 'a':
-      textAlphaBits = min(max(MIN_ALPHA_BITS, atoi(optarg)), MAX_ALPHA_BITS);
+      textAlphaBits = min(max(MIN_ALPHA_BITS, atoi(optarg)),
+			  MAX_ALPHA_BITS);
       if (textAlphaBits == 3) {
 	error("cannot use 3 bits of antialiasing information");
 	exit(1);
       }
       break;
     case 'g':
-      graphicAlphaBits = min(max(MIN_ALPHA_BITS, atoi(optarg)), MAX_ALPHA_BITS);
+      graphicAlphaBits = min(max(MIN_ALPHA_BITS, atoi(optarg)),
+			     MAX_ALPHA_BITS);
       if (graphicAlphaBits == 3) {
 	error("cannot use 3 bits of antialiasing information");
 	exit(1);
@@ -1412,19 +1560,19 @@ int scanArguments (int argc, char **argv)
 }
 
 /*
- *  makeTempFiles - name the temporary files
+ *  makeTempFiles - Name the temporary files.
  */
 
-static int makeTempFiles (void)
+static int makeTempFiles(void)
 {
 #if defined(DEBUGGING)
-  psFileName     = "/tmp/prehtml-ps";
-  regionFileName = "/tmp/prehtml-region";
-  imagePageName  = "/tmp/prehtml-page";
-  psPageName     = "/tmp/prehtml-psn";
-  troffFileName  = "/tmp/prehtml-troff";
-  htmlFileName   = "/tmp/prehtml-html";
-#else
+  psFileName = __tmpfile"prehtml-ps";
+  regionFileName = __tmpfile"prehtml-region";
+  imagePageName = __tmpfile"prehtml-page";
+  psPageName = __tmpfile"prehtml-psn";
+  troffFileName = __tmpfile"prehtml-troff";
+  htmlFileName = __tmpfile"prehtml-html";
+#else /* not DEBUGGING */
   FILE *f;
 
   /* psPageName contains a single page of postscript */
@@ -1467,7 +1615,7 @@ static int makeTempFiles (void)
   }
   fclose(f);
 
-#endif
+#endif /* not DEBUGGING */
   return 0;
 }
 
@@ -1475,9 +1623,21 @@ int main(int argc, char **argv)
 {
   program_name = argv[0];
   int i;
-  int found=0;
-  int ok=1;
-
+  int found = 0;
+  int ok = 1;
+
+#ifdef CAPTURE_MODE
+  FILE *dump;
+  fprintf(stderr, "%s: invoked with %d arguments ...\n", argv[0], argc);
+  for (i = 0; i < argc; i++)
+    fprintf(stderr, "%2d: %s\n", i, argv[i]);
+  if ((dump = fopen(__tmpfile"pre-html-data", "wb")) != NULL) {
+    while((i = fgetc(stdin)) >= 0)
+      fputc(i, dump);
+    fclose(dump);
+  }
+  exit(1);
+#endif /* CAPTURE_MODE */
   postscriptRes = get_resolution();
   i = scanArguments(argc, argv);
   setupAntiAlias();
@@ -1487,19 +1647,15 @@ int main(int argc, char **argv)
     if (argv[i][0] != '-') {
       /* found source file */
       ok = do_file(argv[i]);
-      if (! ok) {
-	return( 0 );
-      }
+      if (!ok)
+	return 0;
       found = 1;
     }
     i++;
   }
 
-  copyofstdoutfd=dup(stdoutfd);
-
-  if (! found) {
+  if (!found)
     do_file("-");
-  }
   if (makeTempFiles())
     return 1;
   ok = inputFile.do_image(argc, argv);
@@ -1515,9 +1671,9 @@ static int do_file(const char *filename)
   FILE *fp;
 
   current_filename = filename;
-  if (strcmp(filename, "-") == 0) {
+  if (strcmp(filename, "-") == 0)
     fp = stdin;
-  } else {
+  else {
     fp = fopen(filename, "r");
     if (fp == 0) {
       error("can't open `%1': %2", filename, strerror(errno));
@@ -1526,6 +1682,7 @@ static int do_file(const char *filename)
   }
 
   if (inputFile.read_file(fp)) {
+    // XXX
   }
 
   if (fp != stdin)