#if INTERFACE
/*
** Flag parameters to the text_diff() routine used to control the formatting
** of the diff output.
*/
#define DIFF_CONTEXT_MASK ((u64)0x0000ffff) /* Lines of context. Default if 0 */
#define DIFF_WIDTH_MASK   ((u64)0x00ff0000) /* side-by-side column width */
#define DIFF_IGNORE_EOLWS ((u64)0x01000000) /* Ignore end-of-line whitespace */
#define DIFF_IGNORE_ALLWS ((u64)0x03000000) /* Ignore all whitespace */
#define DIFF_SIDEBYSIDE   ((u64)0x04000000) /* Generate a side-by-side diff */
#define DIFF_VERBOSE      ((u64)0x08000000) /* Missing shown as empty files */
#define DIFF_BRIEF        ((u64)0x10000000) /* Show filenames only */
#define DIFF_HTML         ((u64)0x20000000) /* Render for HTML */
#define DIFF_LINENO       ((u64)0x40000000) /* Show line numbers */
#define DIFF_NUMSTAT      ((u64)0x80000000) /* Show line count of changes */
#define DIFF_NOOPT        (((u64)0x01)<<32) /* Suppress optimizations (debug) */
#define DIFF_INVERT       (((u64)0x02)<<32) /* Invert the diff (debug) */
#define DIFF_CONTEXT_EX   (((u64)0x04)<<32) /* Use context even if zero */
#define DIFF_NOTTOOBIG    (((u64)0x08)<<32) /* Only display if not too big */
#define DIFF_STRIP_EOLCR  (((u64)0x10)<<32) /* Strip trailing CR */
#define DIFF_SLOW_SBS     (((u64)0x20)<<32) /* Better but slower side-by-side */
#define DIFF_WEBPAGE   (((u64)0x00040)<<32) /* Complete webpage */
#define DIFF_BROWSER   (((u64)0x00080)<<32) /* The --browser option */
#define DIFF_JSON      (((u64)0x00100)<<32) /* JSON output */
#define DIFF_DEBUG     (((u64)0x00200)<<32) /* Debugging diff output */
#define DIFF_RAW       (((u64)0x00400)<<32) /* Raw triples - for debugging */
#define DIFF_TCL       (((u64)0x00800)<<32) /* For the --tk option */
#define DIFF_INCBINARY (((u64)0x01000)<<32) /* The --diff-binary option */

/*
** These error messages are shared in multiple locations.  They are defined
** here for consistency.
*/
#define DIFF_CANNOT_COMPUTE_BINARY \
    "cannot compute difference between binary files\n"

**
**    *   Number of lines of context surrounding each difference block
**
**    *   Width of output columns for text side-by-side diffop          
*/
struct DiffConfig {
  u64 diffFlags;           /* Diff flags */


  u32 nFile;               /* Number of files diffed so far */
  const char *zDiffCmd;    /* External diff command to use instead of builtin */
  const char *zBinGlob;    /* GLOB pattern for binary files */
  ReCompiled *pRe;         /* Show only changes matching this pattern */
};

#endif /* INTERFACE */

}

/*
** Extract the number of lines of context from diffFlags.  Supply an
** appropriate default if no context width is specified.
*/
int diff_context_lines(DiffConfig *pCfg){
  int n = pCfg->diffFlags & DIFF_CONTEXT_MASK;
  if( n==0 && (pCfg->diffFlags & DIFF_CONTEXT_EX)==0 ) n = 5;
  return n;
}

/*
** Extract the width of columns for side-by-side diff.  Supply an
** appropriate default if no width is given.
**
** Calculate the default automatically, based on terminal's current width:
**   term-width = 2*diff-col + diff-marker + 1
**   diff-col = lineno + lmargin + text-width + rmargin
**
**   text-width = (term-width - diff-marker - 1)/2 - lineno - lmargin - rmargin
*/
int diff_width(DiffConfig *pCfg){
  int w = (pCfg->diffFlags & DIFF_WIDTH_MASK)/(DIFF_CONTEXT_MASK+1);
  if( w==0 ){
    static struct {
      unsigned int lineno, lmargin, text, rmargin, marker;
    } sbsW = { 5, 2, 0, 0, 3 };
    const unsigned int wMin = 24, wMax = 132;
    unsigned int tw = terminal_get_width(80);
    unsigned int twMin =

/*
** Initialize the DiffConfig object using command-line options.
**
** Process diff-related command-line options and return an appropriate
** "diffFlags" integer.
**
**   --brief                      Show filenames only        DIFF_BRIEF
**   -c|--context N               N lines of context.        DIFF_CONTEXT_MASK
**   --html                       Format for HTML            DIFF_HTML
**   --invert                     Invert the diff            DIFF_INVERT
**   -n|--linenum                 Show line numbers          DIFF_LINENO
**   --noopt                      Disable optimization       DIFF_NOOPT
**   --numstat                    Show change counts         DIFF_NUMSTAT
**   --strip-trailing-cr          Strip trailing CR          DIFF_STRIP_EOLCR
**   --unified                    Unified diff.              ~DIFF_SIDEBYSIDE
**   -w|--ignore-all-space        Ignore all whitespaces     DIFF_IGNORE_ALLWS
**   -W|--width N                 N character lines.         DIFF_WIDTH_MASK
**   -y|--side-by-side            Side-by-side diff.         DIFF_SIDEBYSIDE
**   -Z|--ignore-trailing-space   Ignore eol-whitespaces     DIFF_IGNORE_EOLWS
*/
void diff_options(DiffConfig *pCfg, int isGDiff, int bUnifiedTextOnly){
  u64 diffFlags = 0;
  const char *z;
  int f;

    /* Undocumented and unsupported flags used for development
    ** debugging and analysis: */
    if( find_option("debug",0,0)!=0 ) diffFlags |= DIFF_DEBUG;
    if( find_option("raw",0,0)!=0 )   diffFlags |= DIFF_RAW;
  }
  if( (z = find_option("context","c",1))!=0 && (f = atoi(z))>=0 ){
    if( f > DIFF_CONTEXT_MASK ) f = DIFF_CONTEXT_MASK;
    diffFlags |= f + DIFF_CONTEXT_EX;
  }
  if( (z = find_option("width","W",1))!=0 && (f = atoi(z))>0 ){
    f *= DIFF_CONTEXT_MASK+1;
    if( f > DIFF_WIDTH_MASK ) f = DIFF_CONTEXT_MASK;
    diffFlags |= f;
  }
  if( find_option("linenum","n",0)!=0 ) diffFlags |= DIFF_LINENO;
  if( find_option("noopt",0,0)!=0 ) diffFlags |= DIFF_NOOPT;
  if( find_option("numstat",0,0)!=0 ) diffFlags |= DIFF_NUMSTAT;
  if( find_option("invert",0,0)!=0 ) diffFlags |= DIFF_INVERT;
  if( find_option("brief",0,0)!=0 ) diffFlags |= DIFF_BRIEF;
  if( find_option("internal","i",0)==0

** Construct an appropriate diffFlag for text_diff() based on query
** parameters and the to boolean arguments.
*/
DiffConfig *construct_diff_flags(int diffType, DiffConfig *pCfg){
  u64 diffFlags = 0;  /* Zero means do not show any diff */
  if( diffType>0 ){
    int x;
    if( diffType==2 ){
      diffFlags = DIFF_SIDEBYSIDE;

      /* "dw" query parameter determines width of each column */
      x = atoi(PD("dw","80"))*(DIFF_CONTEXT_MASK+1);
      if( x<0 || x>DIFF_WIDTH_MASK ) x = DIFF_WIDTH_MASK;
      diffFlags += x;
    }

    if( P("w") ){
      diffFlags |= DIFF_IGNORE_ALLWS;
    }
    /* "dc" query parameter determines lines of context */
    x = atoi(PD("dc","7"));
    if( x<0 || x>DIFF_CONTEXT_MASK ) x = DIFF_CONTEXT_MASK;
    diffFlags += x;

    /* The "noopt" parameter disables diff optimization */
    if( PD("noopt",0)!=0 ) diffFlags |= DIFF_NOOPT;
    diffFlags |= DIFF_STRIP_EOLCR;
    diff_config_init(pCfg, diffFlags);
    return pCfg;
  }else{
    diff_config_init(pCfg, 0);
    return 0;
  }
}