if( zFilename==0 || zFilename[0]==0
        || (zFilename[0]=='-' && zFilename[1]==0) ){
    return blob_read_from_channel(pBlob, stdin, -1);
  }
  size = file_size(zFilename);
  blob_zero(pBlob);
  if( size<0 ){
    fossil_fatal("no such file: %s", zFilename);
  }
  if( size==0 ){
    return 0;
  }
  blob_resize(pBlob, size);
  in = fopen(zFilename, "rb");
  if( in==0 ){

  }
  if( j>LENGTH_MASK ){
    return 0;
  }
  a = malloc( nLine*sizeof(a[0]) );
  if( a==0 ) fossil_panic("out of memory");
  memset(a, 0, nLine*sizeof(a[0]) );
  if( n==0 ){
    *pnLine = 0;
    return a;
  }

  /* Fill in the array */
  for(i=0; i<nLine; i++){
    a[i].z = z;
    for(j=0; z[j] && z[j]!='\n'; j++){}
    k = j;
    while( ignoreWS && k>0 && isspace(z[k-1]) ){ k--; }

**
** This file contains code used to implement the "diff" command
*/
#include "config.h"
#include "diffcmd.h"
#include <assert.h>

/*
** Diff option flags
*/
#define DIFF_NEWFILE  0x01    /* Treat non-existing fails as empty files */
#define DIFF_NOEOLWS  0x02    /* Ignore whitespace at the end of lines */

/*
** This function implements a cross-platform "system()" interface.
*/
int portable_system(const char *zOrigCmd){
  int rc;
#if defined(_WIN32)
  /* On windows, we have to put double-quotes around the entire command.

** command zDiffCmd to do the diffing.
*/
static void diff_file(
  Blob *pFile1,             /* In memory content to compare from */
  const char *zFile2,       /* On disk content to compare to */
  const char *zName,        /* Display name of the file */
  const char *zDiffCmd,     /* Command for comparison */
  int ignoreEolWs           /* Ignore whitespace at end of line */
){
  if( zDiffCmd==0 ){
    Blob out;                 /* Diff output text */
    Blob file2;               /* Content of zFile2 */
    const char *zName2;       /* Name of zFile2 for display */

    /* Read content of zFile2 into memory */
    blob_zero(&file2);
    if( file_size(zFile2)<0 ){
      zName2 = "/dev/null";
    }else{
      blob_read_from_file(&file2, zFile2);
      zName2 = zName;
    }

    /* Compute and output the differences */
    blob_zero(&out);
    text_diff(pFile1, &file2, &out, 5, ignoreEolWs);
    printf("--- %s\n+++ %s\n", zName, zName2);
    printf("%s\n", blob_str(&out));

    /* Release memory resources */
    blob_reset(&file2);
    blob_reset(&out);
  }else{
    int cnt = 0;

** Run a diff between the version zFrom and files on disk.  zFrom might
** be NULL which means to simply show the difference between the edited
** files on disk and the check-out on which they are based.
*/
static void diff_all_against_disk(
  const char *zFrom,        /* Version to difference from */
  const char *zDiffCmd,     /* Use this diff command.  NULL for built-in */
  int diffFlags             /* Flags controlling diff output */
){
  int vid;
  Blob sql;
  Stmt q;
  int ignoreEolWs;          /* Ignore end-of-line whitespace */
  int asNewFile;            /* Treat non-existant files as empty files */

  ignoreEolWs = (diffFlags & DIFF_NOEOLWS)!=0;
  asNewFile = (diffFlags & DIFF_NEWFILE)!=0;
  vid = db_lget_int("checkout", 0);
  vfile_check_signature(vid, 1);
  blob_zero(&sql);
  db_begin_transaction();
  if( zFrom ){
    int rid = name_to_rid(zFrom);
    if( !is_a_version(rid) ){

  }
  db_prepare(&q, blob_str(&sql));
  while( db_step(&q)==SQLITE_ROW ){
    const char *zPathname = db_column_text(&q,0);
    int isDeleted = db_column_int(&q, 1);
    int isChnged = db_column_int(&q,2);
    int isNew = db_column_int(&q,3);
    int srcid = db_column_int(&q, 4);
    char *zFullName = mprintf("%s%s", g.zLocalRoot, zPathname);
    int showDiff = 1;
    if( isDeleted ){
      printf("DELETED  %s\n", zPathname);
      if( !asNewFile ){ showDiff = 0; zFullName = "/dev/null"; }
    }else if( access(zFullName, 0) ){
      printf("MISSING  %s\n", zPathname);
      if( !asNewFile ){ showDiff = 0; }
    }else if( isNew ){
      printf("ADDED    %s\n", zPathname);
      srcid = 0;
      if( !asNewFile ){ showDiff = 0; }
    }else if( isChnged==3 ){
      printf("ADDED_BY_MERGE %s\n", zPathname);

      srcid = 0;
      if( !asNewFile ){ showDiff = 0; }
    }
    if( showDiff ){
      Blob content;
      if( srcid>0 ){
        content_get(srcid, &content);
      }else{
        blob_zero(&content);
      }
      printf("Index: %s\n======================================="
             "============================\n",
             zPathname
      );
      diff_file(&content, zFullName, zPathname, zDiffCmd, ignoreEolWs);
      blob_reset(&content);
    }

/*
** Output the differences between two check-ins.
*/
static void diff_all_two_versions(
  const char *zFrom,
  const char *zTo,
  const char *zDiffCmd,
  int diffFlags
){
  Manifest mFrom, mTo;
  int iFrom, iTo;
  int ignoreEolWs = (diffFlags & DIFF_NOEOLWS)!=0 ? 1 : 0;
  /* int asNewFlag = (diffFlags & DIFF_NEWFILE)!=0 ? 1 : 0; */

  manifest_from_name(zFrom, &mFrom);
  manifest_from_name(zTo, &mTo);
  iFrom = iTo = 0;
  while( iFrom<mFrom.nFile && iTo<mTo.nFile ){
    int cmp;
    if( iFrom>=mFrom.nFile ){

** rather than any external diff program that might be configured using
** the "setting" command.  If no external diff program is configured, then
** the "-i" option is a no-op.  The "-i" option converts "gdiff" into "diff".
*/
void diff_cmd(void){
  int isGDiff;               /* True for gdiff.  False for normal diff */
  int isInternDiff;          /* True for internal diff */
  int hasNFlag;              /* True if -N or --new-file flag is used */
  const char *zFrom;         /* Source version number */
  const char *zTo;           /* Target version number */
  const char *zDiffCmd = 0;  /* External diff command. NULL for internal diff */
  int diffFlags = 0;         /* Flags to control the DIFF */

  isGDiff = g.argv[1][0]=='g';
  isInternDiff = find_option("internal","i",0)!=0;
  zFrom = find_option("from", "r", 1);
  zTo = find_option("to", 0, 1);
  hasNFlag = find_option("new-file","N",0)!=0;


  if( hasNFlag ) diffFlags |= DIFF_NEWFILE;
  if( zTo==0 ){
    db_must_be_within_tree();
    verify_all_options();
    if( !isInternDiff ){
      zDiffCmd = db_get(isGDiff ? "gdiff-command" : "diff-command", 0);
    }
    if( g.argc==3 ){
      diff_one_against_disk(zFrom, zDiffCmd, 0);
    }else{
      diff_all_against_disk(zFrom, zDiffCmd, diffFlags);
    }
  }else if( zFrom==0 ){
    fossil_fatal("must use --from if --to is present");
  }else{
    db_find_and_open_repository(1);
    verify_all_options();
    if( !isInternDiff ){
      zDiffCmd = db_get(isGDiff ? "gdiff-command" : "diff-command", 0);
    }
    if( g.argc==3 ){
      diff_one_two_versions(zFrom, zTo, zDiffCmd, 0);
    }else{
      diff_all_two_versions(zFrom, zTo, zDiffCmd, diffFlags);
    }
  }
}