xref.cc

swf文件查看工具,能够看flash文件的格式

//========================================================================
//
// XRef.cc
//
// Copyright 1996-2003 Glyph & Cog, LLC
//
//========================================================================

#include <aconf.h>

#ifdef USE_GCC_PRAGMAS
#pragma implementation
#endif

#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <ctype.h>
#include "gmem.h"
#include "Object.h"
#include "Stream.h"
#include "Lexer.h"
#include "Parser.h"
#include "Dict.h"
#include "Error.h"
#include "ErrorCodes.h"
#include "XRef.h"

//------------------------------------------------------------------------

#define xrefSearchSize 1024	// read this many bytes at end of file
				//   to look for 'startxref'

//------------------------------------------------------------------------
// Permission bits
//------------------------------------------------------------------------

#define permPrint    (1<<2)
#define permChange   (1<<3)
#define permCopy     (1<<4)
#define permNotes    (1<<5)
#define defPermFlags 0xfffc

//------------------------------------------------------------------------
// ObjectStream
//------------------------------------------------------------------------

class ObjectStream {
public:

  // Create an object stream, using object number <objStrNum>,
  // generation 0.
  ObjectStream(XRef *xref, int objStrNumA);

  ~ObjectStream();

  // Return the object number of this object stream.
  int getObjStrNum() { return objStrNum; }

  // Get the <objIdx>th object from this stream, which should be
  // object number <objNum>, generation 0.
  Object *getObject(int objIdx, int objNum, Object *obj);

private:

  int objStrNum;		// object number of the object stream
  int nObjects;			// number of objects in the stream
  Object *objs;			// the objects (length = nObjects)
  int *objNums;			// the object numbers (length = nObjects)
};

ObjectStream::ObjectStream(XRef *xref, int objStrNumA) {
  Stream *str;
  Parser *parser;
  int *offsets;
  Object objStr, obj1, obj2;
  int first, i;

  objStrNum = objStrNumA;
  nObjects = 0;
  objs = NULL;
  objNums = NULL;

  if (!xref->fetch(objStrNum, 0, &objStr)->isStream()) {
    goto err1;
  }

  if (!objStr.streamGetDict()->lookup("N", &obj1)->isInt()) {
    obj1.free();
    goto err1;
  }
  nObjects = obj1.getInt();
  obj1.free();
  if (nObjects <= 0) {
    goto err1;
  }

  if (!objStr.streamGetDict()->lookup("First", &obj1)->isInt()) {
    obj1.free();
    goto err1;
  }
  first = obj1.getInt();
  obj1.free();
  if (first < 0) {
    goto err1;
  }

  objs = new Object[nObjects];
  objNums = (int *)gmallocn(nObjects, sizeof(int));
  offsets = (int *)gmallocn(nObjects, sizeof(int));

  // parse the header: object numbers and offsets
  objStr.streamReset();
  obj1.initNull();
  str = new EmbedStream(objStr.getStream(), &obj1, gTrue, first);
  parser = new Parser(xref, new Lexer(xref, str), gFalse);
  for (i = 0; i < nObjects; ++i) {
    parser->getObj(&obj1);
    parser->getObj(&obj2);
    if (!obj1.isInt() || !obj2.isInt()) {
      obj1.free();
      obj2.free();
      delete parser;
      gfree(offsets);
      goto err1;
    }
    objNums[i] = obj1.getInt();
    offsets[i] = obj2.getInt();
    obj1.free();
    obj2.free();
    if (objNums[i] < 0 || offsets[i] < 0 ||
	(i > 0 && offsets[i] < offsets[i-1])) {
      delete parser;
      gfree(offsets);
      goto err1;
    }
  }
  while (str->getChar() != EOF) ;
  delete parser;

  // skip to the first object - this shouldn't be necessary because
  // the First key is supposed to be equal to offsets[0], but just in
  // case...
  for (i = first; i < offsets[0]; ++i) {
    objStr.getStream()->getChar();
  }

  // parse the objects
  for (i = 0; i < nObjects; ++i) {
    obj1.initNull();
    if (i == nObjects - 1) {
      str = new EmbedStream(objStr.getStream(), &obj1, gFalse, 0);
    } else {
      str = new EmbedStream(objStr.getStream(), &obj1, gTrue,
			    offsets[i+1] - offsets[i]);
    }
    parser = new Parser(xref, new Lexer(xref, str), gFalse);
    parser->getObj(&objs[i]);
    while (str->getChar() != EOF) ;
    delete parser;
  }

  gfree(offsets);

 err1:
  objStr.free();
  return;
}

ObjectStream::~ObjectStream() {
  int i;

  if (objs) {
    for (i = 0; i < nObjects; ++i) {
      objs[i].free();
    }
    delete[] objs;
  }
  gfree(objNums);
}

Object *ObjectStream::getObject(int objIdx, int objNum, Object *obj) {
  if (objIdx < 0 || objIdx >= nObjects || objNum != objNums[objIdx]) {
    return obj->initNull();
  }
  return objs[objIdx].copy(obj);
}

//------------------------------------------------------------------------
// XRef
//------------------------------------------------------------------------

XRef::XRef(BaseStream *strA) {
  Guint pos;
  Object obj;

  ok = gTrue;
  errCode = errNone;
  size = 0;
  entries = NULL;
  streamEnds = NULL;
  streamEndsLen = 0;
  objStr = NULL;

  encrypted = gFalse;
  permFlags = defPermFlags;
  ownerPasswordOk = gFalse;

  // read the trailer
  str = strA;
  start = str->getStart();
  pos = getStartXref();

  // if there was a problem with the 'startxref' position, try to
  // reconstruct the xref table
  if (pos == 0) {
    if (!(ok = constructXRef())) {
      errCode = errDamaged;
      return;
    }

  // read the xref table
  } else {
    while (readXRef(&pos)) ;

    // if there was a problem with the xref table,
    // try to reconstruct it
    if (!ok) {
      if (!(ok = constructXRef())) {
	errCode = errDamaged;
	return;
      }
    }
  }

  // get the root dictionary (catalog) object
  trailerDict.dictLookupNF("Root", &obj);
  if (obj.isRef()) {
    rootNum = obj.getRefNum();
    rootGen = obj.getRefGen();
    obj.free();
  } else {
    obj.free();
    if (!(ok = constructXRef())) {
      errCode = errDamaged;
      return;
    }
  }

  // now set the trailer dictionary's xref pointer so we can fetch
  // indirect objects from it
  trailerDict.getDict()->setXRef(this);
}

XRef::~XRef() {
  gfree(entries);
  trailerDict.free();
  if (streamEnds) {
    gfree(streamEnds);
  }
  if (objStr) {
    delete objStr;
  }
}

// Read the 'startxref' position.
Guint XRef::getStartXref() {
  char buf[xrefSearchSize+1];
  char *p;
  int c, n, i;

  // read last xrefSearchSize bytes
  str->setPos(xrefSearchSize, -1);
  for (n = 0; n < xrefSearchSize; ++n) {
    if ((c = str->getChar()) == EOF) {
      break;
    }
    buf[n] = c;
  }
  buf[n] = '\0';

  // find startxref
  for (i = n - 9; i >= 0; --i) {
    if (!strncmp(&buf[i], "startxref", 9)) {
      break;
    }
  }
  if (i < 0) {
    return 0;
  }
  for (p = &buf[i+9]; isspace(*p); ++p) ;
  lastXRefPos = strToUnsigned(p);

  return lastXRefPos;
}

// Read one xref table section.  Also reads the associated trailer
// dictionary, and returns the prev pointer (if any).
GBool XRef::readXRef(Guint *pos) {
  Parser *parser;
  Object obj;
  GBool more;

  // start up a parser, parse one token
  obj.initNull();
  parser = new Parser(NULL,
	     new Lexer(NULL,
	       str->makeSubStream(start + *pos, gFalse, 0, &obj)),
	     gTrue);
  parser->getObj(&obj);

  // parse an old-style xref table
  if (obj.isCmd("xref")) {
    obj.free();
    more = readXRefTable(parser, pos);

  // parse an xref stream
  } else if (obj.isInt()) {
    obj.free();
    if (!parser->getObj(&obj)->isInt()) {
      goto err1;
    }
    obj.free();
    if (!parser->getObj(&obj)->isCmd("obj")) {
      goto err1;
    }
    obj.free();
    if (!parser->getObj(&obj)->isStream()) {
      goto err1;
    }
    more = readXRefStream(obj.getStream(), pos);
    obj.free();

  } else {
    goto err1;
  }

  delete parser;
  return more;

 err1:
  obj.free();
  delete parser;
  ok = gFalse;
  return gFalse;
}

GBool XRef::readXRefTable(Parser *parser, Guint *pos) {
  XRefEntry entry;
  GBool more;
  Object obj, obj2;
  Guint pos2;
  int first, n, newSize, i;

  while (1) {
    parser->getObj(&obj);
    if (obj.isCmd("trailer")) {
      obj.free();
      break;
    }
    if (!obj.isInt()) {
      goto err1;
    }
    first = obj.getInt();
    obj.free();
    if (!parser->getObj(&obj)->isInt()) {
      goto err1;
    }
    n = obj.getInt();
    obj.free();
    if (first < 0 || n < 0 || first + n < 0) {
      goto err1;
    }
    if (first + n > size) {
      for (newSize = size ? 2 * size : 1024;
	   first + n > newSize && newSize > 0;
	   newSize <<= 1) ;
      if (newSize < 0) {
	goto err1;
      }
      entries = (XRefEntry *)greallocn(entries, newSize, sizeof(XRefEntry));
      for (i = size; i < newSize; ++i) {
	entries[i].offset = 0xffffffff;
	entries[i].type = xrefEntryFree;
      }
      size = newSize;
    }
    for (i = first; i < first + n; ++i) {
      if (!parser->getObj(&obj)->isInt()) {
	goto err1;
      }
      entry.offset = (Guint)obj.getInt();
      obj.free();
      if (!parser->getObj(&obj)->isInt()) {
	goto err1;
      }
      entry.gen = obj.getInt();
      obj.free();
      parser->getObj(&obj);
      if (obj.isCmd("n")) {
	entry.type = xrefEntryUncompressed;
      } else if (obj.isCmd("f")) {
	entry.type = xrefEntryFree;
      } else {
	goto err1;
      }
      obj.free();
      if (entries[i].offset == 0xffffffff) {
	entries[i] = entry;
	// PDF files of patents from the IBM Intellectual Property
	// Network have a bug: the xref table claims to start at 1
	// instead of 0.
	if (i == 1 && first == 1 &&
	    entries[1].offset == 0 && entries[1].gen == 65535 &&
	    entries[1].type == xrefEntryFree) {
	  i = first = 0;
	  entries[0] = entries[1];
	  entries[1].offset = 0xffffffff;
	}
      }
    }
  }

  // read the trailer dictionary
  if (!parser->getObj(&obj)->isDict()) {
    goto err1;
  }

  // get the 'Prev' pointer
  obj.getDict()->lookupNF("Prev", &obj2);
  if (obj2.isInt()) {
    *pos = (Guint)obj2.getInt();
    more = gTrue;
  } else if (obj2.isRef()) {
    // certain buggy PDF generators generate "/Prev NNN 0 R" instead
    // of "/Prev NNN"
    *pos = (Guint)obj2.getRefNum();
    more = gTrue;
  } else {
    more = gFalse;
  }
  obj2.free();

  // save the first trailer dictionary
  if (trailerDict.isNone()) {
    obj.copy(&trailerDict);
  }

  // check for an 'XRefStm' key