Initial revision

1 files changed, 443 insertions, 0 deletions

diff --git a/pdf/xpdf/XRef.cc b/pdf/xpdf/XRef.cc
new file mode 100644
index 0000000..cc9bee8
--- /dev/null
+++ b/pdf/xpdf/XRef.cc
@@ -0,0 +1,443 @@
+//========================================================================
+//
+// XRef.cc
+//
+// Copyright 1996 Derek B. Noonburg
+//
+//========================================================================
+
+#ifdef __GNUC__
+#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 "XRef.h"
+
+//------------------------------------------------------------------------
+
+#define xrefSearchSize 1024	// read this many bytes at end of file
+				//   to look for 'startxref'
+
+//------------------------------------------------------------------------
+// The global xref table
+//------------------------------------------------------------------------
+
+XRef *xref = NULL;
+
+//------------------------------------------------------------------------
+// XRef
+//------------------------------------------------------------------------
+
+XRef::XRef(FileStream *str) {
+  XRef *oldXref;
+  int pos;
+  int i;
+
+  ok = gTrue;
+  size = 0;
+  entries = NULL;
+
+  // get rid of old xref (otherwise it will try to fetch the Root object
+  // in the new document, using the old xref)
+  oldXref = xref;
+  xref = NULL;
+
+  // read the trailer
+  file = str->getFile();
+  start = str->getStart();
+  pos = readTrailer(str);
+
+  // if there was a problem with the trailer,
+  // try to reconstruct the xref table
+  if (pos == 0) {
+    if (!(ok = constructXRef(str))) {
+      xref = oldXref;
+      return;
+    }
+
+  // trailer is ok - read the xref table
+  } else {
+    entries = (XRefEntry *)gmalloc(size * sizeof(XRefEntry));
+    for (i = 0; i < size; ++i) {
+      entries[i].offset = -1;
+      entries[i].used = gFalse;
+    }
+    while (readXRef(str, &pos)) ;
+
+    // if there was a problem with the xref table,
+    // try to reconstruct it
+    if (!ok) {
+      gfree(entries);
+      size = 0;
+      entries = NULL;
+      if (!(ok = constructXRef(str))) {
+	xref = oldXref;
+	return;
+      }
+    }
+  }
+
+  // set up new xref table
+  xref = this;
+
+  // check for encryption
+  if (checkEncrypted()) {
+    ok = gFalse;
+    xref = oldXref;
+    return;
+  }
+}
+
+XRef::~XRef() {
+  gfree(entries);
+  trailerDict.free();
+}
+
+// Read startxref position, xref table size, and root.  Returns
+// first xref position.
+int XRef::readTrailer(FileStream *str) {
+  Parser *parser;
+  Object obj;
+  char buf[xrefSearchSize+1];
+  int n, pos, pos1;
+  char *p;
+  int c;
+  int i;
+
+  // read last xrefSearchSize bytes
+  str->setPos(-xrefSearchSize);
+  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) ;
+  pos = atoi(p);
+
+  // find trailer dict by looking after first xref table
+  // (NB: we can't just use the trailer dict at the end of the file --
+  // this won't work for linearized files.)
+  str->setPos(start + pos);
+  for (i = 0; i < 4; ++i)
+    buf[i] = str->getChar();
+  if (strncmp(buf, "xref", 4))
+    return 0;
+  pos1 = pos + 4;
+  while (1) {
+    str->setPos(start + pos1);
+    for (i = 0; i < 35; ++i) {
+      if ((c = str->getChar()) == EOF)
+	return 0;
+      buf[i] = c;
+    }
+    if (!strncmp(buf, "trailer", 7))
+      break;
+    p = buf;
+    while (isspace(*p)) ++p;
+    while ('0' <= *p && *p <= '9') ++p;
+    while (isspace(*p)) ++p;
+    n = atoi(p);
+    while ('0' <= *p && *p <= '9') ++p;
+    while (isspace(*p)) ++p;
+    if (p == buf)
+      return 0;
+    pos1 += (p - buf) + n * 20;
+  }
+  pos1 += 7;
+
+  // read trailer dict
+  obj.initNull();
+  parser = new Parser(new Lexer(new FileStream(file, start + pos1, -1, &obj)));
+  parser->getObj(&trailerDict);
+  if (trailerDict.isDict()) {
+    trailerDict.dictLookupNF("Size", &obj);
+    if (obj.isInt())
+      size = obj.getInt();
+    else
+      pos = 0;
+    obj.free();
+    trailerDict.dictLookupNF("Root", &obj);
+    if (obj.isRef()) {
+      rootNum = obj.getRefNum();
+      rootGen = obj.getRefGen();
+    } else {
+      pos = 0;
+    }
+    obj.free();
+  } else {
+    pos = 0;
+  }
+  delete parser;
+
+  // return first xref position
+  return pos;
+}
+
+// Read an xref table and the prev pointer from the trailer.
+GBool XRef::readXRef(FileStream *str, int *pos) {
+  Parser *parser;
+  Object obj, obj2;
+  char s[20];
+  GBool more;
+  int first, n, i, j;
+  int c;
+
+  // seek to xref in stream
+  str->setPos(start + *pos);
+
+  // make sure it's an xref table
+  while ((c = str->getChar()) != EOF && isspace(c)) ;
+  s[0] = (char)c;
+  s[1] = (char)str->getChar();
+  s[2] = (char)str->getChar();
+  s[3] = (char)str->getChar();
+  if (!(s[0] == 'x' && s[1] == 'r' && s[2] == 'e' && s[3] == 'f'))
+    goto err2;
+
+  // read xref
+  while (1) {
+    while ((c = str->lookChar()) != EOF && isspace(c))
+      str->getChar();
+    if (c == 't')
+      break;
+    for (i = 0; (c = str->getChar()) != EOF && isdigit(c) && i < 20; ++i)
+      s[i] = (char)c;
+    if (i == 0)
+      goto err2;
+    s[i] = '\0';
+    first = atoi(s);
+    while ((c = str->lookChar()) != EOF && isspace(c))
+      str->getChar();
+    for (i = 0; (c = str->getChar()) != EOF && isdigit(c) && i < 20; ++i)
+      s[i] = (char)c;
+    if (i == 0)
+      goto err2;
+    s[i] = '\0';
+    n = atoi(s);
+    while ((c = str->lookChar()) != EOF && isspace(c))
+      str->getChar();
+    for (i = first; i < first + n; ++i) {
+      for (j = 0; j < 20; ++j) {
+	if ((c = str->getChar()) == EOF)
+	  goto err2;
+	s[j] = (char)c;
+      }
+      if (entries[i].offset < 0) {
+	s[10] = '\0';
+	entries[i].offset = atoi(s);
+	s[16] = '\0';
+	entries[i].gen = atoi(&s[11]);
+	if (s[17] == 'n')
+	  entries[i].used = gTrue;
+	else if (s[17] == 'f')
+	  entries[i].used = gFalse;
+	else
+	  goto err2;
+      }
+    }
+  }
+
+  // read prev pointer from trailer dictionary
+  obj.initNull();
+  parser = new Parser(new Lexer(
+    new FileStream(file, str->getPos(), -1, &obj)));
+  parser->getObj(&obj);
+  if (!obj.isCmd("trailer"))
+    goto err1;
+  obj.free();
+  parser->getObj(&obj);
+  if (!obj.isDict())
+    goto err1;
+  obj.getDict()->lookupNF("Prev", &obj2);
+  if (obj2.isInt()) {
+    *pos = obj2.getInt();
+    more = gTrue;
+  } else {
+    more = gFalse;
+  }
+  obj.free();
+  obj2.free();
+
+  delete parser;
+  return more;
+
+ err1:
+  obj.free();
+ err2:
+  ok = gFalse;
+  return gFalse;
+}
+
+// Attempt to construct an xref table for a damaged file.
+GBool XRef::constructXRef(FileStream *str) {
+  Parser *parser;
+  Object obj;
+  char buf[256];
+  int pos;
+  int num, gen;
+  int newSize;
+  char *p;
+  int i;
+  GBool gotRoot;
+
+  error(0, "PDF file is damaged - attempting to reconstruct xref table...");
+  gotRoot = gFalse;
+
+  str->reset();
+  while (1) {
+    pos = str->getPos();
+    if (!str->getLine(buf, 256))
+      break;
+    p = buf;
+
+    // got trailer dictionary
+    if (!strncmp(p, "trailer", 7)) {
+      obj.initNull();
+      parser = new Parser(new Lexer(
+		 new FileStream(file, start + pos + 8, -1, &obj)));
+      if (!trailerDict.isNone())
+	trailerDict.free();
+      parser->getObj(&trailerDict);
+      if (trailerDict.isDict()) {
+	trailerDict.dictLookupNF("Root", &obj);
+	if (obj.isRef()) {
+	  rootNum = obj.getRefNum();
+	  rootGen = obj.getRefGen();
+	  gotRoot = gTrue;
+	}
+	obj.free();
+      } else {
+	pos = 0;
+      }
+      delete parser;
+
+    // look for object
+    } else if (isdigit(*p)) {
+      num = atoi(p);
+      do {
+	++p;
+      } while (*p && isdigit(*p));
+      if (isspace(*p)) {
+	do {
+	  ++p;
+	} while (*p && isspace(*p));
+	if (isdigit(*p)) {
+	  gen = atoi(p);
+	  do {
+	    ++p;
+	  } while (*p && isdigit(*p));
+	  if (isspace(*p)) {
+	    do {
+	      ++p;
+	    } while (*p && isspace(*p));
+	    if (!strncmp(p, "obj", 3)) {
+	      if (num >= size) {
+		newSize = (num + 1 + 255) & ~255;
+		entries = (XRefEntry *)
+		            grealloc(entries, newSize * sizeof(XRefEntry));
+		for (i = size; i < newSize; ++i) {
+		  entries[i].offset = -1;
+		  entries[i].used = gFalse;
+		}
+		size = newSize;
+	      }
+	      if (!entries[num].used || gen >= entries[num].gen) {
+		entries[num].offset = pos - start;
+		entries[num].gen = gen;
+		entries[num].used = gTrue;
+	      }
+	    }
+	  }
+	}
+      }
+    }
+  }
+
+  if (gotRoot)
+    return gTrue;
+
+  error(-1, "Couldn't find trailer dictionary");
+  return gFalse;
+}
+
+GBool XRef::checkEncrypted() {
+  Object obj;
+  GBool encrypted;
+
+  trailerDict.dictLookup("Encrypt", &obj);
+  if ((encrypted = !obj.isNull())) {
+    error(-1, "PDF file is encrypted and cannot be displayed");
+    error(-1, "* Decryption support is currently not included in xpdf");
+    error(-1, "* due to legal restrictions: the U.S.A. still has bogus");
+    error(-1, "* export controls on cryptography software.");
+  }
+  obj.free();
+  return encrypted;
+}
+
+GBool XRef::okToPrint() {
+  return gTrue;
+}
+
+GBool XRef::okToCopy() {
+  return gTrue;
+}
+
+Object *XRef::fetch(int num, int gen, Object *obj) {
+  XRefEntry *e;
+  Parser *parser;
+  Object obj1, obj2, obj3;
+
+  // check for bogus ref - this can happen in corrupted PDF files
+  if (num < 0 || num >= size) {
+    obj->initNull();
+    return obj;
+  }
+
+  e = &entries[num];
+  if (e->gen == gen && e->offset >= 0) {
+    obj1.initNull();
+    parser = new Parser(new Lexer(
+      new FileStream(file, start + e->offset, -1, &obj1)));
+    parser->getObj(&obj1);
+    parser->getObj(&obj2);
+    parser->getObj(&obj3);
+    if (obj1.isInt() && obj1.getInt() == num &&
+	obj2.isInt() && obj2.getInt() == gen &&
+	obj3.isCmd("obj")) {
+      parser->getObj(obj);
+    } else {
+      obj->initNull();
+    }
+    obj1.free();
+    obj2.free();
+    obj3.free();
+    delete parser;
+  } else {
+    obj->initNull();
+  }
+  return obj;
+}
+
+Object *XRef::getDocInfo(Object *obj) {
+  return trailerDict.dictLookup("Info", obj);
+}