Implement tellg() on ZStream, make multify -t work with .pz/.gz compressed multifiles

panda/src/downloadertools/multify.cxx

@@ -18,6 +18,7 @@
 #include "filename.h"
 #include "pset.h"
 #include "vector_string.h"
+#include "virtualFileSystem.h"
 #include <stdio.h>
 #include <time.h>
 
@@ -631,8 +632,17 @@ list_files(const vector_string &params) {
     cerr << multifile_name << " not found.\n";
     return false;
   }
+  // We happen to know that we can read the index without doing a seek.
+  // So this is the only place where we accept a .pz/.gz compressed .mf.
+  VirtualFileSystem *vfs = VirtualFileSystem::get_global_ptr();
+  istream *istr = vfs->open_read_file(multifile_name, true);
+  if (istr == NULL) {
+    cerr << "Unable to open " << multifile_name << " for reading.\n";
+    return false;
+  }
+
   PT(Multifile) multifile = new Multifile;
-  if (!multifile->open_read(multifile_name)) {
+  if (!multifile->open_read(new IStreamWrapper(istr, true), true)) {
     cerr << "Unable to open " << multifile_name << " for reading.\n";
     return false;
   }

panda/src/express/multifile.cxx

@@ -2297,9 +2297,11 @@ read_index() {
   }
 
   // Now read the index out.
-  _next_index = read->tellg() - _offset;
-  _next_index = normalize_streampos(_next_index);
-  read->seekg(_next_index + _offset);
+  streampos curr_pos = read->tellg() - _offset;
+  _next_index = normalize_streampos(curr_pos);
+  if (_next_index > curr_pos) {
+    read->ignore(_next_index - curr_pos);
+  }
   _last_index = 0;
   _last_data_byte = 0;
   streampos index_forward;
@@ -2336,7 +2338,9 @@ read_index() {
     }
     streampos curr_pos = normalize_streampos(read->tellg() - _offset);
     bytes_skipped = index_forward - curr_pos;
-    read->seekg(index_forward + _offset);
+    if (bytes_skipped > 0) {
+      read->ignore(bytes_skipped);
+    }
     _next_index = index_forward;
     subfile = new Subfile;
     index_forward = subfile->read_index(*read, _next_index, this);

panda/src/express/zStreamBuf.cxx

@@ -176,26 +176,26 @@ close_write() {
  */
 streampos ZStreamBuf::
 seekoff(streamoff off, ios_seekdir dir, ios_openmode which) {
-  // Necessary for tellg() to work after seeking to 0.
-  if (dir == ios::cur && off == 0) {
-    if (_source->tellg() == (streampos)0) {
-      return 0;
-    } else {
-      return -1;
-    }
+  if (which != ios::in) {
+    // We can only do this with the input stream.
+    return -1;
   }
 
-  if (off != 0 || dir != ios::beg) {
-    // We only know how to reposition to the beginning.
-    return -1;
+  // Determine the current position.
+  size_t n = egptr() - gptr();
+  streampos gpos = _z_source.total_out - n;
+
+  // Implement tellg() and seeks to current position.
+  if ((dir == ios::cur && off == 0) ||
+      (dir == ios::beg && off == gpos)) {
+    return gpos;
   }
 
-  if (which != ios::in) {
-    // We can only do this with the input stream.
+  if (off != 0 || dir != ios::beg) {
+    // We only know how to reposition to the beginning.
     return -1;
   }
 
-  size_t n = egptr() - gptr();
   gbump(n);
 
   _source->seekg(0, ios::beg);