Fail to extract binary file from Tar archive using libarchive - c++

Question

Update
The example below does work. I had misread the intention of the flag ARCHIVE_EXTRACT_TIME and was expecting to see the newly created file. Instead the file was being extracted correctly but with its original creation date. It was a long week! :-)
I have the following data stored in a Tar archive:
opt/
fw.bin
ad/
bin/
installer.sh
I have the following code, running on Ubuntu (g++ version 5.2.1), to extract the contents of the archive in memory using libarchive, largely taken from the examples:
int copy_data(struct archive *ar, struct archive *aw)
{
int r;
const void *buff;
size_t size;
#if ARCHIVE_VERSION_NUMBER >= 3000000
int64_t offset;
#else
off_t offset;
#endif
for (;;) {
r = archive_read_data_block(ar, &buff, &size, &offset);
if (r == ARCHIVE_EOF)
return (ARCHIVE_OK);
if (r != ARCHIVE_OK)
return (r);
r = archive_write_data(aw, buff, size);
if (size != r)
{
std::cerr << "Failed to write " << (size - r) << " Bytes\n";
}
}
}
}
int main(int argc, char** argv)
{
std::ifstream input("archive.tar.gz", std::ios::binary | std::ios::ate );
auto const size = input.tellg();
char* buffer = new char[size];
input.seekg(0);
input.read(buffer, size);
input.close();
struct archive *a;
struct archive *ext;
struct archive_entry *entry;
int retCode;
int flags = ARCHIVE_EXTRACT_TIME;
a = archive_read_new();
archive_read_support_format_all(a);
ext = archive_write_disk_new();
archive_write_disk_set_options(ext, flags);
archive_write_disk_set_standard_lookup(ext);
if ((retCode = archive_read_open_memory(a, buffer, size)))
for (;;) {
retCode = archive_read_next_header(a, &entry);
if (retCode == ARCHIVE_EOF)
{
break;
}
if (retCode != ARCHIVE_OK)
{
return -1;
}
retCode = archive_write_header(ext, entry);
if (retCode != ARCHIVE_OK)
{
return -1;
}
else
{
if (archive_entry_size(entry) > 0)
{
copy_data(a, ext);
}
retCode = archive_write_finish_entry(ext);
if (retCode != ARCHIVE_OK)
{
return -1;
}
}
}
archive_read_close(a);
archive_read_free(a);
archive_write_close(ext);
archive_write_free(ext);
return 0;
}
It unpacks the directories correctly as above and writes the installer.sh file. However, the binary file (fw.bin) is missing.
Are there specific settings I am missing in order to write binary files to disk? Am I using the wrong API calls?