Obtain file information via unshield_get_file_descriptor

[ScaledLizard]

I am the maintainer of ArchiveAccess, an access software for archives:

https://sourceforge.net/projects/archiveaccess/

ArchiveAccess uses libunshield to unpack .cab files. ArchiveAccess provides data about files that can be unpacked, to allow the user to choose what to inspect closer. I currently obtain this information via unshield_get_file_descriptor:

UnshieldFileGroup* file_group = unshield_file_group_get(mUnshieldData, i);
if (file_group != nullptr) {
for (unsigned int j = file_group->first_file; j <= file_group->last_file; j++) {
CPString filename = CPString(unshield_file_name(mUnshieldData, j), (Codepage)fncp);
CPString dirName = CPString(file_group->name, (Codepage)fncp);
FileDescriptor* fd = unshield_get_file_descriptor(mUnshieldData, j);
...
fileInfo.UncompressedFileSize = fd->expanded_size;
fileInfo.CompressedFileSize = fd->compressed_size;
fileInfo.attributes = fd->flags;

In order to do this, I export the function unshield_get_file_descriptor, which is an internal function in official builds. However, a cleaner way to do this would be via proper access functions. I propose to provide several access functions:

uint64_t unshield_get_uncompressed_size(Unshield* unshield, UnshieldFileGroup* file_group, int index);
uint64_t unshield_get_compressed_size(Unshield* unshield, UnshieldFileGroup* file_group, int index);
uint32_t unshield_get_attributes(Unshield* unshield, UnshieldFileGroup* file_group, int index);

There are other ways, like exposing all this data via one function, but these approaches would be less flexible. My questions:

1. If I would implement this, would you accept it in libunshield, or you would you rather go a different route?
2. Did I miss that there is a feature for doing this already?

Thanks in advance
Björn

[twogood]

Hi Björn,

I would basically accept this contribution, it just needs to blend in with the existing public API. The current public interface uses unshield_file_ prefix for file information and no existing API takes UnshieldFileGroup* as a parameter.

We already have unshield_file_size for the uncompressed size, so it could get a sibling for compressed size.

Regarding unshield_get_attributes I guess we also would need to expose the FILE_* values for the flags. Maybe a name like unshield_file_raw_flags or unshield_file_flags_raw would be more suitable to blend in?

So maybe these functions?

uint64_t unshield_file_size_compressed(Unshield* unshield, int index);
uint32_t/uint16_t unshield_file_flags_raw(Unshield* unshield, int index);

Cheers,

David

[ScaledLizard]

Here is the pull request:

#230