#### Problem
AccountOffset currently uses `usize`, which size is platform dependent.
We want a fixed size type that is consist to what we persist in the tiered-storage file.
#### Summary of Changes
This PR makes AccountOffset use u32.
#### Problem
IndexOffset currently uses `usize`, which size is platform dependent.
We want a fixed size type that is consist to what we persist in the tiered-storage file.
#### Summary of Changes
This PR makes IndexOffset use u32.
#### Problem
In TieredStorage, we want to make AccountOffset and IndexOffset u32 instead
of usize just like OwnerOffset. However, we need to first change what we persist
in the storage. Currently, IndexBlock persists offsets as u64 instead of u32.
#### Summary of Changes
This PR makes IndexBlock persist u32 offsets.
#### Test Plan
Existing test cases.
#### Problem
TieredAccountMeta currently uses `u32` for owner_offset, while
we already have a dedicate type for that --- OwnerOffset.
#### Summary of Changes
This PR makes TieredAccountMeta use OwnerOffset for its
owner_offset field.
#### Test Plan
Existing unit-tests.
#### Problem
The current OwnerOffset is defined as usize, which actual size could be u32 or u64.
On the other hand, the OwnerOffset is used to access the ith owner in one
TieredStorageFile. As a result, u32 is more than enough to represent the number of
owners inside one TieredStorageFile while u16 might not be always enough.
#### Summary of Changes
This PR defines OwnerOffset as u32.
#### Test Plan
Existing test cases.
#### Problem
The HotStorageReader does not have an API to obtain owners_address.
#### Summary of Changes
This PR adds HotStorageReader::get_owner_address().
#### Test Plan
A new unit-test is added to this PR.
#### Problem
#34032 mentioned nice-to-have a formatting improvement that
can improve the readability.
#### Summary of Changes
Improve the code formatting in test_hot_storage_get_account_offset_and_address().
#### Problem
HotStorageReader currently not yet has an API to obtain account_address
#### Summary of Changes
This PR adds HotStorageReader::get_account_address() which returns
the Pubkey of the account associated with the specified IndexOffset.
#### Test Plan
Augmented an existing unit-test to cover get_account_address() case.
#### Problem
TieredStorageFooter::owners_offset refers to the offset to the
owners block, which looks very similar to OwnerOffset that
has a completely different concept -- the offset to access the
address of an owner in the owners-block.
#### Summary of Changes
Similar to the previous renaming index_offset to index_block_offset,
this PR renames owners_offset to owners_block_offset to
avoid confusion.
#### Problem
HotStorageReader currently not yet has an API to obtain account_offset
#### Summary of Changes
This PR adds HotStorageReader::get_account_offset() which takes
IndexOffset and returns AccountOffset.
#### Test Plan
A new unit-test is included in this PR.
#### Problem
#33927 introduced a new type AccountOffset, but HotStorageReader
still uses `usize` to access accounts.
#### Summary of Changes
This PR makes HotStorageReader use the new AccountOffset type.
#### Problem
The current tiered-storage code uses "account-index" to call index-block.
This could lead to confusion especially as we start giving each offset/position/index a specific type.
#### Summary of Changes
This PR renames all structs/variables that use account-index to refer to index-block.
#### Problem
HotStorageReader currently only implements get_footer(). It does not
have a function to obtain the account meta.
#### Summary of Changes
This PR implements HotStorageReader::get_account_meta_from_offset().
A function that returns the account meta located at the specified offset.
This will be the helper function that will be later used to obtain the account
meta when the offset is available from the index block of a hot storage file.
#### Test Plan
A new test is included in this PR.
#### Problem
HotStorageReader currently doesn't have a test that covers its footer.
#### Summary of Changes
This PR includes a test for HotStorageReader that verifies the footer.
Yueh-Hsuan Chiang
Brooks
Pankaj Garg