Archive

The Archive function provides a general purpose data storage facility paid with usage tokens. You can Look at an archive entry by its hash, which lets you read the content but not change it. You can also Touch an entry directly by its location, which lets you change the content with the Write operation. Writing new content costs 1 usage token per 16 bytes of encrypted data added to the database, or yields a 1 token refund per 16 bytes reduced. (There can be a few bytes of overhead added in the encryption process.)

Before you can write an entry, you must first Buy its location for 1 usage token. This helps prevent accidentally writing to an incorrect location. You may then write arbitrary content into the purchased location. Later, if you want to Sell the location back to receive a 1 token refund, you must first clear it out by writing null content into it.

All content is encrypted in the database using a key derived from the archive location.

Example API Call

Here is a url which writes the string "abc" into archive location c80481226973dfec6dc06c8dfe8a5b1c, paying for the storage from usage location 29013fc66a653f6765151dd352675d0f. Note that in order for this to work, you must have already bought the archive location.

https://loom.cc/?function=archive&action=write
	&usage=29013fc66a653f6765151dd352675d0f
	&loc=c80481226973dfec6dc06c8dfe8a5b1c
	&content=abc

(The url is broken up across lines for clarity. In practice you would keep the entire url on a single line.)

You may use content with multiple lines or arbitrary binary characters. All you have to do is "uri_escape" the content to convert it into a form suitable for use in a url. (For you perl programmers, see the URI::Escape module.) For example, this multi-line string:

first/line
second/line

would be encoded by uri_escape as:

first%2Fline%0Asecond%2Fline%0A

For better support of very large content, there will soon be an API call which is compatible with the HTTP "file upload" protocol. But for now, the simple "write" operation should suffice just fine for most purposes (even with large content).

Archive Operations

Here we describe the API (application programming interface) for the Archive. The operations are Buy, Sell, Touch, Look, and Write.

Buy

Buy a location in the archive. This costs 1 usage token. The location must currently be vacant (not bought) in order to buy it. The input is:

Key Value Description
function archive
action buy Name of operation
loc id Location to buy
usage id Location of usage tokens

If the Buy operation succeeds, you will see the following keys in the result:

Key Value Description
status success Everything went well.
cost qty Cost of operation
usage_balance qty New usage balance
hash hash Hash of location

If the operation fails, the status will be fail, and the reason for the failure will be indicated with any keys below which apply:

Key Value Description
status fail Something went wrong.
error_loc not_valid_id loc is not a valid id
error_loc occupied loc is already occupied (bought)
content string existing content at loc if occupied
error_usage not_valid_id usage is not a valid id
error_usage insufficent usage location did not have at least one usage token

Sell

Sell a location in the archive. This refunds 1 usage token. The content at the location must currently be empty (null) in order to sell the location. The input is:

Key Value Description
function archive
action sell Name of operation
loc id Location to sell
usage id Location of usage tokens

If the Sell operation succeeds, you will see the following keys in the result:

Key Value Description
status success Everything went well.
cost qty Cost of operation (-1 meaning refund)
usage_balance qty New usage balance
hash hash Hash of location

If the operation fails, the status will be fail, and the reason for the failure will be indicated with any keys below which apply:

Key Value Description
status fail Something went wrong.
error_loc not_valid_id loc is not a valid id
error_loc vacant loc is already vacant (sold)
error_loc not_empty loc has non-empty content
content string existing content at loc (if non-empty)
error_usage not_valid_id usage is not a valid id

Touch

Touch a location in the archive. The input is:

Key Value Description
function archive
action touch Name of operation
loc id Location to touch

If the Touch operation succeeds, you will see the following keys in the result:

Key Value Description
status success Everything went well.
content string Content at archive location
hash hash Hash of location
content_hash hash Hash of content

If the operation fails, the status will be fail, and the reason for the failure will be indicated with any keys below which apply:

Key Value Description
status fail Something went wrong.
error_loc not_valid_id loc is not a valid id
error_loc vacant loc is vacant (sold)

Look

Look at a location in the archive by its hash. The input is:

Key Value Description
function archive
action look Name of operation
hash hash Hash of location to examine

If the Look operation succeeds, you will see the following keys in the result:

Key Value Description
status success Everything went well.
content string Content at hash of location
content_hash hash Hash of content

If the operation fails, the status will be fail, and the reason for the failure will be indicated with any keys below which apply:

Key Value Description
status fail Something went wrong.
error_hash not_valid_id hash is not a valid hash
error_loc vacant loc is vacant (sold)

Write

Write content into the archive. The system first encrypts the content using a key derived from the location. This may impose an overhead of a few bytes. It then compares the new encrypted length with the length of any existing content at this location, and determines how many bytes would be added or subtracted on net if it were to write out the new content. It then charges 1 usage token per 16 bytes added, or refunds 1 usage token per 16 bytes subtracted.

The input is:

Key Value Description
function archive
action write Name of operation
loc id Location to write
content id Content to write into that location
usage id Location of usage tokens
guard hash Optional SHA256 hash of previous content to guard against overlapping writes

If the Write operation succeeds, you will see the following keys in the result:

Key Value Description
status success Everything went well.
cost qty Cost of operation
usage_balance qty New usage balance
hash hash Hash of location
content_hash hash Hash of content

NOTE: the "content" key supplied in the input is not echoed back in the result, because that would just be a waste of time and bandwidth.

If the operation fails, the status will be fail, and the reason for the failure will be indicated with any keys below which apply:

Key Value Description
status fail Something went wrong.
error_loc not_valid_id loc is not a valid id
error_loc vacant loc is vacant (sold)
error_usage not_valid_id usage is not a valid id
error_usage insufficent usage location is vacant or did not have enough usage tokens to cover the cost
error_guard not_valid_hash guard was specified and is not a valid hash
error_guard changed The hash of the previous content did not match the specified guard, so the new content was not written. Essentially this means that the content changed "under our feet" since the last time we looked at it, so we don't clobber those changes.