+
+ // IndexTo writes a complete list of locators with the given
+ // prefix for which Get() can retrieve data.
+ //
+ // prefix consists of zero or more lowercase hexadecimal
+ // digits.
+ //
+ // Each locator must be written to the given writer using the
+ // following format:
+ //
+ // loc "+" size " " timestamp "\n"
+ //
+ // where:
+ //
+ // - size is the number of bytes of content, given as a
+ // decimal number with one or more digits
+ //
+ // - timestamp is the timestamp stored for the locator,
+ // given as a decimal number of seconds after January 1,
+ // 1970 UTC.
+ //
+ // IndexTo must not write any other data to writer: for
+ // example, it must not write any blank lines.
+ //
+ // If an error makes it impossible to provide a complete
+ // index, IndexTo must return a non-nil error. It is
+ // acceptable to return a non-nil error after writing a
+ // partial index to writer.
+ //
+ // The resulting index is not expected to be sorted in any
+ // particular order.
+ IndexTo(prefix string, writer io.Writer) error
+
+ // Delete deletes the block data from the underlying storage
+ // device.
+ //
+ // loc is as described in Get.
+ //
+ // If the timestamp for the given locator is newer than
+ // blobSignatureTTL, Delete must not delete the data.
+ //
+ // If a Delete operation overlaps with any Touch or Put
+ // operations on the same locator, the implementation must
+ // ensure one of the following outcomes:
+ //
+ // - Touch and Put return a non-nil error, or
+ // - Delete does not delete the block, or
+ // - Both of the above.
+ //
+ // If it is possible for the storage device to be accessed by
+ // a different process or host, the synchronization mechanism
+ // should also guard against races with other processes and
+ // hosts. If such a mechanism is not available, there must be
+ // a mechanism for detecting unsafe configurations, alerting
+ // the operator, and aborting or falling back to a read-only
+ // state. In other words, running multiple keepstore processes
+ // with the same underlying storage device must either work
+ // reliably or fail outright.
+ //
+ // Corollary: A successful Touch or Put guarantees a block
+ // will not be deleted for at least blobSignatureTTL
+ // seconds.