common

Generally useful helper Erlang helper functions

db

Just basics that gloss over annoying bits of the mnesia api. Mostly taken from the examples in Programming Erlang, and not my own creations

do/1 (qlc:q term) -> transaction result

Takes a qlc:q expression, and wraps it in a transaction+fun+qlc:e. Returns the result of the query rather than {atomic, Result} (fails on non-atomic results).

transaction/1 (fun) -> transaction result

Takes a fun and wraps it in a mnesia:transaction/1, returning Result rather than {atomic, Result}. Fails on non-atomic results. Called in db:do/1.

atomic_insert/1 (Record || [Records]) -> result of atomic write

Takes record or list of records, and returns the result of doing an atomic insertion on the input. If a list of records is provided, map is inside the transaction, so they will either all be inserted or none of them will be.

push_to/3 (Index, Rec, NewVal) -> modified Rec

Takes a record index, a record and a value. Returns Rec with NewVal pushed into Index. Note that unlike relate/6 and decouple/6, this function does no checking on the target (it will happily add duplicates if called).

remove_from/3 (Index, Rec, Prey) -> modified Rec

Takes a record index, a record and a value. Returns Rec with the first instance of Prey removed from Rec.

relate/6 (Rec1, Id1, Index1, Rec2, Id2, Index2) -> ok || false

Takes two records, and their corresponding IDs + ID indexes. Atomically relates the two records in mnesia. This and decouple/6 are used in managing many-to-many relationships (this one mutually adds the appropriate Id to the appropriate Index). This function only succeeds if the given records are currently unrelated, it returns false otherwise.

decouple/6 (Rec1, Id1, Index1, Rec2, Id2, Index2) -> ok || false

Takes two records, and their corresponding IDs + ID indexes. Atomically decuples the two records in mnesia. This and relate/6 are used in managing many-to-many relationships (this one mutually removes the appropriate Id from the appropriate Index). This function only succeeds if the given records are mutually related, it returns false otherwise.

common

Simple functions that I use in lots of places. I'm not entirely sure why they're not in the standard libraries.

now_to_seconds/1 ({A, B, C}) -> SecondsFromEpoch

Takes a now() and converts it to a number of seconds. Useful in time/duration comparisons.

binary_to_hex/1 (<<Binary>>) -> HexString

Takes a binary and returns its hex string representation. Useful when displaying the results of hash/encryption functions.

make_tempname/0 () -> TempName
make_tempname/1 (TargetDir) -> TempName

Returns a unique temporary pathname. Doesn't use os:cmd("mktemp"). in an effort to stay kind of platform independent. The default directory is /tmp (wrapped with a filename:nativename/1 call, so it does \\tmp on Windows). Optionally takes a target directory.

gpg

basic, command-line bindings to GPG. Don't use this, it's still very raw.