Some operations cannot be implemented with the prior API:
* Iterating over the map and deleting keys
* Iterating over the map and replacing items
* Calling APIs that expect a native Go map
Add a Map.WithLock method that acquires a write-lock on the map
and then calls a user-provided closure with the underlying Go map.
This allows users to interact with the Map as a regular Go map,
but with the gaurantees that it is concurrent safe.
Updates tailscale/corp#9115
Signed-off-by: Joe Tsai <joetsai@digital-static.net>
If AtomicValue[T] is used with a T that is an interface kind,
then Store may panic if different concret types are ever stored.
Fix this by always wrapping in a concrete type.
Technically, this is only needed if T is an interface kind,
but there is no harm in doing it also for non-interface kinds.
Updates #cleanup
Signed-off-by: Joe Tsai <joetsai@digital-static.net>
To mimic sync.Map.Swap, sync/atomic.Value.Swap, etc.
Updates tailscale/corp#1297
Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: If7627da1bce8b552873b21d7e5ebb98904e9a650
The LoadFunc loads a value and calls a user-provided function.
The utility of this method is to ensure that the map lock is held
while executing user-provided logic.
This allows us to solve TOCTOU bugs that would be nearly imposible
to the solve without this API.
Updates tailscale/corp#14772
Signed-off-by: Joe Tsai <joetsai@digital-static.net>
I was reviewing some code that was performing this by hand, and wanted
to suggest using syncs.Map, however as the code in question was
allocating a non-trivial structure this would be necessary to meet the
target.
Updates #cleanup
Signed-off-by: James Tucker <james@tailscale.com>
This updates all source files to use a new standard header for copyright
and license declaration. Notably, copyright no longer includes a date,
and we now use the standard SPDX-License-Identifier header.
This commit was done almost entirely mechanically with perl, and then
some minimal manual fixes.
Updates #6865
Signed-off-by: Will Norris <will@tailscale.com>
Map is a concurrent safe map that is a trivial wrapper
over a Go map and a sync.RWMutex.
It is optimized for use-cases where the entries change often,
which is the opposite use-case of what sync.Map is optimized for.
The API is patterned off of sync.Map, but made generic.
Signed-off-by: Joe Tsai <joetsai@digital-static.net>
