Codec that allows read and write simultaneously?

[ruant]

Is there a codec that allows me to read from a recorded file while I'm still recording to it?

I need to start cutting clips from a live recording to make a smash up of the live recording ready to be played as soon as possible after the recording has finished.

Like a highlight reel of the basketball game of the first half that should be played in the halftime break.

[pandy]

Rather container than codec and depend on your expectations.
Probably it must be Intra type codec.
Container MPEG Transport Stream (TS) usually offer this kind of functionality - packets are 188 byte big and accessible almost immediately after write.