Cache of Email headers

The Header Cache saves data from email headers to a local store in order to speed up network mailboxes.

See also: store; compress

Operation

When NeoMutt parses an email, it stores the results in a number of structures (listed below). To save time and network traffic, NeoMutt can save the results into a store (optionally using compress).

See also: Address Body Buffer Email Envelope ListNode Parameter

To save the data, the Header Cache uses a set of 'dump' functions (Email-object serialiser) to 'serialise' the structures. The cache also stores a CRC checksum of the C structs that were used. When retrieving the data, the Header Cache uses a set of 'restore' functions to turn the data back into structs.

The CRC checksum is created by hcache/hcachever.sh during the build process. Whenever the definition of any of the structs changes, the CRC will change, invalidating any existing cached data.

Note: Adding or removing a field from the set of serialised fields will not affect the CRC. In this case, it is vital that you bump the BASEVERSION variable in hcache/hcachever.sh

Source

File	Description
hcache/config.c	Config used by Header Cache
hcache/hcache.c	Header cache multiplexor
hcache/serialize.c	Email-object serialiser

Functions

Function	Description	Links
hcache_close()	Close the connection to the header cache
hcache_delete_email()	Delete a key / data pair
hcache_delete_raw()	Delete a key / data pair
hcache_fetch_email()	Fetch and validate a message's header from the cache
hcache_open()	Open the connection to the header cache
hcache_store_email()	Store a Header along with a validity datum