`<util/imgcache.h>`¶

Small cache of loaded program images, keyed by path.

Lets a shell spawn the same program again without re-reading it from fsd. An entry is valid while the file's size and modification time match.

#include <util/imgcache.h>

Constants¶

Name	Value	Description
`IMGCACHE_SLOTS`	`8`	Number of images kept; the least recently used is evicted beyond that.
`IMGCACHE_PATH_MAX`	`128`	Longest path that can be cached, including the NUL.

One cached image.

Field	Type	Description
`path`	`char`	Path the image was read from.
`size`	`uint32_t`	File size when it was cached.
`mtime`	`uint32_t`	File modification time when it was cached.
`last_used`	`uint32_t`	Value of the cache clock at the last hit; for LRU eviction.
`obj`	`Handle`	Memory object holding the image, or -1 if the slot is free.

The cache. A zero-initialised ImgCache is ready to use.

Field	Type	Description
`slots`	`ImgCacheEntry`	Cached images.
`clock`	`uint32_t`	Counter bumped on every hit or insert.
`ready`	`bool`	Set once the slots have been initialised.

Handle ImgCacheGet(ImgCache *c, const char *path, uint32_t size, uint32_t mtime);

Looks up the image cached for path.

An entry whose size or mtime no longer matches is dropped and counts as a miss.

Parameter	Direction	Description
`c`	inout	The cache.
`path`	in	Path of the program.
`size`	in	Current file size.
`mtime`	in	Current file modification time.

Returns: The image object, still owned by the cache, or -1 on a miss.

bool ImgCachePut(ImgCache *c, const char *path, uint32_t size, uint32_t mtime, Handle obj);

Caches obj under path and takes ownership of it.

Replaces any previous entry for path; when every slot is taken, closes the least recently used entry.

Parameter	Direction	Description
`c`	inout	The cache.
`path`	in	Path of the program.
`size`	in	File size.
`mtime`	in	File modification time.
`obj`	in	Memory object holding the image.

Returns: true if cached; false if path is too long, and the caller still owns obj.

void ImgCacheDrop(ImgCache *c, const char *path);

Closes and forgets the entry for path, if any.

Parameter	Direction	Description
`c`	inout	The cache.
`path`	in	Path of the program.