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pollen/cache.rkt

50 lines
1.7 KiB
Racket

#lang racket/base
(require racket/rerequire "world.rkt")
;; The cache is a hash with paths as keys.
;; The cache values are also hashes, with key/value pairs for that path.
(provide reset-cache current-cache make-cache cached-require cache-ref)
;; Don't initialize a cache when the module is loaded. This induces reliance.
;; The cache only makes sense if a single one is used across a whole session (e.g., via parameterize).
(define current-cache (make-parameter #f))
(define (make-cache) (make-hash))
(define (reset-cache) (hash-clear! (current-cache)))
(define (->complete-path path-string)
(path->complete-path (if (string? path-string) (string->path path-string) path-string)))
(define (cache-ref path-string)
(hash-ref (current-cache) (->complete-path path-string)))
(define (cache-has-key? path)
(hash-has-key? (current-cache) path))
(define (cache path)
(dynamic-rerequire path)
(hash-set! (current-cache) path (make-hash))
(define cache-hash (cache-ref path))
(hash-set! cache-hash 'mod-time (file-or-directory-modify-seconds path))
(hash-set! cache-hash world:main-pollen-export (dynamic-require path world:main-pollen-export))
(hash-set! cache-hash world:meta-pollen-export (dynamic-require path world:meta-pollen-export))
(void))
(define (cached-require path-string key)
(when (not (current-cache)) (error "cached-require: No cache set up."))
(define path
(with-handlers ([exn:fail? (λ(exn) (displayln (format "cached-require: ~a is not a valid path" path-string)))])
(->complete-path path-string)))
(when (or (not (cache-has-key? path))
(> (file-or-directory-modify-seconds path) (hash-ref (cache-ref path) 'mod-time)))
(cache path))
(hash-ref (cache-ref path) key))