build.hashers.combined-clean
- Special meaning of keys?
- No, they are passed as-is to the combined hashers.
A combined hasher. Accepts several hashers as its inputs and marks a key as dirty only all of the hashers agree that it is dirty. Basically it is an and for hashers.
Usage
local COMBINED_CLEAN = require "build.hashers.combined-clean"
local Hasher = COMBINED_CLEAN (...)
local hasher = Hasher.create_combined_hashers(...)In the first call, the arguments to the COMBINED_CLEAN functor must be the structures of all the hashers to combine. In the second call, the arguments to the create_combined_hashers() function must be all the instances of the hashers in the same order than the structures.
Example
For example, let’s combine the mtime and the sha1 hashers to create a new hasher that considers a file dirty if both its SHA1 hash and its modification time have changed.
local Posix_File_System = require "build.file-systems.posix"
local COMBINED_CLEAN = require "build.hashers.combined-clean"
local Sha1_Hasher = require "build.hashers.sha1" (Posix_File_System)
local Mtime_Hasher = require "build.hashers.mtime" (Posix_File_System)
local Combined_Hasher = COMBINED_CLEAN(Sha1_Hasher, Mtime_Hasher)
local fs = Posix_File_System.global()
local sha1_hasher = Sha1_Hasher.create(fs)
local mtime_hasher = Mtime_Hasher.create(fs)
local combined_hasher = Combined_Hasher.create_combined_hashers(sha1_hasher, mtime_hasher)
-- Use `combined_hasher` freely