77 lines
2.9 KiB
Bash
77 lines
2.9 KiB
Bash
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#!/usr/bin/env bash
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#
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# SPDX-License-Identifier: GPL-2.0
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#
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# Copyright (c) 2013-2023 Igor Pecovnik, igor@armbian.com
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#
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# This file is a part of the Armbian Build Framework
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# https://github.com/armbian/build/
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# This does many tricks. Beware.
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# Also, 'memoize' is a misnomer. It's more like 'cache'.
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# It works with bash dictionaries (associative arrays) and references to functions
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# It uses bash "declare -f" trick to obtain the function body as a string and use it as part of the caching hash.
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# So any changes to the memoized function automatically invalidate the cache.
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# It also uses a "cache_id" to allow for multiple caches to be used and to determine the directory name to cache under.
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# Call:
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# run_memoized VAR_NAME cache_id memoized_function_name [function_args]
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function run_memoized() {
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declare var_n="${1}"
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shift
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declare cache_id="${1}"
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shift
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declare memoized_func="${1}"
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shift
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declare extra_args=("${@}")
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# shellcheck disable=SC2178 # nope, that's a nameref.
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declare -n MEMO_DICT="${var_n}" # nameref
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#display_alert "memoize" "before" "info"
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#debug_dict MEMO_DICT
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MEMO_DICT+=(["MEMO_TYPE"]="${cache_id}")
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declare single_string_input="${cache_id}"
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single_string_input="$(declare -p "${var_n}")" # this might use random order...
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MEMO_DICT+=(["MEMO_INPUT_HASH"]="$(echo "${var_n}-${single_string_input}--$(declare -f "${memoized_func}")" "${extra_args[@]}" | sha256sum | cut -f1 -d' ')")
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declare disk_cache_dir="${SRC}/cache/memoize/${MEMO_DICT[MEMO_TYPE]}"
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mkdir -p "${disk_cache_dir}"
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declare disk_cache_file="${disk_cache_dir}/${MEMO_DICT[MEMO_INPUT_HASH]}"
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# Lock...
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exec {lock_fd}> "${disk_cache_file}.lock" || exit_with_error "failed to lock"
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flock "${lock_fd}" || exit_with_error "flock() failed"
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display_alert "Lock obtained" "${disk_cache_file}.lock" "debug"
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if [[ -f "${disk_cache_file}" ]]; then
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declare disk_cache_file_mtime_seconds
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disk_cache_file_mtime_seconds="$(stat -c %Y "${disk_cache_file}")"
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# if disk_cache_file is older than 1 hour, delete it and continue.
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if [[ "${disk_cache_file_mtime_seconds}" -lt "$(($(date +%s) - 3600))" ]]; then
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display_alert "Deleting stale cache file" "${disk_cache_file}" "debug"
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rm -f "${disk_cache_file}"
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else
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display_alert "Using memoized ${var_n} from ${disk_cache_file}" "${MEMO_DICT[MEMO_INPUT]}" "debug"
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display_alert "Using cached" "${var_n}" "info"
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# shellcheck disable=SC1090 # yep, I'm sourcing the cache here. produced below.
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source "${disk_cache_file}"
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return 0
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fi
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fi
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# if cache miss, run the memoized_func...
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display_alert "Memoizing ${var_n} to ${disk_cache_file}" "${MEMO_DICT[MEMO_INPUT]}" "debug"
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display_alert "Producing new & caching" "${var_n}" "info"
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${memoized_func} "${var_n}" "${extra_args[@]}"
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# ... and save the output to the cache; twist declare -p's output due to the nameref
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declare -p "${var_n}" | sed -e 's|^declare -A ||' > "${disk_cache_file}"
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# ... unlock.
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flock -u "${lock_fd}"
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return 0
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}
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