b810c46a45
users.sterni.nix.utf8 implements UTF-8 decoding in pure nix. We implement the decoding as a simple state machine which is fed one byte at a time. Decoding whole strings is possible by subsequently calling step. This is done in decode which uses builtins.foldl' to get around recursion restrictions and a neat trick using builtins.deepSeq puck showed me limiting the size of the thunks in a foldl' (which can also cause a stack overflow). This makes decoding arbitrarily large UTF-8 files into codepoints using nix theoretically possible, but it is not really practical: Decoding a 36KB LaTeX file I had lying around takes ~160s on my laptop. Change-Id: Iab8c973dac89074ec280b4880a7408e0b3d19bc7 Reviewed-on: https://cl.tvl.fyi/c/depot/+/2590 Tested-by: BuildkiteCI Reviewed-by: sterni <sternenseemann@systemli.org>
121 lines
4.1 KiB
Nix
121 lines
4.1 KiB
Nix
{ depot, lib, ... }:
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let
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inherit (depot.third_party)
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runCommandLocal
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;
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inherit (depot.nix.runTestsuite)
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runTestsuite
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it
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assertEq
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assertThrows
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assertDoesNotThrow
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;
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inherit (depot.users.Profpatsch.writers)
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rustSimple
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;
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inherit (depot.users.sterni.nix)
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int
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utf8
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string
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char
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;
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rustDecoder = rustSimple {
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name = "utf8-decode";
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} ''
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use std::io::{self, Read};
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fn main() -> std::io::Result<()> {
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let mut buffer = String::new();
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io::stdin().read_to_string(&mut buffer)?;
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print!("[ ");
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for c in buffer.chars() {
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print!("{} ", u32::from(c));
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}
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print!("]");
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Ok(())
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}
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'';
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rustDecode = s:
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let
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expr = runCommandLocal "${s}-decoded" {} ''
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printf '%s' ${lib.escapeShellArg s} | ${rustDecoder} > $out
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'';
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in import expr;
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hexDecode = l:
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utf8.decode (string.fromBytes (builtins.map int.fromHex l));
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testFailures = it "checks UTF-8 decoding failures" [
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(assertThrows "emtpy bytestring throws" (utf8.decode ""))
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(assertThrows "truncated UTF-8 string throws" (hexDecode [ "F0" "9F" ]))
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# examples from The Unicode Standard
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(assertThrows "ill-formed: C0 AF" (hexDecode [ "C0" "AF" ]))
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(assertThrows "ill-formed: E0 9F 80" (hexDecode [ "E0" "9F" "80" ]))
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(assertEq "well-formed: F4 80 83 92" (hexDecode [ "F4" "80" "83" "92" ]) [ 1048786 ])
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];
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testAscii = it "checks decoding of ascii strings"
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(builtins.map (s: assertEq "ASCII decoding is equal to UTF-8 decoding for \"${s}\""
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(string.toBytes s) (utf8.decode s)) [
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"foo bar"
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"hello\nworld"
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"carriage\r\nreturn"
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"1238398494829304 []<><>({})[]!!)"
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(string.take 127 char.allChars)
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]);
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randomUnicode = [
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"🥰👨👨👧👦🐈⬛👩🏽🦰"
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# https://kermitproject.org/utf8.html
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"ᚠᛇᚻ᛫ᛒᛦᚦ᛫ᚠᚱᚩᚠᚢᚱ᛫ᚠᛁᚱᚪ᛫ᚷᛖᚻᚹᛦᛚᚳᚢᛗ"
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"An preost wes on leoden, Laȝamon was ihoten"
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"Sîne klâwen durh die wolken sint geslagen,"
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"Τὴ γλῶσσα μοῦ ἔδωσαν ἑλληνικὴ"
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"На берегу пустынных волн"
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"ვეპხის ტყაოსანი შოთა რუსთაველი"
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"யாமறிந்த மொழிகளிலே தமிழ்மொழி போல் இனிதாவது எங்கும் காணோம், "
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"ಬಾ ಇಲ್ಲಿ ಸಂಭವಿಸು "
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];
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# https://kermitproject.org/utf8.html
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glassSentences = [
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"Euro Symbol: €."
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"Greek: Μπορώ να φάω σπασμένα γυαλιά χωρίς να πάθω τίποτα."
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"Íslenska / Icelandic: Ég get etið gler án þess að meiða mig."
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"Polish: Mogę jeść szkło, i mi nie szkodzi."
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"Romanian: Pot să mănânc sticlă și ea nu mă rănește."
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"Ukrainian: Я можу їсти шкло, й воно мені не пошкодить."
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"Armenian: Կրնամ ապակի ուտել և ինծի անհանգիստ չըներ։"
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"Georgian: მინას ვჭამ და არა მტკივა."
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"Hindi: मैं काँच खा सकता हूँ, मुझे उस से कोई पीडा नहीं होती."
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"Hebrew(2): אני יכול לאכול זכוכית וזה לא מזיק לי."
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"Yiddish(2): איך קען עסן גלאָז און עס טוט מיר נישט װײ."
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"Arabic(2): أنا قادر على أكل الزجاج و هذا لا يؤلمني."
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"Japanese: 私はガラスを食べられます。それは私を傷つけません。"
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"Thai: ฉันกินกระจกได้ แต่มันไม่ทำให้ฉันเจ็บ "
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];
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testDecoding = it "checks decoding of UTF-8 strings against Rust's String"
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(builtins.map
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(s: assertEq "Decoding of “${s}” is correct" (utf8.decode s) (rustDecode s))
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(lib.flatten [
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glassSentences
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randomUnicode
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]));
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in
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runTestsuite "nix.utf8" [
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testFailures
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testAscii
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testDecoding
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]
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