feat: support case-insensitive lookups (fixes gh #232)

.maintainer-scripts/unicode-case-fold.pl

@@ -0,0 +1,38 @@
+#!/usr/bin/perl -w
+use strict;
+use warnings;
+
+# Input data: https://www.unicode.org/Public/UCD/latest/ucd/CaseFolding.txt
+
+my %map;
+
+while (<>) {
+    chomp;
+    next if /^(#|\s*$)/;
+    my($char, $status, $fold, $comment) = split /\s*;\s*/;
+    if ($status =~ /^[CS]$/) {
+        $comment =~ s/^#\s*//;
+        # print "    case 0x$char: return 0x$fold; // [$status] $comment\n";
+        $map{hex($char)} = hex($fold);
+    }
+}
+
+my @valid_code_points = (0..0xD7FF, 0xE000..0x10FFFF);
+
+sub cp_to_str {
+  my $cp = shift;
+  my $fmt = $cp < 0x10000 ? "\\u%04X" : "\\U%08X";
+  return sprintf $fmt, $cp;
+}
+
+while (@valid_code_points) {
+  my @cps = splice @valid_code_points, 0, 256;
+  my $orig;
+  my $folded;
+  for my $cp (@cps) {
+    my $fold = $map{$cp} // $cp;
+    $orig .= cp_to_str($cp);
+    $folded .= cp_to_str($fold);
+  }
+  print "    {u8\"$orig\"sv, u8\"$folded\"sv},\n" if $orig ne $folded;
+}

CMakeLists.txt

@@ -450,6 +450,7 @@ if(WITH_TESTS)
       pcmaudio_categorizer_test
       speedometer_test
       terminal_test
+      unicode_test
       utils_test
       file_utils_test
       worker_group_test

cmake/libdwarfs.cmake

@@ -49,6 +49,7 @@ add_library(
   src/internal/fs_section.cpp
   src/internal/glob_to_regex.cpp
   src/internal/string_table.cpp
+  src/internal/unicode_case_folding.cpp
   src/internal/wcwidth.c
   src/internal/worker_group.cpp
 

doc/dwarfs.md

@@ -104,6 +104,17 @@ options:
   overlays and want the file system to reflect its read-only
   state, you can set this option.
 
+- `-o case_insensitive`:
+  Perform case-insensitive lookups in the mounted file system,
+  i.e. an entry orignally named `ReadMe.txt` can be accessed as
+  `readme.txt`, `README.TXT`, or `rEaDmE.tXt`. This works across
+  all platforms. When mounting a file system with many files, this
+  may be slightly slower and consume slightly more memory as case-
+  insensitive lookup requires an additional mapping table that is
+  built on-demand. Note that this is not supported if the file
+  system contains directories with entries that only differ in
+  case.
+
 - `-o (no_)cache_image`:
   By default, `dwarfs` tries to ensure that the compressed file
   system image will not be cached by the kernel (i.e. the default

include/dwarfs/internal/unicode_case_folding.h

@@ -0,0 +1,32 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/**
+ * \author     Marcus Holland-Moritz ([email protected])
+ * \copyright  Copyright (c) Marcus Holland-Moritz
+ *
+ * This file is part of dwarfs.
+ *
+ * dwarfs is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * dwarfs is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with dwarfs.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <string>
+#include <string_view>
+
+namespace dwarfs::internal {
+
+std::string utf8_case_fold(std::string_view in);
+std::string utf8_case_fold_unchecked(std::string_view in);
+
+} // namespace dwarfs::internal

include/dwarfs/reader/metadata_options.h

@@ -32,6 +32,7 @@ struct metadata_options {
   bool enable_nlink{false};
   bool readonly{false};
   bool check_consistency{false};
+  bool case_insensitive_lookup{false};
   size_t block_size{512};
   std::optional<file_stat::uid_type> fs_uid{};
   std::optional<file_stat::gid_type> fs_gid{};