Add script to aid generation of perfect hash table

Author: nielsdos

ext/mbstring/libmbfl/mbfl/generate_name_perfect_hash_table.php

@@ -0,0 +1,112 @@
+<?php
+
+function read_encoding_pointer_array(): array {
+    // read the encoding pointer array
+    $file_content = file_get_contents(__DIR__ . '/mbfl_encoding.c');
+    $pattern = '/static const mbfl_encoding \*mbfl_encoding_ptr_list\[\][\s\S]*?\{([^}]*)\};/';
+    preg_match($pattern, $file_content, $matches);
+    assert(isset($matches[1]));
+    $array = explode(",\n", $matches[1]);
+    $array = array_map(function ($item) {
+        return trim($item, "&\n\t ");
+    }, $array);
+    array_pop($array); // Remove NULL
+    return $array;
+}
+
+function search_struct_in_file(array &$result, $struct_names, $file_path)
+{
+    $fileContent = file_get_contents($file_path);
+    $pattern = '/const mbfl_encoding\s+(' . implode('|', $struct_names) . ')\s* = {([^}]*)}/';
+    preg_match_all($pattern, $fileContent, $matches, PREG_SET_ORDER);
+    foreach ($matches as $match) {
+        $current_struct_name = $match[1];
+        $struct_definition = $match[2];
+        // Note: name is the second file
+        $name = explode(',', $struct_definition)[1];
+        $result[$current_struct_name] = trim($name, " \n\t\"");
+    }
+}
+
+function search_struct_in_dir($struct_names): array
+{
+    $result = [];
+    foreach (glob(__DIR__ . "/../**/*.c") as $file) {
+        search_struct_in_file($result, $struct_names, $file);
+    }
+    return $result;
+}
+
+$encoding_pointer_array = read_encoding_pointer_array();
+$encoding_pointer_array_name_mapping = search_struct_in_dir($encoding_pointer_array);
+
+// The single byte encodings are generated and cannot be found in dedicated generated structs
+$fixed_encodings = [
+    'mbfl_encoding_cp1251' => 'Windows-1251',
+    'mbfl_encoding_cp1252' => 'Windows-1252',
+    'mbfl_encoding_cp1254' => 'Windows-1254',
+    'mbfl_encoding_8859_1' => 'ISO-8859-1',
+    'mbfl_encoding_8859_2' => 'ISO-8859-2',
+    'mbfl_encoding_8859_3' => 'ISO-8859-3',
+    'mbfl_encoding_8859_4' => 'ISO-8859-4',
+    'mbfl_encoding_8859_5' => 'ISO-8859-5',
+    'mbfl_encoding_8859_6' => 'ISO-8859-6',
+    'mbfl_encoding_8859_7' => 'ISO-8859-7',
+    'mbfl_encoding_8859_8' => 'ISO-8859-8',
+    'mbfl_encoding_8859_9' => 'ISO-8859-9',
+    'mbfl_encoding_8859_10' => 'ISO-8859-10',
+    'mbfl_encoding_8859_13' => 'ISO-8859-13',
+    'mbfl_encoding_8859_14' => 'ISO-8859-14',
+    'mbfl_encoding_8859_15' => 'ISO-8859-15',
+    'mbfl_encoding_8859_16' => 'ISO-8859-16',
+    'mbfl_encoding_cp866' => 'CP866',
+    'mbfl_encoding_cp850' => 'CP850',
+    'mbfl_encoding_koi8r' => 'KOI8-R',
+    'mbfl_encoding_koi8u' => 'KOI8-U',
+    'mbfl_encoding_armscii8' => 'ArmSCII-8',
+    'mbfl_encoding_ascii' => 'ASCII',
+];
+
+// Add the fixed encodings
+foreach ($fixed_encodings as $encoding_pointer => $encoding_name) {
+    $encoding_pointer_array_name_mapping[$encoding_pointer] = $encoding_name;
+}
+
+// Consistency check: all of the encoding pointer array entries should be found
+foreach ($encoding_pointer_array as $encoding_pointer) {
+    assert(isset($encoding_pointer_array_name_mapping[$encoding_pointer]), "Missing entry for $encoding_pointer");
+}
+
+$ordered_name_list = array_map(function ($encoding_pointer) use ($encoding_pointer_array_name_mapping) {
+    return $encoding_pointer_array_name_mapping[$encoding_pointer];
+}, $encoding_pointer_array);
+
+// Write out ordered name list, and invoke gperf for computing the perfect hash table
+file_put_contents(__DIR__ . '/encodings.txt', implode("\n", $ordered_name_list));
+ob_start();
+passthru('gperf ' . escapeshellarg(__DIR__ . '/encodings.txt') . ' --readonly-tables --null-strings --ignore-case -m 1000');
+$output = ob_get_clean();
+@unlink(__DIR__ . '/encodings.txt');
+
+// Find asso_values array in $output
+$pattern = '/static const unsigned char asso_values\[\] =([^}]*)\};/';
+preg_match($pattern, $output, $matches);
+assert(isset($matches[1]));
+$asso_values = trim($matches[1], "\t \n{");
+echo "===--- Copy and paste the following values in the asso_values array in mbfl_encoding.c ---===\n";
+echo $asso_values, "\n";
+
+// Find word_list array in $output
+$pattern = '/static const char \* const wordlist\[\] =([^}]*)\};/';
+preg_match($pattern, $output, $matches);
+assert(isset($matches[1]));
+$word_list = trim($matches[1], "\t \n{");
+$word_list = str_replace('(char*)0', '-1', $word_list);
+foreach ($encoding_pointer_array_name_mapping as $key => $value)
+{
+    $index = array_search($key, $encoding_pointer_array);
+    $word_list = str_replace("\"$value\"", $index, $word_list);
+}
+
+echo "===--- Copy and paste the following values in the mbfl_encoding_ptr_list_after_hashing array in mbfl_encoding.c ---===\n";
+echo $word_list, "\n";