Implement string length

lib/UTF8.php

@@ -10,6 +10,7 @@ class UTF8 {
     protected $string;
     protected $posByte = 0;
     protected $posChar = 0;
+    protected $length = null;
 
 
     public function __construct(string $string) {
@@ -165,6 +166,22 @@ class UTF8 {
         return $out;
     }
 
+    /** Calculates the length of the string in code points 
+     * 
+     * Note that this involves processing to the end of the string
+    */
+    public function len(): int {
+        return $this->length ?? (function() {
+            $pC = $this->posChar;
+            $pB = $this->posByte;
+            while ($this->nextChr() !== "");
+            $this->length = $this->posChar;
+            $this->posChar = $pC;
+            $this->posByte = $pB;
+            return $this->length;
+        })();
+    }
+
     /** Synchronize to the byte offset of the start of the nearest character at or before byte offset $pos */
     protected function sync(int $pos) {
         $b = ord(@$this->string[$pos]);

tests/cases/TestInstance.php

@@ -17,6 +17,7 @@ class TestInstance extends \PHPUnit\Framework\TestCase {
     */
     public function testDecodeMultipleCharactersAsCodePoints(string $input, array $exp) {
         $s = new UTF8($input);
+        $out = [];
         while (($p = $s->nextOrd()) !== false) {
             $out[] = $p ?? 0xFFFD;
         }
@@ -29,6 +30,7 @@ class TestInstance extends \PHPUnit\Framework\TestCase {
      * @covers \MensBeam\UTF8\UTF8::nextChr
     */
     public function testDecodeMultipleCharactersAsStrings(string $input, array $exp) {
+        $out = [];
         $exp = array_map(function ($v) {
             return \IntlChar::chr($v);
         }, $exp);
@@ -46,6 +48,7 @@ class TestInstance extends \PHPUnit\Framework\TestCase {
     public function testSTepBackThroughAString(string $input, array $points) {
         $s = new UTF8($input);
         $a = 0;
+        $this->assertTrue(true); // prevent risky test of empty string
         while (($p1 = $s->nextOrd() ?? 0xFFFD) !== false) {
             $this->assertSame(0, $s->seek(-1));
             $p2 = $s->nextOrd() ?? 0xFFFD;
@@ -219,10 +222,26 @@ class TestInstance extends \PHPUnit\Framework\TestCase {
         $this->assertSame(5, $s->posChr());
         $this->assertSame(13, $s->posByte());
     }
+    
+    /**
+     * @dataProvider provideStrings
+     * @covers \MensBeam\UTF8\UTF8::len
+    */
+    public function testGetStringLength(string $input, array $points) {
+        $s = new UTF8($input);
+        $s->seek(1);
+        $posChar = $s->posChr();
+        $posByte = $s->posByte();
+
+        $this->assertSame(sizeof($points), $s->len());
+        $this->assertSame($posChar, $s->posChr());
+        $this->assertSame($posByte, $s->posByte());
+    }
 
     public function provideStrings() {
         return [
             // control samples
+            'empty string' => ["", []],
             'sanity check' => ["\x61\x62\x63\x31\x32\x33", [97, 98, 99, 49, 50, 51]],
             'multibyte control' => ["\xE5\x8F\xA4\xE6\xB1\xA0\xE3\x82\x84\xE8\x9B\x99\xE9\xA3\x9B\xE3\x81\xB3\xE8\xBE\xBC\xE3\x82\x80\xE6\xB0\xB4\xE3\x81\xAE\xE9\x9F\xB3", [21476, 27744, 12420, 34521, 39131, 12403, 36796, 12416, 27700, 12398, 38899]],
             'mixed sample' => ["\x7A\xC2\xA2\xE6\xB0\xB4\xF0\x9D\x84\x9E\xEF\xA3\xBF\xF4\x8F\xBF\xBD\xEF\xBF\xBE", [122, 162, 27700, 119070, 63743, 1114109, 65534]],