feat: Add ByteString implementation for CBOR Major Type 2

Author: shahmal1yev

src/CBOR/MajorTypes/ByteString.php

@@ -0,0 +1,80 @@
+<?php
+
+namespace ATProto\Core\CBOR\MajorTypes;
+
+use ValueError;
+
+class ByteString
+{
+    public const int MAJOR_TYPE = 0x02;
+
+    public static function validate(string $input): bool
+    {
+        return ((ord($input[0]) >> 5) & 0x07) === self::MAJOR_TYPE;
+    }
+
+    public static function encode(string $input): string
+    {
+        $len = strlen($input);
+
+        if ($len <= 0x17) {
+            $header = chr((self::MAJOR_TYPE << 5) | $len);
+        } else if ($len <= 0xFF) {
+            $header = chr((self::MAJOR_TYPE << 5) | 24) . chr($len);
+        } else if ($len <= 0xFFFF) {
+            $header = chr((self::MAJOR_TYPE << 5) | 25) . pack('n', $len);
+        } else if ($len <= 0xFFFFFFFF) {
+            $header = chr((self::MAJOR_TYPE << 5) | 26) . pack('N', $len);
+        } else {
+            $header = chr((self::MAJOR_TYPE << 5) | 27) . pack('J', $len);
+        }
+
+        return $header . $input;
+    }
+
+    public static function decode(string $input): string
+    {
+        if (! self::validate($input)) {
+            throw new ValueError("Invalid CBOR ByteString major type.");
+        }
+
+        $addInfo = ord($input[0]) & 0x1F;
+        $offset = 1;
+
+        if ($addInfo <= 23) {
+            $length = $addInfo;
+        }
+
+        if ($addInfo === 24) {
+            $length = ord($input[$offset]);
+            $offset += 1;
+        }
+
+        if ($addInfo === 25) {
+            $length = unpack('n', substr($input, $offset, 2))[1];
+            $offset += 2;
+        }
+
+        if ($addInfo === 26) {
+            $length = unpack('N', substr($input, $offset, 4))[1];
+            $offset += 4;
+        }
+
+        if ($addInfo === 27) {
+            $length = unpack('J', substr($input, $offset, 8))[1];
+            $offset += 8;
+        }
+
+        if (! isset($length)) {
+            throw new \ValueError('Invalid CBOR ByteString length information.');
+        }
+
+        $text = substr($input, $offset, $length);
+
+        if (strlen($text) !== $length) {
+            throw new \ValueError("Invalid CBOR ByteString length mismatch.");
+        }
+
+        return $text;
+    }
+}

tests/Unit/CBOR/MajorTypes/ByteStringTest.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace Tests\Unit\CBOR\MajorTypes;
+
+use ATProto\Core\CBOR\MajorTypes\ByteString;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+class ByteStringTest extends TestCase
+{
+    #[DataProvider('provideValidCases')]
+    public function testValidate(string $input, string $header): void
+    {
+        $this->assertTrue(ByteString::validate($header . $input));
+    }
+
+    public static function provideValidCases(): array
+    {
+        return [
+            ['f', "\x41"],
+            ['fo', "\x42"],
+            ['foo', "\x43"],
+            ['foob', "\x44"],
+            ['fooba', "\x45"],
+            ['foobar', "\x46"],
+            [
+                str_repeat("This is a longer string.", 4),
+                "\x58\x60"
+            ],
+            [
+                str_repeat("This is a longer string.", 12),
+                "\x59\x01\x20"
+            ],
+            [
+                str_repeat("This is a longer string.", 2731),
+                "\x5A\x00\x01\x00\x08"
+            ],
+        ];
+    }
+
+    #[DataProvider('provideValidCases')]
+    public function testEncode(string $input, string $header): void
+    {
+        $expected = $header . $input;
+        $actual = ByteString::encode($input);
+
+        $this->assertSame(bin2hex($expected), bin2hex($actual));
+    }
+
+    #[DataProvider('provideValidCases')]
+    public function testDecode(string $input, string $header): void
+    {
+        $actual = ByteString::decode($header . $input);
+
+        $this->assertSame($input, $actual);
+    }
+
+    public function testDecodeThrowsExceptionForInvalidMajorType(): void
+    {
+        $this->expectException(\ValueError::class);
+        $this->expectExceptionMessage("Invalid CBOR ByteString major type.");
+
+        ByteString::decode("\x0C");
+    }
+
+    public function testDecodeThrowsExceptionForLengthMismatch(): void
+    {
+        $this->expectException(\ValueError::class);
+        $this->expectExceptionMessage("Invalid CBOR ByteString length mismatch.");
+
+        ByteString::decode("\x45\x66\x6F\x6F\x62");
+    }
+
+    public function testDecodeThrowsExceptionForInvalidAdditionalInformation(): void
+    {
+        $this->expectException(\ValueError::class);
+        $this->expectExceptionMessage("Invalid CBOR ByteString length information.");
+
+        ByteString::decode("\x5F");
+    }
+}