diff --git a/src/Codec/GuidStringCodec.php b/src/Codec/GuidStringCodec.php
index 48f9ab1..40d8d71 100644
--- a/src/Codec/GuidStringCodec.php
+++ b/src/Codec/GuidStringCodec.php
@@ -14,8 +14,6 @@ declare(strict_types=1);
 
 namespace Ramsey\Uuid\Codec;
 
-use Ramsey\Uuid\Exception\InvalidArgumentException;
-use Ramsey\Uuid\Exception\InvalidUuidStringException;
 use Ramsey\Uuid\UuidInterface;
 
 /**
@@ -26,34 +24,18 @@ use Ramsey\Uuid\UuidInterface;
 class GuidStringCodec extends StringCodec
 {
     /**
-     * @psalm-pure
-     */
-    public function encodeBinary(UuidInterface $uuid): string
-    {
-        $components = $this->swapBytes($this->extractComponents($uuid->toString()));
-
-        return (string) hex2bin(implode('', $components));
-    }
-
-    /**
-     * @throws InvalidUuidStringException
-     *
      * @inheritDoc
-     *
      * @psalm-pure
      */
     public function decode(string $encodedUuid): UuidInterface
     {
-        $components = $this->swapBytes($this->extractComponents($encodedUuid));
+        $bytes = $this->getBytes($encodedUuid);
 
-        return $this->getBuilder()->build($this, $this->getFields($components));
+        return $this->getBuilder()->build($this, $this->swapBytes($bytes));
     }
 
     /**
-     * @throws InvalidArgumentException if $bytes is an invalid length
-     *
      * @inheritDoc
-     *
      * @psalm-pure
      */
     public function decodeBytes(string $bytes): UuidInterface
@@ -63,22 +45,15 @@ class GuidStringCodec extends StringCodec
     }
 
     /**
-     * @param string[] $fields The fields that comprise this UUID
-     *
-     * @return string[]
+     * Swaps bytes according to the GUID rules
      *
      * @psalm-pure
      */
-    private function swapBytes(array $fields): array
+    private function swapBytes(string $bytes): string
     {
-        $fields = array_values($fields);
-
-        // Swap bytes to support GUID byte order.
-        $bytes = (string) hex2bin(implode('', $fields));
-        $fields[0] = bin2hex($bytes[3] . $bytes[2] . $bytes[1] . $bytes[0]);
-        $fields[1] = bin2hex($bytes[5] . $bytes[4]);
-        $fields[2] = bin2hex($bytes[7] . $bytes[6]);
-
-        return $fields;
+        return $bytes[3] . $bytes[2] . $bytes[1] . $bytes[0]
+            . $bytes[5] . $bytes[4]
+            . $bytes[7] . $bytes[6]
+            . substr($bytes, 8);
     }
 }
diff --git a/src/Codec/OrderedTimeCodec.php b/src/Codec/OrderedTimeCodec.php
index f30cf58..8dc4ebe 100644
--- a/src/Codec/OrderedTimeCodec.php
+++ b/src/Codec/OrderedTimeCodec.php
@@ -58,19 +58,12 @@ class OrderedTimeCodec extends StringCodec
             );
         }
 
-        /** @var Rfc4122FieldsInterface $fields */
-        $fields = $uuid->getFields();
+        $bytes = $uuid->getFields()->getBytes();
 
-        $optimized = [
-            $fields->getTimeHiAndVersion()->toString(),
-            $fields->getTimeMid()->toString(),
-            $fields->getTimeLow()->toString(),
-            $fields->getClockSeqHiAndReserved()->toString(),
-            $fields->getClockSeqLow()->toString(),
-            $fields->getNode()->toString(),
-        ];
-
-        return (string) hex2bin(implode('', $optimized));
+        return $bytes[6] . $bytes[7]
+            . $bytes[4] . $bytes[5]
+            . $bytes[0] . $bytes[1] . $bytes[2] . $bytes[3]
+            . substr($bytes, 8);
     }
 
     /**
@@ -92,10 +85,9 @@ class OrderedTimeCodec extends StringCodec
         }
 
         // Rearrange the bytes to their original order.
-        $rearrangedBytes = substr($bytes, 4, 2)
-            . substr($bytes, 6, 2)
-            . substr($bytes, 2, 2)
-            . substr($bytes, 0, 2)
+        $rearrangedBytes = $bytes[4] . $bytes[5] . $bytes[6] . $bytes[7]
+            . $bytes[2] . $bytes[3]
+            . $bytes[0] . $bytes[1]
             . substr($bytes, 8);
 
         $uuid = parent::decodeBytes($rearrangedBytes);
diff --git a/src/Codec/StringCodec.php b/src/Codec/StringCodec.php
index 1321601..64455bf 100644
--- a/src/Codec/StringCodec.php
+++ b/src/Codec/StringCodec.php
@@ -51,19 +51,16 @@ class StringCodec implements CodecInterface
         /** @var FieldsInterface $fields */
         $fields = $uuid->getFields();
 
-        $components = [
-            $fields->getTimeLow()->toString(),
-            $fields->getTimeMid()->toString(),
-            $fields->getTimeHiAndVersion()->toString(),
-            $fields->getClockSeqHiAndReserved()->toString(),
-            $fields->getClockSeqLow()->toString(),
-            $fields->getNode()->toString(),
-        ];
-
-        return vsprintf(
-            '%08s-%04s-%04s-%02s%02s-%012s',
-            $components
-        );
+        return $fields->getTimeLow()->toString()
+            . '-'
+            . $fields->getTimeMid()->toString()
+            . '-'
+            . $fields->getTimeHiAndVersion()->toString()
+            . '-'
+            . $fields->getClockSeqHiAndReserved()->toString()
+            . $fields->getClockSeqLow()->toString()
+            . '-'
+            . $fields->getNode()->toString();
     }
 
     /**
@@ -71,7 +68,7 @@ class StringCodec implements CodecInterface
      */
     public function encodeBinary(UuidInterface $uuid): string
     {
-        return (string) hex2bin($uuid->getHex());
+        return $uuid->getFields()->getBytes();
     }
 
     /**
@@ -83,17 +80,11 @@ class StringCodec implements CodecInterface
      */
     public function decode(string $encodedUuid): UuidInterface
     {
-        $components = $this->extractComponents($encodedUuid);
-        $fields = $this->getFields($components);
-
-        return $this->builder->build($this, $fields);
+        return $this->builder->build($this, $this->getBytes($encodedUuid));
     }
 
     /**
-     * @throws InvalidArgumentException if $bytes is an invalid length
-     *
      * @inheritDoc
-     *
      * @psalm-pure
      */
     public function decodeBytes(string $bytes): UuidInterface
@@ -104,9 +95,7 @@ class StringCodec implements CodecInterface
             );
         }
 
-        $hexUuid = unpack('H*', $bytes);
-
-        return $this->decode((string) $hexUuid[1]);
+        return $this->builder->build($this, $bytes);
     }
 
     /**
@@ -118,69 +107,32 @@ class StringCodec implements CodecInterface
     }
 
     /**
-     * Returns an array of UUID components (the UUID exploded on its dashes)
-     *
-     * @param string $encodedUuid A hexadecimal string representation of a UUID
-     *
-     * @return string[]
-     *
-     * @throws InvalidUuidStringException
+     * Returns a byte string of the UUID
      *
      * @psalm-pure
      */
-    protected function extractComponents(string $encodedUuid): array
+    protected function getBytes(string $encodedUuid): string
     {
-        $nameParsed = str_replace([
-            'urn:',
-            'uuid:',
-            '{',
-            '}',
-            '-',
-        ], '', $encodedUuid);
+        $parsedUuid = str_replace(
+            ['urn:', 'uuid:', 'URN:', 'UUID:', '{', '}', '-'],
+            '',
+            $encodedUuid
+        );
 
-        // We have stripped out the dashes and are breaking up the string using
-        // substr(). In this way, we can accept a full hex value that doesn't
-        // contain dashes.
         $components = [
-            substr($nameParsed, 0, 8),
-            substr($nameParsed, 8, 4),
-            substr($nameParsed, 12, 4),
-            substr($nameParsed, 16, 4),
-            substr($nameParsed, 20),
+            substr($parsedUuid, 0, 8),
+            substr($parsedUuid, 8, 4),
+            substr($parsedUuid, 12, 4),
+            substr($parsedUuid, 16, 4),
+            substr($parsedUuid, 20),
         ];
 
-        $nameParsed = implode('-', $components);
-
-        if (!Uuid::isValid($nameParsed)) {
+        if (!Uuid::isValid(implode('-', $components))) {
             throw new InvalidUuidStringException(
                 'Invalid UUID string: ' . $encodedUuid
             );
         }
 
-        return $components;
-    }
-
-    /**
-     * Returns the fields that make up this UUID
-     *
-     * @param string[] $components An array of hexadecimal strings representing
-     *     the fields of an RFC 4122 UUID
-     *
-     * @return string The byte string for the UUID
-     *
-     * @psalm-pure
-     */
-    protected function getFields(array $components): string
-    {
-        $fields = [
-            'time_low' => str_pad($components[0], 8, '0', STR_PAD_LEFT),
-            'time_mid' => str_pad($components[1], 4, '0', STR_PAD_LEFT),
-            'time_hi_and_version' => str_pad($components[2], 4, '0', STR_PAD_LEFT),
-            'clock_seq_hi_and_reserved' => str_pad(substr($components[3], 0, 2), 2, '0', STR_PAD_LEFT),
-            'clock_seq_low' => str_pad(substr($components[3], 2), 2, '0', STR_PAD_LEFT),
-            'node' => str_pad($components[4], 12, '0', STR_PAD_LEFT),
-        ];
-
-        return (string) hex2bin(implode('', $fields));
+        return (string) hex2bin($parsedUuid);
     }
 }
diff --git a/src/Codec/TimestampFirstCombCodec.php b/src/Codec/TimestampFirstCombCodec.php
index bff41fa..5ea4d62 100644
--- a/src/Codec/TimestampFirstCombCodec.php
+++ b/src/Codec/TimestampFirstCombCodec.php
@@ -14,9 +14,7 @@ declare(strict_types=1);
 
 namespace Ramsey\Uuid\Codec;
 
-use Ramsey\Uuid\Exception\InvalidArgumentException;
 use Ramsey\Uuid\Exception\InvalidUuidStringException;
-use Ramsey\Uuid\Rfc4122\FieldsInterface;
 use Ramsey\Uuid\UuidInterface;
 
 /**
@@ -50,23 +48,15 @@ class TimestampFirstCombCodec extends StringCodec
      */
     public function encode(UuidInterface $uuid): string
     {
-        /** @var FieldsInterface $fields */
-        $fields = $uuid->getFields();
+        $bytes = $this->swapBytes($uuid->getFields()->getBytes());
 
-        $sixPieceComponents = [
-            $fields->getTimeLow()->toString(),
-            $fields->getTimeMid()->toString(),
-            $fields->getTimeHiAndVersion()->toString(),
-            $fields->getClockSeqHiAndReserved()->toString(),
-            $fields->getClockSeqLow()->toString(),
-            $fields->getNode()->toString(),
-        ];
-
-        $sixPieceComponents = $this->swapTimestampAndRandomBits($sixPieceComponents);
-
-        return vsprintf(
-            '%08s-%04s-%04s-%02s%02s-%012s',
-            $sixPieceComponents
+        return sprintf(
+            '%08s-%04s-%04s-%04s-%012s',
+            bin2hex(substr($bytes, 0, 4)),
+            bin2hex(substr($bytes, 4, 2)),
+            bin2hex(substr($bytes, 6, 2)),
+            bin2hex(substr($bytes, 8, 2)),
+            bin2hex(substr($bytes, 10))
         );
     }
 
@@ -75,9 +65,7 @@ class TimestampFirstCombCodec extends StringCodec
      */
     public function encodeBinary(UuidInterface $uuid): string
     {
-        $stringEncoding = $this->encode($uuid);
-
-        return (string) hex2bin(str_replace('-', '', $stringEncoding));
+        return $this->swapBytes($uuid->getFields()->getBytes());
     }
 
     /**
@@ -89,48 +77,33 @@ class TimestampFirstCombCodec extends StringCodec
      */
     public function decode(string $encodedUuid): UuidInterface
     {
-        $fivePieceComponents = $this->extractComponents($encodedUuid);
+        $bytes = $this->getBytes($encodedUuid);
 
-        $fivePieceComponents = $this->swapTimestampAndRandomBits($fivePieceComponents);
-
-        return $this->getBuilder()->build($this, $this->getFields($fivePieceComponents));
+        return $this->getBuilder()->build($this, $this->swapBytes($bytes));
     }
 
     /**
-     * @throws InvalidArgumentException if $bytes is an invalid length
-     *
      * @inheritDoc
-     *
      * @psalm-pure
      */
     public function decodeBytes(string $bytes): UuidInterface
     {
-        return $this->decode(bin2hex($bytes));
+        return $this->getBuilder()->build($this, $this->swapBytes($bytes));
     }
 
     /**
-     * Swaps the first 48 bits with the last 48 bits
-     *
-     * @param string[] $components An array of UUID components (the UUID exploded on its dashes)
-     *
-     * @return string[] The adjusted components
+     * Swaps bytes according to the timestamp-first COMB rules
      *
      * @psalm-pure
      */
-    private function swapTimestampAndRandomBits(array $components): array
+    private function swapBytes(string $bytes): string
     {
-        $last48Bits = $components[4];
+        $first48Bits = substr($bytes, 0, 6);
+        $last48Bits = substr($bytes, -6);
 
-        if (count($components) === 6) {
-            $last48Bits = $components[5];
-            $components[5] = $components[0] . $components[1];
-        } else {
-            $components[4] = $components[0] . $components[1];
-        }
+        $bytes = substr_replace($bytes, $last48Bits, 0, 6);
+        $bytes = substr_replace($bytes, $first48Bits, -6);
 
-        $components[0] = substr($last48Bits, 0, 8);
-        $components[1] = substr($last48Bits, 8, 4);
-
-        return $components;
+        return $bytes;
     }
 }
diff --git a/tests/Codec/StringCodecTest.php b/tests/Codec/StringCodecTest.php
index f8b4ac0..f457d0a 100644
--- a/tests/Codec/StringCodecTest.php
+++ b/tests/Codec/StringCodecTest.php
@@ -4,10 +4,12 @@ declare(strict_types=1);
 
 namespace Ramsey\Uuid\Test\Codec;
 
+use Mockery;
 use PHPUnit\Framework\MockObject\MockObject;
 use Ramsey\Uuid\Builder\UuidBuilderInterface;
 use Ramsey\Uuid\Codec\StringCodec;
 use Ramsey\Uuid\Rfc4122\Fields;
+use Ramsey\Uuid\Rfc4122\FieldsInterface;
 use Ramsey\Uuid\Test\TestCase;
 use Ramsey\Uuid\UuidInterface;
 
@@ -68,10 +70,13 @@ class StringCodecTest extends TestCase
     public function testEncodeBinaryReturnsBinaryString(): void
     {
         $expected = hex2bin('123456781234abcdabef1234abcd4321');
-        $this->uuid->method('getHex')
-            ->willReturn('123456781234abcdabef1234abcd4321');
-        $this->uuid->method('getBytes')
-            ->willReturn(hex2bin('123456781234abcdabef1234abcd4321'));
+
+        $fields = Mockery::mock(FieldsInterface::class, [
+            'getBytes' => hex2bin('123456781234abcdabef1234abcd4321'),
+        ]);
+
+        $this->uuid->method('getFields')->willReturn($fields);
+
         $codec = new StringCodec($this->builder);
         $result = $codec->encodeBinary($this->uuid);
         $this->assertSame($expected, $result);
diff --git a/tests/Encoder/TimestampLastCombCodecTest.php b/tests/Encoder/TimestampLastCombCodecTest.php
index 3985ecf..4c81098 100644
--- a/tests/Encoder/TimestampLastCombCodecTest.php
+++ b/tests/Encoder/TimestampLastCombCodecTest.php
@@ -10,6 +10,7 @@ use Ramsey\Uuid\Builder\UuidBuilderInterface;
 use Ramsey\Uuid\Codec\CodecInterface;
 use Ramsey\Uuid\Codec\TimestampLastCombCodec;
 use Ramsey\Uuid\Rfc4122\Fields;
+use Ramsey\Uuid\Rfc4122\FieldsInterface;
 use Ramsey\Uuid\Test\TestCase;
 use Ramsey\Uuid\UuidInterface;
 
@@ -46,14 +47,14 @@ class TimestampLastCombCodecTest extends TestCase
 
     public function testBinaryEncoding(): void
     {
+        $fields = Mockery::mock(FieldsInterface::class, [
+            'getBytes' => hex2bin('0800200c9a6611e19b21ff6f8cb0c57d'),
+        ]);
+
         /** @var MockObject & UuidInterface $uuidMock */
         $uuidMock = $this->getMockBuilder(UuidInterface::class)->getMock();
-        $uuidMock->expects($this->any())
-            ->method('getHex')
-            ->willReturn('0800200c9a6611e19b21ff6f8cb0c57d');
-        $uuidMock->expects($this->any())
-            ->method('getBytes')
-            ->willReturn(hex2bin('0800200c9a6611e19b21ff6f8cb0c57d'));
+        $uuidMock->expects($this->any())->method('getFields')->willReturn($fields);
+
         $encodedUuid = $this->codec->encodeBinary($uuidMock);
 
         $this->assertSame(hex2bin('0800200c9a6611e19b21ff6f8cb0c57d'), $encodedUuid);