Add basic implementation for reading index files

src/IndexFile.php

@@ -0,0 +1,147 @@
+<?php
+
+namespace adrianclay\git;
+
+/**
+ * @see https://git-scm.com/docs/index-format
+ * @todo Support more functionality + extensions
+ */
+class IndexFile implements \Countable, \Iterator
+{
+    /**
+     * @var false|resource
+     */
+    private $indexFile;
+
+    /**
+     * @var int
+     */
+    private $iteratorIndex;
+
+    /**
+     * @var int
+     */
+    private $count;
+
+    /**
+     * @var IndexEntry
+     */
+    private $current;
+
+    public function __construct( string $string )
+    {
+        $this->indexFile = \fopen($string, 'r');
+        $this->rewind();
+    }
+
+    private function _count(): void
+    {
+        \fseek($this->indexFile, 0);
+        $headerString = \fread($this->indexFile, 12);
+        $header = \unpack(\implode('/', ['Nversion', 'NindexEntries']), $headerString, 4);
+        $this->count = $header['indexEntries'];
+    }
+
+    public function count(): int
+    {
+        return $this->count;
+    }
+
+    private function readIndexEntry(): IndexEntry
+    {
+        // 32-bit ctime seconds, the last time a file's metadata changed
+        // 32-bit ctime nanosecond fractions
+        // 32-bit mtime seconds, the last time a file's data changed
+        // 32-bit mtime nanosecond fractions
+        // 32-bit dev
+        // 32-bit ino
+        // 32-bit mode, split into (high to low bits)
+        // 4-bit object type
+        // 3-bit unused
+        // 9-bit unix permission. Only 0755 and 0644 are valid for regular files.
+        // 32-bit uid
+        // 32-bit gid
+        // 32-bit file size
+        // Object name for the represented object (20 bytes)
+        // A 16-bit 'flags' field split into (high to low bits)
+        //
+        \fseek($this->indexFile, 40, SEEK_CUR);
+        $objectName = fread($this->indexFile, GitObject::SHA_BIN_SIZE);
+        \fseek($this->indexFile, 2, SEEK_CUR);
+        $name = $this->read_null_terminated_name_string();
+        return new IndexEntry($name, bin2hex($objectName));
+    }
+
+    private function read_null_terminated_name_string(): string
+    {
+        $name = '';
+        while(($char = fgetc($this->indexFile)) !== false) {
+            if(!ord($char)) {
+                break;
+            }
+            $name .= $char;
+        }
+        $padding = 8 - (6 + strlen($name) + 1) % 8;
+        if($padding == 8) {
+            $padding = 0;
+        }
+        \fseek($this->indexFile, $padding, SEEK_CUR);
+        return $name;
+    }
+
+    public function next(): void
+    {
+        $this->iteratorIndex++;
+        $this->current = $this->readIndexEntry();
+    }
+
+    public function key(): int
+    {
+        return $this->iteratorIndex;
+    }
+
+    public function valid(): bool
+    {
+        return $this->iteratorIndex < $this->count();
+    }
+
+    public function rewind(): void
+    {
+        $this->iteratorIndex = 0;
+        $this->_count();
+        $this->current = $this->readIndexEntry();
+    }
+
+    public function current(): IndexEntry
+    {
+        return $this->current;
+    }
+}
+
+class IndexEntry implements SHAReference {
+    /**
+     * @var string
+     */
+    private $name;
+
+    /**
+     * @var string
+     */
+    private $sha;
+
+    public function __construct(string $name, string $sha)
+    {
+        $this->name = $name;
+        $this->sha = $sha;
+    }
+
+    public function name(): string
+    {
+        return $this->name;
+    }
+
+    public function getSHA(): string
+    {
+        return $this->sha;
+    }
+}

tests/IndexFileTest.php

@@ -0,0 +1,104 @@
+<?php
+namespace adrianclay\git;
+
+use PHPUnit\Framework\TestCase;
+
+class IndexFileTest extends TestCase
+{
+    public function testCountForZeroEntries()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/zero-entries");
+        $this->assertCount(0, $indexFile );
+    }
+
+    public function testCountForOneEntry()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/one-entry");
+        $this->assertCount(1, $indexFile );
+    }
+
+    public function testCountCanBeCalledTwiceWithSameResult()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/one-entry");
+        $this->assertCount(1, $indexFile );
+        $this->assertCount(1, $indexFile );
+    }
+
+    public function testNameForOneEntry()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/one-entry");
+        $this->assertEquals('a', $indexFile->current()->name());
+    }
+
+    public function testValidIsFalseForZeroEntries()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/zero-entries");
+        $this->assertFalse($indexFile->valid());
+    }
+
+    public function testValidBecomesFalseAfterOneCallToNextForOneEntry()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/one-entry");
+        $this->assertTrue($indexFile->valid());
+        $indexFile->next();
+        $this->assertFalse($indexFile->valid());
+    }
+
+    public function testGetShaForOneEntry()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/one-entry");
+        $this->assertEquals('e69de29bb2d1d6434b8b29ae775ad8c2e48c5391', $indexFile->current()->getSHA());
+    }
+
+    public function testShaForSecondEntry()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/two-entries-with-names-of-length-two");
+        $indexFile->current();
+        $indexFile->next();
+        $this->assertEquals('3b18e512dba79e4c8300dd08aeb37f8e728b8dad', $indexFile->current()->getSHA());
+    }
+
+    public function testTwoNamesEachOfLengthTwo()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/two-entries-with-names-of-length-two");
+        $this->assertEquals('00', $indexFile->current()->name());
+        $indexFile->next();
+        $this->assertEquals('ab', $indexFile->current()->name());
+        $indexFile->next();
+        $this->assertFalse($indexFile->valid());
+    }
+
+    public function testCallingNextAdvancesToSecondEntry()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/two-entries-with-names-of-length-two");
+        $indexFile->next();
+        $this->assertEquals('ab', $indexFile->current()->name());
+    }
+
+    public function testFetchesNameContainingAZero()
+    {
+        // Need to be careful to handle '0' and '\0' characters differently
+        // within the name field.
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/two-entries-with-names-of-length-two");
+        $this->assertEquals('00', $indexFile->current()->name());
+    }
+
+    public function testIterationIsDeterministic()
+    {
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/two-entries-with-names-of-length-two");
+        $firstIteration = iterator_to_array($indexFile, false);
+        $secondIteration = iterator_to_array($indexFile, false);
+        $this->assertEquals($firstIteration, $secondIteration);
+    }
+
+    public function testNameHandlesZeroLengthNamePadding()
+    {
+        // Entries have padding added depending on their name length.
+        // Checks that the padding calculation works correctly in the case that there is zero padding.
+        $indexFile = new IndexFile(__DIR__ . "/fixtures/index-files/two-entries-with-zero-length-name-padding");
+        $indexFile->next();
+        // Padding calculation only observable when looking at the second value retrieved.
+        $this->assertEquals("1", $indexFile->current()->name());
+        $this->assertEquals("e69de29bb2d1d6434b8b29ae775ad8c2e48c5391", $indexFile->current()->getSHA());
+    }
+}