Subversion Repositories php_utils

<?php

/*

 * PHP git functions

 * Copyright 2021 Daniel Marschall, ViaThinkSoft

 * Revision 2021-10-03

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

function git_get_latest_commit_message($git_dir) {

        $cont = file_get_contents($git_dir.'/HEAD');

        if (!preg_match('@ref: (.+)[\r\n]@', "$cont\n", $m)) throw new Exception("Cannot find HEAD ref");

        $commit_object = trim(file_get_contents($git_dir.'/'.$m[1]));

        $objects_dir = $git_dir . '/objects';

        $pack_files = glob($objects_dir.'/pack/pack-*.pack');

        $last_exception = 'No pack files found';

        foreach ($pack_files as $basename) {

                $basename = substr(basename($basename),0,strlen(basename($basename))-5);

                try {

                        return git_read_object($commit_object,

                                $objects_dir.'/pack/'.$basename.'.idx',

                                $objects_dir.'/pack/'.$basename.'.pack',

                                false

                        );

                } catch (Exception $e) {

                        $last_exception = $e;

                }

        }

        throw new Exception($last_exception);

}

function git_read_object($object_wanted, $idx_file, $pack_file, $debug=false) {

        // More info about the IDX and PACK format: https://git-scm.com/docs/pack-format

        // Do some checks

        if (!preg_match('/^[0-9a-fA-F]{40}$/', $object_wanted, $m)) throw new Exception("Is not a valid object: $object_wanted");

        if (!file_exists($idx_file)) throw new Exception("Idx file $idx_file not found");

        if (!file_exists($pack_file)) throw new Exception("Pack file $pack_file not found");

        // Open index file

        $fp = fopen($idx_file, 'rb');

        if (!$fp) throw new Exception("Cannot open index file $idx_file");

        // Read version

        fseek($fp, 0);

        $unpacked = unpack('N', fread($fp, 4)); // vorzeichenloser Long-Typ (immer 32 Bit, Byte-Folge Big-Endian)

        if ($unpacked[1] === 0xFF744F63) {

                $version = unpack('N', fread($fp, 4))[1]; // vorzeichenloser Long-Typ (immer 32 Bit, Byte-Folge Big-Endian)

                $fanout_offset = 8;

                if ($version != 2) throw new Exception("Version $version unknown");

        } else {

                $version = 1;

                $fanout_offset = 0;

        }

        if ($debug) echo "Index file version = $version\n";

        // Read fanout table

        fseek($fp, $fanout_offset);

        $fanout_ary[0] = 0;

        $fanout_ary = unpack('N*', fread($fp, 4*256));

        $num_objects = $fanout_ary[256];

        // Find out approximate object number (from fanout table)

        $fanout_index = hexdec(substr($object_wanted,0,2));

        if ($debug) echo "Fanout index = ".($fanout_index-1)."\n";

        $object_no = $fanout_ary[$fanout_index]; // approximate

        if ($debug) echo "Object no approx $object_no\n";

        // Find the exact object number

        fseek($fp, $fanout_offset + 4*256 + 20*$object_no);

        $object_no--;

        do {

                $object_no++;

                if ($version == 1) {

                        $pack_offset = fread($fp, 4);

                }

                $binary = fread($fp, 20);

                if (substr(bin2hex($binary),0,2) != substr(strtolower($object_wanted),0,2)) {

                        throw new Exception("Object $object_wanted not found");

                }

        } while (bin2hex($binary) != strtolower($object_wanted));

        if ($debug) echo "Exact object no = $object_no\n";

        if ($version == 2) {

                // Get CRC32

                fseek($fp, $fanout_offset + 4*256 + 20*$num_objects + 4*$object_no);

                $crc32 = unpack('N', fread($fp,4))[1];

                if ($debug) echo "CRC32 = ".sprintf('0x%08x',$crc32)."\n";

                // Get offset (32 bit)

                fseek($fp, $fanout_offset + 4*256 + 20*$num_objects + 4*$num_objects + 4*$object_no);

                $offset_info = unpack('N', fread($fp,4))[1];

                if ($offset_info >= 0x80000000) {

                        // MSB set, so the offset is 64 bit

                        if ($debug) echo "64 bit pack offset\n";

                        $offset_info &= 0x7FFFFFFF;

                        fseek($fp, $fanout_offset + 4*256 + 20*$num_objects + 4*$num_objects + 4*$num_objects + 8*$offset_info);

                        $pack_offset = unpack('J', fread($fp,8))[1];

                } else {

                        // MSB is not set, so the offset is 32 bit

                        if ($debug) echo "32 bit pack offset\n";

                        $offset_info &= 0x7FFFFFFF;

                        $pack_offset = $offset_info;

                }

        }

        if ($debug) echo "Pack file offset = ".sprintf('0x%x',$pack_offset)."\n";

        // Close index file

        fclose($fp);

        // Open pack file

        $fp = fopen($pack_file, 'rb');

        if (!$fp) throw new Exception("Cannot open pack file $pack_file");

        // Find out type

        fseek($fp, $pack_offset);

        $size_info = unpack('C', fread($fp,1))[1];

        $type = ($size_info & 0xE0) >> 5; /*0b11100000*/

        switch ($type) {

                case 1:

                        if ($debug) echo "Type = OBJ_COMMIT ($type)\n";

                        break;

                case 2:

                        if ($debug) echo "Type = OBJ_TREE ($type)\n";

                        break;

                case 3:

                        if ($debug) echo "Type = OBJ_BLOB ($type)\n";

                        break;

                case 4:

                        if ($debug) echo "Type = OBJ_TAG ($type)\n";

                        break;

                case 6:

                        if ($debug) echo "Type = OBJ_OFS_DELTA ($type)\n";

                        break;

                case 7:

                        if ($debug) echo "Type = OBJ_REF_DELTA ($type)\n";

                        break;

                default:

                        if ($debug) echo "Type = Invalid ($type)\n";

                        break;

        }

        // Find out size

        $size = $size_info & 0x1F /*0x00011111*/;

        $shift_info = 5;

        do {

                $size_info = unpack('C', fread($fp,1))[1];

                $size = (($size_info & 0x7F) << $shift_info) + $size;

                $shift_info += 8;

        } while ($offset_info >= 0x80000000);

        if ($debug) echo "Packed size = ".sprintf('0x%x',$size)."\n";

        // Read delta base type

        if ($type == 6/*OBJ_OFS_DELTA*/) {

                // "a negative relative offset from the delta object's position in the pack

                // if this is an OBJ_OFS_DELTA object"

                $delta_info = unpack('C*', fread($fp,4))[1]; // TODO?!

                if ($debug) echo "Delta negative offset: $delta_info\n";

        }

        if ($type == 7/*OBJ_REF_DELTA*/) {

                // "base object name if OBJ_REF_DELTA"

                $delta_info = bin2hex(fread($fp,20))[1]; // TODO?!

                if ($debug) echo "Delta base object name: $delta_info\n";

        }

        // Read compressed data

        $compressed = fread($fp,$size);

        // Uncompress

        $uncompressed = @gzuncompress($compressed);

        if ($uncompressed === false) throw new Exception("Decompression failed");

        if ($debug) echo "$uncompressed\n";

        // Close pack file

        fclose($fp);

        // Check CRC32

        // TODO: Does not fit, not crc32 nor crc32b...

        // if ($debug) echo "CRC32 found = 0x".hash('crc32',$compressed)."\n";

        return $uncompressed;

}