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Kaitai Struct: PHP notes

The Kaitai Struct runtime for PHP requires PHP >= 7.0 and can be used in two different ways:

1) As part of Kaitai Struct (recommended approach)

2) Independently as Composer’s library (not recommended approach)

The first approach is recommended as the second one is considered for internal usage in Kaitai Struct PHP Runtime and its API can be changed. The first approach is similar to how other runtimes are supposed to be used.

1. Usage as part of Kaitai Struct (recommended approach)

mkdir kaitai-test
cd kaitai-test

#######################################################################################
# Download Kaitai Struct Compiler, link can be found at https://kaitai.io/#download page

curl -OL https://bintray.com/artifact/download/kaitai-io/universal/0.10/kaitai-struct-compiler-0.10.zip

unzip kaitai-struct-compiler-0.10.zip

cd kaitai-struct-compiler-0.10

###############
# Check version

bin/kaitai-struct-compiler --version
# Shows kaitai-struct-compiler 0.10

################################################
# Download and compile ELF file format - elf.ksy

curl -OL https://raw.githubusercontent.com/kaitai-io/kaitai_struct_formats/master/executable/elf.ksy

bin/kaitai-struct-compiler --target php --outdir my-elf-parser --php-namespace 'My\Parser' elf.ksy

#################################
# Check the result of compilation

ls my-elf-parser
# Shows Elf.php

########################
# Use the generated file

cd my-elf-parser

# Install PHP runtime
cat <<'OUT' > composer.json
{
    "minimum-stability": "dev",
    "require": {
        "kaitai-io/kaitai_struct_php_runtime": "dev-master"
    },
    "repositories": [
        {
            "type": "vcs",
            "url":  "[email protected]:kaitai-io/kaitai_struct_php_runtime.git"
        }
    ]
}
OUT
composer install

# E.g. of usage
cat <<'OUT' > elf-parser.php
<?php
// Include Kaitai Struct PHP Runtime.
require __DIR__ . '/vendor/autoload.php';
// Include the generated classes.
require __DIR__ . '/Elf.php';

// Note: the same namespace is used as was used in command line (--php-namespace option).
$elfFile = \My\Parser\Elf::fromFile('/usr/bin/bash');

$entryPoint = $elfFile->header()->entryPoint();

echo "Entry point 0x" . dechex($entryPoint) . " (as int: $entryPoint)";
OUT

php elf-parser.php
# Shows "Entry point 0x41b6e0 (as int: 4306656)"

2. Independent usage as Composer’s library (not recommended approach)

# Create composer.json
cat <<'OUT' > composer.json
{
    "minimum-stability": "dev",
    "require": {
        "kaitai-io/kaitai_struct_php_runtime": "dev-master"
    },
    "repositories": [
        {
            "type": "vcs",
            "url":  "[email protected]:kaitai-io/kaitai_struct_php_runtime.git"
        }
    ]
}
OUT

# Install the library
composer install --prefer-source --no-dev

# Usage example
cat <<'OUT' > bash-ep.php
<?php
require __DIR__ . '/vendor/autoload.php';

$binStream = new \Kaitai\Struct\Stream(fopen('/usr/bin/bash', 'rb'));
$binStream->seek(5);
$endianness = $binStream->readS1();
$binStream->seek(24);
if ($endianness === 1) {
    // Read on little-endian machine
    $entryPoint = $binStream->readU8le();
} else {
    // Read on bin-endian machine
    $entryPoint = $binStream->readU8be();
}
echo "Entry point 0x" . dechex($entryPoint) . " (as int: $entryPoint)";
OUT

php bash-ep.php
# Shows "Entry point 0x41b6e0 (as int: 4306656)"