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Instead of using lookup tables, we can use a combination of shifts and
byte swapping to achieve the same thing in less cycles and with less
code.
Benchmark files
---------------
pack1.php:
```php
for ($i = 0; $i < 10_000_000; ++$i) {
pack("J", 0x7FFFFFFFFFFFFFFF);
}
```
pack2.php:
```php
for ($i = 0; $i < 4000000; ++$i) {
pack("nvc*", 0x1234, 0x5678, 65, 66);
}
```
On an i7-4790:
```
Benchmark 1: ./sapi/cli/php pack1.php
Time (mean ± σ): 408.8 ms ± 3.4 ms [User: 406.1 ms, System: 1.6 ms]
Range (min … max): 403.6 ms … 413.6 ms 10 runs
Benchmark 2: ./sapi/cli/php_old pack1.php
Time (mean ± σ): 451.7 ms ± 7.7 ms [User: 448.5 ms, System: 2.0 ms]
Range (min … max): 442.8 ms … 461.2 ms 10 runs
Summary
./sapi/cli/php pack1.php ran
1.11 ± 0.02 times faster than ./sapi/cli/php_old pack1.php
Benchmark 1: ./sapi/cli/php pack2.php
Time (mean ± σ): 239.3 ms ± 6.0 ms [User: 236.2 ms, System: 2.3 ms]
Range (min … max): 233.2 ms … 256.8 ms 12 runs
Benchmark 2: ./sapi/cli/php_old pack2.php
Time (mean ± σ): 271.9 ms ± 3.3 ms [User: 269.7 ms, System: 1.3 ms]
Range (min … max): 267.4 ms … 279.0 ms 11 runs
Summary
./sapi/cli/php pack2.php ran
1.14 ± 0.03 times faster than ./sapi/cli/php_old pack2.php
```
On an i7-1185G7:
```
Benchmark 1: ./sapi/cli/php pack1.php
Time (mean ± σ): 263.7 ms ± 1.8 ms [User: 262.6 ms, System: 0.9 ms]
Range (min … max): 261.5 ms … 268.2 ms 11 runs
Benchmark 2: ./sapi/cli/php_old pack1.php
Time (mean ± σ): 303.3 ms ± 6.5 ms [User: 300.7 ms, System: 2.3 ms]
Range (min … max): 297.4 ms … 318.1 ms 10 runs
Summary
./sapi/cli/php pack1.php ran
1.15 ± 0.03 times faster than ./sapi/cli/php_old pack1.php
Benchmark 1: ./sapi/cli/php pack2.php
Time (mean ± σ): 156.7 ms ± 2.9 ms [User: 154.7 ms, System: 1.7 ms]
Range (min … max): 151.6 ms … 164.7 ms 19 runs
Benchmark 2: ./sapi/cli/php_old pack2.php
Time (mean ± σ): 174.6 ms ± 3.3 ms [User: 171.9 ms, System: 2.3 ms]
Range (min … max): 170.7 ms … 180.4 ms 17 runs
Summary
./sapi/cli/php pack2.php ran
1.11 ± 0.03 times faster than ./sapi/cli/php_old pack2.php
```
Closes GH-18524.
Co-authored-by: divinity76 <divinity76@gmail.com>