Issue #21796 has been updated by matz (Yukihiro Matsumoto). I like `^` specifier too. Matz. ---------------------------------------- Feature #21796: unpack variant that returns the final offset https://bugs.ruby-lang.org/issues/21796#change-115856 * Author: nobu (Nobuyoshi Nakada) * Status: Open ---------------------------------------- mame (Yusuke Endoh) wrote in [#note-4](https://bugs.ruby-lang.org/issues/21785#note-4):
It's a shame `unpack` doesn't tell you how many bytes it read. You'd probably want a `unpack` variant that returns the final offset too, or a specifier that returns the current offset (like `o`?).
```ruby bytes = "\x01\x02\x03" offset = 0 leb128_value1, offset = bytes.unpack("Ro", offset: offset) #=> 1 leb128_value2, offset = bytes.unpack("Ro", offset: offset) #=> 2 leb128_value3, offset = bytes.unpack("Ro", offset: offset) #=> 3 ```
mame (Yusuke Endoh) wrote in [#note-6](https://bugs.ruby-lang.org/issues/21785#note-6):
You could tell how many bytes you read based on the size of the leb128_value returned.
That apparoach is unreliable because LEB128 is redundant. For example, both `"\x03"` and `"\x83\x00"` are valid LEB128 encodings of the value 3. See the note of the section Values - Integers, in the Wasm spec. https://webassembly.github.io/spec/core/binary/values.html#integers