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Edgar 2022-09-07 17:18:59 +02:00
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content/blog/bencode-parser-with-nom.md
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@ -7,11 +7,11 @@ draft = true
categories = ["rust"]
+++
Since long I have wanted try out nom, at first I boldly started parsing [PDFs](https://github.com/edg-l/nompdf) but after realizing the scope of such project, I put it off and started with a way smaller idea: a bencode parser.
Since long I wanted try out nom, at first I boldly started parsing [PDFs](https://github.com/edg-l/nompdf) but after realizing the scope of such project, I put it off and started with a way smaller idea: a bencode parser.
If you have never delved into the BitTorrent protocol you probably don't know what bencoding is so let me explain it.
# Bencode Spec
# The Bencode Spec
[Bencode](https://en.wikipedia.org/wiki/Bencode) is the encoding used by the BitTorrent protocol to store data, `.torrent` files are encoded using this.
@ -105,7 +105,7 @@ We will also define the type alias BenResult, so we don't need to type as much e
type BenResult<'a> = IResult<&'a [u8], Value<'a>, Error<&'a [u8]>>;
```
We use `&'a [u8]` since thats the type of data our parsers will be dealing with.
We use `&[u8]` since thats the type of data our parsers will be dealing with.
# Representing all the possible bencode value types
@ -123,7 +123,7 @@ pub enum Value<'a> {
# Parsing the byte string
Lets start with the easiest one, the byte strings, as you can recall, made up of an ASCII integer, a colon and the data:
Lets start with the easiest one, byte strings, as you can recall, they are made up of the a textual integer, a colon and the data:
`4:spam`
@ -232,7 +232,7 @@ We will use the following new nom parsers:
- [many_till(f, g)](https://docs.rs/nom/7.1.1/nom/multi/fn.many_till.html): Applies the parser f until the parser g produces a result. Returns a pair consisting of the results of f in a Vec and the result of g.
We will apply the parser `alt` parser, until the `char` parser recognizes the end character `e`:
We will apply the parser `alt` until the `char` parser recognizes the end character `e`:
```rust
// Self here is the enum Value