1
1
mirror of https://github.com/wader/fq.git synced 2024-12-23 21:31:33 +03:00
fq/format/bencode/bencode.go
Mattias Wadman 9b81d4d3ab decode: More type safe API and split scalar into multiple types
Preparation to make decoder use less memory and API more type safe.
Now each scalar type has it's own struct type so it can store different
things and enables to have a scalar interface.
Also own types will enable experimenting with decode DLS designs like
using chained methods that are type aware.
2022-12-14 16:23:58 +01:00

98 lines
2.1 KiB
Go

package bencode
// https://wiki.theory.org/BitTorrentSpecification#Bencoding
import (
"embed"
"strconv"
"github.com/wader/fq/format"
"github.com/wader/fq/pkg/decode"
"github.com/wader/fq/pkg/interp"
"github.com/wader/fq/pkg/scalar"
)
//go:embed bencode.jq
//go:embed bencode.md
var bencodeFS embed.FS
func init() {
interp.RegisterFormat(decode.Format{
Name: format.BENCODE,
Description: "BitTorrent bencoding",
DecodeFn: decodeBencode,
Functions: []string{"torepr"},
})
interp.RegisterFS(bencodeFS)
}
var typeToNames = scalar.StrMapSymStr{
"d": "dictionary",
"i": "integer",
"l": "list",
"0": "string",
"1": "string",
"2": "string",
"3": "string",
"4": "string",
"5": "string",
"6": "string",
"7": "string",
"8": "string",
"9": "string",
}
func decodeStrIntUntil(b byte) func(d *decode.D) int64 {
return func(d *decode.D) int64 {
// 21 is sign + longest 64 bit in base 10
i := d.PeekFindByte(b, 21)
if i == -1 {
d.Fatalf("decodeStrIntUntil: failed to find %v", b)
}
s := d.UTF8(int(i))
n, err := strconv.ParseInt(s, 10, 64)
if err != nil {
d.Fatalf("decodeStrIntUntil: %q: %s", s, err)
}
return n
}
}
func decodeBencodeValue(d *decode.D) {
typ := d.FieldUTF8("type", 1, typeToNames)
switch typ {
case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9":
d.SeekRel(-8)
length := d.FieldSintFn("length", decodeStrIntUntil(':'))
d.FieldUTF8("separator", 1, d.StrAssert(":"))
d.FieldUTF8("value", int(length))
case "i":
d.FieldSintFn("value", decodeStrIntUntil('e'))
d.FieldUTF8("end", 1, d.StrAssert("e"))
case "l":
d.FieldArray("values", func(d *decode.D) {
for d.PeekBits(8) != 'e' {
d.FieldStruct("value", decodeBencodeValue)
}
})
d.FieldUTF8("end", 1, d.StrAssert("e"))
case "d":
d.FieldArray("pairs", func(d *decode.D) {
for d.PeekBits(8) != 'e' {
d.FieldStruct("pair", func(d *decode.D) {
d.FieldStruct("key", decodeBencodeValue)
d.FieldStruct("value", decodeBencodeValue)
})
}
})
d.FieldUTF8("end", 1, d.StrAssert("e"))
default:
d.Fatalf("unknown type %v", typ)
}
}
func decodeBencode(d *decode.D, _ any) any {
decodeBencodeValue(d)
return nil
}