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module chunked
import strings
// See: https://en.wikipedia.org/wiki/Chunked_transfer_encoding
// /////////////////////////////////////////////////////////////
// The chunk size is transferred as a hexadecimal number
// followed by \r\n as a line separator,
// followed by a chunk of data of the given size.
// The end is marked with a chunk with size 0.
struct ChunkScanner {
mut:
pos int
text string
}
fn (mut s ChunkScanner) read_chunk_size() int {
mut n := 0
for {
if s.pos >= s.text.len {
break
}
c := s.text[s.pos]
if !c.is_hex_digit() {
break
}
n = n << 4
n += int(unhex(c))
s.pos++
}
return n
}
fn unhex(c byte) byte {
if `0` <= c && c <= `9` {
return c - `0`
} else if `a` <= c && c <= `f` {
return c - `a` + 10
} else if `A` <= c && c <= `F` {
return c - `A` + 10
}
return 0
}
fn (mut s ChunkScanner) skip_crlf() {
s.pos += 2
}
fn (mut s ChunkScanner) read_chunk(chunksize int) string {
startpos := s.pos
s.pos += chunksize
return s.text[startpos..s.pos]
}
pub fn decode(text string) string {
mut sb := strings.new_builder(100)
mut cscanner := ChunkScanner{
pos: 0
text: text
}
for {
csize := cscanner.read_chunk_size()
if 0 == csize {
break
}
cscanner.skip_crlf()
sb.write_string(cscanner.read_chunk(csize))
cscanner.skip_crlf()
}
cscanner.skip_crlf()
return sb.str()
}
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