v/vlib/http/chunked/dechunk.v

64 lines
1.3 KiB
V

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 (s mut 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 (s mut ChunkScanner) skip_crlf() {
s.pos += 2
}
fn (s mut ChunkScanner) read_chunk(chunksize int) string {
startpos := s.pos
s.pos += chunksize
return s.text.substr(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( cscanner.read_chunk(csize) )
cscanner.skip_crlf()
}
cscanner.skip_crlf()
return sb.str()
}