v/vlib/io/reader.v

79 lines
1.8 KiB
V

module io
// Reader represents a stream of data that can be read
pub interface Reader {
// read reads up to buf.len bytes and places
// them into buf.
// A type that implements this should return
// `none` on end of stream (EOF) instead of just returning 0
read(mut buf []byte) ?int
}
// make_reader is a temp that converts a type to a reader
// (e.g. for use in struct initialisation)
// (this shouldnt need to be a thing but until coercion gets made better
// it is required)
pub fn make_reader(r Reader) Reader {
return r
}
const (
read_all_len = 10 * 1024
read_all_grow_len = 1024
)
// ReadAllConfig allows options to be passed for the behaviour
// of read_all
pub struct ReadAllConfig {
reader Reader
read_to_end_of_stream bool
}
// read_all reads all bytes from a reader until either a 0 length read
// or if read_to_end_of_stream is true then the end of the stream (`none`)
pub fn read_all(config ReadAllConfig) ?[]byte {
r := config.reader
read_till_eof := config.read_to_end_of_stream
mut b := []byte{len: read_all_len}
mut read := 0
for {
new_read := r.read(mut b[read..]) or {
break
}
read += new_read
if !read_till_eof && read == 0 {
break
}
if b.len == read {
b.grow_len(read_all_grow_len)
}
}
return b[..read]
}
// read_any reads any available bytes from a reader
// (until the reader returns a read of 0 length)
pub fn read_any(r Reader) ?[]byte {
mut b := []byte{len: read_all_len}
mut read := 0
for {
new_read := r.read(mut b[read..]) or {
break
}
read += new_read
if new_read == 0 {
break
}
if b.len == read {
b.grow_len(read_all_grow_len)
}
}
return b[..read]
}
// RandomReader represents a stream of data that can be read from at a random location
interface RandomReader {
read_from(pos int, mut buf []byte) ?int
}