import io struct StringReader { text string mut: place int } fn imin(a int, b int) int { return if a < b { a } else { b } } fn (mut s StringReader) read(mut buf []u8) !int { $if debug { eprintln('>>>> StringReader.read output buf.len: $buf.len') } if s.place > s.text.len + 1 { return IError(io.Eof{}) } mut howmany := imin(buf.len, s.text.len - s.place) xxx := s.text[s.place..s.place + howmany].bytes() read := copy(mut buf, xxx) s.place += read return read } fn read_from_string(text string, capacity int) []u8 { mut str := StringReader{ text: text } mut stream := io.new_buffered_reader(reader: str, cap: capacity) // mut buf := []u8{len: 1} mut res := []u8{} mut i := 0 for { z := stream.read(mut buf) or { break } res << buf $if debug { println('capacity: $capacity, i: $i, buf: $buf | z: $z') } i++ } return res } pub fn test_reading_from_a_string() { for capacity in 1 .. 1000 { assert read_from_string('a', capacity) == [u8(`a`)] assert read_from_string('ab', capacity) == [u8(`a`), `b`] assert read_from_string('abc', capacity) == [u8(`a`), `b`, `c`] assert read_from_string('abcde', capacity) == [u8(`a`), `b`, `c`, `d`, `e`] large_string_bytes := []u8{len: 1000, init: `x`} large_string := large_string_bytes.bytestr() assert read_from_string(large_string, capacity) == large_string_bytes } }