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v/vlib/io/custom_string_reading_test.v

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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 []byte) ?int {
$if debug {
eprintln('>>>> StringReader.read output buf.len: $buf.len')
}
if s.place > s.text.len + 1 {
return none
}
mut howmany := imin(buf.len, s.text.len - s.place)
xxx := s.text[s.place..s.place + howmany].bytes()
read := copy(buf, xxx)
s.place += read
return read
}
fn read_from_string(text string, capacity int) []byte {
mut str := StringReader{
text: text
}
mut stream := io.new_buffered_reader(reader: str, cap: capacity)
//
mut buf := []byte{len: 1}
mut res := []byte{}
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) == [byte(`a`)]
assert read_from_string('ab', capacity) == [byte(`a`), `b`]
assert read_from_string('abc', capacity) == [byte(`a`), `b`, `c`]
assert read_from_string('abcde', capacity) == [byte(`a`), `b`, `c`, `d`, `e`]
large_string_bytes := []byte{len: 1000, init: `x`}
large_string := large_string_bytes.bytestr()
assert read_from_string(large_string, capacity) == large_string_bytes
}
}