vieter/src/util/stream.v

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2022-05-16 14:22:53 +02:00
// Functions for interacting with `io.Reader` & `io.Writer` objects.
module util
import io
import os
// reader_to_writer tries to consume the entire reader & write it to the writer.
pub fn reader_to_writer(mut reader io.Reader, mut writer io.Writer) ? {
mut buf := []u8{len: 10 * 1024}
for {
bytes_read := reader.read(mut buf) or { break }
mut bytes_written := 0
for bytes_written < bytes_read {
c := writer.write(buf[bytes_written..bytes_read]) or { break }
bytes_written += c
}
}
}
// reader_to_file writes the contents of a BufferedReader to a file
pub fn reader_to_file(mut reader io.BufferedReader, length int, path string) ? {
mut file := os.create(path)?
defer {
file.close()
}
mut buf := []u8{len: reader_buf_size}
mut bytes_left := length
// Repeat as long as the stream still has data
for bytes_left > 0 {
// TODO check if just breaking here is safe
bytes_read := reader.read(mut buf) or { break }
bytes_left -= bytes_read
mut to_write := bytes_read
for to_write > 0 {
// TODO don't just loop infinitely here
bytes_written := file.write(buf[bytes_read - to_write..bytes_read]) or { continue }
// file.flush()
to_write = to_write - bytes_written
}
}
}
// match_array_in_array<T> returns how many elements of a2 overlap with a1. For
// example, if a1 = "abcd" & a2 = "cd", the result will be 2. If the match is
// not at the end of a1, the result is 0.
pub fn match_array_in_array<T>(a1 []T, a2 []T) int {
mut i := 0
mut match_len := 0
for i + match_len < a1.len {
if a1[i + match_len] == a2[match_len] {
match_len += 1
} else {
i += match_len + 1
match_len = 0
}
}
return match_len
}
// read_until_separator consumes an io.Reader until it encounters some
// separator array. The data read is stored inside the provided res array.
pub fn read_until_separator(mut reader io.Reader, mut res []u8, sep []u8) ? {
mut buf := []u8{len: sep.len}
for {
c := reader.read(mut buf)?
res << buf[..c]
match_len := match_array_in_array(buf[..c], sep)
if match_len == sep.len {
break
}
if match_len > 0 {
match_left := sep.len - match_len
c2 := reader.read(mut buf[..match_left])?
res << buf[..c2]
if buf[..c2] == sep[match_len..] {
break
}
}
}
}