io: add MultiWriter (#10021)

pull/10038/head^2
Leigh McCulloch 2021-05-08 04:21:53 -07:00 committed by GitHub
parent 3dfbd2351b
commit 68c8709343
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 99 additions and 0 deletions

View File

@ -0,0 +1,33 @@
module io
// new_multi_writer returns a Writer that writes to all writers. The write
// function of the returned Writer writes to all writers of the MultiWriter,
// returns the length of bytes written, and if any writer fails to write the
// full length an error is returned and writing to other writers stops, and if
// any writer returns an error the error is returned immediately and writing to
// other writers stops.
pub fn new_multi_writer(writers []Writer) Writer {
return &MultiWriter{
writers: writers
}
}
// MultiWriter writes to all its writers.
pub struct MultiWriter {
pub:
writers []Writer
}
// write writes to all writers of the MultiWriter. Returns the length of bytes
// written. If any writer fails to write the full length an error is returned
// and writing to other writers stops. If any writer returns an error the error
// is returned immediately and writing to other writers stops.
pub fn (m MultiWriter) write(buf []byte) ?int {
for w in m.writers {
n := w.write(buf) ?
if n != buf.len {
return error('io: incomplete write to writer of MultiWriter')
}
}
return buf.len
}

View File

@ -0,0 +1,66 @@
module io
fn test_multi_writer_write_successful() {
w0 := TestWriter{}
w1 := TestWriter{}
mw := new_multi_writer([w0, w1])
n := mw.write('0123456789'.bytes()) or {
assert false
return
}
assert n == 10
assert w0.bytes == '0123456789'.bytes()
assert w1.bytes == '0123456789'.bytes()
}
fn test_multi_writer_write_incomplete() {
w0 := TestWriter{}
w1 := TestIncompleteWriter{}
mw := new_multi_writer([w0, w1])
n := mw.write('0123456789'.bytes()) or {
assert w0.bytes == '0123456789'.bytes()
assert w1.bytes == '012345678'.bytes()
return
}
assert false
}
fn test_multi_writer_write_error() {
w0 := TestWriter{}
w1 := TestErrorWriter{}
w2 := TestWriter{}
mw := new_multi_writer([w0, w1, w2])
n := mw.write('0123456789'.bytes()) or {
assert w0.bytes == '0123456789'.bytes()
assert w2.bytes == []
return
}
assert false
}
struct TestWriter {
pub mut:
bytes []byte
}
fn (mut w TestWriter) write(buf []byte) ?int {
w.bytes << buf
return buf.len
}
struct TestIncompleteWriter {
pub mut:
bytes []byte
}
fn (mut w TestIncompleteWriter) write(buf []byte) ?int {
b := buf[..buf.len - 1]
w.bytes << b
return b.len
}
struct TestErrorWriter {}
fn (mut w TestErrorWriter) write(buf []byte) ?int {
return error('error writer errored')
}