forgejo-federation/vendor/github.com/djherbis/nio/v3/sync.go

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package nio
import (
"io"
"sync"
)
// PipeReader is the read half of the pipe.
type PipeReader struct {
*bufpipe
}
// CloseWithError closes the reader; subsequent writes to the write half of the pipe will return the error err.
func (r *PipeReader) CloseWithError(err error) error {
if err == nil {
err = io.ErrClosedPipe
}
r.bufpipe.l.Lock()
defer r.bufpipe.l.Unlock()
if r.bufpipe.rerr == nil {
r.bufpipe.rerr = err
r.bufpipe.rwait.Signal()
r.bufpipe.wwait.Signal()
}
return nil
}
// Close closes the reader; subsequent writes to the write half of the pipe will return the error io.ErrClosedPipe.
func (r *PipeReader) Close() error {
return r.CloseWithError(nil)
}
// A PipeWriter is the write half of a pipe.
type PipeWriter struct {
*bufpipe
}
// CloseWithError closes the writer; once the buffer is empty subsequent reads from the read half of the pipe will return
// no bytes and the error err, or io.EOF if err is nil. CloseWithError always returns nil.
func (w *PipeWriter) CloseWithError(err error) error {
if err == nil {
err = io.EOF
}
w.bufpipe.l.Lock()
defer w.bufpipe.l.Unlock()
if w.bufpipe.werr == nil {
w.bufpipe.werr = err
w.bufpipe.rwait.Signal()
w.bufpipe.wwait.Signal()
}
return nil
}
// Close closes the writer; once the buffer is empty subsequent reads from the read half of the pipe will return
// no bytes and io.EOF after all the buffer has been read. CloseWithError always returns nil.
func (w *PipeWriter) Close() error {
return w.CloseWithError(nil)
}
type bufpipe struct {
rl sync.Mutex
wl sync.Mutex
l sync.Mutex
rwait sync.Cond
wwait sync.Cond
b Buffer
rerr error // if reader closed, error to give writes
werr error // if writer closed, error to give reads
}
func newBufferedPipe(buf Buffer) *bufpipe {
s := &bufpipe{
b: buf,
}
s.rwait.L = &s.l
s.wwait.L = &s.l
return s
}
func empty(buf Buffer) bool {
return buf.Len() == 0
}
func gap(buf Buffer) int64 {
return buf.Cap() - buf.Len()
}
func (r *PipeReader) Read(p []byte) (n int, err error) {
r.rl.Lock()
defer r.rl.Unlock()
r.l.Lock()
defer r.wwait.Signal()
defer r.l.Unlock()
for empty(r.b) {
if r.rerr != nil {
return 0, io.ErrClosedPipe
}
if r.werr != nil {
return 0, r.werr
}
r.wwait.Signal()
r.rwait.Wait()
}
n, err = r.b.Read(p)
if err == io.EOF {
err = nil
}
return n, err
}
func (w *PipeWriter) Write(p []byte) (int, error) {
var m int
var n, space int64
var err error
sliceLen := int64(len(p))
w.wl.Lock()
defer w.wl.Unlock()
w.l.Lock()
defer w.rwait.Signal()
defer w.l.Unlock()
if w.werr != nil {
return 0, io.ErrClosedPipe
}
// while there is data to write
for writeLen := sliceLen; writeLen > 0 && err == nil; writeLen = sliceLen - n {
// wait for some buffer space to become available (while no errs)
for space = gap(w.b); space == 0 && w.rerr == nil && w.werr == nil; space = gap(w.b) {
w.rwait.Signal()
w.wwait.Wait()
}
if w.rerr != nil {
err = w.rerr
break
}
if w.werr != nil {
err = io.ErrClosedPipe
break
}
// space > 0, and locked
var nn int64
if space < writeLen {
// => writeLen - space > 0
// => (sliceLen - n) - space > 0
// => sliceLen > n + space
// nn is safe to use for p[:nn]
nn = n + space
} else {
nn = sliceLen
}
m, err = w.b.Write(p[n:nn])
n += int64(m)
// one of the following cases has occurred:
// 1. done writing -> writeLen == 0
// 2. ran out of buffer space -> gap(w.b) == 0
// 3. an error occurred err != nil
// all of these cases are handled at the top of this loop
}
return int(n), err
}