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|
package build
import (
"bufio"
"bytes"
"io"
"sync"
)
type SyncMultiReader struct {
source *bufio.Reader
buffer []byte
static []byte
mu sync.Mutex
cond *sync.Cond
readers []*syncReader
err error
offset int
}
type syncReader struct {
mr *SyncMultiReader
offset int
closed bool
}
func NewSyncMultiReader(source io.Reader) *SyncMultiReader {
mr := &SyncMultiReader{
source: bufio.NewReader(source),
buffer: make([]byte, 0, 32*1024),
}
mr.cond = sync.NewCond(&mr.mu)
return mr
}
func (mr *SyncMultiReader) Peek(n int) ([]byte, error) {
mr.mu.Lock()
defer mr.mu.Unlock()
if mr.static != nil {
return mr.static[min(n, len(mr.static)):], nil
}
return mr.source.Peek(n)
}
func (mr *SyncMultiReader) Reset(dt []byte) {
mr.mu.Lock()
defer mr.mu.Unlock()
mr.static = dt
}
func (mr *SyncMultiReader) NewReadCloser() io.ReadCloser {
mr.mu.Lock()
defer mr.mu.Unlock()
if mr.static != nil {
return io.NopCloser(bytes.NewReader(mr.static))
}
reader := &syncReader{
mr: mr,
}
mr.readers = append(mr.readers, reader)
return reader
}
func (sr *syncReader) Read(p []byte) (int, error) {
sr.mr.mu.Lock()
defer sr.mr.mu.Unlock()
return sr.read(p)
}
func (sr *syncReader) read(p []byte) (int, error) {
end := sr.mr.offset + len(sr.mr.buffer)
loop0:
for {
if sr.closed {
return 0, io.EOF
}
end := sr.mr.offset + len(sr.mr.buffer)
if sr.mr.err != nil && sr.offset == end {
return 0, sr.mr.err
}
start := sr.offset - sr.mr.offset
dt := sr.mr.buffer[start:]
if len(dt) > 0 {
n := copy(p, dt)
sr.offset += n
sr.mr.cond.Broadcast()
return n, nil
}
// check for readers that have not caught up
hasOpen := false
for _, r := range sr.mr.readers {
if !r.closed {
hasOpen = true
} else {
continue
}
if r.offset < end {
sr.mr.cond.Wait()
continue loop0
}
}
if !hasOpen {
return 0, io.EOF
}
break
}
last := sr.mr.offset + len(sr.mr.buffer)
// another reader has already updated the buffer
if last > end || sr.mr.err != nil {
return sr.read(p)
}
sr.mr.offset += len(sr.mr.buffer)
sr.mr.buffer = sr.mr.buffer[:cap(sr.mr.buffer)]
n, err := sr.mr.source.Read(sr.mr.buffer)
if n >= 0 {
sr.mr.buffer = sr.mr.buffer[:n]
} else {
sr.mr.buffer = sr.mr.buffer[:0]
}
sr.mr.cond.Broadcast()
if err != nil {
sr.mr.err = err
return 0, err
}
nn := copy(p, sr.mr.buffer)
sr.offset += nn
return nn, nil
}
func (sr *syncReader) Close() error {
sr.mr.mu.Lock()
defer sr.mr.mu.Unlock()
if sr.closed {
return nil
}
sr.closed = true
sr.mr.cond.Broadcast()
return nil
}
|
