83 lines
2.1 KiB
Go
83 lines
2.1 KiB
Go
|
package ioutils
|
||
|
|
|
||
|
|
const maxCap = 10 * 1e6
|
||
|
|
|
||
|
|
// BytesPipe is io.ReadWriter which works similary to pipe(queue).
|
||
|
|
// All written data could be read only once. Also BytesPipe trying to adjust
|
||
|
|
// internal []byte slice to current needs, so there won't be overgrown buffer
|
||
|
|
// after highload peak.
|
||
|
|
// BytesPipe isn't goroutine-safe, caller must synchronize it if needed.
|
||
|
|
type BytesPipe struct {
|
||
|
|
buf []byte
|
||
|
|
lastRead int
|
||
|
|
}
|
||
|
|
|
||
|
|
// NewBytesPipe creates new BytesPipe, initialized by specified slice.
|
||
|
|
// If buf is nil, then it will be initialized with slice which cap is 64.
|
||
|
|
// buf will be adjusted in a way that len(buf) == 0, cap(buf) == cap(buf).
|
||
|
|
func NewBytesPipe(buf []byte) *BytesPipe {
|
||
|
|
if cap(buf) == 0 {
|
||
|
|
buf = make([]byte, 0, 64)
|
||
|
|
}
|
||
|
|
return &BytesPipe{
|
||
|
|
buf: buf[:0],
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
func (bp *BytesPipe) grow(n int) {
|
||
|
|
if len(bp.buf)+n > cap(bp.buf) {
|
||
|
|
// not enough space
|
||
|
|
var buf []byte
|
||
|
|
remain := bp.len()
|
||
|
|
if remain+n <= cap(bp.buf)/2 {
|
||
|
|
// enough space in current buffer, just move data to head
|
||
|
|
copy(bp.buf, bp.buf[bp.lastRead:])
|
||
|
|
buf = bp.buf[:remain]
|
||
|
|
} else {
|
||
|
|
// reallocate buffer
|
||
|
|
buf = make([]byte, remain, 2*cap(bp.buf)+n)
|
||
|
|
copy(buf, bp.buf[bp.lastRead:])
|
||
|
|
}
|
||
|
|
bp.buf = buf
|
||
|
|
bp.lastRead = 0
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Write writes p to BytesPipe.
|
||
|
|
// It can increase cap of internal []byte slice in a process of writing.
|
||
|
|
func (bp *BytesPipe) Write(p []byte) (n int, err error) {
|
||
|
|
bp.grow(len(p))
|
||
|
|
bp.buf = append(bp.buf, p...)
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
func (bp *BytesPipe) len() int {
|
||
|
|
return len(bp.buf) - bp.lastRead
|
||
|
|
}
|
||
|
|
|
||
|
|
func (bp *BytesPipe) crop() {
|
||
|
|
// shortcut for empty buffer
|
||
|
|
if bp.lastRead == len(bp.buf) {
|
||
|
|
bp.lastRead = 0
|
||
|
|
bp.buf = bp.buf[:0]
|
||
|
|
}
|
||
|
|
r := bp.len()
|
||
|
|
// if we have too large buffer for too small data
|
||
|
|
if cap(bp.buf) > maxCap && r < cap(bp.buf)/10 {
|
||
|
|
copy(bp.buf, bp.buf[bp.lastRead:])
|
||
|
|
// will use same underlying slice until reach cap
|
||
|
|
bp.buf = bp.buf[:r : cap(bp.buf)/2]
|
||
|
|
bp.lastRead = 0
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Read reads bytes from BytesPipe.
|
||
|
|
// Data could be read only once.
|
||
|
|
// Internal []byte slice could be shrinked.
|
||
|
|
func (bp *BytesPipe) Read(p []byte) (n int, err error) {
|
||
|
|
n = copy(p, bp.buf[bp.lastRead:])
|
||
|
|
bp.lastRead += n
|
||
|
|
bp.crop()
|
||
|
|
return
|
||
|
|
}
|