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gitea/vendor/github.com/djherbis/buffer/partition_at.go

187 lines
3.3 KiB

package buffer
import (
"encoding/gob"
"errors"
"io"
"math"
)
type partitionAt struct {
ListAt
PoolAt
}
// NewPartitionAt returns a BufferAt which uses a PoolAt to extend or shrink its size as needed.
// It automatically allocates new buffers with pool.Get() to extend is length, and
// pool.Put() to release unused buffers as it shrinks.
func NewPartitionAt(pool PoolAt, buffers ...BufferAt) BufferAt {
return &partitionAt{
PoolAt: pool,
ListAt: buffers,
}
}
func (buf *partitionAt) Cap() int64 {
return math.MaxInt64
}
func (buf *partitionAt) Read(p []byte) (n int, err error) {
for len(p) > 0 {
if len(buf.ListAt) == 0 {
return n, io.EOF
}
buffer := buf.ListAt[0]
if Empty(buffer) {
buf.PoolAt.Put(buf.Pop())
continue
}
m, er := buffer.Read(p)
n += m
p = p[m:]
if er != nil && er != io.EOF {
return n, er
}
}
return n, nil
}
func (buf *partitionAt) ReadAt(p []byte, off int64) (n int, err error) {
if off < 0 {
return 0, errors.New("buffer.PartionAt.ReadAt: negative offset")
}
for _, buffer := range buf.ListAt {
// Find the buffer where this offset is found.
if buffer.Len() <= off {
off -= buffer.Len()
continue
}
m, er := buffer.ReadAt(p, off)
n += m
p = p[m:]
if er != nil && er != io.EOF {
return n, er
}
if len(p) == 0 {
return n, er
}
// We need to read more, starting from 0 in the next buffer.
off = 0
}
if len(p) > 0 {
return n, io.EOF
}
return n, nil
}
func (buf *partitionAt) grow() error {
next, err := buf.PoolAt.Get()
if err != nil {
return err
}
buf.Push(next)
return nil
}
func (buf *partitionAt) Write(p []byte) (n int, err error) {
for len(p) > 0 {
if len(buf.ListAt) == 0 {
if err := buf.grow(); err != nil {
return n, err
}
}
buffer := buf.ListAt[len(buf.ListAt)-1]
if Full(buffer) {
if err := buf.grow(); err != nil {
return n, err
}
continue
}
m, er := buffer.Write(p)
n += m
p = p[m:]
if er != nil && er != io.ErrShortWrite {
return n, er
}
}
return n, nil
}
func (buf *partitionAt) WriteAt(p []byte, off int64) (n int, err error) {
if off < 0 {
return 0, errors.New("buffer.PartionAt.WriteAt: negative offset")
}
if off == buf.Len() { // writing at the end special case
if err := buf.grow(); err != nil {
return 0, err
}
}
fitCheck := BufferAt.Len
for i := 0; i < len(buf.ListAt); i++ {
buffer := buf.ListAt[i]
// Find the buffer where this offset is found.
if fitCheck(buffer) < off {
off -= fitCheck(buffer)
continue
}
if i+1 == len(buf.ListAt) {
fitCheck = BufferAt.Cap
}
endOff := off + int64(len(p))
if fitCheck(buffer) >= endOff {
// Everything should fit.
return buffer.WriteAt(p, off)
}
// Assume it won't all fit, only write what should fit.
canFit := int(fitCheck(buffer) - off)
if len(p[:canFit]) > 0 {
var m int
m, err = buffer.WriteAt(p[:canFit], off)
n += m
p = p[m:]
}
off = 0 // All writes are at offset 0 of following buffers now.
if err != nil || len(p) == 0 {
return n, err
}
if i+1 == len(buf.ListAt) {
if err := buf.grow(); err != nil {
return 0, err
}
fitCheck = BufferAt.Cap
}
}
if len(p) > 0 {
err = io.ErrShortWrite
}
return n, err
}
func (buf *partitionAt) Reset() {
for len(buf.ListAt) > 0 {
buf.PoolAt.Put(buf.Pop())
}
}
func init() {
gob.Register(&partitionAt{})
}