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buffer.go
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buffer.go
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package modsecurity
import (
"bytes"
"errors"
"io"
"io/ioutil"
"os"
)
func newBuffer(dir string, memLimit, fileLimit int64) (*buffer, error) {
err := makeBufferDir(dir)
if err != nil {
return nil, err
}
return &buffer{
dir: dir,
memLimit: memLimit,
fileLimit: fileLimit,
memBuf: bytes.NewBuffer(nil),
}, nil
}
type buffer struct {
dir string
length int64
memLimit int64
fileLimit int64
memBuf *bytes.Buffer
memReader *bytes.Reader
fileBuf *os.File
readed bool
}
var ErrOutOfFileLimit = errors.New("out of file limit")
var ErrOutOfMemLimit = errors.New("out of memory limit")
var ErrBufferReaded = errors.New("buffer can't write after read")
func (b *buffer) Write(p []byte) (wn int, err error) {
if b.readed {
return 0, ErrBufferReaded
}
switch {
case b.length+int64(len(p)) > b.fileLimit:
return 0, ErrOutOfFileLimit
case b.fileBuf == nil && b.length+int64(len(p)) > b.memLimit:
b.memBuf.Write(p[:b.memLimit-b.length])
b.fileBuf, err = ioutil.TempFile(b.dir, "modsecurity-buffer-*.data")
if err != nil {
return 0, err
}
_, err = b.fileBuf.Write(b.memBuf.Bytes())
if err != nil {
return 0, err
}
wn, err = b.fileBuf.Write(p)
case b.fileBuf == nil:
wn, err = b.memBuf.Write(p)
default:
wn, err = b.fileBuf.Write(p)
}
b.length += int64(wn)
return wn, err
}
func (b *buffer) String() (string, error) {
var err error
b.initRead()
if b.fileBuf != nil {
err = ErrOutOfMemLimit
}
return b.memBuf.String(), err
}
func (b *buffer) Bytes() ([]byte, error) {
var err error
b.initRead()
if b.fileBuf != nil {
err = ErrOutOfMemLimit
}
return b.memBuf.Bytes(), err
}
func (b *buffer) Len() int64 {
return b.length
}
func (b *buffer) initRead() {
if !b.readed {
b.memReader = bytes.NewReader(b.memBuf.Bytes())
b.fileBuf.Seek(0, 0)
}
return
}
func (b *buffer) Read(p []byte) (n int, err error) {
b.initRead()
if b.fileBuf == nil {
return b.memReader.Read(p)
}
return b.fileBuf.Read(p)
}
func (b *buffer) WriteTo(w io.Writer) (n int64, err error) {
b.initRead()
if b.fileBuf == nil {
return b.memReader.WriteTo(w)
}
return io.Copy(w, b.fileBuf)
}
func (b *buffer) Seek(offset int64, whence int) (int64, error) {
b.initRead()
if b.fileBuf == nil {
return b.memReader.Seek(offset, whence)
}
return b.fileBuf.Seek(offset, whence)
}
func (b *buffer) Close() error {
filename := b.fileBuf.Name()
err := b.fileBuf.Close()
err2 := os.Remove(filename)
switch {
case err != nil:
return err
case err2 != nil:
return err2
}
return nil
}
func makeBufferDir(dir string) error {
_, err := os.Stat(dir)
if err != nil {
if os.IsNotExist(err) {
if err := os.MkdirAll(dir, 0700); err != nil {
return err
}
} else {
return err
}
}
return nil
}