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delim.go
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delim.go
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package memdump
import (
"errors"
"io"
)
// delim is used to recognize the end of the memory dump
var delim = []byte{
130, 14, 133, 49, 108, 178, 125, 95,
35, 126, 41, 129, 229, 48, 16, 94,
}
// ErrBufferTooSmall is returned by delimetedReader if the input buffer
// is smaller than the length of the delimeter
var ErrBufferTooSmall = errors.New(
"cannot read into buffer of size less than 16 bytes (due to delim)")
// ErrUnexpectedEOF is returned by delimetedReader if EOF is reached
// before finding a delimeter
var ErrUnexpectedEOF = errors.New(
"got EOF before finding the delimeter")
// DelimitedReader reads delimited segments
type DelimitedReader struct {
r io.Reader
buf []byte
begin int
end int
}
// NewDelimitedReader creates a reader for delimited segments
func NewDelimitedReader(r io.Reader) *DelimitedReader {
return &DelimitedReader{
r: r,
}
}
// Next returns the next segment, or (nil, io.EOF) if there are no more segments.
// The data is only valid until the next call to Next().
func (r *DelimitedReader) Next() ([]byte, error) {
var state, offset int
for {
// look for the next delimiter
for i, b := range r.buf[r.begin+offset : r.end] {
if b != delim[state] {
state = 0
}
// do not use "else" here because we updated state above
if b == delim[state] {
state++
if state == len(delim) {
out := r.buf[r.begin : r.begin+offset+i-len(delim)+1]
r.begin = r.begin + offset + i + 1
return out, nil
}
}
}
offset = r.end - r.begin
// allocate a larger buffer
if r.buf == nil {
r.buf = make([]byte, 16384)
} else {
var newbuf []byte
newbuf = make([]byte, 4*len(r.buf))
copy(newbuf, r.buf[r.begin:r.end])
r.end -= r.begin
r.begin = 0
r.buf = newbuf
}
// fill the rest of the buffer
n, err := r.r.Read(r.buf[r.end:])
r.end += n
// check for exit conditions
if n == 0 && err == io.EOF {
if offset == 0 {
return nil, io.EOF
}
return nil, ErrUnexpectedEOF
} else if err != nil {
return nil, err
}
}
}