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package system
import (
"bytes"
"errors"
"fmt"
"io"
"os"
"syscall"
)
// CopyFile reads up to n bytes from src and writes the resulting byte slice to payloadP.
func (sys *I) CopyFile(payloadP *[]byte, src string, cap int, n int64) *I {
buf := new(bytes.Buffer)
buf.Grow(cap)
sys.ops = append(sys.ops, &tmpfileOp{payloadP, src, n, buf})
return sys
}
// tmpfileOp implements [I.CopyFile].
type tmpfileOp struct {
payload *[]byte
src string
n int64
buf *bytes.Buffer
}
func (t *tmpfileOp) Type() Enablement { return Process }
func (t *tmpfileOp) apply(sys *I) error {
if t.payload == nil {
// this is a misuse of the API; do not return a wrapped error
return errors.New("invalid payload")
}
sys.verbose("copying", t)
if b, err := sys.stat(t.src); err != nil {
return newOpError("tmpfile", err, false)
} else {
if b.IsDir() {
return newOpError("tmpfile", &os.PathError{Op: "stat", Path: t.src, Err: syscall.EISDIR}, false)
}
if s := b.Size(); s > t.n {
return newOpError("tmpfile", &os.PathError{Op: "stat", Path: t.src, Err: syscall.ENOMEM}, false)
}
}
var r io.ReadCloser
if f, err := sys.open(t.src); err != nil {
return newOpError("tmpfile", err, false)
} else {
r = f
}
if n, err := io.CopyN(t.buf, r, t.n); err != nil {
if !errors.Is(err, io.EOF) {
_ = r.Close()
return newOpError("tmpfile", err, false)
}
sys.verbosef("copied %d bytes from %q", n, t.src)
}
if err := r.Close(); err != nil {
return newOpError("tmpfile", err, false)
}
*t.payload = t.buf.Bytes()
return nil
}
func (t *tmpfileOp) revert(*I, *Criteria) error { t.buf.Reset(); return nil }
func (t *tmpfileOp) Is(o Op) bool {
target, ok := o.(*tmpfileOp)
return ok && t != nil && target != nil &&
t.src == target.src && t.n == target.n
}
func (t *tmpfileOp) Path() string { return t.src }
func (t *tmpfileOp) String() string { return fmt.Sprintf("up to %d bytes from %q", t.n, t.src) }
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