77 lines
1.8 KiB
Go
77 lines
1.8 KiB
Go
package system
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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"os"
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"syscall"
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)
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// CopyFile registers an Op that copies from src.
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// A buffer is initialised with size cap and the Op faults if bytes read exceed n.
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func (sys *I) CopyFile(payload *[]byte, src string, cap int, n int64) *I {
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buf := new(bytes.Buffer)
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buf.Grow(cap)
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sys.lock.Lock()
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sys.ops = append(sys.ops, &Tmpfile{payload, src, n, buf})
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sys.lock.Unlock()
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return sys
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}
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type Tmpfile struct {
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payload *[]byte
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src string
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n int64
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buf *bytes.Buffer
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}
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func (t *Tmpfile) Type() Enablement { return Process }
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func (t *Tmpfile) apply(sys *I) error {
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sys.println("copying", t)
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if t.payload == nil {
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// this is a misuse of the API; do not return an error message
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return errors.New("invalid payload")
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}
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if b, err := os.Stat(t.src); err != nil {
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return sys.wrapErrSuffix(err,
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fmt.Sprintf("cannot stat %q:", t.src))
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} else {
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if b.IsDir() {
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return sys.wrapErrSuffix(syscall.EISDIR,
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fmt.Sprintf("%q is a directory", t.src))
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}
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if s := b.Size(); s > t.n {
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return sys.wrapErrSuffix(syscall.ENOMEM,
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fmt.Sprintf("file %q is too long: %d > %d",
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t.src, s, t.n))
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}
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}
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if f, err := os.Open(t.src); err != nil {
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return sys.wrapErrSuffix(err,
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fmt.Sprintf("cannot open %q:", t.src))
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} else if _, err = io.CopyN(t.buf, f, t.n); err != nil {
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return sys.wrapErrSuffix(err,
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fmt.Sprintf("cannot read from %q:", t.src))
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}
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*t.payload = t.buf.Bytes()
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return nil
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}
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func (t *Tmpfile) revert(*I, *Criteria) error { t.buf.Reset(); return nil }
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func (t *Tmpfile) Is(o Op) bool {
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t0, ok := o.(*Tmpfile)
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return ok && t0 != nil &&
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t.src == t0.src && t.n == t0.n
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}
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func (t *Tmpfile) Path() string { return t.src }
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func (t *Tmpfile) String() string { return fmt.Sprintf("up to %d bytes from %q", t.n, t.src) }
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