go-ceph/internal/cutil/iovec.go

79 lines
1.7 KiB
Go

package cutil
/*
#include <stdlib.h>
#include <sys/uio.h>
*/
import "C"
import (
"unsafe"
)
var iovecSize uintptr
// StructIovecPtr is an unsafe pointer wrapping C's `*struct iovec`.
type StructIovecPtr unsafe.Pointer
// Iovec helps manage struct iovec arrays needed by some C functions.
type Iovec struct {
// cvec represents an array of struct iovec C memory
cvec unsafe.Pointer
// length of the array (in elements)
length int
}
// NewIovec creates an Iovec, and underlying C memory, of the specified size.
func NewIovec(l int) *Iovec {
r := &Iovec{
cvec: C.malloc(C.size_t(l) * C.size_t(iovecSize)),
length: l,
}
return r
}
// ByteSlicesToIovec takes a slice of byte slices and returns a new iovec that
// maps the slice data to struct iovec entries.
func ByteSlicesToIovec(data [][]byte) *Iovec {
iov := NewIovec(len(data))
for i := range data {
iov.Set(i, data[i])
}
return iov
}
// Pointer returns a StructIovecPtr that represents the C memory of the
// underlying array.
func (v *Iovec) Pointer() StructIovecPtr {
return StructIovecPtr(unsafe.Pointer(v.cvec))
}
// Len returns the number of entries in the Iovec.
func (v *Iovec) Len() int {
return v.length
}
// Free the C memory in the Iovec.
func (v *Iovec) Free() {
if v.cvec != nil {
C.free(v.cvec)
v.cvec = nil
v.length = 0
}
}
// Set will map the memory of the given byte slice to the iovec at the
// specified position.
func (v *Iovec) Set(i int, buf []byte) {
offset := uintptr(i) * iovecSize
iov := (*C.struct_iovec)(unsafe.Pointer(
uintptr(unsafe.Pointer(v.cvec)) + offset))
iov.iov_base = unsafe.Pointer(&buf[0])
iov.iov_len = C.size_t(len(buf))
}
func init() {
var iovec C.struct_iovec
iovecSize = unsafe.Sizeof(iovec)
}