go-ceph/internal/cutil/buffergroup.go

90 lines
2.2 KiB
Go

package cutil
// #include <stdlib.h>
import "C"
import (
"unsafe"
)
// BufferGroup is a helper structure that holds Go-allocated slices of
// C-allocated strings and their respective lengths. Useful for C functions
// that consume byte buffers with explicit length instead of null-terminated
// strings. When used as input arguments in C functions, caller must make sure
// the C code will not hold any pointers to either of the struct's attributes
// after that C function returns.
type BufferGroup struct {
// C-allocated buffers.
Buffers []CharPtr
// Lengths of C buffers, where Lengths[i] = length(Buffers[i]).
Lengths []SizeT
}
// TODO: should BufferGroup implementation change and the slices would contain
// nested Go pointers, they must be pinned with PtrGuard.
// NewBufferGroupStrings returns new BufferGroup constructed from strings.
func NewBufferGroupStrings(strs []string) *BufferGroup {
s := &BufferGroup{
Buffers: make([]CharPtr, len(strs)),
Lengths: make([]SizeT, len(strs)),
}
for i, str := range strs {
bs := []byte(str)
s.Buffers[i] = CharPtr(C.CBytes(bs))
s.Lengths[i] = SizeT(len(bs))
}
return s
}
// NewBufferGroupBytes returns new BufferGroup constructed
// from slice of byte slices.
func NewBufferGroupBytes(bss [][]byte) *BufferGroup {
s := &BufferGroup{
Buffers: make([]CharPtr, len(bss)),
Lengths: make([]SizeT, len(bss)),
}
for i, bs := range bss {
s.Buffers[i] = CharPtr(C.CBytes(bs))
s.Lengths[i] = SizeT(len(bs))
}
return s
}
// Free free()s the C-allocated memory.
func (s *BufferGroup) Free() {
for _, ptr := range s.Buffers {
C.free(unsafe.Pointer(ptr))
}
s.Buffers = nil
s.Lengths = nil
}
// BuffersPtr returns a pointer to the beginning of the Buffers slice.
func (s *BufferGroup) BuffersPtr() CharPtrPtr {
if len(s.Buffers) == 0 {
return nil
}
return CharPtrPtr(&s.Buffers[0])
}
// LengthsPtr returns a pointer to the beginning of the Lengths slice.
func (s *BufferGroup) LengthsPtr() SizeTPtr {
if len(s.Lengths) == 0 {
return nil
}
return SizeTPtr(&s.Lengths[0])
}
func testBufferGroupGet(s *BufferGroup, index int) (str string, length int) {
bs := C.GoBytes(unsafe.Pointer(s.Buffers[index]), C.int(s.Lengths[index]))
return string(bs), int(s.Lengths[index])
}