cwrap.go

package mtbl

/*
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
*/
import "C"

import "reflect"
import "unsafe"

//export go_merge_callback
func go_merge_callback(pfunc unsafe.Pointer,
	pkey *C.uint8_t, len_key C.size_t,
	pval0 *C.uint8_t, len_val0 C.size_t,
	pval1 *C.uint8_t, len_val1 C.size_t,
	pmerged_val **C.uint8_t, len_merged_val *C.size_t) {
	if merge := (*MergeFunc)(pfunc); merge != nil {
		var key []byte
		var val0 []byte
		var val1 []byte

		sh_key := (*reflect.SliceHeader)(unsafe.Pointer(&key))
		sh_key.Data = uintptr(unsafe.Pointer(pkey))
		sh_key.Len = int(len_key)
		sh_key.Cap = int(len_key)

		sh_val0 := (*reflect.SliceHeader)(unsafe.Pointer(&val0))
		sh_val0.Data = uintptr(unsafe.Pointer(pval0))
		sh_val0.Len = int(len_val0)
		sh_val0.Cap = int(len_val0)

		sh_val1 := (*reflect.SliceHeader)(unsafe.Pointer(&val1))
		sh_val1.Data = uintptr(unsafe.Pointer(pval1))
		sh_val1.Len = int(len_val1)
		sh_val1.Cap = int(len_val1)

		merged_val := (*merge)(key, val0, val1)

		*pmerged_val = (*C.uint8_t)(C.malloc(C.size_t(len(merged_val))))
		*len_merged_val = (C.size_t)(len(merged_val))

		C.memcpy(
			unsafe.Pointer(*pmerged_val),
			unsafe.Pointer(&merged_val[0]),
			C.size_t(len(merged_val)),
		)
	} else {
		panic("go_merge_callback() got a nil callback function")
	}
}