/*
 * Copyright 2021 ByteDance Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package rt

import (
    `unsafe`
    `reflect`
)

//go:nosplit
func Get16(v []byte) int16 {
    return *(*int16)((*GoSlice)(unsafe.Pointer(&v)).Ptr)
}

//go:nosplit
func Get32(v []byte) int32 {
    return *(*int32)((*GoSlice)(unsafe.Pointer(&v)).Ptr)
}

//go:nosplit
func Get64(v []byte) int64 {
    return *(*int64)((*GoSlice)(unsafe.Pointer(&v)).Ptr)
}

//go:nosplit
func Mem2Str(v []byte) (s string) {
    (*GoString)(unsafe.Pointer(&s)).Len = (*GoSlice)(unsafe.Pointer(&v)).Len
    (*GoString)(unsafe.Pointer(&s)).Ptr = (*GoSlice)(unsafe.Pointer(&v)).Ptr
    return
}

//go:nosplit
func Str2Mem(s string) (v []byte) {
    (*GoSlice)(unsafe.Pointer(&v)).Cap = (*GoString)(unsafe.Pointer(&s)).Len
    (*GoSlice)(unsafe.Pointer(&v)).Len = (*GoString)(unsafe.Pointer(&s)).Len
    (*GoSlice)(unsafe.Pointer(&v)).Ptr = (*GoString)(unsafe.Pointer(&s)).Ptr
    return
}

func BytesFrom(p unsafe.Pointer, n int, c int) (r []byte) {
    (*GoSlice)(unsafe.Pointer(&r)).Ptr = p
    (*GoSlice)(unsafe.Pointer(&r)).Len = n
    (*GoSlice)(unsafe.Pointer(&r)).Cap = c
    return
}

func FuncAddr(f interface{}) unsafe.Pointer {
    if vv := UnpackEface(f); vv.Type.Kind() != reflect.Func {
        panic("f is not a function")
    } else {
        return *(*unsafe.Pointer)(vv.Value)
    }
}

//go:nocheckptr
func IndexChar(src string, index int) unsafe.Pointer {
	return unsafe.Pointer(uintptr((*GoString)(unsafe.Pointer(&src)).Ptr) + uintptr(index))
}

//go:nocheckptr
func IndexByte(ptr []byte, index int) unsafe.Pointer {
	return unsafe.Pointer(uintptr((*GoSlice)(unsafe.Pointer(&ptr)).Ptr) + uintptr(index))
}

func GuardSlice(buf *[]byte, n int) {
	c := cap(*buf)
	l := len(*buf)
	if c-l < n {
		c = c>>1 + n + l
		if c < 32 {
			c = 32
		}
		tmp := make([]byte, l, c)
		copy(tmp, *buf)
		*buf = tmp
	}
}

//go:nosplit
func Ptr2SlicePtr(s unsafe.Pointer, l int, c int) unsafe.Pointer {
    slice := &GoSlice{
        Ptr: s,
        Len: l,
        Cap: c,
    }
    return unsafe.Pointer(slice)
}

//go:nosplit
func StrPtr(s string) unsafe.Pointer {
    return (*GoString)(unsafe.Pointer(&s)).Ptr
}

//go:nosplit
func StrFrom(p unsafe.Pointer, n int64) (s string) {
    (*GoString)(unsafe.Pointer(&s)).Ptr = p
    (*GoString)(unsafe.Pointer(&s)).Len = int(n)
    return
}

// NoEscape hides a pointer from escape analysis. NoEscape is
// the identity function but escape analysis doesn't think the
// output depends on the input. NoEscape is inlined and currently
// compiles down to zero instructions.
// USE CAREFULLY!
//go:nosplit
//goland:noinspection GoVetUnsafePointer
func NoEscape(p unsafe.Pointer) unsafe.Pointer {
    x := uintptr(p)
    return unsafe.Pointer(x ^ 0)
}