service/vendor/github.com/bytedance/sonic/loader/pcdata.go

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2023-12-21 22:17:40 +08:00
/**
* Copyright 2023 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 loader
const (
_N_PCDATA = 4
_PCDATA_UnsafePoint = 0
_PCDATA_StackMapIndex = 1
_PCDATA_InlTreeIndex = 2
_PCDATA_ArgLiveIndex = 3
_PCDATA_INVALID_OFFSET = 0
)
const (
// PCDATA_UnsafePoint values.
PCDATA_UnsafePointSafe = -1 // Safe for async preemption
PCDATA_UnsafePointUnsafe = -2 // Unsafe for async preemption
// PCDATA_Restart1(2) apply on a sequence of instructions, within
// which if an async preemption happens, we should back off the PC
// to the start of the sequence when resume.
// We need two so we can distinguish the start/end of the sequence
// in case that two sequences are next to each other.
PCDATA_Restart1 = -3
PCDATA_Restart2 = -4
// Like PCDATA_RestartAtEntry, but back to function entry if async
// preempted.
PCDATA_RestartAtEntry = -5
_PCDATA_START_VAL = -1
)
var emptyByte byte
func encodeValue(v int) []byte {
return encodeVariant(toZigzag(v))
}
func toZigzag(v int) int {
return (v << 1) ^ (v >> 31)
}
func encodeVariant(v int) []byte {
var u int
var r []byte
/* split every 7 bits */
for v > 127 {
u = v & 0x7f
v = v >> 7
r = append(r, byte(u) | 0x80)
}
/* check for last one */
if v == 0 {
return r
}
/* add the last one */
r = append(r, byte(v))
return r
}
type Pcvalue struct {
PC uint32 // PC offset from func entry
Val int32
}
type Pcdata []Pcvalue
// see https://docs.google.com/document/d/1lyPIbmsYbXnpNj57a261hgOYVpNRcgydurVQIyZOz_o/pub
func (self Pcdata) MarshalBinary() (data []byte, err error) {
// delta value always starts from -1
sv := int32(_PCDATA_START_VAL)
sp := uint32(0)
for _, v := range self {
data = append(data, encodeVariant(toZigzag(int(v.Val - sv)))...)
data = append(data, encodeVariant(int(v.PC - sp))...)
sp = v.PC
sv = v.Val
}
return
}