实现基础web服务器

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

@@ -0,0 +1,100 @@
+/**
+ * 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
+}