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94 lines
2.1 KiB
94 lines
2.1 KiB
// Copyright (c) 2020 Couchbase, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package zap
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import (
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"fmt"
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)
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type memUvarintReader struct {
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C int // index of next byte to read from S
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S []byte
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}
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func newMemUvarintReader(s []byte) *memUvarintReader {
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return &memUvarintReader{S: s}
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}
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// Len returns the number of unread bytes.
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func (r *memUvarintReader) Len() int {
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n := len(r.S) - r.C
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if n < 0 {
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return 0
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}
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return n
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}
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// ReadUvarint reads an encoded uint64. The original code this was
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// based on is at encoding/binary/ReadUvarint().
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func (r *memUvarintReader) ReadUvarint() (uint64, error) {
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var x uint64
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var s uint
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var C = r.C
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var S = r.S
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for {
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b := S[C]
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C++
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if b < 0x80 {
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r.C = C
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// why 63? The original code had an 'i += 1' loop var and
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// checked for i > 9 || i == 9 ...; but, we no longer
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// check for the i var, but instead check here for s,
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// which is incremented by 7. So, 7*9 == 63.
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//
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// why the "extra" >= check? The normal case is that s <
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// 63, so we check this single >= guard first so that we
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// hit the normal, nil-error return pathway sooner.
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if s >= 63 && (s > 63 || s == 63 && b > 1) {
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return 0, fmt.Errorf("memUvarintReader overflow")
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}
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return x | uint64(b)<<s, nil
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}
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x |= uint64(b&0x7f) << s
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s += 7
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}
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}
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// SkipUvarint skips ahead one encoded uint64.
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func (r *memUvarintReader) SkipUvarint() {
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for {
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b := r.S[r.C]
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r.C++
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if b < 0x80 {
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return
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}
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}
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}
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// SkipBytes skips a count number of bytes.
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func (r *memUvarintReader) SkipBytes(count int) {
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r.C = r.C + count
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}
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func (r *memUvarintReader) Reset(s []byte) {
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r.C = 0
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r.S = s
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}
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