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sawkasawka
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working on a buffered log viewer class (#1301)
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2 files changed

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2 files changed

+348
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‎pkg/util/logview/logview.go

Lines changed: 217 additions & 0 deletions
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// Copyright 2024, Command Line Inc.
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// SPDX-License-Identifier: Apache-2.0
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package logview
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import (
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"fmt"
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"io"
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"os"
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"regexp"
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)
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const BufSize = 256 * 1024
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const MaxLineSize = 1024
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type LinePtr struct {
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Offset int64
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RealLineNum int64
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LineNum int64
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}
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type LogView struct {
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File *os.File
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MultiBuf *MultiBufferByteGetter
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MatchRe *regexp.Regexp
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}
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func MakeLogView(file *os.File) *LogView {
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return &LogView{
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File: file,
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MultiBuf: MakeMultiBufferByteGetter(file, BufSize),
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}
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}
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func (lv *LogView) Close() {
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lv.File.Close()
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}
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func (lv *LogView) ReadLineData(linePtr *LinePtr) ([]byte, error) {
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return lv.readLineAt(linePtr.Offset)
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}
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func (lv *LogView) readLineAt(offset int64) ([]byte, error) {
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var rtn []byte
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for {
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if len(rtn) > MaxLineSize {
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break
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}
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b, err := lv.MultiBuf.GetByte(offset)
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if err == io.EOF {
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break
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}
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if err != nil {
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return nil, err
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}
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if b == '\n' {
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break
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}
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rtn = append(rtn, b)
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offset++
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}
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return rtn, nil
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}
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func (lv *LogView) FirstLinePtr() (*LinePtr, error) {
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linePtr := &LinePtr{Offset: 0, RealLineNum: 1, LineNum: 1}
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if lv.isLineMatch(0) {
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return linePtr, nil
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}
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return lv.NextLinePtr(linePtr)
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}
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func (lv *LogView) isLineMatch(offset int64) bool {
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if lv.MatchRe == nil {
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return true
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}
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lineData, err := lv.readLineAt(offset)
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if err != nil {
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return false
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}
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return lv.MatchRe.Match(lineData)
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}
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func (lv *LogView) NextLinePtr(linePtr *LinePtr) (*LinePtr, error) {
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if linePtr == nil {
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return nil, fmt.Errorf("linePtr is nil")
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}
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numLines := int64(0)
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offset := linePtr.Offset
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for {
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var err error
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nextOffset, err := lv.MultiBuf.NextLine(offset)
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if err == io.EOF {
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return nil, nil
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}
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if err != nil {
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return nil, err
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}
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numLines++
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if lv.isLineMatch(nextOffset) {
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return &LinePtr{Offset: nextOffset, RealLineNum: linePtr.RealLineNum + numLines, LineNum: linePtr.LineNum + 1}, nil
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}
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offset = nextOffset
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}
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}
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func (lv *LogView) PrevLinePtr(linePtr *LinePtr) (*LinePtr, error) {
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if linePtr == nil {
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return nil, fmt.Errorf("linePtr is nil")
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}
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numLines := int64(0)
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offset := linePtr.Offset
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for {
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var err error
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prevOffset, err := lv.MultiBuf.PrevLine(offset)
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if err == ErrBOF {
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return nil, nil
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}
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if err != nil {
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return nil, err
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}
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numLines++
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if lv.isLineMatch(prevOffset) {
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return &LinePtr{Offset: prevOffset, RealLineNum: linePtr.RealLineNum - numLines, LineNum: linePtr.LineNum - 1}, nil
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}
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offset = prevOffset
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}
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}
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func (lv *LogView) Move(linePtr *LinePtr, offset int) (int, *LinePtr, error) {
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var n int
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if offset > 0 {
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for {
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nextLinePtr, err := lv.NextLinePtr(linePtr)
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if err == io.EOF {
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break
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}
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if err != nil {
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return 0, nil, err
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}
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linePtr = nextLinePtr
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n++
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if n == offset {
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break
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}
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}
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return n, linePtr, nil
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}
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if offset < 0 {
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for {
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prevLinePtr, err := lv.PrevLinePtr(linePtr)
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if err == ErrBOF {
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break
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}
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if err != nil {
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return 0, nil, err
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}
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linePtr = prevLinePtr
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n--
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if n == offset {
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break
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}
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}
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return n, linePtr, nil
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}
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return 0, linePtr, nil
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}
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func (lv *LogView) LastLinePtr(linePtr *LinePtr) (*LinePtr, error) {
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if linePtr == nil {
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var err error
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linePtr, err = lv.FirstLinePtr()
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if err != nil {
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return nil, err
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}
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}
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if linePtr == nil {
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return nil, nil
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}
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for {
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nextLinePtr, err := lv.NextLinePtr(linePtr)
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if err == io.EOF {
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break
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}
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if err != nil {
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return nil, err
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}
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if nextLinePtr == nil {
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break
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}
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linePtr = nextLinePtr
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}
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return linePtr, nil
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}
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func (lv *LogView) ReadWindow(linePtr *LinePtr, winSize int) ([][]byte, error) {
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if linePtr == nil {
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return nil, nil
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}
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var rtn [][]byte
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for len(rtn) < winSize {
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lineData, err := lv.readLineAt(linePtr.Offset)
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if err != nil {
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return nil, err
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}
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rtn = append(rtn, lineData)
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nextLinePtr, err := lv.NextLinePtr(linePtr)
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if err != nil {
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return nil, err
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}
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if nextLinePtr == nil {
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break
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}
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linePtr = nextLinePtr
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}
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return rtn, nil
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}

‎pkg/util/logview/multibuf.go

Lines changed: 131 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,131 @@
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// Copyright 2024, Command Line Inc.
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// SPDX-License-Identifier: Apache-2.0
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package logview
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import (
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"errors"
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"io"
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"os"
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)
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type MultiBufferByteGetter struct {
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File *os.File
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Offset int64
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EOF bool
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Buffers [][]byte
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BufSize int64
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}
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var ErrBOF = errors.New("beginning of file")
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func MakeMultiBufferByteGetter(file *os.File, bufSize int64) *MultiBufferByteGetter {
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return &MultiBufferByteGetter{
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File: file,
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Offset: 0,
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EOF: false,
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Buffers: [][]byte{},
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BufSize: bufSize,
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}
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}
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func (mb *MultiBufferByteGetter) readFromBuffer(offset int64) (byte, bool) {
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if offset < mb.Offset || offset >= mb.Offset+int64(mb.bufSize()) {
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return 0, false
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}
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bufIdx := int((offset - mb.Offset) / mb.BufSize)
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bufOffset := (offset - mb.Offset) % mb.BufSize
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return mb.Buffers[bufIdx][bufOffset], true
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}
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func (mb *MultiBufferByteGetter) bufSize() int {
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return len(mb.Buffers) * int(mb.BufSize)
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}
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func (mb *MultiBufferByteGetter) rebuffer(newOffset int64) error {
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partNum := int(newOffset / mb.BufSize)
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partOffset := int64(partNum) * mb.BufSize
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newBuf := make([]byte, mb.BufSize)
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n, err := mb.File.ReadAt(newBuf, partOffset)
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var isEOF bool
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if err == io.EOF {
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newBuf = newBuf[:n]
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isEOF = true
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}
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if err != nil {
56+
return err
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}
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var newBuffers [][]byte
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if len(mb.Buffers) > 0 {
60+
firstBufPartNum := int(mb.Offset / mb.BufSize)
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lastBufPartNum := int((mb.Offset + int64(mb.bufSize())) / mb.BufSize)
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if firstBufPartNum == partNum+1 {
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newBuffers = [][]byte{newBuf, mb.Buffers[0]}
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} else if lastBufPartNum == partNum-1 {
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newBuffers = [][]byte{mb.Buffers[0], newBuf}
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} else {
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newBuffers = [][]byte{newBuf}
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}
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} else {
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newBuffers = [][]byte{newBuf}
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}
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mb.Buffers = newBuffers
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mb.Offset = partOffset
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mb.EOF = isEOF
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return nil
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}
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func (mb *MultiBufferByteGetter) GetByte(offset int64) (byte, error) {
79+
b, ok := mb.readFromBuffer(offset)
80+
if ok {
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return b, nil
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}
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if mb.EOF && offset >= mb.Offset+int64(mb.bufSize()) {
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return 0, io.EOF
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}
86+
err := mb.rebuffer(offset)
87+
if err != nil {
88+
return 0, err
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}
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b, _ = mb.readFromBuffer(offset)
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return b, nil
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}
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func (mb *MultiBufferByteGetter) NextLine(offset int64) (int64, error) {
95+
for {
96+
b, err := mb.GetByte(offset)
97+
if err != nil {
98+
return 0, err
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}
100+
if b == '\n' {
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break
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}
103+
offset++
104+
}
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_, lastErr := mb.GetByte(offset + 1)
106+
if lastErr == io.EOF {
107+
return 0, io.EOF
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}
109+
return offset + 1, nil
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}
111+
112+
func (mb *MultiBufferByteGetter) PrevLine(offset int64) (int64, error) {
113+
if offset == 0 {
114+
return 0, ErrBOF
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}
116+
offset = offset - 2
117+
for {
118+
if offset < 0 {
119+
break
120+
}
121+
b, err := mb.GetByte(offset)
122+
if err != nil {
123+
return 0, err
124+
}
125+
if b == '\n' {
126+
break
127+
}
128+
offset--
129+
}
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return offset + 1, nil
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}

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