batch.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package trace
     6  
     7  import (
     8  	"bytes"
     9  	"encoding/binary"
    10  	"fmt"
    11  	"io"
    12  
    13  	"internal/trace/tracev2"
    14  	"internal/trace/version"
    15  )
    16  
    17  // timestamp is an unprocessed timestamp.
    18  type timestamp uint64
    19  
    20  // batch represents a batch of trace events.
    21  // It is unparsed except for its header.
    22  type batch struct {
    23  	m    ThreadID
    24  	time timestamp
    25  	data []byte
    26  	exp  tracev2.Experiment
    27  }
    28  
    29  func (b *batch) isStringsBatch() bool {
    30  	return b.exp == tracev2.NoExperiment && len(b.data) > 0 && tracev2.EventType(b.data[0]) == tracev2.EvStrings
    31  }
    32  
    33  func (b *batch) isStacksBatch() bool {
    34  	return b.exp == tracev2.NoExperiment && len(b.data) > 0 && tracev2.EventType(b.data[0]) == tracev2.EvStacks
    35  }
    36  
    37  func (b *batch) isCPUSamplesBatch() bool {
    38  	return b.exp == tracev2.NoExperiment && len(b.data) > 0 && tracev2.EventType(b.data[0]) == tracev2.EvCPUSamples
    39  }
    40  
    41  func (b *batch) isSyncBatch(ver version.Version) bool {
    42  	return (b.exp == tracev2.NoExperiment && len(b.data) > 0) &&
    43  		((tracev2.EventType(b.data[0]) == tracev2.EvFrequency && ver < version.Go125) ||
    44  			(tracev2.EventType(b.data[0]) == tracev2.EvSync && ver >= version.Go125))
    45  }
    46  
    47  // readBatch reads the next full batch from r.
    48  func readBatch(r interface {
    49  	io.Reader
    50  	io.ByteReader
    51  }) (batch, uint64, error) {
    52  	// Read batch header byte.
    53  	b, err := r.ReadByte()
    54  	if err != nil {
    55  		return batch{}, 0, err
    56  	}
    57  	if typ := tracev2.EventType(b); typ != tracev2.EvEventBatch && typ != tracev2.EvExperimentalBatch {
    58  		return batch{}, 0, fmt.Errorf("expected batch event, got event %d", typ)
    59  	}
    60  
    61  	// Read the experiment of we have one.
    62  	exp := tracev2.NoExperiment
    63  	if tracev2.EventType(b) == tracev2.EvExperimentalBatch {
    64  		e, err := r.ReadByte()
    65  		if err != nil {
    66  			return batch{}, 0, err
    67  		}
    68  		exp = tracev2.Experiment(e)
    69  	}
    70  
    71  	// Read the batch header: gen (generation), thread (M) ID, base timestamp
    72  	// for the batch.
    73  	gen, err := binary.ReadUvarint(r)
    74  	if err != nil {
    75  		return batch{}, gen, fmt.Errorf("error reading batch gen: %w", err)
    76  	}
    77  	m, err := binary.ReadUvarint(r)
    78  	if err != nil {
    79  		return batch{}, gen, fmt.Errorf("error reading batch M ID: %w", err)
    80  	}
    81  	ts, err := binary.ReadUvarint(r)
    82  	if err != nil {
    83  		return batch{}, gen, fmt.Errorf("error reading batch timestamp: %w", err)
    84  	}
    85  
    86  	// Read in the size of the batch to follow.
    87  	size, err := binary.ReadUvarint(r)
    88  	if err != nil {
    89  		return batch{}, gen, fmt.Errorf("error reading batch size: %w", err)
    90  	}
    91  	if size > tracev2.MaxBatchSize {
    92  		return batch{}, gen, fmt.Errorf("invalid batch size %d, maximum is %d", size, tracev2.MaxBatchSize)
    93  	}
    94  
    95  	// Copy out the batch for later processing.
    96  	var data bytes.Buffer
    97  	data.Grow(int(size))
    98  	n, err := io.CopyN(&data, r, int64(size))
    99  	if n != int64(size) {
   100  		return batch{}, gen, fmt.Errorf("failed to read full batch: read %d but wanted %d", n, size)
   101  	}
   102  	if err != nil {
   103  		return batch{}, gen, fmt.Errorf("copying batch data: %w", err)
   104  	}
   105  
   106  	// Return the batch.
   107  	return batch{
   108  		m:    ThreadID(m),
   109  		time: timestamp(ts),
   110  		data: data.Bytes(),
   111  		exp:  exp,
   112  	}, gen, nil
   113  }
   114
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