batch.go

Documentation: internal/trace/v2

     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  	"bufio"
     9  	"bytes"
    10  	"encoding/binary"
    11  	"fmt"
    12  	"io"
    13  
    14  	"internal/trace/v2/event"
    15  	"internal/trace/v2/event/go122"
    16  )
    17  
    18  // timestamp is an unprocessed timestamp.
    19  type timestamp uint64
    20  
    21  // batch represents a batch of trace events.
    22  // It is unparsed except for its header.
    23  type batch struct {
    24  	m    ThreadID
    25  	time timestamp
    26  	data []byte
    27  }
    28  
    29  func (b *batch) isStringsBatch() bool {
    30  	return len(b.data) > 0 && event.Type(b.data[0]) == go122.EvStrings
    31  }
    32  
    33  func (b *batch) isStacksBatch() bool {
    34  	return len(b.data) > 0 && event.Type(b.data[0]) == go122.EvStacks
    35  }
    36  
    37  func (b *batch) isCPUSamplesBatch() bool {
    38  	return len(b.data) > 0 && event.Type(b.data[0]) == go122.EvCPUSamples
    39  }
    40  
    41  func (b *batch) isFreqBatch() bool {
    42  	return len(b.data) > 0 && event.Type(b.data[0]) == go122.EvFrequency
    43  }
    44  
    45  // readBatch reads the next full batch from r.
    46  func readBatch(r *bufio.Reader) (batch, uint64, error) {
    47  	// Read batch header byte.
    48  	b, err := r.ReadByte()
    49  	if err != nil {
    50  		return batch{}, 0, err
    51  	}
    52  	if typ := event.Type(b); typ != go122.EvEventBatch {
    53  		return batch{}, 0, fmt.Errorf("expected batch event (%s), got %s", go122.EventString(go122.EvEventBatch), go122.EventString(typ))
    54  	}
    55  
    56  	// Read the batch header: gen (generation), thread (M) ID, base timestamp
    57  	// for the batch.
    58  	gen, err := binary.ReadUvarint(r)
    59  	if err != nil {
    60  		return batch{}, gen, fmt.Errorf("error reading batch gen: %w", err)
    61  	}
    62  	m, err := binary.ReadUvarint(r)
    63  	if err != nil {
    64  		return batch{}, gen, fmt.Errorf("error reading batch M ID: %w", err)
    65  	}
    66  	ts, err := binary.ReadUvarint(r)
    67  	if err != nil {
    68  		return batch{}, gen, fmt.Errorf("error reading batch timestamp: %w", err)
    69  	}
    70  
    71  	// Read in the size of the batch to follow.
    72  	size, err := binary.ReadUvarint(r)
    73  	if err != nil {
    74  		return batch{}, gen, fmt.Errorf("error reading batch size: %w", err)
    75  	}
    76  	if size > go122.MaxBatchSize {
    77  		return batch{}, gen, fmt.Errorf("invalid batch size %d, maximum is %d", size, go122.MaxBatchSize)
    78  	}
    79  
    80  	// Copy out the batch for later processing.
    81  	var data bytes.Buffer
    82  	data.Grow(int(size))
    83  	n, err := io.CopyN(&data, r, int64(size))
    84  	if n != int64(size) {
    85  		return batch{}, gen, fmt.Errorf("failed to read full batch: read %d but wanted %d", n, size)
    86  	}
    87  	if err != nil {
    88  		return batch{}, gen, fmt.Errorf("copying batch data: %w", err)
    89  	}
    90  
    91  	// Return the batch.
    92  	return batch{
    93  		m:    ThreadID(m),
    94  		time: timestamp(ts),
    95  		data: data.Bytes(),
    96  	}, gen, nil
    97  }
    98
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