encoding.go

     1  // Copyright 2025 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  	"errors"
     9  )
    10  
    11  // maxVarintLenN is the maximum length of a varint-encoded N-bit integer.
    12  const maxVarintLen64 = 10
    13  
    14  var (
    15  	errOverflow = errors.New("binary: varint overflows a 64-bit integer")
    16  	errEOB      = errors.New("binary: end of buffer")
    17  )
    18  
    19  // TODO deduplicate this function.
    20  func readUvarint(b []byte) (uint64, int, error) {
    21  	var x uint64
    22  	var s uint
    23  	var byt byte
    24  	for i := 0; i < maxVarintLen64 && i < len(b); i++ {
    25  		byt = b[i]
    26  		if byt < 0x80 {
    27  			if i == maxVarintLen64-1 && byt > 1 {
    28  				return x, i, errOverflow
    29  			}
    30  			return x | uint64(byt)<<s, i + 1, nil
    31  		}
    32  		x |= uint64(byt&0x7f) << s
    33  		s += 7
    34  	}
    35  	return x, len(b), errOverflow
    36  }
    37  
    38  // putUvarint encodes a uint64 into buf and returns the number of bytes written.
    39  // If the buffer is too small, PutUvarint will panic.
    40  // TODO deduplicate this function.
    41  func putUvarint(buf []byte, x uint64) int {
    42  	i := 0
    43  	for x >= 0x80 {
    44  		buf[i] = byte(x) | 0x80
    45  		x >>= 7
    46  		i++
    47  	}
    48  	buf[i] = byte(x)
    49  	return i + 1
    50  }
    51
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