varint.go

Documentation: golang.org/x/text/internal/catmsg

     1  // Copyright 2017 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 catmsg
     6  
     7  // This file implements varint encoding analogous to the one in encoding/binary.
     8  // We need a string version of this function, so we add that here and then add
     9  // the rest for consistency.
    10  
    11  import "errors"
    12  
    13  var (
    14  	errIllegalVarint  = errors.New("catmsg: illegal varint")
    15  	errVarintTooLarge = errors.New("catmsg: varint too large for uint64")
    16  )
    17  
    18  const maxVarintBytes = 10 // maximum length of a varint
    19  
    20  // encodeUint encodes x as a variable-sized integer into buf and returns the
    21  // number of bytes written. buf must be at least maxVarintBytes long
    22  func encodeUint(buf []byte, x uint64) (n int) {
    23  	for ; x > 127; n++ {
    24  		buf[n] = 0x80 | uint8(x&0x7F)
    25  		x >>= 7
    26  	}
    27  	buf[n] = uint8(x)
    28  	n++
    29  	return n
    30  }
    31  
    32  func decodeUintString(s string) (x uint64, size int, err error) {
    33  	i := 0
    34  	for shift := uint(0); shift < 64; shift += 7 {
    35  		if i >= len(s) {
    36  			return 0, i, errIllegalVarint
    37  		}
    38  		b := uint64(s[i])
    39  		i++
    40  		x |= (b & 0x7F) << shift
    41  		if b&0x80 == 0 {
    42  			return x, i, nil
    43  		}
    44  	}
    45  	return 0, i, errVarintTooLarge
    46  }
    47  
    48  func decodeUint(b []byte) (x uint64, size int, err error) {
    49  	i := 0
    50  	for shift := uint(0); shift < 64; shift += 7 {
    51  		if i >= len(b) {
    52  			return 0, i, errIllegalVarint
    53  		}
    54  		c := uint64(b[i])
    55  		i++
    56  		x |= (c & 0x7F) << shift
    57  		if c&0x80 == 0 {
    58  			return x, i, nil
    59  		}
    60  	}
    61  	return 0, i, errVarintTooLarge
    62  }
    63
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