status-go/vendor/github.com/ipfs/go-cid/varint.go

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2019-06-09 07:24:20 +00:00
package cid
// Version of varint function that work with a string rather than
// []byte to avoid unnecessary allocation
// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license as given at https://golang.org/LICENSE
// uvarint decodes a uint64 from buf and returns that value and the
// number of characters read (> 0). If an error occurred, the value is 0
// and the number of bytes n is <= 0 meaning:
//
// n == 0: buf too small
// n < 0: value larger than 64 bits (overflow)
// and -n is the number of bytes read
//
func uvarint(buf string) (uint64, int) {
var x uint64
var s uint
// we have a binary string so we can't use a range loope
for i := 0; i < len(buf); i++ {
b := buf[i]
if b < 0x80 {
if i > 9 || i == 9 && b > 1 {
return 0, -(i + 1) // overflow
}
return x | uint64(b)<<s, i + 1
}
x |= uint64(b&0x7f) << s
s += 7
}
return 0, 0
}