github.com/deroproject/derosuite@v2.1.6-1.0.20200307070847-0f2e589c7a2b+incompatible/crypto/ringct/varint.go (about)

     1  // Copyright 2017-2018 DERO Project. All rights reserved.
     2  // Use of this source code in any form is governed by RESEARCH license.
     3  // license can be found in the LICENSE file.
     4  // GPG: 0F39 E425 8C65 3947 702A  8234 08B2 0360 A03A 9DE8
     5  //
     6  //
     7  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
     8  // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     9  // MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
    10  // THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    11  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    12  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    13  // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
    14  // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
    15  // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    16  
    17  package ringct
    18  
    19  import "io"
    20  import "fmt"
    21  
    22  // these functions basically what golang varint does, (  however theere is a minor spec diff, so these are here for exact compatibility)
    23  
    24  func ReadVarInt(buf io.Reader) (result uint64, err error) {
    25  	b := make([]byte, 1)
    26  	var r uint64
    27  	var n int
    28  	for i := 0; ; i++ {
    29  		n, err = buf.Read(b)
    30  		if err != nil {
    31  			return
    32  		}
    33  		if n != 1 {
    34  			err = fmt.Errorf("Buffer ended prematurely for varint")
    35  			return
    36  		}
    37  		r += (uint64(b[0]) & 0x7f) << uint(i*7)
    38  		if uint64(b[0])&0x80 == 0 {
    39  			break
    40  		}
    41  	}
    42  	result = r
    43  	return
    44  }
    45  
    46  func Uint64ToBytes(num uint64) (result []byte) {
    47  	for ; num >= 0x80; num >>= 7 {
    48  		result = append(result, byte((num&0x7f)|0x80))
    49  	}
    50  	result = append(result, byte(num))
    51  	return
    52  }