Initial commit

application/commands/integer.go

@@ -0,0 +1,120 @@
+// Sshwifty - A Web SSH client
+//
+// Copyright (C) 2019 Rui NI <nirui@gmx.com>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package commands
+
+import (
+	"errors"
+
+	"github.com/niruix/sshwifty/application/rw"
+)
+
+// Errors
+var (
+	ErrIntegerMarshalNotEnoughBuffer = errors.New(
+		"Not enough buffer to marshal the integer")
+
+	ErrIntegerMarshalTooLarge = errors.New(
+		"Integer cannot be marshalled, because the vaule was too large")
+)
+
+// Integer is a 16bit unsigned integer data
+//
+// Format:
+// +-------------------------------------+--------------+
+// | 1 bit                               | 7 bits       |
+// +-------------------------------------+--------------+
+// | 1 when current byte is the end byte | Integer data |
+// +-------------------------------------+--------------+
+//
+// Example:
+//   - 00000000 00000000: 0
+//   - 01111111:          127
+//   - 11111111 01000000: 255
+type Integer uint16
+
+const (
+	integerHasNextBit  = 0x80
+	integerValueCutter = 0x7f
+)
+
+// Consts
+const (
+	MaxInteger      = 0x3fff
+	MaxIntegerBytes = 2
+)
+
+// ByteSize returns how many bytes current integer will be encoded into
+func (i *Integer) ByteSize() int {
+	if *i > integerValueCutter {
+		return 2
+	}
+
+	return 1
+}
+
+// Int returns a int of current Integer
+func (i *Integer) Int() int {
+	return int(*i)
+}
+
+// Marshal build serialized data of the integer
+func (i *Integer) Marshal(b []byte) (int, error) {
+	bLen := len(b)
+
+	if *i > MaxInteger {
+		return 0, ErrIntegerMarshalTooLarge
+	}
+
+	if bLen < i.ByteSize() {
+		return 0, ErrIntegerMarshalNotEnoughBuffer
+	}
+
+	if *i <= integerValueCutter {
+		b[0] = byte(*i & integerValueCutter)
+
+		return 1, nil
+	}
+
+	b[0] = byte((*i >> 7) | integerHasNextBit)
+	b[1] = byte(*i & integerValueCutter)
+
+	return 2, nil
+}
+
+// Unmarshal read data and parse the integer
+func (i *Integer) Unmarshal(reader rw.ReaderFunc) error {
+	buf := [1]byte{}
+
+	for j := 0; j < MaxIntegerBytes; j++ {
+		_, rErr := rw.ReadFull(reader, buf[:])
+
+		if rErr != nil {
+			return rErr
+		}
+
+		*i |= Integer(buf[0] & integerValueCutter)
+
+		if integerHasNextBit&buf[0] == 0 {
+			return nil
+		}
+
+		*i <<= 7
+	}
+
+	return nil
+}