Don Newton | 379ae25 | 2019-04-01 12:17:06 -0400 | [diff] [blame^] | 1 | // Copyright (C) MongoDB, Inc. 2017-present. |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); you may |
| 4 | // not use this file except in compliance with the License. You may obtain |
| 5 | // a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 |
| 6 | |
| 7 | package wiremessage |
| 8 | |
| 9 | import ( |
| 10 | "fmt" |
| 11 | ) |
| 12 | |
| 13 | // ErrInvalidHeader is returned when methods are called on a malformed Header. |
| 14 | var ErrInvalidHeader error = Error{Type: ErrHeader, Message: "invalid header"} |
| 15 | |
| 16 | // ErrHeaderTooSmall is returned when the size of the header is too small to be valid. |
| 17 | var ErrHeaderTooSmall error = Error{Type: ErrHeader, Message: "the header is too small to be valid"} |
| 18 | |
| 19 | // ErrHeaderTooFewBytes is returned when a call to ReadHeader does not contain enough |
| 20 | // bytes to be a valid header. |
| 21 | var ErrHeaderTooFewBytes error = Error{Type: ErrHeader, Message: "invalid header because []byte too small"} |
| 22 | |
| 23 | // ErrHeaderInvalidLength is returned when the MessageLength of a header is |
| 24 | // set but is not set to the correct size. |
| 25 | var ErrHeaderInvalidLength error = Error{Type: ErrHeader, Message: "invalid header because MessageLength is imporperly set"} |
| 26 | |
| 27 | // ErrHeaderIncorrectOpCode is returned when the OpCode on a header is set but |
| 28 | // is not set to the correct OpCode. |
| 29 | var ErrHeaderIncorrectOpCode error = Error{Type: ErrHeader, Message: "invalid header because OpCode is improperly set"} |
| 30 | |
| 31 | // Header represents the header of a MongoDB wire protocol message. |
| 32 | type Header struct { |
| 33 | MessageLength int32 |
| 34 | RequestID int32 |
| 35 | ResponseTo int32 |
| 36 | OpCode OpCode |
| 37 | } |
| 38 | |
| 39 | // ReadHeader reads a header from the given slice of bytes starting at offset |
| 40 | // pos. |
| 41 | func ReadHeader(b []byte, pos int32) (Header, error) { |
| 42 | if len(b) < 16 { |
| 43 | return Header{}, ErrHeaderTooFewBytes |
| 44 | } |
| 45 | return Header{ |
| 46 | MessageLength: readInt32(b, 0), |
| 47 | RequestID: readInt32(b, 4), |
| 48 | ResponseTo: readInt32(b, 8), |
| 49 | OpCode: OpCode(readInt32(b, 12)), |
| 50 | }, nil |
| 51 | } |
| 52 | |
| 53 | func (h Header) String() string { |
| 54 | return fmt.Sprintf( |
| 55 | `Header{MessageLength: %d, RequestID: %d, ResponseTo: %d, OpCode: %v}`, |
| 56 | h.MessageLength, h.RequestID, h.ResponseTo, h.OpCode, |
| 57 | ) |
| 58 | } |
| 59 | |
| 60 | // AppendHeader will append this header to the given slice of bytes. |
| 61 | func (h Header) AppendHeader(b []byte) []byte { |
| 62 | b = appendInt32(b, h.MessageLength) |
| 63 | b = appendInt32(b, h.RequestID) |
| 64 | b = appendInt32(b, h.ResponseTo) |
| 65 | b = appendInt32(b, int32(h.OpCode)) |
| 66 | |
| 67 | return b |
| 68 | } |
| 69 | |
| 70 | // SetDefaults sets the length and opcode of this header. |
| 71 | func (h *Header) SetDefaults(length int, opcode OpCode) error { |
| 72 | switch h.MessageLength { |
| 73 | case int32(length): |
| 74 | case 0: |
| 75 | h.MessageLength = int32(length) |
| 76 | default: |
| 77 | return ErrHeaderInvalidLength |
| 78 | } |
| 79 | switch h.OpCode { |
| 80 | case opcode: |
| 81 | case OpCode(0): |
| 82 | h.OpCode = opcode |
| 83 | default: |
| 84 | return ErrHeaderIncorrectOpCode |
| 85 | } |
| 86 | return nil |
| 87 | } |