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
7package wiremessage
8
9import (
10	"bytes"
11	"errors"
12
13	"go.mongodb.org/mongo-driver/bson"
14)
15
16func readInt32(b []byte, pos int32) int32 {
17	return (int32(b[pos+0])) | (int32(b[pos+1]) << 8) | (int32(b[pos+2]) << 16) | (int32(b[pos+3]) << 24)
18}
19
20func readCString(b []byte, pos int32) (string, error) {
21	null := bytes.IndexByte(b[pos:], 0x00)
22	if null == -1 {
23		return "", errors.New("invalid cstring")
24	}
25	return string(b[pos : int(pos)+null]), nil
26}
27
28func readInt64(b []byte, pos int32) int64 {
29	return (int64(b[pos+0])) | (int64(b[pos+1]) << 8) | (int64(b[pos+2]) << 16) | (int64(b[pos+3]) << 24) | (int64(b[pos+4]) << 32) |
30		(int64(b[pos+5]) << 40) | (int64(b[pos+6]) << 48) | (int64(b[pos+7]) << 56)
31
32}
33
34// readDocument will attempt to read a bson.Reader from the given slice of bytes
35// from the given position.
36func readDocument(b []byte, pos int32) (bson.Raw, int, Error) {
37	if int(pos)+4 > len(b) {
38		return nil, 0, Error{Message: "document too small to be valid"}
39	}
40	size := int(readInt32(b, int32(pos)))
41	if int(pos)+size > len(b) {
42		return nil, 0, Error{Message: "document size is larger than available bytes"}
43	}
44	if b[int(pos)+size-1] != 0x00 {
45		return nil, 0, Error{Message: "document invalid, last byte is not null"}
46	}
47	// TODO(GODRIVER-138): When we add 3.0 support, alter this so we either do one larger make or use a pool.
48	rdr := make(bson.Raw, size)
49	copy(rdr, b[pos:int(pos)+size])
50	return rdr, size, Error{Type: ErrNil}
51}
52