Re: Help fixing NativeMessaging host: read 32-bit message length in native byte order

[guest271314]

Yes. I was trying to read 1 char. I think we have at least two working
examples not for how to read the length of the message from the client.

On Mon, Jun 26, 2023 at 5:27 AM alex xmb ratchev <fxmbsw7@gmail.com> wrote:

>
>
> On Sat, Jun 24, 2023, 15:34 guest271314 <guest271314@gmail.com> wrote:
>
>> I have been trying to write a Native Messaging host in Bash comparable to
>> C, C++, Python, and JavaScript versions, trying to determine if Bash is
>> capable of doing so after reading
>>
>> https://stackoverflow.com/questions/24764657/how-do-i-use-a-shell-script-as-chrome-native-messaging-host-application
>> .
>> This is the Native messaging protocol
>>
>> https://developer.chrome.com/docs/extensions/mv3/nativeMessaging/#native-messaging-host-protocol
>> .
>>
>> > Chrome starts each native messaging host in a separate process and
>> communicates with it using standard input (stdin) and standard output
>> (stdout). The same format is used to send messages in both directions;
>> each
>> message is serialized using JSON, UTF-8 encoded and is preceded with
>> 32-bit
>> message length in native byte order. The maximum size of a single message
>> from the native messaging host is 1 MB, mainly to protect Chrome from
>> misbehaving native applications. The maximum size of the message sent to
>> the native messaging host is 4 GB.
>>
>> This is what I came up for getMessage
>> https://github.com/guest271314/native-messaging-bash/blob/main/nm_bash.sh
>> ,
>> the part I need help with is reading message length. In C, C++, Python,
>> JavaScript I can pass new Array(209715) from JavaScript (1 MB) to the host
>> and get the message echo'ed back. In the code below new Array(408) (JSON
>> length 2041) is echo'ed back, over that input length no message is echo'ed
>> back. How do I reliably read 32-bit message length in native byte order
>> using GN Core Utilities in Bash?
>>
>> getMessage() {
>>   read -N 1 uint32
>>   # https://unix.stackexchange.com/a/13141
>>   header=0x$(printf "%s" "$uint32" |
>>   od -t x8 -An |
>>   tr -dc '[:alnum:]')
>>   messageLength=$(printf "%d" "$header")
>>   array=()
>>   read -N "$messageLength" json
>>   array+=("$json")
>>   sendMessage "${array[@]}"
>> }
>>
>
> u realize .. -N 1 to read may read 0 - 9 , one number , not 32 or anything
> else but ' 1 char / number '
> or am i lost ..
>
>>