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So I have a function where I need to accept arbitrary sized U8 slices, but rust will not let me. How can I fix this?
note: I am in an embedded env, I cannot use allocation, I cannot use std, I cannot use vectors, lists, etc - they require allocation.
It really needs to be done with slices passed by reference
The actual application is HUGE to large to put here.
The small example that i can create that is small and to the point
accepts:
(A) A binary input slice, and
(B) produces an ASCII output slice.
fn bin2ascii( bin_data_input : &[u8], ascii_data_output : &[u8] )
{
/* I really want this to be generic for all cases.
* I do not want "FIXED SIZED" slices.
* The actual function in the larger context creates packet..
* But my simple example produces ascii hex in the out buffer.
*/
}
/* I have several hundred "msg functions" like this.
* Each msg is a different length in ascii.
*
* An other example might be creating a UDP network msg.
* The OUTPUT buffer must always be large enough to hold the msg.
*/
fn sendMsgA( cmd_packet : &[u8:75] )
{
// Sort of dumb cause the next function effectively initializes this.
let ascii_bytes : [u8 ; MSG_A_LEN ] = [0;MSG_A_LEN]
// ERROR[E0053]: See below, second example
send_msg( ascii_bytes, MSG_A_LEN );
}
fn sendMsgB( cmd_packet : &[u8:32] )
{
let ascii_bytes : [u8 ; MSG_B_LEN ] = [0;MSG_B_LEN]
// ERROR[E0053]: ascii_bytes
// expected an array with a size of 64, found one with a size of 129
bin2ascii( cmd_packet, ascii_bytes );
send_msg( ascii_bytes, MSG_B_LEN );
}
other things I have considered:
A) using one common buffer size( the largest of them all) presents other problems - It is embedded, so I need to control stack allocation and not be stupid about it, so creating one giant output buffer that is massive is a no go.
B) Or I have a UNIQUE bin2ascii function for every possible size/combination - that seems to be insane
What is necessary is the buffer is large enough for the message.
It is sufficient if the buffer is LARGER then the message
How can I pass an 'large enough buffer' to the common function that formats the data?
2 posts - 2 participants
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