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#include <mpack.h>
#include <stdio.h>
// MIN() macro
#include <sys/param.h>
#include "i2ctcpv1.h"
int i2ctcp_read(i2ctcp_msg_t * target, const char * buf, size_t buf_sz) {
// a new reader is used per buffer block passed to this function
mpack_reader_t reader;
mpack_reader_init_data(&reader, buf, buf_sz);
// at start of message
if (target->_rdata == 0) {
// NOTE: The entire start of a message needs to be readable from the buffer
// at this point. When target->addr can be read and target->length is past
// the end of the current buffer block, this function will crash and burn.
// This is a highly unlikely scenario, as i2ctcp_read is called for each
// chunk of a TCP frame, and frames (should) include only one puzzle bus
// message. The check here is kind of optional.
if (buf_sz < 4) return -1;
target->addr = mpack_expect_u16(&reader);
target->length = target->_rdata = mpack_expect_bin(&reader);
target->data = (char *) malloc(target->length);
}
// continue reading chunks of target->data until the amount of bytes
// specified in target->length
size_t to_read = MIN(mpack_reader_remaining(&reader, NULL), target->_rdata);
char * data = target->data + target->length - target->_rdata;
mpack_read_bytes(&reader, data, to_read);
target->_rdata -= to_read;
// if rdata = 0, the message was completely read
return target->_rdata;
}
void i2ctcp_read_reset(i2ctcp_msg_t * target) {
target->_rdata = 0;
}
bool i2ctcp_write(const i2ctcp_msg_t * target, char ** buf, size_t * buf_sz) {
mpack_writer_t writer;
mpack_writer_init_growable(&writer, buf, buf_sz);
mpack_write_u16(&writer, target->addr);
mpack_write_bin(&writer, target->data, target->length);
// finish writing
return mpack_writer_destroy(&writer) == mpack_ok;
}
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