Modbus

refactor: rename some variables

2022-10-16, Mario de Sousa
835e9dad64d9
Parents e319814f1c17
Children 74e9ff734cea
refactor: rename some variables
1 files changed, 137 insertions(+), 134 deletions(-)
  • +137 -134
    mb_master.c
    • --- a/mb_master.c Mon Jun 07 11:21:26 2021 +0200
    +++ b/mb_master.c Sun Oct 16 07:09:48 2022 +0100
    @@ -183,9 +183,9 @@
    * >2 -> SUCCESS: frame length
    * 0..2 -> will never be returned!
    */
    -static int mb_transaction(u8 *packet,
    +static int mb_transaction(u8 *query_packet,
    int query_length,
    - u8 **data,
    + u8 **response_packet,
    int fd,
    int send_retries,
    u8 *error_code,
    @@ -212,7 +212,7 @@
    for (send_retries++; send_retries > 0; send_retries--) {
    error = TIMEOUT;
    - if (modbus_write(ttyfd, packet, query_length, send_transaction_id, response_timeout) < 0)
    + if (modbus_write(ttyfd, query_packet, query_length, send_transaction_id, response_timeout) < 0)
    {error = PORT_FAILURE; continue;}
    /* if we receive a correct response but with a wrong transaction id or wrong modbus function, we try to
    @@ -221,8 +221,8 @@
    * response we are waiting for could be coming 'any minute now'.
    */
    do {
    - response_length = modbus_read(&ttyfd, data, &recv_transaction_id,
    - packet, query_length, response_timeout);
    + response_length = modbus_read(&ttyfd, response_packet, &recv_transaction_id,
    + query_packet, query_length, response_timeout);
    /* TIMEOUT condition */
    /* However, if we had previously received an invalid frame, or some other error,
    @@ -243,17 +243,17 @@
    (send_transaction_id != recv_transaction_id)
    /* not a response frame to _our_ query */
    ||
    - (((*data)[1] & ~0x80) != packet[1])
    - /* NOTE: no need to check whether (*data)[0] = slave! */
    + (((*response_packet)[1] & ~0x80) != query_packet[1])
    + /* NOTE: no need to check whether (*response_packet)[0] = slave! */
    /* This has already been done by the modbus_read() function! */
    );
    if(response_length < 0) {error = PORT_FAILURE; continue;}
    /* Now check whether we received a Modbus Exception frame */
    - if (((*data)[1] & 0x80) != 0) { /* we have an exception frame! */
    - /* NOTE: we have already checked above that data[2] exists! */
    - if (error_code != NULL) *error_code = (*data)[2];
    + if (((*response_packet)[1] & 0x80) != 0) { /* we have an exception frame! */
    + /* NOTE: we have already checked above that response_packet[2] exists! */
    + if (error_code != NULL) *error_code = (*response_packet)[2];
    return MODBUS_ERROR;
    }
    /* success! Let's get out of the send retry loop... */
    @@ -291,26 +291,26 @@
    const struct timespec *response_timeout,
    pthread_mutex_t *data_access_mutex) {
    - u8 packet[QUERY_BUFFER_SIZE];
    - u8 *data;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    int response_length, query_length;
    int temp, i, bit, dest_pos = 0;
    int coils_processed = 0;
    - query_length = build_packet(slave, function, start_addr, count, packet);
    + query_length = build_packet(slave, function, start_addr, count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    - response_length = mb_transaction(packet, query_length, &data, ttyfd,
    + response_length = mb_transaction(query_packet, query_length, &response_packet, ttyfd,
    send_retries, error_code, response_timeout);
    if (response_length < 0) return response_length;
    /* NOTE: Integer division. (count+7)/8 is equivalent to ceil(count/8) */
    - if (response_length != 3 + (count+7)/8) return INVALID_FRAME;
    - if (data[2] != (count+7)/8) return INVALID_FRAME;
    + if (response_length != 3 + (count+7)/8) return INVALID_FRAME;
    + if (response_packet[2] != (count+7)/8) return INVALID_FRAME;
    if (NULL != data_access_mutex) pthread_mutex_lock(data_access_mutex);
    - for( i = 0; (i < data[2]) && (i < dest_size); i++ ) {
    - temp = data[3 + i];
    + for( i = 0; (i < response_packet[2]) && (i < dest_size); i++ ) {
    + temp = response_packet[3 + i];
    for( bit = 0x01; (bit & 0xff) && (coils_processed < count); ) {
    dest[dest_pos] = (temp & bit)?1:0;
    coils_processed++;
    @@ -340,31 +340,34 @@
    int send_retries,
    u8 *error_code,
    const struct timespec *response_timeout) {
    - u8 packet[QUERY_BUFFER_SIZE];
    - u8 *data;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    int response_length, query_length;
    int byte_count, i, dest_pos = 0;
    - query_length = build_packet(slave, function, start_addr, count, packet);
    + query_length = build_packet(slave, function, start_addr, count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    - response_length = mb_transaction(packet, query_length, &data, ttyfd,
    + response_length = mb_transaction(query_packet, query_length, &response_packet, ttyfd,
    send_retries, error_code, response_timeout);
    if (response_length < 0) return response_length;
    /* NOTE: Integer division. (count+7)/8 is equivalent to ceil(count/8) */
    - if (response_length != 3 + (count+7)/8) return INVALID_FRAME;
    - if (data[2] != (count+7)/8) return INVALID_FRAME;
    + if (response_length != 3 + (count+7)/8) return INVALID_FRAME;
    + if (response_packet[2] != (count+7)/8) return INVALID_FRAME;
    - byte_count = data[2];
    - data += 3;
    + byte_count = response_packet[2];
    + response_packet += 3;
    /* handle groups of 4 bytes... */
    for(i = 0, dest_pos = 0; i + 3 < byte_count; i += 4, dest_pos++)
    - dest[dest_pos] = data[i] + data[i+1]*0x100 + data[i+2]*0x10000 + data[i+3]*0x1000000;
    + dest[dest_pos] = response_packet[i]
    + + response_packet[i+1]*0x100
    + + response_packet[i+2]*0x10000
    + + response_packet[i+3]*0x1000000;
    /* handle any remaining bytes... begining with the last! */
    if (i < byte_count) dest[dest_pos] = 0;
    for(byte_count--; i <= byte_count; byte_count--)
    - dest[dest_pos] = dest[dest_pos]*0x100 + data[byte_count];
    + dest[dest_pos] = dest[dest_pos]*0x100 + response_packet[byte_count];
    return response_length;
    }
    @@ -494,26 +497,26 @@
    u8 *error_code,
    const struct timespec *response_timeout,
    pthread_mutex_t *data_access_mutex) {
    - u8 *data;
    - u8 packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    int response_length;
    int query_length;
    int temp,i;
    - query_length = build_packet(slave, function, start_addr, count, packet);
    + query_length = build_packet(slave, function, start_addr, count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    - response_length = mb_transaction(packet, query_length, &data, ttyfd,
    + response_length = mb_transaction(query_packet, query_length, &response_packet, ttyfd,
    send_retries, error_code, response_timeout);
    - if (response_length < 0) return response_length;
    - if (response_length != 3 + 2*count) return INVALID_FRAME;
    - if (data[2] != 2*count) return INVALID_FRAME;
    + if (response_length < 0) return response_length;
    + if (response_length != 3 + 2*count) return INVALID_FRAME;
    + if (response_packet[2] != 2*count) return INVALID_FRAME;
    if (NULL != data_access_mutex) pthread_mutex_lock(data_access_mutex);
    - for(i = 0; (i < (data[2]*2)) && (i < dest_size); i++ ) {
    - temp = data[3 + i *2] << 8; /* copy reg hi byte to temp hi byte*/
    - temp = temp | data[4 + i * 2]; /* copy reg lo byte to temp lo byte*/
    + for(i = 0; (i < (response_packet[2]*2)) && (i < dest_size); i++ ) {
    + temp = response_packet[3 + i *2 ] << 8; /* copy reg hi byte to temp hi byte*/
    + temp |= response_packet[4 + i * 2]; /* copy reg lo byte to temp lo byte*/
    dest[i] = temp;
    }
    if (NULL != data_access_mutex) pthread_mutex_unlock(data_access_mutex);
    @@ -538,35 +541,35 @@
    int send_retries,
    u8 *error_code,
    const struct timespec *response_timeout) {
    - u8 *data;
    - u8 packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    int response_length;
    int query_length;
    int i, byte_count;
    - query_length = build_packet(slave, function, start_addr, count, packet);
    + query_length = build_packet(slave, function, start_addr, count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    - response_length = mb_transaction(packet, query_length, &data, ttyfd,
    + response_length = mb_transaction(query_packet, query_length, &response_packet, ttyfd,
    send_retries, error_code, response_timeout);
    - if (response_length < 0) return response_length;
    - if (response_length != 3 + 2*count) return INVALID_FRAME;
    - if (data[2] != 2*count) return INVALID_FRAME;
    + if (response_length < 0) return response_length;
    + if (response_length != 3 + 2*count) return INVALID_FRAME;
    + if (response_packet[2] != 2*count) return INVALID_FRAME;
    - byte_count = data[2];
    - data = data + 3; /* & data[3] */
    + byte_count = response_packet[2];
    + response_packet = response_packet + 3; /* & response_packet[3] */
    if (ntohs(0x0102) != 0x0102) {
    /* little endian host... => we need to swap the bytes! */
    for(i = 0; i < byte_count; i++ ) {
    /* the following 3 lines result in the two values being exchanged! */
    - data[i ] = data[i] ^ data[i+1];
    - data[i+1] = data[i] ^ data[i+1];
    - data[i ] = data[i] ^ data[i+1];
    + response_packet[i ] = response_packet[i] ^ response_packet[i+1];
    + response_packet[i+1] = response_packet[i] ^ response_packet[i+1];
    + response_packet[i ] = response_packet[i] ^ response_packet[i+1];
    }
    }
    - *dest = (u16 *)data;
    + *dest = (u16 *)response_packet;
    return byte_count;
    }
    @@ -588,61 +591,61 @@
    int send_retries,
    u8 *error_code,
    const struct timespec *response_timeout) {
    - u8 *data;
    - u8 packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    int response_length;
    int query_length;
    int i, byte_count, dest_pos;
    - query_length = build_packet(slave, function, start_addr, count, packet);
    + query_length = build_packet(slave, function, start_addr, count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    - response_length = mb_transaction(packet, query_length, &data, ttyfd,
    + response_length = mb_transaction(query_packet, query_length, &response_packet, ttyfd,
    send_retries, error_code, response_timeout);
    - if (response_length < 0) return response_length;
    - if (response_length != 3 + 2*count) return INVALID_FRAME;
    - if (data[2] != 2*count) return INVALID_FRAME;
    + if (response_length < 0) return response_length;
    + if (response_length != 3 + 2*count) return INVALID_FRAME;
    + if (response_packet[2] != 2*count) return INVALID_FRAME;
    - byte_count = data[2];
    - data += 3;
    + byte_count = response_packet[2];
    + response_packet += 3;
    if (ntohs(0x0102) == 0x0102) {
    /* big endian host... */
    /* handle groups of 4 bytes... */
    for(i = 0, dest_pos = 0; i + 3 < byte_count; i += 4, dest_pos++) {
    - *(((u8 *)(dest + dest_pos))+ 0) = *(data+i+3);
    - *(((u8 *)(dest + dest_pos))+ 1) = *(data+i+4);
    - *(((u8 *)(dest + dest_pos))+ 2) = *(data+i+0);
    - *(((u8 *)(dest + dest_pos))+ 3) = *(data+i+1);
    + *(((u8 *)(dest + dest_pos))+ 0) = *(response_packet+i+3);
    + *(((u8 *)(dest + dest_pos))+ 1) = *(response_packet+i+4);
    + *(((u8 *)(dest + dest_pos))+ 2) = *(response_packet+i+0);
    + *(((u8 *)(dest + dest_pos))+ 3) = *(response_packet+i+1);
    }
    /* handle any remaining bytes...
    * since byte_count is supposed to be multiple of 2,
    - * (and has already been verified above 'if (data[2] != 2*count)')
    + * (and has already been verified above 'if (response_packet[2] != 2*count)')
    * this will be either 2, or none at all!
    */
    if (i + 1 < byte_count)
    *(((u8 *)(dest + dest_pos))+ 0) = 0;
    *(((u8 *)(dest + dest_pos))+ 1) = 0;
    - *(((u8 *)(dest + dest_pos))+ 2) = *(data+i+0);
    - *(((u8 *)(dest + dest_pos))+ 3) = *(data+i+1);
    + *(((u8 *)(dest + dest_pos))+ 2) = *(response_packet+i+0);
    + *(((u8 *)(dest + dest_pos))+ 3) = *(response_packet+i+1);
    } else {
    /* little endian host... */
    /* handle groups of 4 bytes... */
    for(i = 0, dest_pos = 0; i + 3 < byte_count; i += 4, dest_pos++) {
    - *(((u8 *)(dest + dest_pos))+ 0) = *(data+i+1);
    - *(((u8 *)(dest + dest_pos))+ 1) = *(data+i+0);
    - *(((u8 *)(dest + dest_pos))+ 2) = *(data+i+3);
    - *(((u8 *)(dest + dest_pos))+ 3) = *(data+i+2);
    + *(((u8 *)(dest + dest_pos))+ 0) = *(response_packet+i+1);
    + *(((u8 *)(dest + dest_pos))+ 1) = *(response_packet+i+0);
    + *(((u8 *)(dest + dest_pos))+ 2) = *(response_packet+i+3);
    + *(((u8 *)(dest + dest_pos))+ 3) = *(response_packet+i+2);
    }
    /* handle any remaining bytes...
    * since byte_count is supposed to be multiple of 2,
    - * (and has already been verified above 'if (data[2] != 2*count)')
    + * (and has already been verified above 'if (response_packet[2] != 2*count)')
    * this will be either 2, or none at all!
    */
    if (i + 1 < byte_count)
    - *(((u8 *)(dest + dest_pos))+ 0) = *(data+i+1);
    - *(((u8 *)(dest + dest_pos))+ 1) = *(data+i+0);
    + *(((u8 *)(dest + dest_pos))+ 0) = *(response_packet+i+1);
    + *(((u8 *)(dest + dest_pos))+ 1) = *(response_packet+i+0);
    *(((u8 *)(dest + dest_pos))+ 2) = 0;
    *(((u8 *)(dest + dest_pos))+ 3) = 0;
    }
    @@ -824,23 +827,23 @@
    u8 *error_code,
    const struct timespec *response_timeout,
    pthread_mutex_t *data_access_mutex) {
    - u8 packet[QUERY_BUFFER_SIZE];
    - u8 *data;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    int query_length, response_length;
    if (NULL != data_access_mutex) pthread_mutex_lock(data_access_mutex);
    - query_length = build_packet(slave, function, addr, value, packet);
    + query_length = build_packet(slave, function, addr, value, query_packet);
    if (NULL != data_access_mutex) pthread_mutex_unlock(data_access_mutex);
    if (query_length < 0) return INTERNAL_ERROR;
    - response_length = mb_transaction(packet, query_length, &data, ttyfd, send_retries,
    + response_length = mb_transaction(query_packet, query_length, &response_packet, ttyfd, send_retries,
    error_code, response_timeout);
    if (response_length < 0) return response_length;
    if (response_length != 6) return INVALID_FRAME;
    - if ((data[2] != packet[2]) || (data[3] != packet[3]) ||
    - (data[4] != packet[4]) || (data[5] != packet[5]))
    + if ((response_packet[2] != query_packet[2]) || (response_packet[3] != query_packet[3]) ||
    + (response_packet[4] != query_packet[4]) || (response_packet[5] != query_packet[5]))
    return INVALID_FRAME;
    return response_length;
    @@ -903,8 +906,8 @@
    int coil_check = 0;
    int data_array_pos = 0;
    int query_length, response_length;
    - u8 packet[QUERY_BUFFER_SIZE];
    - u8 *rdata;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    if( coil_count > MAX_WRITE_COILS ) {
    coil_count = MAX_WRITE_COILS;
    @@ -914,35 +917,35 @@
    }
    query_length = build_packet(slave, 0x0F /* function */,
    - start_addr, coil_count, packet);
    + start_addr, coil_count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    /* NOTE: Integer division. (count+7)/8 is equivalent to ceil(count/8) */
    byte_count = (coil_count+7)/8;
    - packet[query_length] = byte_count;
    + query_packet[query_length] = byte_count;
    if (NULL != data_access_mutex) pthread_mutex_lock(data_access_mutex);
    bit = 0x01;
    for(i = 0; i < byte_count; i++) {
    - packet[++query_length] = 0;
    + query_packet[++query_length] = 0;
    while((bit & 0xFF) && (coil_check++ < coil_count)) {
    - if(data[data_array_pos++]) {packet[query_length] |= bit;}
    - else {packet[query_length] &= ~bit;}
    + if(data[data_array_pos++]) {query_packet[query_length] |= bit;}
    + else {query_packet[query_length] &= ~bit;}
    bit <<= 1;
    }
    bit = 0x01;
    }
    if (NULL != data_access_mutex) pthread_mutex_unlock(data_access_mutex);
    - response_length = mb_transaction(packet, ++query_length, &rdata, ttyfd, send_retries,
    + response_length = mb_transaction(query_packet, ++query_length, &response_packet, ttyfd, send_retries,
    error_code, response_timeout);
    if (response_length < 0) return response_length;
    if (response_length != 6) return INVALID_FRAME;
    - if ((rdata[2] != packet[2]) ||
    - (rdata[3] != packet[3]) ||
    - (rdata[4] != packet[4]) ||
    - (rdata[5] != packet[5])) return INVALID_FRAME;
    + if ((response_packet[2] != query_packet[2]) ||
    + (response_packet[3] != query_packet[3]) ||
    + (response_packet[4] != query_packet[4]) ||
    + (response_packet[5] != query_packet[5])) return INVALID_FRAME;
    return response_length;
    }
    @@ -963,8 +966,8 @@
    const struct timespec *response_timeout) {
    int org_pos, byte_count, i;
    int query_length, response_length;
    - u8 packet[QUERY_BUFFER_SIZE];
    - u8 *rdata;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    if( coil_count > MAX_WRITE_COILS ) {
    coil_count = MAX_WRITE_COILS;
    @@ -974,35 +977,35 @@
    }
    query_length = build_packet(slave, 0x0F /* function */,
    - start_addr, coil_count, packet);
    + start_addr, coil_count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    /* NOTE: Integer division. This is equivalent of determining the ceil(count/8) */
    byte_count = (coil_count+7)/8;
    - packet[query_length] = byte_count;
    + query_packet[query_length] = byte_count;
    /* handle groups of 4 bytes... */
    for(i = 0, org_pos = 0; i + 3 < byte_count; i += 4, org_pos++) {
    - packet[++query_length] = data[org_pos] & 0xFF; data[org_pos] >>= 8;
    - packet[++query_length] = data[org_pos] & 0xFF; data[org_pos] >>= 8;
    - packet[++query_length] = data[org_pos] & 0xFF; data[org_pos] >>= 8;
    - packet[++query_length] = data[org_pos] & 0xFF;
    + query_packet[++query_length] = data[org_pos] & 0xFF; data[org_pos] >>= 8;
    + query_packet[++query_length] = data[org_pos] & 0xFF; data[org_pos] >>= 8;
    + query_packet[++query_length] = data[org_pos] & 0xFF; data[org_pos] >>= 8;
    + query_packet[++query_length] = data[org_pos] & 0xFF;
    }
    /* handle any remaining bytes... */
    for(; i < byte_count; i++) {
    - packet[++query_length] = data[org_pos] & 0xFF;
    + query_packet[++query_length] = data[org_pos] & 0xFF;
    data[org_pos] >>= 8;
    }
    - response_length = mb_transaction(packet, ++query_length, &rdata, ttyfd, send_retries,
    + response_length = mb_transaction(query_packet, ++query_length, &response_packet, ttyfd, send_retries,
    error_code, response_timeout);
    if (response_length < 0) return response_length;
    if (response_length != 6) return INVALID_FRAME;
    - if ((rdata[2] != packet[2]) ||
    - (rdata[3] != packet[3]) ||
    - (rdata[4] != packet[4]) ||
    - (rdata[5] != packet[5])) return INVALID_FRAME;
    + if ((response_packet[2] != query_packet[2]) ||
    + (response_packet[3] != query_packet[3]) ||
    + (response_packet[4] != query_packet[4]) ||
    + (response_packet[5] != query_packet[5])) return INVALID_FRAME;
    return response_length;
    }
    @@ -1023,8 +1026,8 @@
    pthread_mutex_t *data_access_mutex) {
    u8 byte_count;
    int i, query_length, response_length;
    - u8 packet[QUERY_BUFFER_SIZE];
    - u8 *rdata;
    + u8 query_packet[QUERY_BUFFER_SIZE];
    + u8 *response_packet;
    if( reg_count > MAX_WRITE_REGS ) {
    reg_count = MAX_WRITE_REGS;
    @@ -1034,28 +1037,28 @@
    }
    query_length = build_packet(slave, 0x10 /* function */,
    - start_addr, reg_count, packet);
    + start_addr, reg_count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    byte_count = reg_count*2;
    - packet[query_length] = byte_count;
    + query_packet[query_length] = byte_count;
    if (NULL != data_access_mutex) pthread_mutex_lock(data_access_mutex);
    for( i = 0; i < reg_count; i++ ) {
    - packet[++query_length] = data[i] >> 8;
    - packet[++query_length] = data[i] & 0x00FF;
    + query_packet[++query_length] = data[i] >> 8;
    + query_packet[++query_length] = data[i] & 0x00FF;
    }
    if (NULL != data_access_mutex) pthread_mutex_unlock(data_access_mutex);
    - response_length = mb_transaction(packet, ++query_length, &rdata, ttyfd, send_retries,
    + response_length = mb_transaction(query_packet, ++query_length, &response_packet, ttyfd, send_retries,
    error_code, response_timeout);
    if (response_length < 0) return response_length;
    if (response_length != 6) return INVALID_FRAME;
    - if ((rdata[2] != packet[2]) ||
    - (rdata[3] != packet[3]) ||
    - (rdata[4] != packet[4]) ||
    - (rdata[5] != packet[5])) return INVALID_FRAME;
    + if ((response_packet[2] != query_packet[2]) ||
    + (response_packet[3] != query_packet[3]) ||
    + (response_packet[4] != query_packet[4]) ||
    + (response_packet[5] != query_packet[5])) return INVALID_FRAME;
    return response_length;
    }
    @@ -1078,9 +1081,9 @@
    const struct timespec *response_timeout) {
    u8 byte_count;
    int i, query_length, response_length;
    - u8 packet_[QUERY_BUFFER_SIZE];
    - u8 *packet = packet_; /* remove the const'ness of packet_ */
    - u8 *rdata;
    + u8 query_packet_[QUERY_BUFFER_SIZE];
    + u8 *query_packet = query_packet_; /* remove the const'ness of query_packet_ */
    + u8 *response_packet;
    if( reg_count > MAX_WRITE_REGS ) {
    reg_count = MAX_WRITE_REGS;
    @@ -1091,28 +1094,28 @@
    /* Make sure that the de-referencing and up-casting going on later on in
    * this function, i.e. code like the following line:
    - * *((u16 *)packet) = XXX
    + * *((u16 *)query_packet) = XXX
    * will result in u16 words starting off on even addresses.
    * If we don't do this, some compilers (e.g. AVR32 cross-compiler) will
    * generate code which, when executed, will result in 'bus error'.
    *
    - * The following packet++ means that the first byte of the packet array is
    - * essentially never used. Notice too that the size of thepacket array
    + * The following query_packet++ means that the first byte of the query_packet array is
    + * essentially never used. Notice too that the size of the query_packet array
    * already takes into account this un-used byte.
    */
    - packet++;
    + query_packet++;
    query_length = build_packet(slave, 0x10 /* function */,
    - start_addr, reg_count, packet);
    + start_addr, reg_count, query_packet);
    if (query_length < 0) return INTERNAL_ERROR;
    byte_count = reg_count*2;
    - packet[query_length] = byte_count;
    + query_packet[query_length] = byte_count;
    /* handle groups of 4 bytes... */
    for(i = 0; 4*i + 3 < byte_count; i++) {
    - *((u16 *)(packet+(++query_length))) = mb_hton(data[i]); ++query_length;
    - *((u16 *)(packet+(++query_length))) = mb_hton(data[i] >> 16); ++query_length;
    + *((u16 *)(query_packet+(++query_length))) = mb_hton(data[i]); ++query_length;
    + *((u16 *)(query_packet+(++query_length))) = mb_hton(data[i] >> 16); ++query_length;
    }
    /* handle any remaining bytes...
    @@ -1121,18 +1124,18 @@
    * this will be either 2, or none at all!
    */
    if (4*i + 1 < byte_count) {
    - *((u16 *)(packet+(++query_length))) = mb_hton(data[i]); ++query_length;
    + *((u16 *)(query_packet+(++query_length))) = mb_hton(data[i]); ++query_length;
    }
    - response_length = mb_transaction(packet, ++query_length, &rdata, ttyfd, send_retries,
    + response_length = mb_transaction(query_packet, ++query_length, &response_packet, ttyfd, send_retries,
    error_code, response_timeout);
    if (response_length < 0) return response_length;
    if (response_length != 6) return INVALID_FRAME;
    - if ((rdata[2] != packet[2]) ||
    - (rdata[3] != packet[3]) ||
    - (rdata[4] != packet[4]) ||
    - (rdata[5] != packet[5])) return INVALID_FRAME;
    + if ((response_packet[2] != query_packet[2]) ||
    + (response_packet[3] != query_packet[3]) ||
    + (response_packet[4] != query_packet[4]) ||
    + (response_packet[5] != query_packet[5])) return INVALID_FRAME;
    return response_length;
    }