Are you ready for advanced data handling concepts? Want to learn about struct pointer as function parameter? Read through this article to find out.
Introduction
Last time, you learned about basic pointers, structures, and function parameters. Now you can combine these concepts to add flexibility in accessing your data as well as on creating functions. You’ll see that structures mapped and accessed in memory can be useful for complex projects requiring multiple data sets. With this, you’ll make use of struct pointer as function parameter.
Structures and Pointers: Application in Functions Parameters
Structures can classify different kinds of data sets since the struct data type can have various data types within it. A good application of this scenario is when packets come from different sources. Imagine you have multiple peripherals acquiring data and you have to sort each one and modify their data using only a single function. The next part will explain this example in detail.
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Example Application
typedef struct data_set_tag {
int data[8];
int type;
} data_set_t;
After this, you can declare each data set coming from your different peripherals as:
data_set_t data_set_adc, data_set_uart, data_set_can;
You can declare the single function to work on these data sets below:
void work_on_data_set(data_set_t *data_set)
{
if(data_set->type == 1)
{
// do adc functions
printf("Work on data coming from ADC\n");
int i;
for(i=0;i<8;i++)
{
data_set->data[i] = data_set->data[i] + 1;
printf("Data = %i\n", data_set->data[i]);
}
} else {
if(data_set->type == 2)
{
// do uart functions
printf("Work on data coming from UART\n");
int i;
for(i=0;i<8;i++)
{
data_set->data[i]= data_set->data[i] + 2;
printf("Data = %x\n", data_set->data[i]);
}
} else {
if(data_set->type == 3)
{
// do can functions
printf("Work on data coming from CAN\n");
int i;
for(i=0;i<8;i++)
{
data_set->data[i] = data_set->data[i] +3;
printf("Data = %i\n", data_set->data[i]);
}
}
}
}
printf("\n");
}
Note that the data_set parameter is declared as a pointer of type data_set_t. This means the memory location pointed to by this pointer just needs to have as value a data_set_t type. You can readily pass-by-reference the data sets you declared in the beginning of this example as:
// work on the data set
work_on_data_set(&data_set_adc);
work_on_data_set(&data_set_uart);
work_on_data_set(&data_set_can);
Code and Output
#include <stdio.h>
#include <freertos\FreeRTOS.h>
#include <freertos\task.h>
typedef struct data_set_tag {
int data[8];
int type;
} data_set_t;
data_set_t data_set_adc, data_set_uart, data_set_can;
void work_on_data_set(data_set_t *data_set);
void app_main(void)
{
// init data sets simulating data fetch on various devices
data_set_adc.type = 1;
data_set_adc.data[0] = 128;
data_set_adc.data[1] = 128;
data_set_adc.data[2] = 128;
data_set_adc.data[3] = 128;
data_set_adc.data[4] = 120;
data_set_adc.data[5] = 120;
data_set_adc.data[6] = 120;
data_set_adc.data[7] = 120;
data_set_uart.type = 2;
data_set_uart.data[0] = 0x0A;
data_set_uart.data[1] = 0x0B;
data_set_uart.data[2] = 0x0C;
data_set_uart.data[3] = 0x0A;
data_set_uart.data[4] = 0x0B;
data_set_uart.data[5] = 0x0C;
data_set_uart.data[6] = 0x0A;
data_set_uart.data[7] = 0x0B;
data_set_can.type = 3;
data_set_can.data[0] = 25;
data_set_can.data[1] = 25;
data_set_can.data[2] = 30;
data_set_can.data[3] = 30;
data_set_can.data[4] = 30;
data_set_can.data[5] = 31;
data_set_can.data[6] = 32;
data_set_can.data[7] = 32;
// work on the data set
work_on_data_set(&data_set_adc);
work_on_data_set(&data_set_uart);
work_on_data_set(&data_set_can);
while(1)
{
vTaskDelay(100);
}
}
void work_on_data_set(data_set_t *data_set)
{
if(data_set->type == 1)
{
// do adc functions
printf("Work on data coming from ADC\n");
int i;
for(i=0;i<8;i++)
{
data_set->data[i] = data_set->data[i] + 1;
printf("Data = %i\n", data_set->data[i]);
}
} else {
if(data_set->type == 2)
{
// do uart functions
printf("Work on data coming from UART\n");
int i;
for(i=0;i<8;i++)
{
data_set->data[i]= data_set->data[i] + 2;
printf("Data = %x\n", data_set->data[i]);
}
} else {
if(data_set->type == 3)
{
// do can functions
printf("Work on data coming from CAN\n");
int i;
for(i=0;i<8;i++)
{
data_set->data[i] = data_set->data[i] +3;
printf("Data = %i\n", data_set->data[i]);
}
}
}
}
printf("\n");
}
Work on data coming from ADC
Data = 129
Data = 129
Data = 129
Data = 129
Data = 121
Data = 121
Data = 121
Data = 121
Work on data coming from UART
Data = c
Data = d
Data = e
Data = c
Data = d
Data = e
Data = c
Data = d
Work on data coming from CAN
Data = 28
Data = 28
Data = 33
Data = 33
Data = 33
Data = 34
Data = 35
Data = 35
