原文：https://zhuanlan.zhihu.com/p/653484840
In embedded development, commonly used C language tool code is indeed very important.
Today, I will share some sharp-level C language tool code examples, along with brief explanations.
1. Circular Buffer:
typedef struct {
int buffer[SIZE];
int head;
int tail;
int count;
} CircularBuffer;
void push(CircularBuffer *cb, int data) {
if (cb->count < SIZE) {
cb->buffer[cb->head] = data;
cb->head = (cb->head + 1) % SIZE;
cb->count++;
}
}
int pop(CircularBuffer *cb) {
if (cb->count > 0) {
int data = cb->buffer[cb->tail];
cb->tail = (cb->tail + 1) % SIZE;
cb->count--;
return data;
}
return -1; // Buffer is empty
}The circular buffer is an efficient data structure suitable for buffering and data stream applications, such as serial communication receive buffers.
2. Assertion:
#define assert(expression) ((void)0)
#ifndef NDEBUG
#undef assert
#define assert(expression) ((expression) ? (void)0 : assert_failed(__FILE__, __LINE__))
#endif
void assert_failed(const char *file, int line) {
printf("Assertion failed at %s:%d\n", file, line);
// Additional error handling or logging can be added here
}Assertions are used to check whether specific conditions are met in a program. If the condition is false, it triggers an assertion failure and outputs relevant information.
3. Bit Reversal:
unsigned int reverse_bits(unsigned int num) {
unsigned int numOfBits = sizeof(num) * 8;
unsigned int reverseNum = 0;
for (unsigned int i = 0; i < numOfBits; i++) {
if (num & (1 << i)) {
reverseNum |= (1 << ((numOfBits - 1) - i));
}
}
return reverseNum;
}This function reverses the bits of a given unsigned integer, which can be used for bit-level operations in certain embedded systems.
4. Fixed-Point Arithmetic:
typedef int16_t fixed_t;
#define FIXED_SHIFT 8
#define FLOAT_TO_FIXED(f) ((fixed_t)((f) * (1 << FIXED_SHIFT)))
#define FIXED_TO_FLOAT(f) ((float)(f) / (1 << FIXED_SHIFT))
fixed_t fixed_multiply(fixed_t a, fixed_t b) {
return (fixed_t)(((int32_t)a * (int32_t)b) >> FIXED_SHIFT);
}In some embedded systems, floating-point operations can be slow or unsupported. Therefore, using fixed-point arithmetic provides an efficient approximation solution for floating-point numbers.
5. Endianness Conversion:
uint16_t swap_bytes(uint16_t value) { return (value >> 8) | (value << 8); }This function is used to convert between big-endian and little-endian byte orders.
6. Bit Masks:
#define BIT_MASK(bit) (1 << (bit))This is used to create a bitmask with only the specified bit set, which can be used for bit operations.
7. Timer Counting:
#include <avr io.h="">
void setup_timer() {
// Configure timer settings
}
uint16_t read_timer() {
return TCNT1;
}</avr>In AVR embedded systems, timers are used to implement time measurement and timed tasks.
8. Binary Search:
int binary_search(int arr[], int size, int target) {
int left = 0, right = size - 1;
while (left <= right) {
int mid = left + (right - left) / 2;
if (arr[mid] == target) {
return mid;
} else if (arr[mid] < target) {
left = mid + 1;
} else {
right = mid - 1;
}
}
return -1; // Not found
}This function performs a binary search in a sorted array.
9. Bitset:
#include <stdint.h>
typedef struct {
uint32_t bits;
} Bitset;
void set_bit(Bitset *bitset, int bit) {
bitset->bits |= (1U << bit);
}
int get_bit(Bitset *bitset, int bit) {
return (bitset->bits >> bit) & 1U;
}</stdint.h>This implements a simple bitset data structure for managing the state of a set of bits.
These code examples represent some commonly used sharp-level C language tool codes in embedded development.
They have broad applications in embedded system development, helping to optimize performance, save resources, and improve code maintainability.
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