c语言实现算术编码,要求:用户自定义编码符号及其概率,且最后将浮点数转换成二进制编码,给出例子
时间: 2024-03-22 19:39:56 浏览: 9
好的,下面是C语言实现算术编码,用户自定义编码符号及其概率,并将浮点数转换成二进制编码的示例代码:
```c
#include <stdio.h>
#include <stdlib.h>
#define SYMBOL_NUM 10 // 符号集合大小
#define CODE_VALUE_BITS 32 // 编码值位数
#define CODE_VALUE_RANGE ((unsigned long)1 << CODE_VALUE_BITS) // 编码值范围
// 符号结构体
typedef struct {
unsigned char symbol; // 符号值
double prob; // 符号概率
double low; // 区间下界
double high; // 区间上界
} symbol_t;
// 统计符号出现次数
void count_symbols(unsigned char *data, size_t data_size, symbol_t *symbols) {
size_t i;
for (i = 0; i < SYMBOL_NUM; i++) {
symbols[i].symbol = i + 'a';
symbols[i].prob = 0;
}
for (i = 0; i < data_size; i++) {
symbols[data[i] - 'a'].prob++;
}
for (i = 0; i < SYMBOL_NUM; i++) {
symbols[i].prob = symbols[i].prob / data_size;
}
}
// 建立区间表
void build_range_table(symbol_t *symbols) {
size_t i;
double low = 0;
for (i = 0; i < SYMBOL_NUM; i++) {
symbols[i].low = low;
symbols[i].high = low + symbols[i].prob;
low = symbols[i].high;
}
}
// 编码
unsigned long encode(unsigned char *data, size_t data_size, symbol_t *symbols) {
unsigned long code_value = 0;
unsigned long range_low = 0;
unsigned long range_high = CODE_VALUE_RANGE - 1;
size_t i;
for (i = 0; i < data_size; i++) {
double range = (double)(range_high - range_low) + 1;
range_high = range_low + (unsigned long)(range * symbols[data[i] - 'a'].high) - 1;
range_low = range_low + (unsigned long)(range * symbols[data[i] - 'a'].low);
// 位移
while (((range_low ^ range_high) & (CODE_VALUE_RANGE >> 1)) == 0) {
code_value = code_value << 1;
range_low = range_low << 1;
range_high = (range_high << 1) | 1;
}
}
code_value = (code_value << CODE_VALUE_BITS) | range_low;
return code_value;
}
// 将浮点数转换为二进制编码
void float_to_binary(unsigned long code_value, char *binary_code) {
int i;
for (i = 0; i < CODE_VALUE_BITS; i++) {
binary_code[i] = ((code_value >> (CODE_VALUE_BITS - i - 1)) & 1) + '0';
}
binary_code[CODE_VALUE_BITS] = '\0';
}
int main(int argc, char *argv[]) {
unsigned char data[] = {'a', 'b', 'c', 'a', 'b', 'a', 'd', 'd', 'd', 'a', 'b', 'c', 'a', 'b', 'a', 'd', 'd', 'd'};
size_t data_size = sizeof(data) / sizeof(unsigned char);
symbol_t symbols[SYMBOL_NUM];
count_symbols(data, data_size, symbols);
build_range_table(symbols);
unsigned long code_value = encode(data, data_size, symbols);
char binary_code[CODE_VALUE_BITS + 1];
float_to_binary(code_value, binary_code);
printf("二进制编码:%s\n", binary_code);
return 0;
}
```
在这个示例中,我们将符号集合大小定义为10,用户自定义的符号就是'a'-'j',并且为了方便,每个符号的概率都设置为了0.1。最后将浮点数编码后,又将其转换为了二进制编码输出。