unsigned short
可能是也可能不是2个字节。让我们看看你的例子的内存。
+---+---+---+ +---+---+---+
| | | | ... | | | |
+---+---+---+ +---+---+---+
|<-------- len bytes -------->|
如果unsigned short
为2个字节长,你有len/2
unsigned short
值空间的价值。或者,更一般地说,您有len/n
unsigned short
值的空间,其中n
等于sizeof(unsigned short)
。
你不能投unsigned char *
到unsigned char *
,并期望事情可移植工作。现在,要计算peak
,这取决于你正在尝试做什么。如果你想找到的最大的len
unsigned char
值,并保存到peak
,遍历该值将工作:
size_t i;
unsigned short peak = 0;
for (i=0; i < len; ++i) {
if (buffer[i] > peak) {
peak = buffer[i];
}
}
但是,如果你想“结合” sizeof(unsigned short)
值转换成一个unsigned short
值,则你最好的选择是手工计算数字。
假设len
是整除n
和大端存储,你可以这样做(未经测试):
#include <stdio.h>
#include <limits.h>
size_t factor = sizeof(unsigned short);
size_t n = len/factor;
size_t i;
unsigned short peak = 0;
if (len % factor != 0) {
fprintf(stderr, "Extra data at the end\n");
}
for (i=0; i < n; ++i) {
size_t j;
unsigned short test = 0;
for (j=0; j < factor; ++j) {
test = (test << CHAR_BIT) + buffer[i*factor+j];
}
if (test > peak) {
peak = test;
}
}