CSAPP 5.4 Elimination Loop Inefficiencies

7		for (i = 0; i < vec_length(v); i++) {
8			data_t val;
9			get_vec_element(v, i, &val);
10			*dest = *dest OP val;
11		}

1	/* Convert string to lowercase: slow */
2	void lower1(char *s)
3	{
4		long i;
5	
6		for (i = 0; i < strlen(s); i++)
7			if (s[i] >= `A' && s[i] <= `Z')
8				s[i] -= (`A' - `a');
9	}
10	
11	/* Convert string to lowercase: faster */
12	void lower2(char *s)
13	{
14		long i;
15		long len = strlen(s);
16	
17		for (i = 0; i < len; i++)
18			if (s[i] >= `A' && s[i] <= `Z')
19				s[i] -= (`A' - `a');
20	}
21	
22	/* Sample implementation of library function strlen */
23	/* Compute length of string */
24	size_t strlen(const char *s)
25	{
26		long length = 0;
27		while (*s != `\0') {
28				s++;
29				length++;
30		}
31		return length;
32	}