usr.bin/look/look.c

106 	unsigned char *back, *front;
156 		if ((front = mmap(NULL, (size_t)sb.st_size, PROT_READ, MAP_SHARED, fd, (off_t)0)) == MAP_FAILED)
158 		back = front + sb.st_size;
159 		match *= (look(key, front, back));
198 look(wchar_t *string, unsigned char *front, unsigned char *back)
201 	front = binary_search(string, front, back);
202 	front = linear_search(string, front, back);
204 	if (front)
205 		print_from(string, front, back);
206 	return (front ? 0 : 1);
211  * Binary search for "string" in memory between "front" and "back".
218  * 	front points to the beginning of a line at or before the first
225  * 	front = NULL;
230  * 	p = first newline after halfway point from front to back.
233  *	p is the new front.  Otherwise it is the new back.
238  *	since front is always at or before the line to print.
242  *	(back - front), which in turn implies that a linear search will
252 binary_search(wchar_t *string, unsigned char *front, unsigned char *back)
256 	p = front + (back - front) / 2;
263 	while (p < back && back > front) {
265 			front = p;
268 		p = front + (back - front) / 2;
271 	return (front);
275  * Find the first line that starts with string, linearly searching from front
282  * 	o front points at the first character in a line.
283  *	o front is before or at the first line to be printed.
286 linear_search(wchar_t *string, unsigned char *front, unsigned char *back)
288 	while (front < back) {
289 		switch (compare(string, front, back)) {
291 			return (front);
297 		SKIP_PAST_NEWLINE(front, back);
303  * Print as many lines as match string, starting at front.
306 print_from(wchar_t *string, unsigned char *front, unsigned char *back)
308 	for (; front < back && compare(string, front, back) == EQUAL; ++front) {
309 		for (; front < back && *front != '\n'; ++front)
310 			if (putchar(*front) == EOF)