1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
8  * Edward Sze-Tyan Wang.
55 static void r_reg(FILE *, const char *, enum STYLE, off_t, struct stat *);
58  * reverse -- display input in reverse order by line.
60  * There are six separate cases for this -- regular and non-regular
65  *	NOREG	cyclically read characters into a wrap-around buffer
69  *	NOREG	cyclically read lines into a wrap-around array of buffers
73  *	NOREG	cyclically read input into a linked list of buffers
76 reverse(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)  in reverse()  argument
78 	if (style != REVERSE && off == 0)  in reverse()
81 	if (S_ISREG(sbp->st_mode))  in reverse()
82 		r_reg(fp, fn, style, off, sbp);  in reverse()
84 		switch(style) {  in reverse()
102  * r_reg -- display a regular file in reverse order by line.
105 r_reg(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)  in r_reg()  argument
111 	if (!(size = sbp->st_size))  in r_reg()
121 	 * size == 0 is dealt with above, and size == 1 sets curoff to -1.  in r_reg()
123 	curoff = size - 2;  in r_reg()
133 		for (i = curoff - map.mapoff; i >= 0; i--) {  in r_reg()
134 			if (style == RBYTES && --off == 0)  in r_reg()
139 		/* `i' is either the map offset of a '\n', or -1. */  in r_reg()
145 		if (mapprint(&map, curoff + 1, lineend - curoff - 1) != 0) {  in r_reg()
150 		curoff--;  in r_reg()
152 		if (style == RLINES)  in r_reg()
153 			off--;  in r_reg()
155 		if (off == 0 && style != REVERSE) {  in r_reg()
177  * r_buf -- display a non-regular file in reverse order by line.
179  * This is the function that saves the entire input, storing the data in a
183  * particular buffer.  If we run out of memory, input is discarded (and the
209 			enomem += first->len;  in r_buf()
215 		/* Fill the block with input data. */  in r_buf()
218 			p = tl->l + len;  in r_buf()
219 			len += fread(p, 1, BSZ - len, fp);  in r_buf()
226 		tl->len = len;  in r_buf()
247 		for (p = tl->l + tl->len - 1, llen = 0; p >= tl->l;  in r_buf()
248 		    --p, ++llen) {  in r_buf()
249 			int start = (tl == first && p == tl->l);  in r_buf()
266 						if (tr->len)  in r_buf()
267 							WR(&tr->l, tr->len);  in r_buf()
275 		tl->len = llen;  in r_buf()