From bc4c293fe59de042c1ac71793d33bb685c4fb915 Mon Sep 17 00:00:00 2001
From: FRIGN <dev@frign.de>
Date: Wed, 5 Oct 2016 21:18:24 +0200
Subject: [PATCH] Revamp tr(1) set parsing and handling

If you look at GNU coreutils, they do not support the mappings

	$ echo "1234abc" | tr "[:alnum:]" "[:upper:]"

	$ echo "ABCabc" | tr -c "[:upper:]" "[l*]"

to only give a few examples. This commit broadens the scope of tr(1)
as far as humanly possible to map between classes and non-classes,
making tr a usable tool and actually fulfilling user expectations.
Posix really is of no help here as it still kind of assumes the
fixed ASCII table instead of complex Unicode code points or even
Grapheme clusters.
---
 tr.c | 104 ++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 57 insertions(+), 47 deletions(-)

diff --git a/tr.c b/tr.c
index d6d1044..926d1eb 100644
--- a/tr.c
+++ b/tr.c
@@ -119,7 +119,7 @@ nextbrack:
 			}
 
 			/* REPEAT  [_*n] (only allowed in set2) */
-			if (j - i > 2 && rstr[i + 2] == '*' && set1ranges > 0) {
+			if (j - i > 2 && rstr[i + 2] == '*') {
 				/* check if right side of '*' is a number */
 				q = 0;
 				factor = 1;
@@ -138,7 +138,7 @@ nextbrack:
 				}
 				(*set)[setranges].start = rstr[i + 1];
 				(*set)[setranges].end   = rstr[i + 1];
-				(*set)[setranges].quant = q ? q : setlen(set1, set1ranges);
+				(*set)[setranges].quant = q ? q : setlen(set1, MAX(set1ranges, 1));
 				setranges++;
 				i = j;
 				continue;
@@ -196,69 +196,79 @@ main(int argc, char *argv[])
 	set1ranges = makeset(argv[0], &set1, &set1check);
 	if (argc == 2)
 		set2ranges = makeset(argv[1], &set2, &set2check);
-	if (dflag == sflag && !set2ranges && !set2check)
-		eprintf("set2 must be non-empty.\n");
-	if (argc == 2 && !set2check != !set1check)
-		eprintf("can't mix classes with non-classes.\n");
-	if (set2check && set2check != islowerrune && set2check != isupperrune)
-		eprintf("set2 can only be the 'lower' or 'upper' class.\n");
-	if (set2check && cflag && !dflag)
-		eprintf("set2 can't be imaged to from a complement.\n");
+
+	if (!dflag) {
+		/* sanity checks as we are translating */
+		if (!set2ranges && !set2check)
+			eprintf("cannot map to an empty set.\n");
+		if (set2check && set2check != islowerrune &&
+		    set2check != isupperrune) {
+			eprintf("can only map to 'lower' and 'upper' class.\n");
+		}
+	}
 read:
 	if (!efgetrune(&r, stdin, "<stdin>")) {
 		ret |= fshut(stdin, "<stdin>") | fshut(stdout, "<stdout>");
 		return ret;
 	}
-	off1 = off2 = 0;
-	for (i = 0; i < set1ranges; i++) {
+	for (i = 0, off1 = 0; i < set1ranges; i++, off1 += rangelen(set1[i])) {
 		if (set1[i].start <= r && r <= set1[i].end) {
 			if (dflag) {
-				if (!cflag)
-					goto read;
+				if (cflag)
+					continue;
 				else
-					goto write;
+					goto read;
 			}
 			if (cflag)
 				goto write;
-			for (m = 0; m < i; m++)
-				off1 += rangelen(set1[m]);
-			off1 += r - set1[m].start;
-			if (off1 > setlen(set2, set2ranges) - 1) {
-				r = set2[set2ranges - 1].end;
-				goto write;
-			}
-			for (m = 0; m < set2ranges; m++) {
-				if (off2 + rangelen(set2[m]) > off1) {
-					m++;
-					break;
-				}
-				off2 += rangelen(set2[m]);
-			}
-			m--;
-			r = set2[m].start + (off1 - off2) / set2[m].quant;
 
-			if (sflag && (r == lastrune))
-				goto read;
+			/* map r to set2 */
+			if (set2check) {
+				if (set2check == islowerrune)
+					r = tolowerrune(r);
+				else
+					r = toupperrune(r);
+			} else {
+				off1 += r - set1[i].start;
+				if (off1 > setlen(set2, set2ranges) - 1) {
+					r = set2[set2ranges - 1].end;
+					goto write;
+				}
+				for (m = 0, off2 = 0; m < set2ranges; m++) {
+					if (off2 + rangelen(set2[m]) > off1) {
+						m++;
+						break;
+					}
+					off2 += rangelen(set2[m]);
+				}
+				m--;
+				r = set2[m].start + (off1 - off2) / set2[m].quant;
+			}
 			goto write;
 		}
 	}
 	if (set1check && set1check(r)) {
-		if (dflag) {
-			if (!cflag)
-				goto read;
+		if (dflag && !cflag)
+			goto read;
+		if (set2check) {
+			if (set2check == islowerrune)
+				r = tolowerrune(r);
 			else
-				goto write;
+				r = toupperrune(r);
+		} else {
+			r = set2[set2ranges - 1].end;
 		}
-		if (set1check == isupperrune && set2check == islowerrune)
-			r = tolowerrune(r);
-		else if (set1check == islowerrune && set2check == isupperrune)
-			r = toupperrune(r);
-		else if (set2ranges > 0)
-			r = cflag ? r : set2[set2ranges - 1].end;
-		else
-			eprintf("Misaligned character classes.\n");
-	} else if (cflag && set2ranges > 0) {
-		r = set2[set2ranges - 1].end;
+	}
+	if (!dflag && cflag) {
+		if (set2check) {
+			if (set2check == islowerrune)
+				r = tolowerrune(r);
+			else
+				r = toupperrune(r);
+		} else {
+			r = set2[set2ranges - 1].end;
+		}
+		goto write;
 	}
 	if (dflag && cflag)
 		goto read;