tpop

commit d96884ab2efe1565a4492ec95d4c8d6bb810ed2a
parent 9638d22a9a85472930449602bcb6447313623b3c
Author: zerous Naveen Narayanan <zerous@nocebo.space>
Date:   Sat,  9 Mar 2019 21:01:58 +0100

Fix bug - next ptr not set properly after realloc

Diffstat:
M
sw.c
 | 
130
++++++++++++++++++++++++++++++++++++++++++++++++-------------------------------

1 file changed, 79 insertions(+), 51 deletions(-)
diff --git a/sw.c b/sw.c
@@ -1,57 +1,55 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <assert.h>
-/* shuffle newline terminated strings */
+/* shuffle newline/whitespace terminated words */
 
 void shuffle(char *, int);
+int mstrlen(char *);
+char *mstrcpy(char *, char *);
 
 int
-main(int argc, char **argv)
+main(void)
 {
-	char c, *s, *n, *t;
+	int c;
+	char *beg, *next, *s;
 	int nword;
-	size_t gf;
+	size_t siz;
 	
-	(void) argc;
-	(void) argv;
-
-	gf = 512;
-	s = n = NULL;
+	siz = 512;
+	beg = next = NULL;
 	nword = 0;
 
 	for (;(c = getc(stdin)) != EOF;)
 	{
-		if (n == NULL || n >= (s + (gf - 512))) 	/* first time */
+		if (next == NULL || (next - beg) >= (siz - 512)) 	/* first time */
 		{
-			t = realloc(s, gf);
-			if (t != NULL) {
-				s = t;
-				n = t;
-				*n++ = c;
-				gf += 512;
+			if ((s = realloc(beg, siz)) != NULL ) {
+				next = s + (next - beg);
+				beg = s;
+				*next++ = c;
+				siz += 512;
 			} else {
 				printf("err: realloc\n");
 				return 1;
 			}
 		}
 		else if (c == '\n' || c == ' ') {
-			*n++ = '\0';
+			*next++ = '\0';
 			nword++;
 		}
 		else {
-			*n++ = c;
+			*next++ = c;
 		}
 	}
 
-	/* shuffle(s, nword); */
+	shuffle(s, nword);
 
-	for (char *t = s; t < n;) {
+	for (char *t = beg; t < next;) {
 		printf("%s\n", t);
-		t += strlen(t) + 1;
+		t += mstrlen(t) + 1;
 	}
 
-	free(s);
+	free(beg);
 	
 	return 0;
 }
@@ -59,49 +57,79 @@ main(int argc, char **argv)
 void
 shuffle(char *s, int nword)
 {
-	char w[128];
+	char buf1[128], buf2[128];
+	int k, q, l;
+	char *str1, *str2;
 
-	for (int i = 0; i < nword ; i++)
+	for (int i = 0; i < nword && nword > 1; i++)
 	{
-		int k, q, l, r;
-		char *m, *n;
-
-		
+		/* get two rand word indexes */
 		q = rand()%(nword - 1);
-		l = rand()% (nword - 1);
-		k = 0;
+		l = rand()%(nword - 1);
 
+		k = 0;
+		
 		for (char *t = s; k < nword; k++) {
 			if (k == l) 
-				m = t;
+				str1 = t;
 			else if (k == q)
-				n = t;
-			r = strlen(t);
-			t += r + 1;
+				str2 = t;
+			t += mstrlen(t) + 1;
 		}
 
-		assert(strlen(m) < 128);
-		assert(strlen(n) < 128);
+		if (mstrlen(str1) > 128 || mstrlen(str2) > 128) {
+			printf("word too long\n");
+			return;
+		}
 		
-		if (strlen(m) == strlen(n)) {
-			strcpy(w, m);
-			strcpy(m, n);
-			strcpy(n, w);
+		if (mstrlen(str1) == mstrlen(str2)) {
+			mstrcpy(buf1, str1);
+			mstrcpy(str1, str2);
+			mstrcpy(str2, buf1);
 		}
 		else {
-			strcpy(w, m);
-			int t = strlen(m) - strlen(n);
-			if (m > n) {
-				memmove((n + strlen(n) + 1 + t), (n + strlen(m) + 1),
-					m - (n + strlen(n) + 1));
+			mstrcpy(buf1, str1);
+			mstrcpy(buf2, str2);
+			int t = mstrlen(str1) - mstrlen(str2);
+			if (str1 > str2) {
+				memmove((str2 + mstrlen(str2) + 1 + t), /* move words between the words being swapped */
+					(str2 + mstrlen(str2) + 1),
+					str1 - (str2 + mstrlen(str2) + 1));
+				mstrcpy(str2, buf1);
+				mstrcpy(str1 + t, buf2);
 			}
-			else if (m < n) {
-				memmove((m + strlen(m) + 1 - t), (m + strlen(m) + 1),
-					n - (m + strlen(m) + 1));
+			else if (str1 < str2) {
+				memmove((str1 + mstrlen(str1) + 1 - t), /* move words between the words being swapped */
+					(str1 + mstrlen(str1) + 1),
+					str2 - (str1 + mstrlen(str1) + 1));
+				mstrcpy(str1, buf2);
+				mstrcpy(str2 - t, buf1);
 			}
-			strcpy(m, n);
-			strcpy(n, w);
 		}
 	}
 }
+
+char *
+mstrcpy(char *a, char *b)
+{
+	int i;
 	
+	for (i = 0; b[i] != '\0'; i++)
+	{
+		a[i] = b[i];
+	}
+	a[i] = '\0';
+
+	return a;
+}
+
+int
+mstrlen(char *a)
+{
+	int i;
+
+	for (i = 0; a[i] != '\0'; i++)
+		;
+
+	return i;
+}