From: Ralph Corderoy <ralph@inputplus.co.uk>
Date: Wed, 22 Nov 2017 13:44:01 +0000 (+0000)
Subject: Rewrite cpnumber() to fix `%2(msg)' with 123 overflowing to `?23'.
X-Git-Url: https://diplodocus.org/git/nmh/commitdiff_plain/a034d7e5edab2f0d56a62f6e1fcbbc76f3e5f31b?hp=ff168106b44fdfbaed7d7cf08c54a72ee1fe2c0a

Rewrite cpnumber() to fix `%2(msg)' with 123 overflowing to `?23'.

Reported in 1.7 by Ken on nmh-workers yesterday.
`It seems this was introduced in commit 92128dacf'.
We now use the C library to format the number, and then manipulate the
result.  A temporary charstring_t is no longer used.
Also adds left justification using negative width.
---

diff --git a/man/mh-format.man b/man/mh-format.man
index 85604d75..104b8212 100644
--- a/man/mh-format.man
+++ b/man/mh-format.man
@@ -429,9 +429,12 @@ specified by their leading field width argument.  For example,
 size in a field six characters wide filled with leading zeros;
 %14(\fIputstrf\^\fR{\fIfrom\^\fR}) will print the \*(lqFrom:\*(rq header
 component in fourteen characters with trailing spaces added as needed.
-For \fIputstrf\fR, using a negative value for the field width causes
-right-justification of the string within the field, with padding on
+Using a negative value for the field width causes
+right-justification within the field, with padding on
 the left up to the field width.
+Padding is with spaces except for a left-padded
+.I putnumf
+when the width starts with zero.
 The functions (\fIputnum\fR\^) and
 (\fIputstr\fR\^) are somewhat special: they print their result in the
 minimum number of characters required, and ignore any leading field width
diff --git a/sbr/fmt_scan.c b/sbr/fmt_scan.c
index 9ae100c9..67f0a03e 100644
--- a/sbr/fmt_scan.c
+++ b/sbr/fmt_scan.c
@@ -70,56 +70,66 @@ match (char *str, char *sub)
     return 1;
 }
 
-/*
- * copy a number to the destination subject to a maximum width
- */
+/* cpnumber formats num as a signed decimal,
+ * appending it to dest if the result doesn't exceed max.
+ * The absolute value of width is the minimum width to produce.
+ * A smaller string is padded;
+ * on the left if width is positive, else the right.
+ * Left-padding uses fill.  It is either ' ' or '0'.
+ * Right-padding is always with space. */
 void
-cpnumber(charstring_t dest, int num, int wid, char fill, size_t max)
+cpnumber(charstring_t dest, int num, int width, char fill, size_t max)
 {
-    /* Maybe we should handle left padding at some point? */
-    if (wid == 0)
-	return;
-    if (wid < 0)
-        wid = -wid; /* OK because wid originally a short. */
-    if ((size_t)wid < (num >= 0 ? max : max-1)) {
-	/* Build up the string representation of num in reverse. */
-	charstring_t rev = charstring_create (0);
-	int i = num >= 0 ? num : -num;
-
-	do {
-	    charstring_push_back (rev, i % 10  +  '0');
-	    i /= 10;
-	} while (--wid > 0  &&  i > 0);
-	if (i > 0) {
-	    /* Overflowed the field (wid). */
-	    charstring_push_back (rev, '?');
-	} else if (num < 0  &&  wid > 0) {
-	    /* Shouldn't need the wid > 0 check, that's why the condition
-	       at the top checks wid < max-1 when num < 0. */
-	    --wid;
-	    if (fill == ' ') {
-		charstring_push_back (rev, '-');
-	    }
-	}
-	while (wid-- > 0  &&  fill != 0) {
-	    charstring_push_back (rev, fill);
-	}
-	if (num < 0  &&  fill == '0') {
-	    charstring_push_back (rev, '-');
-	}
+    if (width == 0 || width == INT_MIN) {
+        return;
+    }
+
+    bool padright = width < 0;
+    if (padright) {
+        width = -width; /* Can't overflow after above check. */
+    }
+    size_t w = width;
+    if (w > max) {
+        return; /* The padded result can't fit. */
+    }
+    if (num < 0 && w == 1) {
+        return; /* No room for `-' and a digit or `?'. */
+    }
 
-	{
-	    /* Output the string in reverse. */
-	    size_t b = charstring_bytes (rev);
-	    const char *cp = b  ?  &charstring_buffer (rev)[b]  :  NULL;
+    char *s = m_str(num);
+    size_t len = strlen(s);
+    if (len == w) {
+        charstring_append_cstring(dest, s);
+        return;
+    }
 
-	    for (; b > 0; --b) {
-		charstring_push_back (dest, *--cp);
-	    }
-	}
+    bool neg = *s == '-';
+    if (len < w) {
+        if (padright) {
+            charstring_append_cstring(dest, s);
+            while (len++ < w) {
+                charstring_push_back(dest, ' ');
+            }
+            return;
+        }
+
+        if (neg && fill == '0') {
+            charstring_push_back(dest, *s++);
+        }
+        while (len++ < w) {
+            charstring_push_back(dest, fill);
+        }
+        charstring_append_cstring(dest, s);
+        return;
+    }
 
-	charstring_free (rev);
+    /* Transform 1234567 -> 1234?67 and -1234567 -> 1234-?7. */
+    char *news = s + len - w;
+    if (neg) {
+        *news = '-';
     }
+    news[neg] = '?';
+    charstring_append_cstring(dest, news);
 }
 
 /*