lib: strfuncs: Add t_str_oneline().

This puts the string on a single line by replacing all newlines with spaces and
dropping any carriage returns

src/lib/strfuncs.c

@@ -3,6 +3,7 @@
 /* @UNSAFE: whole file */
 
 #include "lib.h"
+#include "str.h"
 #include "printf-format-fix.h"
 #include "strfuncs.h"
 #include "array.h"
@@ -320,6 +321,55 @@ const char *t_str_replace(const char *str, char from, char to)
 	return out;
 }
 
+const char *t_str_oneline(const char *str)
+{
+	string_t *out;
+	size_t len;
+	const char *p, *pend, *poff;
+	bool new_line;
+
+	if (strpbrk(str, "\r\n") == NULL)
+		return str;
+
+	len = strlen(str);
+	out = t_str_new(len + 1);
+	new_line = TRUE;
+	p = poff = str;
+	pend = str + len;
+	while (p < pend) {
+		switch (*p) {
+		case '\r':
+			if (p > poff)
+				str_append_data(out,  poff, p - poff);
+			/* just drop \r */
+			poff = p + 1;
+			break;
+		case '\n':
+			if (p > poff)
+				str_append_data(out,  poff, p - poff);
+			if (new_line) {
+				/* coalesce multiple \n into a single space */
+			} else {
+				/* first \n after text */
+				str_append_c(out, ' ');
+				new_line = TRUE;
+			}
+			poff = p + 1;
+			break;
+		default:
+			new_line = FALSE;
+			break;
+		}
+		p++;
+	}
+
+	if (new_line && str_len(out) > 0)
+		str_truncate(out, str_len(out) - 1);
+	else if (p > poff)
+		str_append_data(out,  poff, p - poff);
+	return str_c(out);
+}
+
 int i_strocpy(char *dest, const char *src, size_t dstsize)
 {
 	if (dstsize == 0)

src/lib/strfuncs.h

@@ -45,6 +45,10 @@ const char *t_strconcat(const char *str1, ...)
 const char *t_strcut(const char *str, char cutchar);
 /* Replace all from->to chars in the string. */
 const char *t_str_replace(const char *str, char from, char to);
+/* Put the string on a single line by replacing all newlines with spaces and
+   dropping any carriage returns. Sequences of several newlines are merged into
+   one space and newlines at the beginning and end of the string are dropped. */
+const char *t_str_oneline(const char *str);
 
 /* Like strlcpy(), but return -1 if buffer was overflown, 0 if not. */
 int i_strocpy(char *dest, const char *src, size_t dstsize);

src/lib/test-strfuncs.c

@@ -175,6 +175,45 @@ static void test_t_str_replace(void)
 	test_end();
 }
 
+static void test_t_str_oneline(void)
+{
+	test_begin("t_str_oneline");
+	test_assert(strcmp(t_str_oneline("\n"), "") == 0);
+	test_assert(strcmp(t_str_oneline("\r"), "") == 0);
+	test_assert(strcmp(t_str_oneline("\n\n"), "") == 0);
+	test_assert(strcmp(t_str_oneline("\r\r"), "") == 0);
+	test_assert(strcmp(t_str_oneline("\r\n"), "") == 0);
+	test_assert(strcmp(t_str_oneline("\r\n\r\n"), "") == 0);
+	test_assert(strcmp(t_str_oneline("\n\r"), "") == 0);
+	test_assert(strcmp(t_str_oneline("\n\r\n\r"), "") == 0);
+	test_assert(strcmp(t_str_oneline("foo"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("\nfoo"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("foo\n"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("\nfoo\n"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("foo\nbar"), "foo bar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\n\nbar"), "foo bar") == 0);
+	test_assert(strcmp(t_str_oneline("\nfoo\nbar"), "foo bar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\nbar\n"), "foo bar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\nbar\nbaz"), "foo bar baz") == 0);
+	test_assert(strcmp(t_str_oneline("\rfoo"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("foo\r"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("\rfoo\r"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("foo\rbar"), "foobar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\r\rbar"), "foobar") == 0);
+	test_assert(strcmp(t_str_oneline("\rfoo\rbar"), "foobar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\rbar\r"), "foobar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\rbar\rbaz"), "foobarbaz") == 0);
+	test_assert(strcmp(t_str_oneline("\r\nfoo\r\n"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("foo\r\n"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("\r\nfoo"), "foo") == 0);
+	test_assert(strcmp(t_str_oneline("foo\r\nbar"), "foo bar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\r\n\r\nbar"), "foo bar") == 0);
+	test_assert(strcmp(t_str_oneline("\r\nfoo\r\nbar"), "foo bar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\r\nbar\r\n"), "foo bar") == 0);
+	test_assert(strcmp(t_str_oneline("foo\r\nbar\r\nbaz"), "foo bar baz") == 0);
+	test_end();
+}
+
 static void test_t_str_trim(void)
 {
 	test_begin("t_str_trim");
@@ -416,6 +455,7 @@ void test_strfuncs(void)
 	test_t_strsplit();
 	test_t_strsplit_spaces();
 	test_t_str_replace();
+	test_t_str_oneline();
 	test_t_str_trim();
 	test_t_str_ltrim();
 	test_t_str_rtrim();