[RFC][PATCH v3 1/2] fdisk: move read_line() to libbb

[Bartosz Golaszewski]

Move read_line() to libbb in order to make it available for other applets.
While we're at it: implement a simple function which displays a prompt message
and waits for user confirmation.

function                                             old     new   delta
read_int                                             449     472     +23
read_nonempty                                         30      49     +19
.rodata                                           152682  152693     +11
read_line                                            101      90     -11
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/1 up/down: 53/-11)             Total: 42 bytes

Signed-off-by: Bartosz Golaszewski <bartekgola at gmail.com>
---
 include/libbb.h    |  2 ++
 libbb/lineedit.c   | 30 ++++++++++++++++++++++++++++++
 util-linux/fdisk.c | 23 ++---------------------
 3 files changed, 34 insertions(+), 21 deletions(-)

diff --git a/include/libbb.h b/include/libbb.h
index 8e8b9ca..21018e5 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1522,6 +1522,8 @@ int read_line_input(const char* prompt, char* command, int maxsize) FAST_FUNC;
 	read_line_input(prompt, command, maxsize)
 #endif
 
+int read_line(const char *prompt, char *line_buffer, size_t buflen, char **line_ptr);
+int user_confirm(const char *prompt);
 
 #ifndef COMM_LEN
 # ifdef TASK_COMM_LEN
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 8564307..a27771d 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -2833,6 +2833,36 @@ int FAST_FUNC read_line_input(const char* prompt, char* command, int maxsize)
 
 #endif  /* !FEATURE_EDITING */
 
+/* Read line; return 0 or first printable char */
+int read_line(const char *prompt, char *line_buffer, size_t buflen, char **line_ptr)
+{
+	int sz;
+
+	sz = read_line_input(NULL, prompt, line_buffer, buflen, /*timeout*/ -1);
+	if (sz <= 0)
+		exit(EXIT_SUCCESS); /* Ctrl-D or Ctrl-C */
+
+	if (line_buffer[sz-1] == '\n')
+		line_buffer[--sz] = '\0';
+
+	*line_ptr = line_buffer;
+	while (**line_ptr != '\0' && (unsigned char)**line_ptr <= ' ')
+		(*line_ptr)++;
+	return **line_ptr;
+}
+
+/*
+ * Display the prompt message followed by a '[y/N]' and wait for user
+ * confirmation. Return 1 if user entered 'y' or 'Y', or 0 otherwise.
+ */
+int user_confirm(const char *prompt)
+{
+	char *line_ptr, buf[3], p[64];
+
+	snprintf(p, sizeof(p), "%s [y/N]: ", prompt);
+
+	return tolower(read_line(p, buf, sizeof(buf), &line_ptr)) == 'y' ? 1 : 0;
+}
 
 /*
  * Testing
diff --git a/util-linux/fdisk.c b/util-linux/fdisk.c
index 39eb27b..4ba1e90 100644
--- a/util-linux/fdisk.c
+++ b/util-linux/fdisk.c
@@ -563,25 +563,6 @@ seek_sector(sector_t secno)
 }
 
 #if ENABLE_FEATURE_FDISK_WRITABLE
-/* Read line; return 0 or first printable char */
-static int
-read_line(const char *prompt)
-{
-	int sz;
-
-	sz = read_line_input(NULL, prompt, line_buffer, sizeof(line_buffer), /*timeout*/ -1);
-	if (sz <= 0)
-		exit(EXIT_SUCCESS); /* Ctrl-D or Ctrl-C */
-
-	if (line_buffer[sz-1] == '\n')
-		line_buffer[--sz] = '\0';
-
-	line_ptr = line_buffer;
-	while (*line_ptr != '\0' && (unsigned char)*line_ptr <= ' ')
-		line_ptr++;
-	return *line_ptr;
-}
-
 static void
 set_all_unchanged(void)
 {
@@ -607,7 +588,7 @@ write_part_table_flag(char *b)
 static char
 read_nonempty(const char *mesg)
 {
-	while (!read_line(mesg))
+	while (!read_line(mesg, line_buffer, sizeof(line_buffer), &line_ptr))
 		continue;
 	return *line_ptr;
 }
@@ -615,7 +596,7 @@ read_nonempty(const char *mesg)
 static char
 read_maybe_empty(const char *mesg)
 {
-	if (!read_line(mesg)) {
+	if (!read_line(mesg, line_buffer, sizeof(line_buffer), &line_ptr)) {
 		line_ptr = line_buffer;
 		line_ptr[0] = '\n';
 		line_ptr[1] = '\0';
-- 
2.1.3