ash: implement -d DELIM option for read

The POSIX standard only requires the read builtin to handle -r:
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/read.html

However, Bash introduced the option -d <DELIM> to override IFS for
just one invocation, and it is quite useful.

It is also super easy to implement in BusyBox' ash, so let's do that.

The motivation: This option is used by Git's test suite.

function                                             old     new   delta
.rodata                                           163505  163587     +82
shell_builtin_read                                  1244    1289     +45
readcmd                                              233     259     +26
builtin_read                                         258     263      +5
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 158/0)             Total: 158 bytes

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

3 files changed, 21 insertions, 7 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 6dc1cfe..fd17723 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -189,6 +189,8 @@
 #define    BASH_HOSTNAME_VAR    ENABLE_ASH_BASH_COMPAT
 #define    BASH_SHLVL_VAR       ENABLE_ASH_BASH_COMPAT
 #define    BASH_XTRACEFD        ENABLE_ASH_BASH_COMPAT
+#define    BASH_READ_D          ENABLE_ASH_BASH_COMPAT
+#define IF_BASH_READ_D              IF_ASH_BASH_COMPAT
 
 #if defined(__ANDROID_API__) && __ANDROID_API__ <= 24
 /* Bionic at least up to version 24 has no glob() */
@@ -13402,10 +13404,10 @@ letcmd(int argc UNUSED_PARAM, char **argv)
  *      -p PROMPT       Display PROMPT on stderr (if input is from tty)
  *      -t SECONDS      Timeout after SECONDS (tty or pipe only)
  *      -u FD           Read from given FD instead of fd 0
+ *      -d DELIM        End on DELIM char, not newline
  * This uses unbuffered input, which may be avoidable in some cases.
  * TODO: bash also has:
  *      -a ARRAY        Read into array[0],[1],etc
- *      -d DELIM        End on DELIM char, not newline
  *      -e              Use line editing (tty only)
  */
 static int FAST_FUNC
@@ -13415,11 +13417,12 @@ readcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
 	char *opt_p = NULL;
 	char *opt_t = NULL;
 	char *opt_u = NULL;
+	char *opt_d = NULL; /* optimized out if !BASH */
 	int read_flags = 0;
 	const char *r;
 	int i;
 
-	while ((i = nextopt("p:u:rt:n:s")) != '\0') {
+	while ((i = nextopt("p:u:rt:n:sd:")) != '\0') {
 		switch (i) {
 		case 'p':
 			opt_p = optionarg;
@@ -13439,6 +13442,11 @@ readcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
 		case 'u':
 			opt_u = optionarg;
 			break;
+#if BASH_READ_D
+		case 'd':
+			opt_d = optionarg;
+			break;
+#endif
 		default:
 			break;
 		}
@@ -13456,7 +13464,8 @@ readcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
 		opt_n,
 		opt_p,
 		opt_t,
-		opt_u
+		opt_u,
+		opt_d
 	);
 	INT_ON;
 
diff --git a/shell/shell_common.c b/shell/shell_common.c
index a9f8d84..2db8ea3 100644
--- a/shell/shell_common.c
+++ b/shell/shell_common.c
@@ -54,7 +54,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
 	const char *opt_n,
 	const char *opt_p,
 	const char *opt_t,
-	const char *opt_u
+	const char *opt_u,
+	const char *opt_d
 )
 {
 	struct pollfd pfd[1];
@@ -237,14 +238,17 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
 				continue;
 			}
 		}
-		if (c == '\n')
+		if (opt_d) {
+			if (c == *opt_d)
+				break;
+		} else if (c == '\n')
 			break;
 
 		/* $IFS splitting. NOT done if we run "read"
 		 * without variable names (bash compat).
 		 * Thus, "read" and "read REPLY" are not the same.
 		 */
-		if (argv[0]) {
+		if (!opt_d && argv[0]) {
 /* http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_05 */
 			const char *is_ifs = strchr(ifs, c);
 			if (startword && is_ifs) {
diff --git a/shell/shell_common.h b/shell/shell_common.h
index a82535c..1b79bff 100644
--- a/shell/shell_common.h
+++ b/shell/shell_common.h
@@ -42,7 +42,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
 	const char *opt_n,
 	const char *opt_p,
 	const char *opt_t,
-	const char *opt_u
+	const char *opt_u,
+	const char *opt_d
 );
 
 int FAST_FUNC