[git commit branch/1_32_stable] shell: Fix "read -d ''" behavior

[Denys Vlasenko]

commit: https://git.busybox.net/busybox/commit/?id=94f6d1ece0b6d023f173c5b5141b92229a3830fa
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/1_32_stable

With bash's read builtin it is possible to read from a file (e.g.
device-tree) until the first '\0' character:

IFS= read -r -d '' VARIABLE < file

In busybox ash the -d extension is also implemented, but checking the
read character for '\0' has to be performed after comparing with the
delimiter.

Signed-off-by: Christian Eggers <ceggers at arri.de>
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
 shell/ash_test/ash-read/read_d0.right   | 1 +
 shell/ash_test/ash-read/read_d0.tests   | 1 +
 shell/hush_test/hush-read/read_d0.right | 1 +
 shell/hush_test/hush-read/read_d0.tests | 1 +
 shell/shell_common.c                    | 4 ++--
 5 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/shell/ash_test/ash-read/read_d0.right b/shell/ash_test/ash-read/read_d0.right
new file mode 100644
index 000000000..9daeafb98
--- /dev/null
+++ b/shell/ash_test/ash-read/read_d0.right
@@ -0,0 +1 @@
+test
diff --git a/shell/ash_test/ash-read/read_d0.tests b/shell/ash_test/ash-read/read_d0.tests
new file mode 100755
index 000000000..630d80787
--- /dev/null
+++ b/shell/ash_test/ash-read/read_d0.tests
@@ -0,0 +1 @@
+printf 'test\0zest\n' | (read -d '' reply; echo "$reply")
diff --git a/shell/hush_test/hush-read/read_d0.right b/shell/hush_test/hush-read/read_d0.right
new file mode 100644
index 000000000..9daeafb98
--- /dev/null
+++ b/shell/hush_test/hush-read/read_d0.right
@@ -0,0 +1 @@
+test
diff --git a/shell/hush_test/hush-read/read_d0.tests b/shell/hush_test/hush-read/read_d0.tests
new file mode 100755
index 000000000..630d80787
--- /dev/null
+++ b/shell/hush_test/hush-read/read_d0.tests
@@ -0,0 +1 @@
+printf 'test\0zest\n' | (read -d '' reply; echo "$reply")
diff --git a/shell/shell_common.c b/shell/shell_common.c
index 12c4a073c..42c4c9c97 100644
--- a/shell/shell_common.c
+++ b/shell/shell_common.c
@@ -209,8 +209,6 @@ shell_builtin_read(struct builtin_read_params *params)
 		}
 
 		c = buffer[bufpos];
-		if (c == '\0')
-			continue;
 		if (!(read_flags & BUILTIN_READ_RAW)) {
 			if (backslash) {
 				backslash = 0;
@@ -225,6 +223,8 @@ shell_builtin_read(struct builtin_read_params *params)
 		}
 		if (c == delim) /* '\n' or -d CHAR */
 			break;
+		if (c == '\0')
+			continue;
 
 		/* $IFS splitting. NOT done if we run "read"
 		 * without variable names (bash compat).