encoding/base32: Fix padding validation for malformed input

Fix a bug where padding characters in the middle of input were
not detected when there was no trailing padding.

The "verify no padding in middle" check was inside `if
padding_count > 0`, so inputs like "MZ===YTBMZXW6YTB" would
incorrectly pass validation.

Test case added for this edge case.

1 files changed, 11 insertions, 3 deletions

diff --git a/tests/core/encoding/base32/base32.odin b/tests/core/encoding/base32/base32.odin
index f757e99e5..2abb244ca 100644
--- a/tests/core/encoding/base32/base32.odin
+++ b/tests/core/encoding/base32/base32.odin
@@ -1,4 +1,3 @@
-#+test
 package test_encoding_base32
 
 import "core:testing"
@@ -83,7 +82,16 @@ test_base32_decode_invalid :: proc(t: ^testing.T) {
 
 	// Section 3.2 - Padding requirements
 	{
-		// Padding must only be at end
+		// Padding in middle without trailing padding
+		input := "MZ===YTBMZXW6YTB" // '===' in middle, no trailing padding
+		output, err := base32.decode(input)
+		if output != nil {
+			defer delete(output)
+		}
+		testing.expect_value(t, err, Error.Malformed_Input)
+	}
+	{
+		// Padding must only be at end (with trailing padding)
 		input := "MZ=Q===="
 		output, err := base32.decode(input)
 		if output != nil {
@@ -228,4 +236,4 @@ test_base32_custom_alphabet :: proc(t: ^testing.T) {
 		}
 		testing.expect_value(t, err, Error.Invalid_Character)
 	}
-}
\ No newline at end of file
+}