ot::error_message

CMakeLists.txt

@@ -20,6 +20,7 @@ add_library(
 	libopustags
 	OBJECT
 	src/cli.cc
+	src/error.cc
 	src/ogg.cc
 	src/opus.cc
 )

src/error.cc

@@ -0,0 +1,26 @@
+#include <opustags.h>
+
+static const char* messages[] = {
+	"OK",
+	"Need to exit",
+	"Bad command-line arguments",
+	"Integer overflow",
+	"Standard error",
+	"End of file",
+	"libogg error",
+	"Bad magic number",
+	"Overflowing magic number",
+	"Overflowing vendor length",
+	"Overflowing vendor data",
+	"Overflowing comment count",
+	"Overflowing comment length",
+	"Overflowing comment data",
+};
+
+const char* ot::error_message(ot::status code)
+{
+if (code >= ot::status::sentinel)
+	return nullptr;
+auto index = static_cast<size_t>(code);
+return messages[index];
+}

src/opustags.h

@@ -15,15 +15,16 @@
 namespace ot {
 
 /**
- * Possible error status.
+ * Possible error status, ranging from #ok (0) to #sentinel.
  *
- * The overflowing error family means that the end of packet was reached when
- * attempting to read the overflowing value. For example,
- * overflowing_comment_count means that after reading the vendor string, less
- * than 4 bytes were left in the packet.
+ * Use #error_message to get an error message from a status code.
+ *
+ * The overflowing error family means that the end of packet was reached when attempting to read the
+ * overflowing value. For example, overflowing_comment_count means that after reading the vendor
+ * string, less than 4 bytes were left in the packet.
  */
 enum class status {
-	ok,
+	ok = 0,
 	exit_now,
 	bad_arguments,
 	int_overflow,
@@ -39,8 +40,15 @@ enum class status {
 	overflowing_comment_count,
 	overflowing_comment_length,
 	overflowing_comment_data,
+	/**
+	 * Last error code, for integrity checking.
+	 * Do not use it, it does not represent any error.
+	 */
+	sentinel,
 };
 
+const char* error_message(status code);
+
 /**
  * \defgroup ogg Ogg
  * \brief Helpers to work with libogg.

t/CMakeLists.txt

@@ -1,8 +1,11 @@
 add_executable(opus.t EXCLUDE_FROM_ALL opus.cc)
 target_link_libraries(opus.t libopustags)
 
+add_executable(error.t EXCLUDE_FROM_ALL error.cc)
+target_link_libraries(error.t libopustags)
+
 add_custom_target(
 	check
 	COMMAND prove "${CMAKE_CURRENT_SOURCE_DIR}" "${CMAKE_CURRENT_BINARY_DIR}"
-	DEPENDS opustags opus.t
+	DEPENDS opustags opus.t error.t
 )

t/error.cc

@@ -0,0 +1,27 @@
+#include <opustags.h>
+#include "tap.h"
+
+static void check_message()
+{
+	if (strcmp(ot::error_message(ot::status::ok), "OK") != 0)
+		throw failure("unexpected message for code ok");
+	if (strcmp(ot::error_message(ot::status::overflowing_comment_data), "Overflowing comment data") != 0)
+		throw failure("unexpected message for overflowing_comment_data");
+}
+
+static void check_sentinel()
+{
+	if (ot::error_message(ot::status::sentinel) != nullptr)
+		throw failure("the sentinel should not have a message");
+	auto too_far = static_cast<ot::status>(static_cast<int>(ot::status::sentinel) + 1);
+	if (ot::error_message(too_far) != nullptr)
+		throw failure("an invalid status should not have a message");
+}
+
+int main()
+{
+	std::cout << "1..2\n";
+	run(check_message, "check a few error messages");
+	run(check_sentinel, "ensure the sentinel is respected");
+	return 0;
+}