1 files changed, 52 insertions, 0 deletions
diff --git a/src/error.c b/src/error.c
index c4af82c..e52cd4d 100644
--- a/src/error.c
+++ b/src/error.c
@@ -8,6 +8,8 @@
 
 #include <aesni/all.h>
 
+#include <assert.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -23,6 +25,56 @@ const char* aesni_strerror(AesNI_ErrorCode ec)
     return err_msgs[ec];
 }
 
+static size_t aesni_format_error_simple(
+    const AesNI_ErrorDetails* err_details,\
+    char* dest,
+    size_t dest_size)
+{
+    const AesNI_ErrorCode ec = aesni_get_error_code(err_details);
+    const char* const msg = aesni_strerror(ec);
+
+    if (dest == NULL && dest_size == 0)
+        return strlen(msg) + 1;
+
+    strncpy(dest, msg, dest_size);
+    dest[dest_size - 1] = '\0';
+    return strlen(dest);
+}
+
+static size_t aesni_format_error_null_argument(
+    const AesNI_ErrorDetails* err_details,
+    char* dest,
+    size_t dest_size)
+{
+    static const char* const fmt = "Invalid argument value NULL (argument name: '%s')";
+    const char* const arg_name = err_details->params.null_arg.arg_name;
+
+    if (dest == NULL && dest_size == 0)
+        return _snprintf(NULL, 0, fmt, arg_name) + 1;
+
+    _snprintf(dest, dest_size, fmt, arg_name);
+    return strlen(dest);
+}
+
+typedef size_t (*AesNI_ErrorFormatter)(const AesNI_ErrorDetails*, char*, size_t);
+
+static AesNI_ErrorFormatter err_formatters[] =
+{
+    &aesni_format_error_simple,
+    &aesni_format_error_null_argument,
+    &aesni_format_error_simple,
+};
+
+size_t aesni_format_error(
+    const AesNI_ErrorDetails* err_details,
+    char* dest,
+    size_t dest_size)
+{
+    assert(err_details);
+
+    return err_formatters[err_details->ec](err_details, dest, dest_size);
+}
+
 static void aesni_make_error(
     AesNI_ErrorDetails* err_details,
     AesNI_ErrorCode ec)