2 files changed, 111 insertions, 17 deletions

diff --git a/include/aesni/buffer.h b/include/aesni/buffer.h
index 6222f4f..fff616f 100644
--- a/include/aesni/buffer.h
+++ b/include/aesni/buffer.h
@@ -18,20 +18,20 @@ extern "C"
 {
 #endif
 
-int aesni_encrypt_buffer_ecb128(
+AesNI_StatusCode aesni_encrypt_buffer_ecb128(
     const void* src,
     size_t src_size,
     void* dest,
     size_t* dest_size,
     AesNI_KeySchedule128* key_schedule,
-    AesNI_ErrorDetails*);
-int aesni_decrypt_buffer_ecb128(
+    AesNI_ErrorDetails* err_details);
+AesNI_StatusCode aesni_decrypt_buffer_ecb128(
     const void* src,
     size_t src_size,
     void* dest,
     size_t* dest_size,
     AesNI_KeySchedule128* inverted_schedule,
-    AesNI_ErrorDetails*);
+    AesNI_ErrorDetails* err_details);
 
 #ifdef __cplusplus
 }
diff --git a/include/aesni/error.h b/include/aesni/error.h
index 91bf168..56a1da1 100644
--- a/include/aesni/error.h
+++ b/include/aesni/error.h
@@ -9,6 +9,28 @@
 
 #pragma once
 
+/**
+ * \defgroup aesni_error_handling Error handling
+ * \ingroup aesni
+ * \brief Error data structures and formatting functions.
+ *
+ * Some library functions cannot fail, which is simple.
+ * Other functions return an error code.
+ * You can check if a function exited with an error by passing the returned
+ * error code to aesni_is_error().
+ *
+ * Some possibly-may-fail functions accept a pointer to an "error details"
+ * structure.
+ * This pointer can always be `NULL`.
+ * In this case, simply an error code is returned.
+ * Otherwise, the error details structure is filled with appropriate info about
+ * the error, possibly including a few details like invalid arguments names,
+ * etc.
+ *
+ * You can format an error details structure using the formatting functions.
+ * \{
+ */
+
 #include <stdlib.h>
 
 #ifdef __cplusplus
@@ -16,45 +38,117 @@ extern "C"
 {
 #endif
 
+/**
+ * \brief API status codes.
+ */
 typedef enum
 {
-    AESNI_ERROR_SUCCESS,
+    AESNI_SUCCESS, ///< Indicates an operation
+
+    AESNI_ERROR_NULL_ARGUMENT, ///< Invalid argument value NULL
 
-    AESNI_ERROR_NULL_ARGUMENT,
+    AESNI_ERROR_INVALID_PKCS7_PADDING, ///< Invalid PKCS7 padding
+}
+AesNI_StatusCode;
 
-    AESNI_ERROR_INVALID_PKCS7_PADDING,
+static __inline int aesni_is_error(AesNI_StatusCode ec)
+{
+    return ec != AESNI_SUCCESS;
 }
-AesNI_ErrorCode;
 
-const char* aesni_strerror(AesNI_ErrorCode);
+/**
+ * \brief Retrieves a simple error message for an error code.
+ *
+ * For example,
+ * \code{.c}
+ * printf("%s\n", aesni_strerror(AESNI_ERROR_NULL_ARGUMENT));
+ * \endcode
+ * would print
+ * \code
+ * Invalid argument value NULL
+ * \endcode
+ *
+ * \param[in] ec The error code.
+ * \return A pointer to a statically-allocated C string.
+ */
+const char* aesni_strerror(AesNI_StatusCode ec);
 
+/**
+ * \brief Stores error details: error code & possibly a few parameters.
+ */
 typedef struct
 {
-    AesNI_ErrorCode ec;
+    AesNI_StatusCode ec; ///< Error code
 
     union
     {
         struct
         {
-            char arg_name[32];
+            char arg_name[32]; ///< Name of the NULL argument
         }
-        null_arg;
+        null_arg; ///< `NULL` argument error parameters
     }
     params;
 }
 AesNI_ErrorDetails;
 
-static __inline AesNI_ErrorCode aesni_get_error_code(const AesNI_ErrorDetails* err_details)
+/**
+ * \brief Extracts an error code from error details.
+ *
+ * \param[in] err_details The error details structure. Must not be `NULL`.
+ * \return The error code stored in the error details.
+ */
+static __inline AesNI_StatusCode aesni_get_error_code(
+    const AesNI_ErrorDetails* err_details)
 {
     return err_details->ec;
 }
 
-size_t aesni_format_error(const AesNI_ErrorDetails*, char*, size_t);
+/**
+ * \brief Formats a pretty error message, including error parameters.
+ *
+ * \param[in] err_details The pointer to error details. Must not be `NULL`.
+ * \param[out] dest The pointer to the destination string buffer.
+ * \param[in] dest_size The size of the destination buffer, in bytes.
+ * \return If `dest` is NULL, the number of bytes required to store the full
+ *         error message, and the number of characters written (excluding the
+ *         terminating '\0' character) otherwise.
+ */
+size_t aesni_format_error(
+    const AesNI_ErrorDetails* err_details,
+    char* dest,
+    size_t dest_size);
 
-void aesni_make_error_success(AesNI_ErrorDetails*);
-void aesni_make_error_null_argument(AesNI_ErrorDetails*, const char* arg_name);
-void aesni_make_error_invalid_pkcs7_padding(AesNI_ErrorDetails*);
+/**
+ * \brief Initializes error details structure.
+ *
+ * \param[out] err_details The error details structure to fill.
+ */
+AesNI_StatusCode aesni_make_error_success(
+    AesNI_ErrorDetails* err_details);
+
+/**
+ * \brief Builds error details from a `NULL` argument error.
+ *
+ * \param[out] err_details The error details structure to fill.
+ * \param[in] arg_name The `NULL` argument name. Must not be `NULL`.
+ */
+AesNI_StatusCode aesni_make_error_null_argument(
+    AesNI_ErrorDetails* err_details,
+    const char* arg_name);
+
+/**
+ * \brief Builds error details from an invalid PKCS7 padding error.
+ *
+ * \param[out] err_details The error details structure to fill.
+ */
+AesNI_StatusCode aesni_make_error_invalid_pkcs7_padding(
+    AesNI_ErrorDetails* err_details);
 
 #ifdef __cplusplus
 }
 #endif
+
+/**
+ * \}
+ */