Make error codes returned by librabbitmq functions opaque

Windows doesn't generally use POSIX error codes, which poses a problem
for librabbitmq's approach of using those error codes in its API.  So
make the librabbitmq error codes opaque: They are still be integers,
but client code is not supposed to assume anything about them, except
that they can be passed to a new amqp_error_string() function which
returns the corresponding error message

Internally, the error codes are either taken from a set of
librabbitmq-specific values, or correspond to an OS-specific (POSIX or
win32) error code, with a simple encoding to indicate which is which.

1 files changed, 25 insertions, 8 deletions

diff --git a/librabbitmq/amqp_private.h b/librabbitmq/amqp_private.h
index 3985619..f922933 100644
--- a/librabbitmq/amqp_private.h
+++ b/librabbitmq/amqp_private.h
@@ -57,6 +57,30 @@ extern "C" {
 
 #include <arpa/inet.h> /* ntohl, htonl, ntohs, htons */
 
+/* Error numbering: Because of differences in error numbering on
+ * different platforms, we want to keep error numbers opaque for
+ * client code.  Internally, we encode the category of an error
+ * (i.e. where its number comes from) in the top bits of the number
+ * (assuming that an int has at least 32 bits).
+ */
+#define ERROR_CATEGORY_MASK (1 << 29)
+
+#define ERROR_CATEGORY_CLIENT (0 << 29) /* librabbitmq error codes */
+#define ERROR_CATEGORY_OS (1 << 29) /* OS-specific error codes */
+
+/* librabbitmq error codes */
+#define ERROR_NO_MEMORY 1
+#define ERROR_BAD_AMQP_DATA 2
+#define ERROR_UNKNOWN_CLASS 3
+#define ERROR_UNKNOWN_METHOD 4
+#define ERROR_HOST_NOT_FOUND 5
+#define ERROR_INCOMPATIBLE_AMQP_VERSION 6
+#define ERROR_CONNECTION_CLOSED 7
+#define ERROR_MAX 7
+
+/* Get the encoded form of errno */
+#define encoded_errno() (errno | ERROR_CATEGORY_OS)
+
 /*
  * Connection states:
  *
@@ -125,7 +149,7 @@ struct amqp_connection_state_t_ {
   amqp_rpc_reply_t most_recent_api_result;
 };
 
-#define CHECK_LIMIT(b, o, l, v) ({ if ((o + l) > (b).len) { return -EFAULT; } (v); })
+#define CHECK_LIMIT(b, o, l, v) ({ if ((o + l) > (b).len) { return -ERROR_BAD_AMQP_DATA; } (v); })
 #define BUF_AT(b, o) (&(((uint8_t *) (b).bytes)[o]))
 
 #define D_8(b, o) CHECK_LIMIT(b, o, 1, * (uint8_t *) BUF_AT(b, o))
@@ -176,13 +200,6 @@ extern int amqp_encode_table(amqp_bytes_t encoded,
 
 #define AMQP_CHECK_RESULT(expr) AMQP_CHECK_RESULT_CLEANUP(expr, )
 
-#define AMQP_CHECK_EOF_RESULT(expr)		\
-  ({						\
-    int _result = (expr);			\
-    if (_result <= 0) return _result;		\
-    _result;					\
-  })
-
 #ifndef NDEBUG
 extern void amqp_dump(void const *buffer, size_t len);
 #else