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, 35 insertions, 0 deletions

diff --git a/librabbitmq/amqp_api.c b/librabbitmq/amqp_api.c
index 91b0bf8..3a4440f 100644
--- a/librabbitmq/amqp_api.c
+++ b/librabbitmq/amqp_api.c
@@ -60,6 +60,41 @@
 
 #include <assert.h>
 
+static const char *client_error_strings[ERROR_MAX] = {
+  "could not allocate memory", /* ERROR_NO_MEMORY */
+  "received bad AMQP data", /* ERROR_BAD_AQMP_DATA */
+  "unknown AMQP class id", /* ERROR_UNKOWN_CLASS */
+  "unknown AMQP method id", /* ERROR_UNKOWN_METHOD */
+  "unknown host", /* ERROR_HOST_NOT_FOUND */
+  "incompatible AMQP version", /* ERROR_INCOMPATIBLE_AMQP_VERSION */
+  "connection closed unexpectedly", /* ERROR_CONNECTION_CLOSED */
+};
+
+const char *amqp_error_string(int err)
+{
+  const char *str;
+  int category = (err & ERROR_CATEGORY_MASK);
+  err = (err & ~ERROR_CATEGORY_MASK);
+
+  switch (category) {
+  case ERROR_CATEGORY_CLIENT:
+    if (err < 1 || err > ERROR_MAX)
+      str = "(undefined librabbitmq error)";
+    else
+      str = client_error_strings[err - 1];
+    break;
+
+  case ERROR_CATEGORY_OS:
+    str = strerror(err);
+    break;
+
+  default:
+    str = "(undefined error category)";
+  }
+
+  return strdup(str);
+}
+
 #define RPC_REPLY(replytype)						\
   (state->most_recent_api_result.reply_type == AMQP_RESPONSE_NORMAL	\
    ? (replytype *) state->most_recent_api_result.reply.decoded		\