Exception handling changes

In preparation for work on progressive loading, update the exception
handling scheme slightly.

Until now, exceptions (as thrown with fz_throw, and caught with
fz_try/fz_catch) have merely had an informative string. They have
never had anything that can be compared to see if an error is of
a particular type.

We now introduce error codes; when we fz_throw, we now always
give an error code, and can optionally (using fz_throw_message)
give both an error code and an informative string.

When we fz_rethrow from within a fz_catch, both the error code and
the error message is maintained. Using fz_rethrow_message we can
'improve' the error message, but the code is maintained.

The error message can be read out using fz_caught_message() and the
error code can be read as fz_caught().

Currently we only define a 'generic' error. This will expand in future
versions to include other error types that may be tested for.

1 files changed, 12 insertions, 2 deletions

diff --git a/include/mupdf/fitz/context.h b/include/mupdf/fitz/context.h
index 5f36370a..5f5df366 100644
--- a/include/mupdf/fitz/context.h
+++ b/include/mupdf/fitz/context.h
@@ -34,6 +34,7 @@ struct fz_error_context_s
 		int code;
 		fz_jmp_buf buffer;
 	} stack[256];
+	int errcode;
 	char message[256];
 };
 
@@ -64,10 +65,19 @@ void fz_var_imp(void *);
 	if (ctx->error->stack[ctx->error->top--].code > 1)
 
 int fz_push_try(fz_error_context *ex);
-void fz_throw(fz_context *, const char *, ...) __printflike(2, 3) FZ_NORETURN;
+void fz_throw(fz_context *, int errcode, const char *, ...) __printflike(3, 4) FZ_NORETURN;
 void fz_rethrow(fz_context *) FZ_NORETURN;
+void fz_rethrow_message(fz_context *, const char *, ...)  __printflike(2, 3) FZ_NORETURN;
 void fz_warn(fz_context *ctx, const char *fmt, ...) __printflike(2, 3);
-const char *fz_caught(fz_context *ctx);
+const char *fz_caught_message(fz_context *ctx);
+int fz_caught(fz_context *ctx);
+
+enum
+{
+	FZ_ERROR_NONE = 0,
+	FZ_ERROR_GENERIC = 1,
+	FZ_ERROR_COUNT
+};
 
 /*
 	fz_flush_warnings: Flush any repeated warnings.