From 7904dbe4fcbe956ee4bf785df97d714a397defc1 Mon Sep 17 00:00:00 2001
From: Nick Bowler <nbowler@draconx.ca>
Date: Wed, 2 Mar 2011 20:07:31 -0500
Subject: [PATCH] libupkg: Simplify handling of format assertions.

---
 src/libupkg.c | 43 +++++++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/src/libupkg.c b/src/libupkg.c
index 40b3913..6b1cfb3 100644
--- a/src/libupkg.c
+++ b/src/libupkg.c
@@ -25,6 +25,19 @@
 
 #define MIN(a, b) ((a) < (b) ? (a) : (b))
 
+/*
+ * Print a message and execute some statement(s) if the expression evaluates
+ * to zero.  Intended to help verify that assumed constraints on the file
+ * format actually are not violated.
+ */
+#define format_assert(expr, body) do { \
+	if (!(expr)) { \
+		fprintf(stderr, "%s: %d: %s: format assertion failed: %s\n", \
+		                __FILE__, __LINE__, __func__, #expr); \
+		body; \
+	} \
+} while (0)
+
 struct upkg_name {
 	unsigned long flags;
 	char *name;
@@ -521,11 +534,8 @@ const char *upkg_export_class(struct upkg *pkg, unsigned long idx,
 
 	export = &pkg->priv->exports[idx];
 
-	/* ASSUMPTION: class references are always imports */
-	if (export->class > 0) {
-		fprintf(stderr, "Assumption Violated: class not import\n");
-		return NULL;
-	}
+	/* Assumption: class references are always imports. */
+	format_assert(export->class <= 0, return NULL);
 
 	/* Get the class. */
 	if (export->class == 0) {
@@ -538,17 +548,12 @@ const char *upkg_export_class(struct upkg *pkg, unsigned long idx,
 		return NULL;
 	iclass = &pkg->priv->imports[pkg_idx];
 
-	/* ASSUMPTION: Class references are always Core.Class */
-	if (strcmp(iclass->class_name, "Class") || strcmp(iclass->class_package, "Core")) {
-		fprintf(stderr, "Assumption Violated: class not Core.Class\n");
-		return NULL;
-	}
+	/* Assumption: class references are always Core.Class. */
+	format_assert(!strcmp(iclass->class_package, "Core"), return NULL);
+	format_assert(!strcmp(iclass->class_name, "Class"), return NULL);
 
-	/* ASSUMPTION: Package references are always imports */
-	if (iclass->package >= 0) {
-		fprintf(stderr, "Assumption Violated: package not import\n");
-		return NULL;
-	}
+	/* Assumption: package references are always imports. */
+	format_assert(iclass->package <= 0, return NULL);
 
 	/* Get the package. */
 	pkg_idx = -(iclass->package + 1);
@@ -556,11 +561,9 @@ const char *upkg_export_class(struct upkg *pkg, unsigned long idx,
 		return NULL;
 	ipackage = &pkg->priv->imports[pkg_idx];
 
-	/* ASSUMPTION: Package references are always Core.Package */
-	if (strcmp(ipackage->class_name, "Package") || strcmp(ipackage->class_package, "Core")) {
-		fprintf(stderr, "Assumption Violated: package not Core.Package\n");
-		return NULL;
-	}
+	/* Assumption: package references are always Core.Package. */
+	format_assert(!strcmp(ipackage->class_package, "Core"), return NULL);
+	format_assert(!strcmp(ipackage->class_name, "Package"), return NULL);
 
 	if (package) *package = ipackage->object_name;
 	return iclass->object_name;
-- 
2.43.0