From d02a614ebe30542176d5b6bbc3ac2d001e96e4ce Mon Sep 17 00:00:00 2001
From: rubidium <rubidium@openttd.org>
Date: Sat, 9 Dec 2006 14:18:08 +0000
Subject: [PATCH] (svn r7452) -Fix: GetRandom(Industry|Town) must return a
 valid industry/town and should not need to loop over the pool for a second
 time.

---
 industry.h | 19 ++++++++++++-------
 town.h     | 24 ++++++++++++++----------
 2 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/industry.h b/industry.h
index e0620f35ba..f8cf63c827 100644
--- a/industry.h
+++ b/industry.h
@@ -90,6 +90,11 @@ static inline bool IsValidIndustry(const Industry *industry)
 	return industry->xy != 0;
 }
 
+static inline bool IsValidIndustryID(IndustryID index)
+{
+	return index < GetIndustryPoolSize() && IsValidIndustry(GetIndustry(index));
+}
+
 VARDEF int _total_industries;
 
 static inline IndustryID GetMaxIndustryIndex(void)
@@ -108,23 +113,23 @@ static inline uint GetNumIndustries(void)
 }
 
 /**
- * Return a random valid town.
+ * Return a random valid industry.
  */
 static inline Industry *GetRandomIndustry(void)
 {
-	uint num = RandomRange(GetNumIndustries());
-	uint index = 0;
+	int num = RandomRange(GetNumIndustries());
+	IndustryID index = INVALID_INDUSTRY;
 
 	if (GetNumIndustries() == 0) return NULL;
 
-	while (num > 0) {
+	while (num >= 0) {
 		num--;
-
 		index++;
+
 		/* Make sure we have a valid industry */
-		while (GetIndustry(index) == NULL) {
+		while (!IsValidIndustryID(index)) {
 			index++;
-			if (index > GetMaxIndustryIndex()) index = 0;
+			assert(index <= GetMaxIndustryIndex());
 		}
 	}
 
diff --git a/town.h b/town.h
index edf6b38d04..d1edca1c85 100644
--- a/town.h
+++ b/town.h
@@ -6,6 +6,10 @@
 #include "oldpool.h"
 #include "player.h"
 
+enum {
+	INVALID_TOWN = 0xFFFF,
+};
+
 struct Town {
 	TileIndex xy;
 
@@ -162,6 +166,11 @@ static inline bool IsValidTown(const Town* town)
 	return town->xy != 0;
 }
 
+static inline bool IsValidTownID(TownID index)
+{
+	return index < GetTownPoolSize() && IsValidTown(GetTown(index));
+}
+
 VARDEF uint _total_towns;
 
 static inline TownID GetMaxTownIndex(void)
@@ -184,28 +193,23 @@ static inline uint GetNumTowns(void)
  */
 static inline Town *GetRandomTown(void)
 {
-	uint num = RandomRange(GetNumTowns());
-	uint index = 0;
+	int num = RandomRange(GetNumTowns());
+	TownID index = INVALID_TOWN;
 
-	while (num > 0) {
+	while (num >= 0) {
 		num--;
 
 		index++;
 		/* Make sure we have a valid industry */
-		while (GetTown(index) == NULL) {
+		while (!IsValidTownID(index)) {
 			index++;
-			if (index > GetMaxTownIndex()) index = 0;
+			assert(index <= GetMaxTownIndex());
 		}
 	}
 
 	return GetTown(index);
 }
 
-static inline bool IsValidTownID(uint index)
-{
-	return index < GetTownPoolSize() && IsValidTown(GetTown(index));
-}
-
 void DestroyTown(Town *t);
 
 static inline void DeleteTown(Town *t)