store world hostname and resolve at runtime

1 files changed, 105 insertions, 0 deletions

diff --git a/src/hostcache.cc b/src/hostcache.cc
new file mode 100644
index 0000000..5d5d46a
--- /dev/null
+++ b/src/hostcache.cc
@@ -0,0 +1,105 @@
+#include "querymanager.hh"
+
+// TODO(fusion): Support windows eventually?
+#if OS_LINUX
+#	include <netdb.h>
+#else
+#	error "Operating system not currently supported."
+#endif
+
+struct THostCacheEntry{
+	char HostName[100];
+	bool Resolved;
+	int IPAddress;
+	int ResolveTime;
+};
+
+static THostCacheEntry *g_CachedHostNames;
+
+bool InitHostCache(void){
+	ASSERT(g_CachedHostNames == NULL);
+	LOG("Max cached host names: %d", g_MaxCachedHostNames);
+	LOG("Host name expire time: %dms", g_HostNameExpireTime);
+	g_CachedHostNames = (THostCacheEntry*)calloc(
+			g_MaxCachedHostNames, sizeof(THostCacheEntry));
+	return true;
+}
+
+void ExitHostCache(void){
+	if(g_CachedHostNames != NULL){
+		free(g_CachedHostNames);
+		g_CachedHostNames = NULL;
+	}
+}
+
+static bool DoResolveHostName(const char *HostName, int *OutAddr){
+	ASSERT(HostName != NULL && OutAddr != NULL);
+	addrinfo *Result = NULL;
+	addrinfo Hints = {};
+	Hints.ai_family = AF_INET;
+	Hints.ai_socktype = SOCK_STREAM;
+	int ErrCode = getaddrinfo(HostName, NULL, &Hints, &Result);
+	if(ErrCode != 0){
+		LOG_ERR("Failed to resolve hostname \"%s\": %s", HostName, gai_strerror(ErrCode));
+		return false;
+	}
+
+	bool Resolved = false;
+	for(addrinfo *AddrInfo = Result;
+			AddrInfo != NULL;
+			AddrInfo = AddrInfo->ai_next){
+		if(AddrInfo->ai_family == AF_INET && AddrInfo->ai_socktype == SOCK_STREAM){
+			ASSERT(AddrInfo->ai_addrlen == sizeof(sockaddr_in));
+			*OutAddr = ntohl(((sockaddr_in*)AddrInfo->ai_addr)->sin_addr.s_addr);
+			Resolved = true;
+			break;
+		}
+	}
+	freeaddrinfo(Result);
+	return Resolved;
+}
+
+bool ResolveHostName(const char *HostName, int *OutAddr){
+	ASSERT(HostName != NULL && !StringEmpty(HostName));
+	THostCacheEntry *Entry = NULL;
+	int LeastRecentlyUsedIndex = 0;
+	int LeastRecentlyUsedTime = g_CachedHostNames[0].ResolveTime;
+	for(int i = 0; i < g_MaxCachedHostNames; i += 1){
+		THostCacheEntry *Current = &g_CachedHostNames[i];
+
+		if((g_MonotonicTimeMS - Current->ResolveTime) >= g_HostNameExpireTime){
+			memset(Current, 0, sizeof(THostCacheEntry));
+		}
+
+		if(Current->ResolveTime < LeastRecentlyUsedTime){
+			LeastRecentlyUsedIndex = i;
+			LeastRecentlyUsedTime = Current->ResolveTime;
+		}
+
+		if(StringEq(HostName, Current->HostName)){
+			Entry = Current;
+			break;
+		}
+	}
+
+	if(Entry == NULL){
+		// NOTE(fusion): We also cache failures.
+		Entry = &g_CachedHostNames[LeastRecentlyUsedIndex];
+		if(!StringCopy(Entry->HostName, sizeof(Entry->HostName), HostName)){
+			LOG_WARN("Hostname \"%s\" was improperly cached because it was"
+					" too long (Length: %d, MaxLength: %d)", HostName,
+					(int)strlen(HostName), (int)sizeof(Entry->HostName));
+		}
+		Entry->Resolved = DoResolveHostName(HostName, &Entry->IPAddress);
+		Entry->ResolveTime = g_MonotonicTimeMS;
+	}
+
+	if(Entry && Entry->Resolved){
+		if(OutAddr){
+			*OutAddr = Entry->IPAddress;
+		}
+		return true;
+	}else{
+		return false;
+	}
+}