+
+/// FindKey - Look up the bucket that contains the specified key. If it exists
+/// in the map, return the bucket number of the key. Otherwise return -1.
+/// This does not modify the map.
+int StringMapImpl::FindKey(const char *KeyStart, const char *KeyEnd) const {
+ unsigned HTSize = NumBuckets;
+ if (HTSize == 0) return -1; // Really empty table?
+ unsigned FullHashValue = HashString(KeyStart, KeyEnd);
+ unsigned BucketNo = FullHashValue & (HTSize-1);
+
+ unsigned ProbeAmt = 1;
+ while (1) {
+ ItemBucket &Bucket = TheTable[BucketNo];
+ StringMapEntryBase *BucketItem = Bucket.Item;
+ // If we found an empty bucket, this key isn't in the table yet, return.
+ if (BucketItem == 0)
+ return -1;
+
+ if (BucketItem == getTombstoneVal()) {
+ // Ignore tombstones.
+ } else if (Bucket.FullHashValue == FullHashValue) {
+ // If the full hash value matches, check deeply for a match. The common
+ // case here is that we are only looking at the buckets (for item info
+ // being non-null and for the full hash value) not at the items. This
+ // is important for cache locality.
+
+ // Do the comparison like this because NameStart isn't necessarily
+ // null-terminated!
+ char *ItemStr = (char*)BucketItem+ItemSize;
+ unsigned ItemStrLen = BucketItem->getKeyLength();
+ if (unsigned(KeyEnd-KeyStart) == ItemStrLen &&
+ memcmp(ItemStr, KeyStart, ItemStrLen) == 0) {
+ // We found a match!
+ return BucketNo;
+ }
+ }
+
+ // Okay, we didn't find the item. Probe to the next bucket.
+ BucketNo = (BucketNo+ProbeAmt) & (HTSize-1);
+
+ // Use quadratic probing, it has fewer clumping artifacts than linear
+ // probing and has good cache behavior in the common case.
+ ++ProbeAmt;
+ }
+}
+
+/// RemoveKey - Remove the specified StringMapEntry from the table, but do not
+/// delete it. This aborts if the value isn't in the table.
+void StringMapImpl::RemoveKey(StringMapEntryBase *V) {
+ const char *VStr = (char*)V + ItemSize;
+ StringMapEntryBase *V2 = RemoveKey(VStr, VStr+V->getKeyLength());
+ V2 = V2;
+ assert(V == V2 && "Didn't find key?");
+}
+
+/// RemoveKey - Remove the StringMapEntry for the specified key from the
+/// table, returning it. If the key is not in the table, this returns null.
+StringMapEntryBase *StringMapImpl::RemoveKey(const char *KeyStart,
+ const char *KeyEnd) {
+ int Bucket = FindKey(KeyStart, KeyEnd);
+ if (Bucket == -1) return 0;
+
+ StringMapEntryBase *Result = TheTable[Bucket].Item;
+ TheTable[Bucket].Item = getTombstoneVal();
+ --NumItems;
+ ++NumTombstones;
+ return Result;
+}
+
+
+