1 files changed, 378 insertions, 0 deletions

diff --git a/minzip/Hash.cpp b/minzip/Hash.cpp
new file mode 100644
index 000000000..ac08935d4
--- /dev/null
+++ b/minzip/Hash.cpp
@@ -0,0 +1,378 @@
+/*
+ * Copyright 2006 The Android Open Source Project
+ *
+ * Hash table.  The dominant calls are add and lookup, with removals
+ * happening very infrequently.  We use probing, and don't worry much
+ * about tombstone removal.
+ */
+#include <stdlib.h>
+#include <assert.h>
+
+#include <android-base/logging.h>
+
+#include "Hash.h"
+
+/* table load factor, i.e. how full can it get before we resize */
+//#define LOAD_NUMER  3       // 75%
+//#define LOAD_DENOM  4
+#define LOAD_NUMER  5       // 62.5%
+#define LOAD_DENOM  8
+//#define LOAD_NUMER  1       // 50%
+//#define LOAD_DENOM  2
+
+/*
+ * Compute the capacity needed for a table to hold "size" elements.
+ */
+size_t mzHashSize(size_t size) {
+    return (size * LOAD_DENOM) / LOAD_NUMER +1;
+}
+
+/*
+ * Round up to the next highest power of 2.
+ *
+ * Found on http://graphics.stanford.edu/~seander/bithacks.html.
+ */
+unsigned int roundUpPower2(unsigned int val)
+{
+    val--;
+    val |= val >> 1;
+    val |= val >> 2;
+    val |= val >> 4;
+    val |= val >> 8;
+    val |= val >> 16;
+    val++;
+
+    return val;
+}
+
+/*
+ * Create and initialize a hash table.
+ */
+HashTable* mzHashTableCreate(size_t initialSize, HashFreeFunc freeFunc)
+{
+    HashTable* pHashTable;
+
+    assert(initialSize > 0);
+
+    pHashTable = (HashTable*) malloc(sizeof(*pHashTable));
+    if (pHashTable == NULL)
+        return NULL;
+
+    pHashTable->tableSize = roundUpPower2(initialSize);
+    pHashTable->numEntries = pHashTable->numDeadEntries = 0;
+    pHashTable->freeFunc = freeFunc;
+    pHashTable->pEntries =
+        (HashEntry*) calloc((size_t)pHashTable->tableSize, sizeof(HashTable));
+    if (pHashTable->pEntries == NULL) {
+        free(pHashTable);
+        return NULL;
+    }
+
+    return pHashTable;
+}
+
+/*
+ * Clear out all entries.
+ */
+void mzHashTableClear(HashTable* pHashTable)
+{
+    HashEntry* pEnt;
+    int i;
+
+    pEnt = pHashTable->pEntries;
+    for (i = 0; i < pHashTable->tableSize; i++, pEnt++) {
+        if (pEnt->data == HASH_TOMBSTONE) {
+            // nuke entry
+            pEnt->data = NULL;
+        } else if (pEnt->data != NULL) {
+            // call free func then nuke entry
+            if (pHashTable->freeFunc != NULL)
+                (*pHashTable->freeFunc)(pEnt->data);
+            pEnt->data = NULL;
+        }
+    }
+
+    pHashTable->numEntries = 0;
+    pHashTable->numDeadEntries = 0;
+}
+
+/*
+ * Free the table.
+ */
+void mzHashTableFree(HashTable* pHashTable)
+{
+    if (pHashTable == NULL)
+        return;
+    mzHashTableClear(pHashTable);
+    free(pHashTable->pEntries);
+    free(pHashTable);
+}
+
+#ifndef NDEBUG
+/*
+ * Count up the number of tombstone entries in the hash table.
+ */
+static int countTombStones(HashTable* pHashTable)
+{
+    int i, count;
+
+    for (count = i = 0; i < pHashTable->tableSize; i++) {
+        if (pHashTable->pEntries[i].data == HASH_TOMBSTONE)
+            count++;
+    }
+    return count;
+}
+#endif
+
+/*
+ * Resize a hash table.  We do this when adding an entry increased the
+ * size of the table beyond its comfy limit.
+ *
+ * This essentially requires re-inserting all elements into the new storage.
+ *
+ * If multiple threads can access the hash table, the table's lock should
+ * have been grabbed before issuing the "lookup+add" call that led to the
+ * resize, so we don't have a synchronization problem here.
+ */
+static bool resizeHash(HashTable* pHashTable, int newSize)
+{
+    HashEntry* pNewEntries;
+    int i;
+
+    assert(countTombStones(pHashTable) == pHashTable->numDeadEntries);
+
+    pNewEntries = (HashEntry*) calloc(newSize, sizeof(HashTable));
+    if (pNewEntries == NULL)
+        return false;
+
+    for (i = 0; i < pHashTable->tableSize; i++) {
+        void* data = pHashTable->pEntries[i].data;
+        if (data != NULL && data != HASH_TOMBSTONE) {
+            int hashValue = pHashTable->pEntries[i].hashValue;
+            int newIdx;
+
+            /* probe for new spot, wrapping around */
+            newIdx = hashValue & (newSize-1);
+            while (pNewEntries[newIdx].data != NULL)
+                newIdx = (newIdx + 1) & (newSize-1);
+
+            pNewEntries[newIdx].hashValue = hashValue;
+            pNewEntries[newIdx].data = data;
+        }
+    }
+
+    free(pHashTable->pEntries);
+    pHashTable->pEntries = pNewEntries;
+    pHashTable->tableSize = newSize;
+    pHashTable->numDeadEntries = 0;
+
+    assert(countTombStones(pHashTable) == 0);
+    return true;
+}
+
+/*
+ * Look up an entry.
+ *
+ * We probe on collisions, wrapping around the table.
+ */
+void* mzHashTableLookup(HashTable* pHashTable, unsigned int itemHash, void* item,
+    HashCompareFunc cmpFunc, bool doAdd)
+{
+    HashEntry* pEntry;
+    HashEntry* pEnd;
+    void* result = NULL;
+
+    assert(pHashTable->tableSize > 0);
+    assert(item != HASH_TOMBSTONE);
+    assert(item != NULL);
+
+    /* jump to the first entry and probe for a match */
+    pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)];
+    pEnd = &pHashTable->pEntries[pHashTable->tableSize];
+    while (pEntry->data != NULL) {
+        if (pEntry->data != HASH_TOMBSTONE &&
+            pEntry->hashValue == itemHash &&
+            (*cmpFunc)(pEntry->data, item) == 0)
+        {
+            /* match */
+            break;
+        }
+
+        pEntry++;
+        if (pEntry == pEnd) {     /* wrap around to start */
+            if (pHashTable->tableSize == 1)
+                break;      /* edge case - single-entry table */
+            pEntry = pHashTable->pEntries;
+        }
+    }
+
+    if (pEntry->data == NULL) {
+        if (doAdd) {
+            pEntry->hashValue = itemHash;
+            pEntry->data = item;
+            pHashTable->numEntries++;
+
+            /*
+             * We've added an entry.  See if this brings us too close to full.
+             */
+            if ((pHashTable->numEntries+pHashTable->numDeadEntries) * LOAD_DENOM
+                > pHashTable->tableSize * LOAD_NUMER)
+            {
+                if (!resizeHash(pHashTable, pHashTable->tableSize * 2)) {
+                    /* don't really have a way to indicate failure */
+                    LOG(FATAL) << "Hash resize failure";
+                }
+                /* note "pEntry" is now invalid */
+            }
+
+            /* full table is bad -- search for nonexistent never halts */
+            assert(pHashTable->numEntries < pHashTable->tableSize);
+            result = item;
+        } else {
+            assert(result == NULL);
+        }
+    } else {
+        result = pEntry->data;
+    }
+
+    return result;
+}
+
+/*
+ * Remove an entry from the table.
+ *
+ * Does NOT invoke the "free" function on the item.
+ */
+bool mzHashTableRemove(HashTable* pHashTable, unsigned int itemHash, void* item)
+{
+    HashEntry* pEntry;
+    HashEntry* pEnd;
+
+    assert(pHashTable->tableSize > 0);
+
+    /* jump to the first entry and probe for a match */
+    pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)];
+    pEnd = &pHashTable->pEntries[pHashTable->tableSize];
+    while (pEntry->data != NULL) {
+        if (pEntry->data == item) {
+            pEntry->data = HASH_TOMBSTONE;
+            pHashTable->numEntries--;
+            pHashTable->numDeadEntries++;
+            return true;
+        }
+
+        pEntry++;
+        if (pEntry == pEnd) {     /* wrap around to start */
+            if (pHashTable->tableSize == 1)
+                break;      /* edge case - single-entry table */
+            pEntry = pHashTable->pEntries;
+        }
+    }
+
+    return false;
+}
+
+/*
+ * Execute a function on every entry in the hash table.
+ *
+ * If "func" returns a nonzero value, terminate early and return the value.
+ */
+int mzHashForeach(HashTable* pHashTable, HashForeachFunc func, void* arg)
+{
+    int i, val;
+
+    for (i = 0; i < pHashTable->tableSize; i++) {
+        HashEntry* pEnt = &pHashTable->pEntries[i];
+
+        if (pEnt->data != NULL && pEnt->data != HASH_TOMBSTONE) {
+            val = (*func)(pEnt->data, arg);
+            if (val != 0)
+                return val;
+        }
+    }
+
+    return 0;
+}
+
+
+/*
+ * Look up an entry, counting the number of times we have to probe.
+ *
+ * Returns -1 if the entry wasn't found.
+ */
+int countProbes(HashTable* pHashTable, unsigned int itemHash, const void* item,
+    HashCompareFunc cmpFunc)
+{
+    HashEntry* pEntry;
+    HashEntry* pEnd;
+    int count = 0;
+
+    assert(pHashTable->tableSize > 0);
+    assert(item != HASH_TOMBSTONE);
+    assert(item != NULL);
+
+    /* jump to the first entry and probe for a match */
+    pEntry = &pHashTable->pEntries[itemHash & (pHashTable->tableSize-1)];
+    pEnd = &pHashTable->pEntries[pHashTable->tableSize];
+    while (pEntry->data != NULL) {
+        if (pEntry->data != HASH_TOMBSTONE &&
+            pEntry->hashValue == itemHash &&
+            (*cmpFunc)(pEntry->data, item) == 0)
+        {
+            /* match */
+            break;
+        }
+
+        pEntry++;
+        if (pEntry == pEnd) {     /* wrap around to start */
+            if (pHashTable->tableSize == 1)
+                break;      /* edge case - single-entry table */
+            pEntry = pHashTable->pEntries;
+        }
+
+        count++;
+    }
+    if (pEntry->data == NULL)
+        return -1;
+
+    return count;
+}
+
+/*
+ * Evaluate the amount of probing required for the specified hash table.
+ *
+ * We do this by running through all entries in the hash table, computing
+ * the hash value and then doing a lookup.
+ *
+ * The caller should lock the table before calling here.
+ */
+void mzHashTableProbeCount(HashTable* pHashTable, HashCalcFunc calcFunc,
+    HashCompareFunc cmpFunc)
+{
+    int numEntries, minProbe, maxProbe, totalProbe;
+    HashIter iter;
+
+    numEntries = maxProbe = totalProbe = 0;
+    minProbe = 65536*32767;
+
+    for (mzHashIterBegin(pHashTable, &iter); !mzHashIterDone(&iter);
+        mzHashIterNext(&iter))
+    {
+        const void* data = (const void*)mzHashIterData(&iter);
+        int count;
+
+        count = countProbes(pHashTable, (*calcFunc)(data), data, cmpFunc);
+
+        numEntries++;
+
+        if (count < minProbe)
+            minProbe = count;
+        if (count > maxProbe)
+            maxProbe = count;
+        totalProbe += count;
+    }
+
+    LOG(VERBOSE) << "Probe: min=" << minProbe << ", max=" << maxProbe << ", total="
+                 << totalProbe <<" in " << numEntries << " (" << pHashTable->tableSize
+                 << "), avg=" << (float) totalProbe / (float) numEntries;
+}