1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/glue/pldhash.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,586 @@
1.4 +/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#ifndef pldhash_h___
1.10 +#define pldhash_h___
1.11 +/*
1.12 + * Double hashing, a la Knuth 6.
1.13 + */
1.14 +#include "mozilla/fallible.h"
1.15 +#include "mozilla/MemoryReporting.h"
1.16 +#include "mozilla/Types.h"
1.17 +#include "nscore.h"
1.18 +
1.19 +#if defined(__GNUC__) && defined(__i386__)
1.20 +#define PL_DHASH_FASTCALL __attribute__ ((regparm (3),stdcall))
1.21 +#elif defined(XP_WIN)
1.22 +#define PL_DHASH_FASTCALL __fastcall
1.23 +#else
1.24 +#define PL_DHASH_FASTCALL
1.25 +#endif
1.26 +
1.27 +/*
1.28 + * Table size limit; do not exceed. The max capacity used to be 1<<23 but that
1.29 + * occasionally that wasn't enough. Making it much bigger than 1<<26 probably
1.30 + * isn't worthwhile -- tables that big are kind of ridiculous. Also, the
1.31 + * growth operation will (deliberately) fail if |capacity * entrySize|
1.32 + * overflows a uint32_t, and entrySize is always at least 8 bytes.
1.33 + */
1.34 +#undef PL_DHASH_MAX_SIZE
1.35 +#define PL_DHASH_MAX_SIZE ((uint32_t)1 << 26)
1.36 +
1.37 +/* Minimum table size, or gross entry count (net is at most .75 loaded). */
1.38 +#ifndef PL_DHASH_MIN_SIZE
1.39 +#define PL_DHASH_MIN_SIZE 16
1.40 +#elif (PL_DHASH_MIN_SIZE & (PL_DHASH_MIN_SIZE - 1)) != 0
1.41 +#error "PL_DHASH_MIN_SIZE must be a power of two!"
1.42 +#endif
1.43 +
1.44 +/*
1.45 + * Multiplicative hash uses an unsigned 32 bit integer and the golden ratio,
1.46 + * expressed as a fixed-point 32-bit fraction.
1.47 + */
1.48 +#define PL_DHASH_BITS 32
1.49 +#define PL_DHASH_GOLDEN_RATIO 0x9E3779B9U
1.50 +
1.51 +/* Primitive and forward-struct typedefs. */
1.52 +typedef uint32_t PLDHashNumber;
1.53 +typedef struct PLDHashEntryHdr PLDHashEntryHdr;
1.54 +typedef struct PLDHashEntryStub PLDHashEntryStub;
1.55 +typedef struct PLDHashTable PLDHashTable;
1.56 +typedef struct PLDHashTableOps PLDHashTableOps;
1.57 +
1.58 +/*
1.59 + * Table entry header structure.
1.60 + *
1.61 + * In order to allow in-line allocation of key and value, we do not declare
1.62 + * either here. Instead, the API uses const void *key as a formal parameter.
1.63 + * The key need not be stored in the entry; it may be part of the value, but
1.64 + * need not be stored at all.
1.65 + *
1.66 + * Callback types are defined below and grouped into the PLDHashTableOps
1.67 + * structure, for single static initialization per hash table sub-type.
1.68 + *
1.69 + * Each hash table sub-type should nest the PLDHashEntryHdr structure at the
1.70 + * front of its particular entry type. The keyHash member contains the result
1.71 + * of multiplying the hash code returned from the hashKey callback (see below)
1.72 + * by PL_DHASH_GOLDEN_RATIO, then constraining the result to avoid the magic 0
1.73 + * and 1 values. The stored keyHash value is table size invariant, and it is
1.74 + * maintained automatically by PL_DHashTableOperate -- users should never set
1.75 + * it, and its only uses should be via the entry macros below.
1.76 + *
1.77 + * The PL_DHASH_ENTRY_IS_LIVE function tests whether entry is neither free nor
1.78 + * removed. An entry may be either busy or free; if busy, it may be live or
1.79 + * removed. Consumers of this API should not access members of entries that
1.80 + * are not live.
1.81 + *
1.82 + * However, use PL_DHASH_ENTRY_IS_BUSY for faster liveness testing of entries
1.83 + * returned by PL_DHashTableOperate, as PL_DHashTableOperate never returns a
1.84 + * non-live, busy (i.e., removed) entry pointer to its caller. See below for
1.85 + * more details on PL_DHashTableOperate's calling rules.
1.86 + */
1.87 +struct PLDHashEntryHdr {
1.88 + PLDHashNumber keyHash; /* every entry must begin like this */
1.89 +};
1.90 +
1.91 +MOZ_ALWAYS_INLINE bool
1.92 +PL_DHASH_ENTRY_IS_FREE(PLDHashEntryHdr* entry)
1.93 +{
1.94 + return entry->keyHash == 0;
1.95 +}
1.96 +
1.97 +MOZ_ALWAYS_INLINE bool
1.98 +PL_DHASH_ENTRY_IS_BUSY(PLDHashEntryHdr* entry)
1.99 +{
1.100 + return !PL_DHASH_ENTRY_IS_FREE(entry);
1.101 +}
1.102 +
1.103 +MOZ_ALWAYS_INLINE bool
1.104 +PL_DHASH_ENTRY_IS_LIVE(PLDHashEntryHdr* entry)
1.105 +{
1.106 + return entry->keyHash >= 2;
1.107 +}
1.108 +
1.109 +/*
1.110 + * A PLDHashTable is currently 8 words (without the PL_DHASHMETER overhead)
1.111 + * on most architectures, and may be allocated on the stack or within another
1.112 + * structure or class (see below for the Init and Finish functions to use).
1.113 + *
1.114 + * To decide whether to use double hashing vs. chaining, we need to develop a
1.115 + * trade-off relation, as follows:
1.116 + *
1.117 + * Let alpha be the load factor, esize the entry size in words, count the
1.118 + * entry count, and pow2 the power-of-two table size in entries.
1.119 + *
1.120 + * (PLDHashTable overhead) > (PLHashTable overhead)
1.121 + * (unused table entry space) > (malloc and .next overhead per entry) +
1.122 + * (buckets overhead)
1.123 + * (1 - alpha) * esize * pow2 > 2 * count + pow2
1.124 + *
1.125 + * Notice that alpha is by definition (count / pow2):
1.126 + *
1.127 + * (1 - alpha) * esize * pow2 > 2 * alpha * pow2 + pow2
1.128 + * (1 - alpha) * esize > 2 * alpha + 1
1.129 + *
1.130 + * esize > (1 + 2 * alpha) / (1 - alpha)
1.131 + *
1.132 + * This assumes both tables must keep keyHash, key, and value for each entry,
1.133 + * where key and value point to separately allocated strings or structures.
1.134 + * If key and value can be combined into one pointer, then the trade-off is:
1.135 + *
1.136 + * esize > (1 + 3 * alpha) / (1 - alpha)
1.137 + *
1.138 + * If the entry value can be a subtype of PLDHashEntryHdr, rather than a type
1.139 + * that must be allocated separately and referenced by an entry.value pointer
1.140 + * member, and provided key's allocation can be fused with its entry's, then
1.141 + * k (the words wasted per entry with chaining) is 4.
1.142 + *
1.143 + * To see these curves, feed gnuplot input like so:
1.144 + *
1.145 + * gnuplot> f(x,k) = (1 + k * x) / (1 - x)
1.146 + * gnuplot> plot [0:.75] f(x,2), f(x,3), f(x,4)
1.147 + *
1.148 + * For k of 2 and a well-loaded table (alpha > .5), esize must be more than 4
1.149 + * words for chaining to be more space-efficient than double hashing.
1.150 + *
1.151 + * Solving for alpha helps us decide when to shrink an underloaded table:
1.152 + *
1.153 + * esize > (1 + k * alpha) / (1 - alpha)
1.154 + * esize - alpha * esize > 1 + k * alpha
1.155 + * esize - 1 > (k + esize) * alpha
1.156 + * (esize - 1) / (k + esize) > alpha
1.157 + *
1.158 + * alpha < (esize - 1) / (esize + k)
1.159 + *
1.160 + * Therefore double hashing should keep alpha >= (esize - 1) / (esize + k),
1.161 + * assuming esize is not too large (in which case, chaining should probably be
1.162 + * used for any alpha). For esize=2 and k=3, we want alpha >= .2; for esize=3
1.163 + * and k=2, we want alpha >= .4. For k=4, esize could be 6, and alpha >= .5
1.164 + * would still obtain.
1.165 + *
1.166 + * The current implementation uses a configurable lower bound on alpha, which
1.167 + * defaults to .25, when deciding to shrink the table (while still respecting
1.168 + * PL_DHASH_MIN_SIZE).
1.169 + *
1.170 + * Note a qualitative difference between chaining and double hashing: under
1.171 + * chaining, entry addresses are stable across table shrinks and grows. With
1.172 + * double hashing, you can't safely hold an entry pointer and use it after an
1.173 + * ADD or REMOVE operation, unless you sample table->generation before adding
1.174 + * or removing, and compare the sample after, dereferencing the entry pointer
1.175 + * only if table->generation has not changed.
1.176 + *
1.177 + * The moral of this story: there is no one-size-fits-all hash table scheme,
1.178 + * but for small table entry size, and assuming entry address stability is not
1.179 + * required, double hashing wins.
1.180 + */
1.181 +struct PLDHashTable {
1.182 + const PLDHashTableOps *ops; /* virtual operations, see below */
1.183 + void *data; /* ops- and instance-specific data */
1.184 + int16_t hashShift; /* multiplicative hash shift */
1.185 + /*
1.186 + * |recursionLevel| is only used in debug builds, but is present in opt
1.187 + * builds to avoid binary compatibility problems when mixing DEBUG and
1.188 + * non-DEBUG components. (Actually, even if it were removed,
1.189 + * sizeof(PLDHashTable) wouldn't change, due to struct padding.)
1.190 + */
1.191 + uint16_t recursionLevel; /* used to detect unsafe re-entry */
1.192 + uint32_t entrySize; /* number of bytes in an entry */
1.193 + uint32_t entryCount; /* number of entries in table */
1.194 + uint32_t removedCount; /* removed entry sentinels in table */
1.195 + uint32_t generation; /* entry storage generation number */
1.196 + char *entryStore; /* entry storage */
1.197 +#ifdef PL_DHASHMETER
1.198 + struct PLDHashStats {
1.199 + uint32_t searches; /* total number of table searches */
1.200 + uint32_t steps; /* hash chain links traversed */
1.201 + uint32_t hits; /* searches that found key */
1.202 + uint32_t misses; /* searches that didn't find key */
1.203 + uint32_t lookups; /* number of PL_DHASH_LOOKUPs */
1.204 + uint32_t addMisses; /* adds that miss, and do work */
1.205 + uint32_t addOverRemoved; /* adds that recycled a removed entry */
1.206 + uint32_t addHits; /* adds that hit an existing entry */
1.207 + uint32_t addFailures; /* out-of-memory during add growth */
1.208 + uint32_t removeHits; /* removes that hit, and do work */
1.209 + uint32_t removeMisses; /* useless removes that miss */
1.210 + uint32_t removeFrees; /* removes that freed entry directly */
1.211 + uint32_t removeEnums; /* removes done by Enumerate */
1.212 + uint32_t grows; /* table expansions */
1.213 + uint32_t shrinks; /* table contractions */
1.214 + uint32_t compresses; /* table compressions */
1.215 + uint32_t enumShrinks; /* contractions after Enumerate */
1.216 + } stats;
1.217 +#endif
1.218 +};
1.219 +
1.220 +/*
1.221 + * Size in entries (gross, not net of free and removed sentinels) for table.
1.222 + * We store hashShift rather than sizeLog2 to optimize the collision-free case
1.223 + * in SearchTable.
1.224 + */
1.225 +#define PL_DHASH_TABLE_SIZE(table) \
1.226 + ((uint32_t)1 << (PL_DHASH_BITS - (table)->hashShift))
1.227 +
1.228 +/*
1.229 + * Table space at entryStore is allocated and freed using these callbacks.
1.230 + * The allocator should return null on error only (not if called with nbytes
1.231 + * equal to 0; but note that pldhash.c code will never call with 0 nbytes).
1.232 + */
1.233 +typedef void *
1.234 +(* PLDHashAllocTable)(PLDHashTable *table, uint32_t nbytes);
1.235 +
1.236 +typedef void
1.237 +(* PLDHashFreeTable) (PLDHashTable *table, void *ptr);
1.238 +
1.239 +/*
1.240 + * Compute the hash code for a given key to be looked up, added, or removed
1.241 + * from table. A hash code may have any PLDHashNumber value.
1.242 + */
1.243 +typedef PLDHashNumber
1.244 +(* PLDHashHashKey) (PLDHashTable *table, const void *key);
1.245 +
1.246 +/*
1.247 + * Compare the key identifying entry in table with the provided key parameter.
1.248 + * Return true if keys match, false otherwise.
1.249 + */
1.250 +typedef bool
1.251 +(* PLDHashMatchEntry)(PLDHashTable *table, const PLDHashEntryHdr *entry,
1.252 + const void *key);
1.253 +
1.254 +/*
1.255 + * Copy the data starting at from to the new entry storage at to. Do not add
1.256 + * reference counts for any strong references in the entry, however, as this
1.257 + * is a "move" operation: the old entry storage at from will be freed without
1.258 + * any reference-decrementing callback shortly.
1.259 + */
1.260 +typedef void
1.261 +(* PLDHashMoveEntry)(PLDHashTable *table, const PLDHashEntryHdr *from,
1.262 + PLDHashEntryHdr *to);
1.263 +
1.264 +/*
1.265 + * Clear the entry and drop any strong references it holds. This callback is
1.266 + * invoked during a PL_DHASH_REMOVE operation (see below for operation codes),
1.267 + * but only if the given key is found in the table.
1.268 + */
1.269 +typedef void
1.270 +(* PLDHashClearEntry)(PLDHashTable *table, PLDHashEntryHdr *entry);
1.271 +
1.272 +/*
1.273 + * Called when a table (whether allocated dynamically by itself, or nested in
1.274 + * a larger structure, or allocated on the stack) is finished. This callback
1.275 + * allows table->ops-specific code to finalize table->data.
1.276 + */
1.277 +typedef void
1.278 +(* PLDHashFinalize) (PLDHashTable *table);
1.279 +
1.280 +/*
1.281 + * Initialize a new entry, apart from keyHash. This function is called when
1.282 + * PL_DHashTableOperate's PL_DHASH_ADD case finds no existing entry for the
1.283 + * given key, and must add a new one. At that point, entry->keyHash is not
1.284 + * set yet, to avoid claiming the last free entry in a severely overloaded
1.285 + * table.
1.286 + */
1.287 +typedef bool
1.288 +(* PLDHashInitEntry)(PLDHashTable *table, PLDHashEntryHdr *entry,
1.289 + const void *key);
1.290 +
1.291 +/*
1.292 + * Finally, the "vtable" structure for PLDHashTable. The first eight hooks
1.293 + * must be provided by implementations; they're called unconditionally by the
1.294 + * generic pldhash.c code. Hooks after these may be null.
1.295 + *
1.296 + * Summary of allocation-related hook usage with C++ placement new emphasis:
1.297 + * allocTable Allocate raw bytes with malloc, no ctors run.
1.298 + * freeTable Free raw bytes with free, no dtors run.
1.299 + * initEntry Call placement new using default key-based ctor.
1.300 + * Return true on success, false on error.
1.301 + * moveEntry Call placement new using copy ctor, run dtor on old
1.302 + * entry storage.
1.303 + * clearEntry Run dtor on entry.
1.304 + * finalize Stub unless table->data was initialized and needs to
1.305 + * be finalized.
1.306 + *
1.307 + * Note the reason why initEntry is optional: the default hooks (stubs) clear
1.308 + * entry storage: On successful PL_DHashTableOperate(tbl, key, PL_DHASH_ADD),
1.309 + * the returned entry pointer addresses an entry struct whose keyHash member
1.310 + * has been set non-zero, but all other entry members are still clear (null).
1.311 + * PL_DHASH_ADD callers can test such members to see whether the entry was
1.312 + * newly created by the PL_DHASH_ADD call that just succeeded. If placement
1.313 + * new or similar initialization is required, define an initEntry hook. Of
1.314 + * course, the clearEntry hook must zero or null appropriately.
1.315 + *
1.316 + * XXX assumes 0 is null for pointer types.
1.317 + */
1.318 +struct PLDHashTableOps {
1.319 + /* Mandatory hooks. All implementations must provide these. */
1.320 + PLDHashAllocTable allocTable;
1.321 + PLDHashFreeTable freeTable;
1.322 + PLDHashHashKey hashKey;
1.323 + PLDHashMatchEntry matchEntry;
1.324 + PLDHashMoveEntry moveEntry;
1.325 + PLDHashClearEntry clearEntry;
1.326 + PLDHashFinalize finalize;
1.327 +
1.328 + /* Optional hooks start here. If null, these are not called. */
1.329 + PLDHashInitEntry initEntry;
1.330 +};
1.331 +
1.332 +/*
1.333 + * Default implementations for the above ops.
1.334 + */
1.335 +NS_COM_GLUE void *
1.336 +PL_DHashAllocTable(PLDHashTable *table, uint32_t nbytes);
1.337 +
1.338 +NS_COM_GLUE void
1.339 +PL_DHashFreeTable(PLDHashTable *table, void *ptr);
1.340 +
1.341 +NS_COM_GLUE PLDHashNumber
1.342 +PL_DHashStringKey(PLDHashTable *table, const void *key);
1.343 +
1.344 +/* A minimal entry contains a keyHash header and a void key pointer. */
1.345 +struct PLDHashEntryStub {
1.346 + PLDHashEntryHdr hdr;
1.347 + const void *key;
1.348 +};
1.349 +
1.350 +NS_COM_GLUE PLDHashNumber
1.351 +PL_DHashVoidPtrKeyStub(PLDHashTable *table, const void *key);
1.352 +
1.353 +NS_COM_GLUE bool
1.354 +PL_DHashMatchEntryStub(PLDHashTable *table,
1.355 + const PLDHashEntryHdr *entry,
1.356 + const void *key);
1.357 +
1.358 +NS_COM_GLUE bool
1.359 +PL_DHashMatchStringKey(PLDHashTable *table,
1.360 + const PLDHashEntryHdr *entry,
1.361 + const void *key);
1.362 +
1.363 +NS_COM_GLUE void
1.364 +PL_DHashMoveEntryStub(PLDHashTable *table,
1.365 + const PLDHashEntryHdr *from,
1.366 + PLDHashEntryHdr *to);
1.367 +
1.368 +NS_COM_GLUE void
1.369 +PL_DHashClearEntryStub(PLDHashTable *table, PLDHashEntryHdr *entry);
1.370 +
1.371 +NS_COM_GLUE void
1.372 +PL_DHashFreeStringKey(PLDHashTable *table, PLDHashEntryHdr *entry);
1.373 +
1.374 +NS_COM_GLUE void
1.375 +PL_DHashFinalizeStub(PLDHashTable *table);
1.376 +
1.377 +/*
1.378 + * If you use PLDHashEntryStub or a subclass of it as your entry struct, and
1.379 + * if your entries move via memcpy and clear via memset(0), you can use these
1.380 + * stub operations.
1.381 + */
1.382 +NS_COM_GLUE const PLDHashTableOps *
1.383 +PL_DHashGetStubOps(void);
1.384 +
1.385 +/*
1.386 + * Dynamically allocate a new PLDHashTable using malloc, initialize it using
1.387 + * PL_DHashTableInit, and return its address. Return null on malloc failure.
1.388 + * Note that the entry storage at table->entryStore will be allocated using
1.389 + * the ops->allocTable callback.
1.390 + */
1.391 +NS_COM_GLUE PLDHashTable *
1.392 +PL_NewDHashTable(const PLDHashTableOps *ops, void *data, uint32_t entrySize,
1.393 + uint32_t capacity);
1.394 +
1.395 +/*
1.396 + * Finalize table's data, free its entry storage (via table->ops->freeTable),
1.397 + * and return the memory starting at table to the malloc heap.
1.398 + */
1.399 +NS_COM_GLUE void
1.400 +PL_DHashTableDestroy(PLDHashTable *table);
1.401 +
1.402 +/*
1.403 + * Initialize table with ops, data, entrySize, and capacity. Capacity is a
1.404 + * guess for the smallest table size at which the table will usually be less
1.405 + * than 75% loaded (the table will grow or shrink as needed; capacity serves
1.406 + * only to avoid inevitable early growth from PL_DHASH_MIN_SIZE). This will
1.407 + * crash if it can't allocate enough memory, or if entrySize or capacity are
1.408 + * too large.
1.409 + */
1.410 +NS_COM_GLUE void
1.411 +PL_DHashTableInit(PLDHashTable *table, const PLDHashTableOps *ops, void *data,
1.412 + uint32_t entrySize, uint32_t capacity);
1.413 +
1.414 +/*
1.415 + * Initialize table. This is the same as PL_DHashTableInit, except that it
1.416 + * returns a boolean indicating success, rather than crashing on failure.
1.417 + */
1.418 +NS_COM_GLUE bool
1.419 +PL_DHashTableInit(PLDHashTable *table, const PLDHashTableOps *ops, void *data,
1.420 + uint32_t entrySize, uint32_t capacity,
1.421 + const mozilla::fallible_t& ) MOZ_WARN_UNUSED_RESULT;
1.422 +
1.423 +/*
1.424 + * Finalize table's data, free its entry storage using table->ops->freeTable,
1.425 + * and leave its members unchanged from their last live values (which leaves
1.426 + * pointers dangling). If you want to burn cycles clearing table, it's up to
1.427 + * your code to call memset.
1.428 + */
1.429 +NS_COM_GLUE void
1.430 +PL_DHashTableFinish(PLDHashTable *table);
1.431 +
1.432 +/*
1.433 + * To consolidate keyHash computation and table grow/shrink code, we use a
1.434 + * single entry point for lookup, add, and remove operations. The operation
1.435 + * codes are declared here, along with codes returned by PLDHashEnumerator
1.436 + * functions, which control PL_DHashTableEnumerate's behavior.
1.437 + */
1.438 +typedef enum PLDHashOperator {
1.439 + PL_DHASH_LOOKUP = 0, /* lookup entry */
1.440 + PL_DHASH_ADD = 1, /* add entry */
1.441 + PL_DHASH_REMOVE = 2, /* remove entry, or enumerator says remove */
1.442 + PL_DHASH_NEXT = 0, /* enumerator says continue */
1.443 + PL_DHASH_STOP = 1 /* enumerator says stop */
1.444 +} PLDHashOperator;
1.445 +
1.446 +/*
1.447 + * To lookup a key in table, call:
1.448 + *
1.449 + * entry = PL_DHashTableOperate(table, key, PL_DHASH_LOOKUP);
1.450 + *
1.451 + * If PL_DHASH_ENTRY_IS_BUSY(entry) is true, key was found and it identifies
1.452 + * entry. If PL_DHASH_ENTRY_IS_FREE(entry) is true, key was not found.
1.453 + *
1.454 + * To add an entry identified by key to table, call:
1.455 + *
1.456 + * entry = PL_DHashTableOperate(table, key, PL_DHASH_ADD);
1.457 + *
1.458 + * If entry is null upon return, then either the table is severely overloaded,
1.459 + * and memory can't be allocated for entry storage via table->ops->allocTable;
1.460 + * Or if table->ops->initEntry is non-null, the table->ops->initEntry op may
1.461 + * have returned false.
1.462 + *
1.463 + * Otherwise, entry->keyHash has been set so that PL_DHASH_ENTRY_IS_BUSY(entry)
1.464 + * is true, and it is up to the caller to initialize the key and value parts
1.465 + * of the entry sub-type, if they have not been set already (i.e. if entry was
1.466 + * not already in the table, and if the optional initEntry hook was not used).
1.467 + *
1.468 + * To remove an entry identified by key from table, call:
1.469 + *
1.470 + * (void) PL_DHashTableOperate(table, key, PL_DHASH_REMOVE);
1.471 + *
1.472 + * If key's entry is found, it is cleared (via table->ops->clearEntry) and
1.473 + * the entry is marked so that PL_DHASH_ENTRY_IS_FREE(entry). This operation
1.474 + * returns null unconditionally; you should ignore its return value.
1.475 + */
1.476 +NS_COM_GLUE PLDHashEntryHdr * PL_DHASH_FASTCALL
1.477 +PL_DHashTableOperate(PLDHashTable *table, const void *key, PLDHashOperator op);
1.478 +
1.479 +/*
1.480 + * Remove an entry already accessed via LOOKUP or ADD.
1.481 + *
1.482 + * NB: this is a "raw" or low-level routine, intended to be used only where
1.483 + * the inefficiency of a full PL_DHashTableOperate (which rehashes in order
1.484 + * to find the entry given its key) is not tolerable. This function does not
1.485 + * shrink the table if it is underloaded. It does not update stats #ifdef
1.486 + * PL_DHASHMETER, either.
1.487 + */
1.488 +NS_COM_GLUE void
1.489 +PL_DHashTableRawRemove(PLDHashTable *table, PLDHashEntryHdr *entry);
1.490 +
1.491 +/*
1.492 + * Enumerate entries in table using etor:
1.493 + *
1.494 + * count = PL_DHashTableEnumerate(table, etor, arg);
1.495 + *
1.496 + * PL_DHashTableEnumerate calls etor like so:
1.497 + *
1.498 + * op = etor(table, entry, number, arg);
1.499 + *
1.500 + * where number is a zero-based ordinal assigned to live entries according to
1.501 + * their order in table->entryStore.
1.502 + *
1.503 + * The return value, op, is treated as a set of flags. If op is PL_DHASH_NEXT,
1.504 + * then continue enumerating. If op contains PL_DHASH_REMOVE, then clear (via
1.505 + * table->ops->clearEntry) and free entry. Then we check whether op contains
1.506 + * PL_DHASH_STOP; if so, stop enumerating and return the number of live entries
1.507 + * that were enumerated so far. Return the total number of live entries when
1.508 + * enumeration completes normally.
1.509 + *
1.510 + * If etor calls PL_DHashTableOperate on table with op != PL_DHASH_LOOKUP, it
1.511 + * must return PL_DHASH_STOP; otherwise undefined behavior results.
1.512 + *
1.513 + * If any enumerator returns PL_DHASH_REMOVE, table->entryStore may be shrunk
1.514 + * or compressed after enumeration, but before PL_DHashTableEnumerate returns.
1.515 + * Such an enumerator therefore can't safely set aside entry pointers, but an
1.516 + * enumerator that never returns PL_DHASH_REMOVE can set pointers to entries
1.517 + * aside, e.g., to avoid copying live entries into an array of the entry type.
1.518 + * Copying entry pointers is cheaper, and safe so long as the caller of such a
1.519 + * "stable" Enumerate doesn't use the set-aside pointers after any call either
1.520 + * to PL_DHashTableOperate, or to an "unstable" form of Enumerate, which might
1.521 + * grow or shrink entryStore.
1.522 + *
1.523 + * If your enumerator wants to remove certain entries, but set aside pointers
1.524 + * to other entries that it retains, it can use PL_DHashTableRawRemove on the
1.525 + * entries to be removed, returning PL_DHASH_NEXT to skip them. Likewise, if
1.526 + * you want to remove entries, but for some reason you do not want entryStore
1.527 + * to be shrunk or compressed, you can call PL_DHashTableRawRemove safely on
1.528 + * the entry being enumerated, rather than returning PL_DHASH_REMOVE.
1.529 + */
1.530 +typedef PLDHashOperator
1.531 +(* PLDHashEnumerator)(PLDHashTable *table, PLDHashEntryHdr *hdr, uint32_t number,
1.532 + void *arg);
1.533 +
1.534 +NS_COM_GLUE uint32_t
1.535 +PL_DHashTableEnumerate(PLDHashTable *table, PLDHashEnumerator etor, void *arg);
1.536 +
1.537 +typedef size_t
1.538 +(* PLDHashSizeOfEntryExcludingThisFun)(PLDHashEntryHdr *hdr,
1.539 + mozilla::MallocSizeOf mallocSizeOf,
1.540 + void *arg);
1.541 +
1.542 +/**
1.543 + * Measure the size of the table's entry storage, and if
1.544 + * |sizeOfEntryExcludingThis| is non-nullptr, measure the size of things
1.545 + * pointed to by entries. Doesn't measure |ops| because it's often shared
1.546 + * between tables, nor |data| because it's opaque.
1.547 + */
1.548 +NS_COM_GLUE size_t
1.549 +PL_DHashTableSizeOfExcludingThis(const PLDHashTable *table,
1.550 + PLDHashSizeOfEntryExcludingThisFun sizeOfEntryExcludingThis,
1.551 + mozilla::MallocSizeOf mallocSizeOf,
1.552 + void *arg = nullptr);
1.553 +
1.554 +/**
1.555 + * Like PL_DHashTableSizeOfExcludingThis, but includes sizeof(*this).
1.556 + */
1.557 +NS_COM_GLUE size_t
1.558 +PL_DHashTableSizeOfIncludingThis(const PLDHashTable *table,
1.559 + PLDHashSizeOfEntryExcludingThisFun sizeOfEntryExcludingThis,
1.560 + mozilla::MallocSizeOf mallocSizeOf,
1.561 + void *arg = nullptr);
1.562 +
1.563 +#ifdef DEBUG
1.564 +/**
1.565 + * Mark a table as immutable for the remainder of its lifetime. This
1.566 + * changes the implementation from ASSERTing one set of invariants to
1.567 + * ASSERTing a different set.
1.568 + *
1.569 + * When a table is NOT marked as immutable, the table implementation
1.570 + * asserts that the table is not mutated from its own callbacks. It
1.571 + * assumes the caller protects the table from being accessed on multiple
1.572 + * threads simultaneously.
1.573 + *
1.574 + * When the table is marked as immutable, the re-entry assertions will
1.575 + * no longer trigger erroneously due to multi-threaded access. Instead,
1.576 + * mutations will cause assertions.
1.577 + */
1.578 +NS_COM_GLUE void
1.579 +PL_DHashMarkTableImmutable(PLDHashTable *table);
1.580 +#endif
1.581 +
1.582 +#ifdef PL_DHASHMETER
1.583 +#include <stdio.h>
1.584 +
1.585 +NS_COM_GLUE void
1.586 +PL_DHashTableDumpMeter(PLDHashTable *table, PLDHashEnumerator dump, FILE *fp);
1.587 +#endif
1.588 +
1.589 +#endif /* pldhash_h___ */
