Add m-esr52 at 52.6.0

1 files changed, 1013 insertions, 0 deletions

diff --git a/modules/libpref/prefapi.cpp b/modules/libpref/prefapi.cpp
new file mode 100644
index 000000000..046a69419
--- /dev/null
+++ b/modules/libpref/prefapi.cpp
@@ -0,0 +1,1013 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+
+#include "prefapi.h"
+#include "prefapi_private_data.h"
+#include "prefread.h"
+#include "MainThreadUtils.h"
+#include "nsReadableUtils.h"
+#include "nsCRT.h"
+
+#define PL_ARENA_CONST_ALIGN_MASK 3
+#include "plarena.h"
+
+#ifdef _WIN32
+  #include "windows.h"
+#endif /* _WIN32 */
+
+#include "plstr.h"
+#include "PLDHashTable.h"
+#include "plbase64.h"
+#include "mozilla/Logging.h"
+#include "prprf.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/dom/PContent.h"
+#include "nsQuickSort.h"
+#include "nsString.h"
+#include "nsPrintfCString.h"
+#include "prlink.h"
+
+using namespace mozilla;
+
+static void
+clearPrefEntry(PLDHashTable *table, PLDHashEntryHdr *entry)
+{
+    PrefHashEntry *pref = static_cast<PrefHashEntry *>(entry);
+    if (pref->prefFlags.IsTypeString())
+    {
+        if (pref->defaultPref.stringVal)
+            PL_strfree(pref->defaultPref.stringVal);
+        if (pref->userPref.stringVal)
+            PL_strfree(pref->userPref.stringVal);
+    }
+    // don't need to free this as it's allocated in memory owned by
+    // gPrefNameArena
+    pref->key = nullptr;
+    memset(entry, 0, table->EntrySize());
+}
+
+static bool
+matchPrefEntry(const PLDHashEntryHdr* entry, const void* key)
+{
+    const PrefHashEntry *prefEntry =
+        static_cast<const PrefHashEntry*>(entry);
+
+    if (prefEntry->key == key) return true;
+
+    if (!prefEntry->key || !key) return false;
+
+    const char *otherKey = reinterpret_cast<const char*>(key);
+    return (strcmp(prefEntry->key, otherKey) == 0);
+}
+
+PLDHashTable*       gHashTable;
+static PLArenaPool  gPrefNameArena;
+
+static struct CallbackNode* gCallbacks = nullptr;
+static bool         gIsAnyPrefLocked = false;
+// These are only used during the call to pref_DoCallback
+static bool         gCallbacksInProgress = false;
+static bool         gShouldCleanupDeadNodes = false;
+
+
+static PLDHashTableOps     pref_HashTableOps = {
+    PLDHashTable::HashStringKey,
+    matchPrefEntry,
+    PLDHashTable::MoveEntryStub,
+    clearPrefEntry,
+    nullptr,
+};
+
+// PR_ALIGN_OF_WORD is only defined on some platforms.  ALIGN_OF_WORD has
+// already been defined to PR_ALIGN_OF_WORD everywhere
+#ifndef PR_ALIGN_OF_WORD
+#define PR_ALIGN_OF_WORD PR_ALIGN_OF_POINTER
+#endif
+
+// making PrefName arena 8k for nice allocation
+#define PREFNAME_ARENA_SIZE 8192
+
+#define WORD_ALIGN_MASK (PR_ALIGN_OF_WORD - 1)
+
+// sanity checking
+#if (PR_ALIGN_OF_WORD & WORD_ALIGN_MASK) != 0
+#error "PR_ALIGN_OF_WORD must be a power of 2!"
+#endif
+
+// equivalent to strdup() - does no error checking,
+// we're assuming we're only called with a valid pointer
+static char *ArenaStrDup(const char* str, PLArenaPool* aArena)
+{
+    void* mem;
+    uint32_t len = strlen(str);
+    PL_ARENA_ALLOCATE(mem, aArena, len+1);
+    if (mem)
+        memcpy(mem, str, len+1);
+    return static_cast<char*>(mem);
+}
+
+static PrefsDirtyFunc gDirtyCallback = nullptr;
+
+inline void MakeDirtyCallback()
+{
+    // Right now the callback function is always set, so we don't need
+    // to complicate the code to cover the scenario where we set the callback
+    // after we've already tried to make it dirty.  If this assert triggers
+    // we will add that code.
+    MOZ_ASSERT(gDirtyCallback);
+    if (gDirtyCallback) {
+        gDirtyCallback();
+    }
+}
+
+void PREF_SetDirtyCallback(PrefsDirtyFunc aFunc)
+{
+    gDirtyCallback = aFunc;
+}
+
+/*---------------------------------------------------------------------------*/
+
+static bool pref_ValueChanged(PrefValue oldValue, PrefValue newValue, PrefType type);
+/* -- Privates */
+struct CallbackNode {
+    char*                   domain;
+    // If someone attempts to remove the node from the callback list while
+    // pref_DoCallback is running, |func| is set to nullptr. Such nodes will
+    // be removed at the end of pref_DoCallback.
+    PrefChangedFunc         func;
+    void*                   data;
+    struct CallbackNode*    next;
+};
+
+/* -- Prototypes */
+static nsresult pref_DoCallback(const char* changed_pref);
+
+enum {
+    kPrefSetDefault = 1,
+    kPrefForceSet = 2,
+    kPrefStickyDefault = 4,
+};
+static nsresult pref_HashPref(const char *key, PrefValue value, PrefType type, uint32_t flags);
+
+#define PREF_HASHTABLE_INITIAL_LENGTH   1024
+
+void PREF_Init()
+{
+    if (!gHashTable) {
+        gHashTable = new PLDHashTable(&pref_HashTableOps,
+                                      sizeof(PrefHashEntry),
+                                      PREF_HASHTABLE_INITIAL_LENGTH);
+
+        PL_INIT_ARENA_POOL(&gPrefNameArena, "PrefNameArena",
+                           PREFNAME_ARENA_SIZE);
+    }
+}
+
+/* Frees the callback list. */
+void PREF_Cleanup()
+{
+    NS_ASSERTION(!gCallbacksInProgress,
+        "PREF_Cleanup was called while gCallbacksInProgress is true!");
+    struct CallbackNode* node = gCallbacks;
+    struct CallbackNode* next_node;
+
+    while (node)
+    {
+        next_node = node->next;
+        PL_strfree(node->domain);
+        free(node);
+        node = next_node;
+    }
+    gCallbacks = nullptr;
+
+    PREF_CleanupPrefs();
+}
+
+/* Frees up all the objects except the callback list. */
+void PREF_CleanupPrefs()
+{
+    if (gHashTable) {
+        delete gHashTable;
+        gHashTable = nullptr;
+        PL_FinishArenaPool(&gPrefNameArena);
+    }
+}
+
+// note that this appends to aResult, and does not assign!
+static void str_escape(const char * original, nsAFlatCString& aResult)
+{
+    /* JavaScript does not allow quotes, slashes, or line terminators inside
+     * strings so we must escape them. ECMAScript defines four line
+     * terminators, but we're only worrying about \r and \n here.  We currently
+     * feed our pref script to the JS interpreter as Latin-1 so  we won't
+     * encounter \u2028 (line separator) or \u2029 (paragraph separator).
+     *
+     * WARNING: There are hints that we may be moving to storing prefs
+     * as utf8. If we ever feed them to the JS compiler as UTF8 then
+     * we'll have to worry about the multibyte sequences that would be
+     * interpreted as \u2028 and \u2029
+     */
+    const char *p;
+
+    if (original == nullptr)
+        return;
+
+    /* Paranoid worst case all slashes will free quickly */
+    for  (p=original; *p; ++p)
+    {
+        switch (*p)
+        {
+            case '\n':
+                aResult.AppendLiteral("\\n");
+                break;
+
+            case '\r':
+                aResult.AppendLiteral("\\r");
+                break;
+
+            case '\\':
+                aResult.AppendLiteral("\\\\");
+                break;
+
+            case '\"':
+                aResult.AppendLiteral("\\\"");
+                break;
+
+            default:
+                aResult.Append(*p);
+                break;
+        }
+    }
+}
+
+/*
+** External calls
+*/
+nsresult
+PREF_SetCharPref(const char *pref_name, const char *value, bool set_default)
+{
+    if ((uint32_t)strlen(value) > MAX_PREF_LENGTH) {
+        return NS_ERROR_ILLEGAL_VALUE;
+    }
+
+    PrefValue pref;
+    pref.stringVal = (char*)value;
+
+    return pref_HashPref(pref_name, pref, PrefType::String, set_default ? kPrefSetDefault : 0);
+}
+
+nsresult
+PREF_SetIntPref(const char *pref_name, int32_t value, bool set_default)
+{
+    PrefValue pref;
+    pref.intVal = value;
+
+    return pref_HashPref(pref_name, pref, PrefType::Int, set_default ? kPrefSetDefault : 0);
+}
+
+nsresult
+PREF_SetBoolPref(const char *pref_name, bool value, bool set_default)
+{
+    PrefValue pref;
+    pref.boolVal = value;
+
+    return pref_HashPref(pref_name, pref, PrefType::Bool, set_default ? kPrefSetDefault : 0);
+}
+
+enum WhichValue { DEFAULT_VALUE, USER_VALUE };
+static nsresult
+SetPrefValue(const char* aPrefName, const dom::PrefValue& aValue,
+             WhichValue aWhich)
+{
+    bool setDefault = (aWhich == DEFAULT_VALUE);
+    switch (aValue.type()) {
+    case dom::PrefValue::TnsCString:
+        return PREF_SetCharPref(aPrefName, aValue.get_nsCString().get(),
+                                setDefault);
+    case dom::PrefValue::Tint32_t:
+        return PREF_SetIntPref(aPrefName, aValue.get_int32_t(),
+                               setDefault);
+    case dom::PrefValue::Tbool:
+        return PREF_SetBoolPref(aPrefName, aValue.get_bool(),
+                                setDefault);
+    default:
+        MOZ_CRASH();
+    }
+}
+
+nsresult
+pref_SetPref(const dom::PrefSetting& aPref)
+{
+    const char* prefName = aPref.name().get();
+    const dom::MaybePrefValue& defaultValue = aPref.defaultValue();
+    const dom::MaybePrefValue& userValue = aPref.userValue();
+
+    nsresult rv;
+    if (defaultValue.type() == dom::MaybePrefValue::TPrefValue) {
+        rv = SetPrefValue(prefName, defaultValue.get_PrefValue(), DEFAULT_VALUE);
+        if (NS_FAILED(rv)) {
+            return rv;
+        }
+    }
+
+    if (userValue.type() == dom::MaybePrefValue::TPrefValue) {
+        rv = SetPrefValue(prefName, userValue.get_PrefValue(), USER_VALUE);
+    } else {
+        rv = PREF_ClearUserPref(prefName);
+    }
+
+    // NB: we should never try to clear a default value, that doesn't
+    // make sense
+
+    return rv;
+}
+
+UniquePtr<char*[]>
+pref_savePrefs(PLDHashTable* aTable, uint32_t* aPrefCount)
+{
+    // This function allocates the entries in the savedPrefs array it returns.
+    // It is the callers responsibility to go through the array and free
+    // all of them.  The aPrefCount entries will be non-null.  Any end padding
+    // is an implementation detail and may change.
+    MOZ_ASSERT(aPrefCount);
+    auto savedPrefs = MakeUnique<char*[]>(aTable->EntryCount());
+
+    // This is not necessary, but leaving it in for now
+    memset(savedPrefs.get(), 0, aTable->EntryCount() * sizeof(char*));
+
+    int32_t j = 0;
+    for (auto iter = aTable->Iter(); !iter.Done(); iter.Next()) {
+        auto pref = static_cast<PrefHashEntry*>(iter.Get());
+
+        nsAutoCString prefValue;
+        nsAutoCString prefPrefix;
+        prefPrefix.AssignLiteral("user_pref(\"");
+
+        // where we're getting our pref from
+        PrefValue* sourcePref;
+
+        if (pref->prefFlags.HasUserValue() &&
+            (pref_ValueChanged(pref->defaultPref,
+                               pref->userPref,
+                               pref->prefFlags.GetPrefType()) ||
+             !(pref->prefFlags.HasDefault()) ||
+             pref->prefFlags.HasStickyDefault())) {
+            sourcePref = &pref->userPref;
+        } else {
+            // do not save default prefs that haven't changed
+            continue;
+        }
+
+        // strings are in quotes!
+        if (pref->prefFlags.IsTypeString()) {
+            prefValue = '\"';
+            str_escape(sourcePref->stringVal, prefValue);
+            prefValue += '\"';
+
+        } else if (pref->prefFlags.IsTypeInt()) {
+            prefValue.AppendInt(sourcePref->intVal);
+
+        } else if (pref->prefFlags.IsTypeBool()) {
+            prefValue = (sourcePref->boolVal) ? "true" : "false";
+        }
+
+        nsAutoCString prefName;
+        str_escape(pref->key, prefName);
+
+        savedPrefs[j++] = ToNewCString(prefPrefix +
+                                       prefName +
+                                       NS_LITERAL_CSTRING("\", ") +
+                                       prefValue +
+                                       NS_LITERAL_CSTRING(");"));
+    }
+    *aPrefCount = j;
+
+    return savedPrefs;
+}
+
+bool
+pref_EntryHasAdvisablySizedValues(PrefHashEntry* aHashEntry)
+{
+    if (aHashEntry->prefFlags.GetPrefType() != PrefType::String) {
+        return true;
+    }
+
+    char* stringVal;
+    if (aHashEntry->prefFlags.HasDefault()) {
+        stringVal = aHashEntry->defaultPref.stringVal;
+        if (strlen(stringVal) > MAX_ADVISABLE_PREF_LENGTH) {
+            return false;
+        }
+    }
+
+    if (aHashEntry->prefFlags.HasUserValue()) {
+        stringVal = aHashEntry->userPref.stringVal;
+        if (strlen(stringVal) > MAX_ADVISABLE_PREF_LENGTH) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static void
+GetPrefValueFromEntry(PrefHashEntry *aHashEntry, dom::PrefSetting* aPref,
+                      WhichValue aWhich)
+{
+    PrefValue* value;
+    dom::PrefValue* settingValue;
+    if (aWhich == USER_VALUE) {
+        value = &aHashEntry->userPref;
+        aPref->userValue() = dom::PrefValue();
+        settingValue = &aPref->userValue().get_PrefValue();
+    } else {
+        value = &aHashEntry->defaultPref;
+        aPref->defaultValue() = dom::PrefValue();
+        settingValue = &aPref->defaultValue().get_PrefValue();
+    }
+
+    switch (aHashEntry->prefFlags.GetPrefType()) {
+      case PrefType::String:
+        *settingValue = nsDependentCString(value->stringVal);
+        return;
+      case PrefType::Int:
+        *settingValue = value->intVal;
+        return;
+      case PrefType::Bool:
+        *settingValue = !!value->boolVal;
+        return;
+    default:
+        MOZ_CRASH();
+    }
+}
+
+void
+pref_GetPrefFromEntry(PrefHashEntry *aHashEntry, dom::PrefSetting* aPref)
+{
+    aPref->name() = aHashEntry->key;
+    if (aHashEntry->prefFlags.HasDefault()) {
+        GetPrefValueFromEntry(aHashEntry, aPref, DEFAULT_VALUE);
+    } else {
+        aPref->defaultValue() = null_t();
+    }
+    if (aHashEntry->prefFlags.HasUserValue()) {
+        GetPrefValueFromEntry(aHashEntry, aPref, USER_VALUE);
+    } else {
+        aPref->userValue() = null_t();
+    }
+
+    MOZ_ASSERT(aPref->defaultValue().type() == dom::MaybePrefValue::Tnull_t ||
+               aPref->userValue().type() == dom::MaybePrefValue::Tnull_t ||
+               (aPref->defaultValue().get_PrefValue().type() ==
+                aPref->userValue().get_PrefValue().type()));
+}
+
+
+int
+pref_CompareStrings(const void *v1, const void *v2, void *unused)
+{
+    char *s1 = *(char**) v1;
+    char *s2 = *(char**) v2;
+
+    if (!s1)
+    {
+        if (!s2)
+            return 0;
+        else
+            return -1;
+    }
+    else if (!s2)
+        return 1;
+    else
+        return strcmp(s1, s2);
+}
+
+bool PREF_HasUserPref(const char *pref_name)
+{
+    if (!gHashTable)
+        return false;
+
+    PrefHashEntry *pref = pref_HashTableLookup(pref_name);
+    return pref && pref->prefFlags.HasUserValue();
+}
+
+nsresult
+PREF_CopyCharPref(const char *pref_name, char ** return_buffer, bool get_default)
+{
+    if (!gHashTable)
+        return NS_ERROR_NOT_INITIALIZED;
+
+    nsresult rv = NS_ERROR_UNEXPECTED;
+    char* stringVal;
+    PrefHashEntry* pref = pref_HashTableLookup(pref_name);
+
+    if (pref && (pref->prefFlags.IsTypeString())) {
+        if (get_default || pref->prefFlags.IsLocked() || !pref->prefFlags.HasUserValue()) {
+            stringVal = pref->defaultPref.stringVal;
+        } else {
+            stringVal = pref->userPref.stringVal;
+        }
+
+        if (stringVal) {
+            *return_buffer = NS_strdup(stringVal);
+            rv = NS_OK;
+        }
+    }
+    return rv;
+}
+
+nsresult PREF_GetIntPref(const char *pref_name,int32_t * return_int, bool get_default)
+{
+    if (!gHashTable)
+        return NS_ERROR_NOT_INITIALIZED;
+
+    nsresult rv = NS_ERROR_UNEXPECTED;
+    PrefHashEntry* pref = pref_HashTableLookup(pref_name);
+    if (pref && (pref->prefFlags.IsTypeInt())) {
+        if (get_default || pref->prefFlags.IsLocked() || !pref->prefFlags.HasUserValue()) {
+            int32_t tempInt = pref->defaultPref.intVal;
+            /* check to see if we even had a default */
+            if (!pref->prefFlags.HasDefault()) {
+                return NS_ERROR_UNEXPECTED;
+            }
+            *return_int = tempInt;
+        } else {
+            *return_int = pref->userPref.intVal;
+        }
+        rv = NS_OK;
+    }
+    return rv;
+}
+
+nsresult PREF_GetBoolPref(const char *pref_name, bool * return_value, bool get_default)
+{
+    if (!gHashTable)
+        return NS_ERROR_NOT_INITIALIZED;
+
+    nsresult rv = NS_ERROR_UNEXPECTED;
+    PrefHashEntry* pref = pref_HashTableLookup(pref_name);
+    //NS_ASSERTION(pref, pref_name);
+    if (pref && (pref->prefFlags.IsTypeBool())) {
+        if (get_default || pref->prefFlags.IsLocked() || !pref->prefFlags.HasUserValue()) {
+            bool tempBool = pref->defaultPref.boolVal;
+            /* check to see if we even had a default */
+            if (pref->prefFlags.HasDefault()) {
+                *return_value = tempBool;
+                rv = NS_OK;
+            }
+        } else {
+            *return_value = pref->userPref.boolVal;
+            rv = NS_OK;
+        }
+    }
+    return rv;
+}
+
+nsresult
+PREF_DeleteBranch(const char *branch_name)
+{
+#ifndef MOZ_B2G
+    MOZ_ASSERT(NS_IsMainThread());
+#endif
+
+    int len = (int)strlen(branch_name);
+
+    if (!gHashTable)
+        return NS_ERROR_NOT_INITIALIZED;
+
+    /* The following check insures that if the branch name already has a "."
+     * at the end, we don't end up with a "..". This fixes an incompatibility
+     * between nsIPref, which needs the period added, and nsIPrefBranch which
+     * does not. When nsIPref goes away this function should be fixed to
+     * never add the period at all.
+     */
+    nsAutoCString branch_dot(branch_name);
+    if ((len > 1) && branch_name[len - 1] != '.')
+        branch_dot += '.';
+
+    /* Delete a branch. Used for deleting mime types */
+    const char *to_delete = branch_dot.get();
+    MOZ_ASSERT(to_delete);
+    len = strlen(to_delete);
+    for (auto iter = gHashTable->Iter(); !iter.Done(); iter.Next()) {
+        auto entry = static_cast<PrefHashEntry*>(iter.Get());
+
+        /* note if we're deleting "ldap" then we want to delete "ldap.xxx"
+            and "ldap" (if such a leaf node exists) but not "ldap_1.xxx" */
+        if (PL_strncmp(entry->key, to_delete, (uint32_t) len) == 0 ||
+            (len-1 == (int)strlen(entry->key) &&
+             PL_strncmp(entry->key, to_delete, (uint32_t)(len-1)) == 0)) {
+            iter.Remove();
+        }
+    }
+
+    MakeDirtyCallback();
+    return NS_OK;
+}
+
+
+nsresult
+PREF_ClearUserPref(const char *pref_name)
+{
+    if (!gHashTable)
+        return NS_ERROR_NOT_INITIALIZED;
+
+    PrefHashEntry* pref = pref_HashTableLookup(pref_name);
+    if (pref && pref->prefFlags.HasUserValue()) {
+        pref->prefFlags.SetHasUserValue(false);
+
+        if (!pref->prefFlags.HasDefault()) {
+            gHashTable->RemoveEntry(pref);
+        }
+
+        pref_DoCallback(pref_name);
+        MakeDirtyCallback();
+    }
+    return NS_OK;
+}
+
+nsresult
+PREF_ClearAllUserPrefs()
+{
+#ifndef MOZ_B2G
+    MOZ_ASSERT(NS_IsMainThread());
+#endif
+
+    if (!gHashTable)
+        return NS_ERROR_NOT_INITIALIZED;
+
+    std::vector<std::string> prefStrings;
+    for (auto iter = gHashTable->Iter(); !iter.Done(); iter.Next()) {
+        auto pref = static_cast<PrefHashEntry*>(iter.Get());
+
+        if (pref->prefFlags.HasUserValue()) {
+            prefStrings.push_back(std::string(pref->key));
+
+            pref->prefFlags.SetHasUserValue(false);
+            if (!pref->prefFlags.HasDefault()) {
+                iter.Remove();
+            }
+        }
+    }
+
+    for (std::string& prefString : prefStrings) {
+        pref_DoCallback(prefString.c_str());
+    }
+
+    MakeDirtyCallback();
+    return NS_OK;
+}
+
+nsresult PREF_LockPref(const char *key, bool lockit)
+{
+    if (!gHashTable)
+        return NS_ERROR_NOT_INITIALIZED;
+
+    PrefHashEntry* pref = pref_HashTableLookup(key);
+    if (!pref)
+        return NS_ERROR_UNEXPECTED;
+
+    if (lockit) {
+        if (!pref->prefFlags.IsLocked()) {
+            pref->prefFlags.SetLocked(true);
+            gIsAnyPrefLocked = true;
+            pref_DoCallback(key);
+        }
+    } else {
+        if (pref->prefFlags.IsLocked()) {
+            pref->prefFlags.SetLocked(false);
+            pref_DoCallback(key);
+        }
+    }
+    return NS_OK;
+}
+
+/*
+ * Hash table functions
+ */
+static bool pref_ValueChanged(PrefValue oldValue, PrefValue newValue, PrefType type)
+{
+    bool changed = true;
+    switch(type) {
+      case PrefType::String:
+        if (oldValue.stringVal && newValue.stringVal) {
+            changed = (strcmp(oldValue.stringVal, newValue.stringVal) != 0);
+        }
+        break;
+      case PrefType::Int:
+        changed = oldValue.intVal != newValue.intVal;
+        break;
+      case PrefType::Bool:
+        changed = oldValue.boolVal != newValue.boolVal;
+        break;
+      case PrefType::Invalid:
+      default:
+        changed = false;
+        break;
+    }
+    return changed;
+}
+
+/*
+ * Overwrite the type and value of an existing preference. Caller must
+ * ensure that they are not changing the type of a preference that has
+ * a default value.
+ */
+static PrefTypeFlags pref_SetValue(PrefValue* existingValue, PrefTypeFlags flags,
+                                   PrefValue newValue, PrefType newType)
+{
+    if (flags.IsTypeString() && existingValue->stringVal) {
+        PL_strfree(existingValue->stringVal);
+    }
+    flags.SetPrefType(newType);
+    if (flags.IsTypeString()) {
+        MOZ_ASSERT(newValue.stringVal);
+        existingValue->stringVal = newValue.stringVal ? PL_strdup(newValue.stringVal) : nullptr;
+    }
+    else {
+        *existingValue = newValue;
+    }
+    return flags;
+}
+
+PrefHashEntry* pref_HashTableLookup(const char *key)
+{
+#ifndef MOZ_B2G
+    MOZ_ASSERT(NS_IsMainThread());
+#endif
+
+    return static_cast<PrefHashEntry*>(gHashTable->Search(key));
+}
+
+nsresult pref_HashPref(const char *key, PrefValue value, PrefType type, uint32_t flags)
+{
+#ifndef MOZ_B2G
+    MOZ_ASSERT(NS_IsMainThread());
+#endif
+
+    if (!gHashTable)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    auto pref = static_cast<PrefHashEntry*>(gHashTable->Add(key, fallible));
+    if (!pref)
+        return NS_ERROR_OUT_OF_MEMORY;
+
+    // new entry, better initialize
+    if (!pref->key) {
+
+        // initialize the pref entry
+        pref->prefFlags.Reset().SetPrefType(type);
+        pref->key = ArenaStrDup(key, &gPrefNameArena);
+        memset(&pref->defaultPref, 0, sizeof(pref->defaultPref));
+        memset(&pref->userPref, 0, sizeof(pref->userPref));
+    } else if (pref->prefFlags.HasDefault() && !pref->prefFlags.IsPrefType(type)) {
+        NS_WARNING(nsPrintfCString("Trying to overwrite value of default pref %s with the wrong type!", key).get());
+        return NS_ERROR_UNEXPECTED;
+    }
+
+    bool valueChanged = false;
+    if (flags & kPrefSetDefault) {
+        if (!pref->prefFlags.IsLocked()) {
+            /* ?? change of semantics? */
+            if (pref_ValueChanged(pref->defaultPref, value, type) ||
+                !pref->prefFlags.HasDefault()) {
+                pref->prefFlags = pref_SetValue(&pref->defaultPref, pref->prefFlags, value, type).SetHasDefault(true);
+                if (flags & kPrefStickyDefault) {
+                    pref->prefFlags.SetHasStickyDefault(true);
+                }
+                if (!pref->prefFlags.HasUserValue()) {
+                    valueChanged = true;
+                }
+            }
+            // What if we change the default to be the same as the user value?
+            // Should we clear the user value?
+        }
+    } else {
+        /* If new value is same as the default value and it's not a "sticky"
+           pref, then un-set the user value.
+           Otherwise, set the user value only if it has changed */
+        if ((pref->prefFlags.HasDefault()) &&
+            !(pref->prefFlags.HasStickyDefault()) &&
+            !pref_ValueChanged(pref->defaultPref, value, type) &&
+            !(flags & kPrefForceSet)) {
+            if (pref->prefFlags.HasUserValue()) {
+                /* XXX should we free a user-set string value if there is one? */
+                pref->prefFlags.SetHasUserValue(false);
+                if (!pref->prefFlags.IsLocked()) {
+                    MakeDirtyCallback();
+                    valueChanged = true;
+                }
+            }
+        } else if (!pref->prefFlags.HasUserValue() ||
+                 !pref->prefFlags.IsPrefType(type) ||
+                 pref_ValueChanged(pref->userPref, value, type) ) {
+            pref->prefFlags = pref_SetValue(&pref->userPref, pref->prefFlags, value, type).SetHasUserValue(true);
+            if (!pref->prefFlags.IsLocked()) {
+                MakeDirtyCallback();
+                valueChanged = true;
+            }
+        }
+    }
+
+    if (valueChanged) {
+        return pref_DoCallback(key);
+    }
+    return NS_OK;
+}
+
+size_t
+pref_SizeOfPrivateData(MallocSizeOf aMallocSizeOf)
+{
+    size_t n = PL_SizeOfArenaPoolExcludingPool(&gPrefNameArena, aMallocSizeOf);
+    for (struct CallbackNode* node = gCallbacks; node; node = node->next) {
+        n += aMallocSizeOf(node);
+        n += aMallocSizeOf(node->domain);
+    }
+    return n;
+}
+
+PrefType
+PREF_GetPrefType(const char *pref_name)
+{
+    if (gHashTable) {
+        PrefHashEntry* pref = pref_HashTableLookup(pref_name);
+        if (pref) {
+            return pref->prefFlags.GetPrefType();
+        }
+    }
+    return PrefType::Invalid;
+}
+
+/* -- */
+
+bool
+PREF_PrefIsLocked(const char *pref_name)
+{
+    bool result = false;
+    if (gIsAnyPrefLocked && gHashTable) {
+        PrefHashEntry* pref = pref_HashTableLookup(pref_name);
+        if (pref && pref->prefFlags.IsLocked()) {
+            result = true;
+        }
+    }
+
+    return result;
+}
+
+/* Adds a node to the beginning of the callback list. */
+void
+PREF_RegisterCallback(const char *pref_node,
+                       PrefChangedFunc callback,
+                       void * instance_data)
+{
+    NS_PRECONDITION(pref_node, "pref_node must not be nullptr");
+    NS_PRECONDITION(callback, "callback must not be nullptr");
+
+    struct CallbackNode* node = (struct CallbackNode*) malloc(sizeof(struct CallbackNode));
+    if (node)
+    {
+        node->domain = PL_strdup(pref_node);
+        node->func = callback;
+        node->data = instance_data;
+        node->next = gCallbacks;
+        gCallbacks = node;
+    }
+    return;
+}
+
+/* Removes |node| from gCallbacks list.
+   Returns the node after the deleted one. */
+struct CallbackNode*
+pref_RemoveCallbackNode(struct CallbackNode* node,
+                        struct CallbackNode* prev_node)
+{
+    NS_PRECONDITION(!prev_node || prev_node->next == node, "invalid params");
+    NS_PRECONDITION(prev_node || gCallbacks == node, "invalid params");
+
+    NS_ASSERTION(!gCallbacksInProgress,
+        "modifying the callback list while gCallbacksInProgress is true");
+
+    struct CallbackNode* next_node = node->next;
+    if (prev_node)
+        prev_node->next = next_node;
+    else
+        gCallbacks = next_node;
+    PL_strfree(node->domain);
+    free(node);
+    return next_node;
+}
+
+/* Deletes a node from the callback list or marks it for deletion. */
+nsresult
+PREF_UnregisterCallback(const char *pref_node,
+                         PrefChangedFunc callback,
+                         void * instance_data)
+{
+    nsresult rv = NS_ERROR_FAILURE;
+    struct CallbackNode* node = gCallbacks;
+    struct CallbackNode* prev_node = nullptr;
+
+    while (node != nullptr)
+    {
+        if ( node->func == callback &&
+             node->data == instance_data &&
+             strcmp(node->domain, pref_node) == 0)
+        {
+            if (gCallbacksInProgress)
+            {
+                // postpone the node removal until after
+                // gCallbacks enumeration is finished.
+                node->func = nullptr;
+                gShouldCleanupDeadNodes = true;
+                prev_node = node;
+                node = node->next;
+            }
+            else
+            {
+                node = pref_RemoveCallbackNode(node, prev_node);
+            }
+            rv = NS_OK;
+        }
+        else
+        {
+            prev_node = node;
+            node = node->next;
+        }
+    }
+    return rv;
+}
+
+static nsresult pref_DoCallback(const char* changed_pref)
+{
+    nsresult rv = NS_OK;
+    struct CallbackNode* node;
+
+    bool reentered = gCallbacksInProgress;
+    gCallbacksInProgress = true;
+    // Nodes must not be deleted while gCallbacksInProgress is true.
+    // Nodes that need to be deleted are marked for deletion by nulling
+    // out the |func| pointer. We release them at the end of this function
+    // if we haven't reentered.
+
+    for (node = gCallbacks; node != nullptr; node = node->next)
+    {
+        if ( node->func &&
+             PL_strncmp(changed_pref,
+                        node->domain,
+                        strlen(node->domain)) == 0 )
+        {
+            (*node->func) (changed_pref, node->data);
+        }
+    }
+
+    gCallbacksInProgress = reentered;
+
+    if (gShouldCleanupDeadNodes && !gCallbacksInProgress)
+    {
+        struct CallbackNode* prev_node = nullptr;
+        node = gCallbacks;
+
+        while (node != nullptr)
+        {
+            if (!node->func)
+            {
+                node = pref_RemoveCallbackNode(node, prev_node);
+            }
+            else
+            {
+                prev_node = node;
+                node = node->next;
+            }
+        }
+        gShouldCleanupDeadNodes = false;
+    }
+
+    return rv;
+}
+
+void PREF_ReaderCallback(void       *closure,
+                         const char *pref,
+                         PrefValue   value,
+                         PrefType    type,
+                         bool        isDefault,
+                         bool        isStickyDefault)
+
+{
+    uint32_t flags = 0;
+    if (isDefault) {
+        flags |= kPrefSetDefault;
+        if (isStickyDefault) {
+            flags |= kPrefStickyDefault;
+        }
+    } else {
+        flags |= kPrefForceSet;
+    }
+    pref_HashPref(pref, value, type, flags);
+}