1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/dom/bindings/DOMString.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,186 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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 mozilla_dom_DOMString_h
1.10 +#define mozilla_dom_DOMString_h
1.11 +
1.12 +#include "nsStringGlue.h"
1.13 +#include "nsStringBuffer.h"
1.14 +#include "mozilla/Assertions.h"
1.15 +#include "mozilla/Attributes.h"
1.16 +#include "mozilla/Maybe.h"
1.17 +#include "nsDOMString.h"
1.18 +#include "nsIAtom.h"
1.19 +
1.20 +namespace mozilla {
1.21 +namespace dom {
1.22 +
1.23 +/**
1.24 + * A class for representing string return values. This can be either passed to
1.25 + * callees that have an nsString or nsAString out param or passed to a callee
1.26 + * that actually knows about this class and can work with it. Such a callee may
1.27 + * call SetStringBuffer or SetOwnedString or SetOwnedAtom on this object, but
1.28 + * only if it plans to keep holding a strong ref to the internal stringbuffer!
1.29 + *
1.30 + * The proper way to store a value in this class is to either to do nothing
1.31 + * (which leaves this as an empty string), to call SetStringBuffer with a
1.32 + * non-null stringbuffer, to call SetOwnedString, to call SetOwnedAtom, to call
1.33 + * SetNull(), or to call AsAString() and set the value in the resulting
1.34 + * nsString. These options are mutually exclusive! Don't do more than one of
1.35 + * them.
1.36 + *
1.37 + * The proper way to extract a value is to check IsNull(). If not null, then
1.38 + * check HasStringBuffer(). If that's true, check for a zero length, and if the
1.39 + * length is nonzero call StringBuffer(). If the length is zero this is the
1.40 + * empty string. If HasStringBuffer() returns false, call AsAString() and get
1.41 + * the value from that.
1.42 + */
1.43 +class MOZ_STACK_CLASS DOMString {
1.44 +public:
1.45 + DOMString()
1.46 + : mStringBuffer(nullptr)
1.47 + , mLength(0)
1.48 + , mIsNull(false)
1.49 + {}
1.50 + ~DOMString()
1.51 + {
1.52 + MOZ_ASSERT(mString.empty() || !mStringBuffer,
1.53 + "Shouldn't have both present!");
1.54 + }
1.55 +
1.56 + operator nsString&()
1.57 + {
1.58 + return AsAString();
1.59 + }
1.60 +
1.61 + nsString& AsAString()
1.62 + {
1.63 + MOZ_ASSERT(!mStringBuffer, "We already have a stringbuffer?");
1.64 + MOZ_ASSERT(!mIsNull, "We're already set as null");
1.65 + if (mString.empty()) {
1.66 + mString.construct();
1.67 + }
1.68 + return mString.ref();
1.69 + }
1.70 +
1.71 + bool HasStringBuffer() const
1.72 + {
1.73 + MOZ_ASSERT(mString.empty() || !mStringBuffer,
1.74 + "Shouldn't have both present!");
1.75 + MOZ_ASSERT(!mIsNull, "Caller should have checked IsNull() first");
1.76 + return mString.empty();
1.77 + }
1.78 +
1.79 + // Get the stringbuffer. This can only be called if HasStringBuffer()
1.80 + // returned true and StringBufferLength() is nonzero. If that's true, it will
1.81 + // never return null.
1.82 + nsStringBuffer* StringBuffer() const
1.83 + {
1.84 + MOZ_ASSERT(!mIsNull, "Caller should have checked IsNull() first");
1.85 + MOZ_ASSERT(HasStringBuffer(),
1.86 + "Don't ask for the stringbuffer if we don't have it");
1.87 + MOZ_ASSERT(StringBufferLength() != 0, "Why are you asking for this?");
1.88 + MOZ_ASSERT(mStringBuffer,
1.89 + "If our length is nonzero, we better have a stringbuffer.");
1.90 + return mStringBuffer;
1.91 + }
1.92 +
1.93 + // Get the length of the stringbuffer. Can only be called if
1.94 + // HasStringBuffer().
1.95 + uint32_t StringBufferLength() const
1.96 + {
1.97 + MOZ_ASSERT(HasStringBuffer(), "Don't call this if there is no stringbuffer");
1.98 + return mLength;
1.99 + }
1.100 +
1.101 + void SetStringBuffer(nsStringBuffer* aStringBuffer, uint32_t aLength)
1.102 + {
1.103 + MOZ_ASSERT(mString.empty(), "We already have a string?");
1.104 + MOZ_ASSERT(!mIsNull, "We're already set as null");
1.105 + MOZ_ASSERT(!mStringBuffer, "Setting stringbuffer twice?");
1.106 + MOZ_ASSERT(aStringBuffer, "Why are we getting null?");
1.107 + mStringBuffer = aStringBuffer;
1.108 + mLength = aLength;
1.109 + }
1.110 +
1.111 + void SetOwnedString(const nsAString& aString)
1.112 + {
1.113 + MOZ_ASSERT(mString.empty(), "We already have a string?");
1.114 + MOZ_ASSERT(!mIsNull, "We're already set as null");
1.115 + MOZ_ASSERT(!mStringBuffer, "Setting stringbuffer twice?");
1.116 + nsStringBuffer* buf = nsStringBuffer::FromString(aString);
1.117 + if (buf) {
1.118 + SetStringBuffer(buf, aString.Length());
1.119 + } else if (aString.IsVoid()) {
1.120 + SetNull();
1.121 + } else if (!aString.IsEmpty()) {
1.122 + AsAString() = aString;
1.123 + }
1.124 + }
1.125 +
1.126 + enum NullHandling
1.127 + {
1.128 + eTreatNullAsNull,
1.129 + eTreatNullAsEmpty,
1.130 + eNullNotExpected
1.131 + };
1.132 +
1.133 + void SetOwnedAtom(nsIAtom* aAtom, NullHandling aNullHandling)
1.134 + {
1.135 + MOZ_ASSERT(mString.empty(), "We already have a string?");
1.136 + MOZ_ASSERT(!mIsNull, "We're already set as null");
1.137 + MOZ_ASSERT(!mStringBuffer, "Setting stringbuffer twice?");
1.138 + MOZ_ASSERT(aAtom || aNullHandling != eNullNotExpected);
1.139 + if (aNullHandling == eNullNotExpected || aAtom) {
1.140 + SetStringBuffer(aAtom->GetStringBuffer(), aAtom->GetLength());
1.141 + } else if (aNullHandling == eTreatNullAsNull) {
1.142 + SetNull();
1.143 + }
1.144 + }
1.145 +
1.146 + void SetNull()
1.147 + {
1.148 + MOZ_ASSERT(!mStringBuffer, "Should have no stringbuffer if null");
1.149 + MOZ_ASSERT(mString.empty(), "Should have no string if null");
1.150 + mIsNull = true;
1.151 + }
1.152 +
1.153 + bool IsNull() const
1.154 + {
1.155 + MOZ_ASSERT(!mStringBuffer || mString.empty(),
1.156 + "How could we have a stringbuffer and a nonempty string?");
1.157 + return mIsNull || (!mString.empty() && mString.ref().IsVoid());
1.158 + }
1.159 +
1.160 + void ToString(nsAString& aString)
1.161 + {
1.162 + if (IsNull()) {
1.163 + SetDOMStringToNull(aString);
1.164 + } else if (HasStringBuffer()) {
1.165 + if (StringBufferLength() == 0) {
1.166 + aString.Truncate();
1.167 + } else {
1.168 + StringBuffer()->ToString(StringBufferLength(), aString);
1.169 + }
1.170 + } else {
1.171 + aString = AsAString();
1.172 + }
1.173 + }
1.174 +
1.175 +private:
1.176 + // We need to be able to act like a string as needed
1.177 + Maybe<nsAutoString> mString;
1.178 +
1.179 + // For callees that know we exist, we can be a stringbuffer/length/null-flag
1.180 + // triple.
1.181 + nsStringBuffer* mStringBuffer;
1.182 + uint32_t mLength;
1.183 + bool mIsNull;
1.184 +};
1.185 +
1.186 +} // namespace dom
1.187 +} // namespace mozilla
1.188 +
1.189 +#endif // mozilla_dom_DOMString_h
