1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 /* This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 #if !defined(MediaSpan_h)
9 # include "MediaData.h"
10 # include "mozilla/RefPtr.h"
11 # include "mozilla/Span.h"
15 // A MediaSpan wraps a MediaByteBuffer and exposes a slice/span, or subregion,
16 // of the buffer. This allows you to slice off a logical subregion without
17 // needing to reallocate a new buffer to hold it. You can also append to a
18 // MediaSpan without affecting other MediaSpans referencing the same buffer
19 // (the MediaSpan receiving the append will allocate a new buffer to store its
20 // result if necessary, to ensure other MediaSpans referencing its original
21 // buffer are unaffected). Note there are no protections here that something
22 // other than MediaSpans doesn't modify the underlying MediaByteBuffer while
23 // a MediaSpan is alive.
26 ~MediaSpan() = default;
28 explicit MediaSpan(const MediaSpan
& aOther
) = default;
30 MediaSpan(MediaSpan
&& aOther
) = default;
32 explicit MediaSpan(const RefPtr
<MediaByteBuffer
>& aBuffer
)
33 : mBuffer(aBuffer
), mStart(0), mLength(aBuffer
? aBuffer
->Length() : 0) {
34 MOZ_DIAGNOSTIC_ASSERT(mBuffer
);
37 explicit MediaSpan(MediaByteBuffer
* aBuffer
)
38 : mBuffer(aBuffer
), mStart(0), mLength(aBuffer
? aBuffer
->Length() : 0) {
39 MOZ_DIAGNOSTIC_ASSERT(mBuffer
);
42 MediaSpan
& operator=(const MediaSpan
& aOther
) = default;
44 static MediaSpan
WithCopyOf(const RefPtr
<MediaByteBuffer
>& aBuffer
) {
45 RefPtr
<MediaByteBuffer
> buffer
= new MediaByteBuffer(aBuffer
->Length());
46 buffer
->AppendElements(*aBuffer
);
47 return MediaSpan(buffer
);
50 bool IsEmpty() const { return Length() == 0; }
52 // Note: It's unsafe to store the pointer returned by this function, as an
53 // append operation could cause the wrapped MediaByteBuffer to be
54 // reallocated, invalidating pointers previously returned by this function.
55 const uint8_t* Elements() const {
56 MOZ_DIAGNOSTIC_ASSERT(mStart
< mBuffer
->Length());
57 return mBuffer
->Elements() + mStart
;
60 size_t Length() const { return mLength
; }
62 uint8_t operator[](size_t aIndex
) const {
63 MOZ_DIAGNOSTIC_ASSERT(aIndex
< Length());
64 return (*mBuffer
)[mStart
+ aIndex
];
67 bool Append(const MediaSpan
& aBuffer
) { return Append(aBuffer
.Buffer()); }
69 bool Append(MediaByteBuffer
* aBuffer
) {
73 if (mStart
+ mLength
< mBuffer
->Length()) {
74 // This MediaSpan finishes before the end of its buffer. The buffer
75 // could be shared with another MediaSpan. So we can't just append to
76 // the underlying buffer without risking damaging other MediaSpans' data.
77 // So we must reallocate a new buffer, copy our old data into it, and
78 // append the new data into it.
79 RefPtr
<MediaByteBuffer
> buffer
=
80 new MediaByteBuffer(mLength
+ aBuffer
->Length());
81 if (!buffer
->AppendElements(Elements(), Length(), fallible
) ||
82 !buffer
->AppendElements(*aBuffer
, fallible
)) {
86 mLength
+= aBuffer
->Length();
89 if (!mBuffer
->AppendElements(*aBuffer
, fallible
)) {
92 mLength
+= aBuffer
->Length();
96 // Returns a new MediaSpan, spanning from the start of this span,
98 MediaSpan
To(size_t aEnd
) const {
99 MOZ_DIAGNOSTIC_ASSERT(aEnd
<= Length());
100 return MediaSpan(mBuffer
, mStart
, aEnd
);
103 // Returns a new MediaSpan, spanning from aStart bytes offset from
104 // the start of this span, until the end of this span.
105 MediaSpan
From(size_t aStart
) const {
106 MOZ_DIAGNOSTIC_ASSERT(aStart
<= Length());
107 return MediaSpan(mBuffer
, mStart
+ aStart
, Length() - aStart
);
110 void RemoveFront(size_t aNumBytes
) {
111 MOZ_DIAGNOSTIC_ASSERT(aNumBytes
<= Length());
113 mLength
-= aNumBytes
;
116 MediaByteBuffer
* Buffer() const { return mBuffer
; }
119 MediaSpan(MediaByteBuffer
* aBuffer
, size_t aStart
, size_t aLength
)
120 : mBuffer(aBuffer
), mStart(aStart
), mLength(aLength
) {
121 MOZ_DIAGNOSTIC_ASSERT(mStart
+ mLength
<= mBuffer
->Length());
124 RefPtr
<MediaByteBuffer
> mBuffer
;
129 } // namespace mozilla
131 #endif // MediaSpan_h