LibMedia: Move FFmpegIOContext into it's own file

This allows it to be reused for video.
Author: https://github.com/Lubrsi Commit: 3412935a62 Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/3892 Reviewed-by: https://github.com/ADKaster
2025-07-28 11:49:44 +00:00 · 2025-03-06 14:30:41 +00:00 · 2025-03-06 14:30:41 +00:00 · 3412935a62 · 2025-03-13 18:35:00 +00:00
commit 3412935a62
parent 2f9d2acdb2
5 changed files with 117 additions and 84 deletions
--- a/Libraries/LibMedia/FFmpeg/FFmpegIOContext.cpp
+++ b/Libraries/LibMedia/FFmpeg/FFmpegIOContext.cpp
@ -0,0 +1,78 @@
+/*
+ * Copyright (c) 2024, Jelle Raaijmakers <jelle@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Stream.h>
+#include <LibMedia/FFmpeg/FFmpegIOContext.h>
+
+namespace Media::FFmpeg {
+
+FFmpegIOContext::FFmpegIOContext(AVIOContext* avio_context)
+    : m_avio_context(avio_context)
+{
+}
+
+FFmpegIOContext::~FFmpegIOContext()
+{
+    // NOTE: free the buffer inside the AVIO context, since it might be changed since its initial allocation
+    av_free(m_avio_context->buffer);
+    avio_context_free(&m_avio_context);
+}
+
+ErrorOr<NonnullOwnPtr<FFmpegIOContext>> FFmpegIOContext::create(AK::SeekableStream& stream)
+{
+    auto* avio_buffer = av_malloc(PAGE_SIZE);
+    if (avio_buffer == nullptr)
+        return Error::from_string_literal("Failed to allocate AVIO buffer");
+
+    // This AVIOContext explains to avformat how to interact with our stream
+    auto* avio_context = avio_alloc_context(
+        static_cast<unsigned char*>(avio_buffer),
+        PAGE_SIZE,
+        0,
+        &stream,
+        [](void* opaque, u8* buffer, int size) -> int {
+            auto& stream = *static_cast<SeekableStream*>(opaque);
+            AK::Bytes buffer_bytes { buffer, AK::min<size_t>(size, PAGE_SIZE) };
+            auto read_bytes_or_error = stream.read_some(buffer_bytes);
+            if (read_bytes_or_error.is_error()) {
+                if (read_bytes_or_error.error().code() == EOF)
+                    return AVERROR_EOF;
+                return AVERROR_UNKNOWN;
+            }
+            int number_of_bytes_read = read_bytes_or_error.value().size();
+            if (number_of_bytes_read == 0)
+                return AVERROR_EOF;
+            return number_of_bytes_read;
+        },
+        nullptr,
+        [](void* opaque, int64_t offset, int whence) -> int64_t {
+            whence &= ~AVSEEK_FORCE;
+
+            auto& stream = *static_cast<SeekableStream*>(opaque);
+            if (whence == AVSEEK_SIZE)
+                return static_cast<int64_t>(stream.size().value());
+
+            auto seek_mode_from_whence = [](int origin) -> SeekMode {
+                if (origin == SEEK_CUR)
+                    return SeekMode::FromCurrentPosition;
+                if (origin == SEEK_END)
+                    return SeekMode::FromEndPosition;
+                return SeekMode::SetPosition;
+            };
+            auto offset_or_error = stream.seek(offset, seek_mode_from_whence(whence));
+            if (offset_or_error.is_error())
+                return -EIO;
+            return 0;
+        });
+    if (avio_context == nullptr) {
+        av_free(avio_buffer);
+        return Error::from_string_literal("Failed to allocate AVIO context");
+    }
+
+    return make<FFmpegIOContext>(avio_context);
+}
+
+}