// Copyright 2025 The Dawn & Tint Authors
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#include "dawn/replay/ReadHead.h"

#include <algorithm>

namespace dawn::replay {

ReadHead::ReadHead(std::span<const uint8_t> data) : mData(data), mReadHead(data.begin()) {}

MaybeError ReadHead::ReadBytes(std::span<uint8_t> dest) {
    auto newHead = mReadHead + dest.size();
    if (newHead <= mData.end()) {
        std::copy_n(mReadHead, dest.size(), dest.begin());
        mReadHead = newHead;
        return {};
    }
    mBad = true;
    return DAWN_INTERNAL_ERROR("Read past end of data");
}

ResultOrError<const uint32_t*> ReadHead::GetData(size_t size) {
    if (size % 4 != 0) {
        mBad = true;
        return DAWN_INTERNAL_ERROR("GetData size not multiple of 4");
    }
    size_t alignedSize = (size + 3) & ~3;
    auto newHead = mReadHead + alignedSize;
    if (newHead <= mData.end()) {
        const uint32_t* data = reinterpret_cast<const uint32_t*>(&*mReadHead);
        mReadHead = newHead;
        return {data};
    }

    mBad = true;
    return DAWN_INTERNAL_ERROR("GetData past end of data");
}

bool ReadHead::IsBad() const {
    return mBad;
}

bool ReadHead::IsDone() const {
    return mBad || mReadHead == mData.end();
}

}  // namespace dawn::replay