IPSPatch.cc

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#include "IPSPatch.hh"
#include "File.hh"
#include "Filename.hh"
#include "MSXException.hh"
#include "ranges.hh"
#include "xrange.hh"
#include <array>
#include <cassert>
 
namespace openmsx {
 
std::vector<IPSPatch::Chunk> IPSPatch::parseChunks() const
{
        std::vector<Chunk> result;
 
        File ipsFile(filename);
 
        std::array<uint8_t, 5> header;
        ipsFile.read(header);
        if (!ranges::equal(header, std::string_view("PATCH"))) {
                throw MSXException("Invalid IPS file: ", filename.getOriginal());
        }
        std::array<uint8_t, 3> offsetBuf;
        ipsFile.read(offsetBuf);
        while (!ranges::equal(offsetBuf, std::string_view("EOF"))) {
                size_t offset = 0x10000 * offsetBuf[0] + 0x100 * offsetBuf[1] + offsetBuf[2];
                std::array<uint8_t, 2> lenBuf;
                ipsFile.read(lenBuf);
                size_t length = 0x100 * lenBuf[0] + lenBuf[1];
                std::vector<uint8_t> v;
                if (length == 0) {
                        // RLE encoded
                        std::array<uint8_t, 3> rleBuf;
                        ipsFile.read(rleBuf);
                        length = 0x100 * rleBuf[0] + rleBuf[1];
                        v.resize(length, rleBuf[2]);
                } else {
                        // patch bytes
                        v.resize(length);
                        ipsFile.read(v);
                }
                // find overlapping or adjacent patch regions
                auto b = ranges::lower_bound(result, offset, {}, &Chunk::startAddress);
                if (b != begin(result)) {
                        --b;
                        if (b->stopAddress() < offset) ++b;
                }
                auto e = ranges::upper_bound(result, offset + v.size(), {}, &Chunk::startAddress);
                if (b != e) {
                        // remove overlapping regions, merge adjacent regions
                        --e;
                        auto start = std::min(b->startAddress, offset);
                        auto stop  = std::max(offset + length, e->stopAddress());
                        auto length2 = stop - start;
                        ++e;
                        std::vector<uint8_t> tmp(length2);
                        for (auto it : xrange(b, e)) {
                                ranges::copy(*it, subspan(tmp, it->startAddress - start));
                        }
                        ranges::copy(v, subspan(tmp, offset - start));
                        *b = Chunk{start, std::move(tmp)};
                        result.erase(b + 1, e);
                } else {
                        // add new region
                        result.emplace(b, Chunk{offset, std::move(v)});
                }
 
                ipsFile.read(offsetBuf);
        }
        return result;
}
 
size_t IPSPatch::calcSize() const
{
        return chunks.empty()
                ? parent->getSize()
                : std::max(parent->getSize(), chunks.back().stopAddress());
}
 
IPSPatch::IPSPatch(Filename filename_,
                   std::unique_ptr<const PatchInterface> parent_)
        : filename(std::move(filename_))
        , parent(std::move(parent_))
        , chunks(parseChunks())
        , size(calcSize())
{
}
 
void IPSPatch::copyBlock(size_t src, std::span<uint8_t> dst) const
{
        parent->copyBlock(src, dst);
 
        auto b = ranges::lower_bound(chunks, src, {}, &Chunk::startAddress);
        if (b != begin(chunks)) --b;
        auto srcEnd = src + dst.size();
        auto e = ranges::upper_bound(chunks, srcEnd - 1, {}, &Chunk::startAddress);
        for (auto it : xrange(b, e)) {
                auto chunkStart = it->startAddress;
                int chunkSize = int(it->size());
                // calc chunkOffset, chunkStart
                int chunkOffset = int(src - chunkStart);
                if (chunkOffset < 0) {
                        // start after src
                        assert(-chunkOffset < int(dst.size())); // dont start past end
                        chunkOffset = 0;
                } else if (chunkOffset >= chunkSize) {
                        // chunk completely before src, skip
                        continue;
                } else {
                        // start before src
                        chunkSize  -= chunkOffset;
                        chunkStart += chunkOffset;
                }
                // calc chunkSize
                assert(src <= chunkStart);
                int overflow = int(chunkStart - src + chunkSize - dst.size());
                if (overflow > 0) {
                        assert(chunkSize > overflow);
                        chunkSize -= overflow;
                }
                // copy
                assert(chunkOffset < int(it->size()));
                assert((chunkOffset + chunkSize) <= int(it->size()));
                assert(src <= chunkStart);
                assert((chunkStart + chunkSize) <= srcEnd);
                ranges::copy(subspan(*it, chunkOffset, size_t(chunkSize)),
                             subspan(dst, chunkStart - src));
        }
}
 
std::vector<Filename> IPSPatch::getFilenames() const
{
        auto result = parent->getFilenames();
        result.push_back(filename);
        return result;
}
 
} // namespace openmsx