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alexbevi
GitHub Repository: alexbevi/BizHawk
 Path: blob/master/libsnes/bsnes/nall/bps/metadata.hpp
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#ifndef NALL_BPS_METADATA_HPP

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#define NALL_BPS_METADATA_HPP

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#include <nall/crc32.hpp>

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#include <nall/file.hpp>

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#include <nall/filemap.hpp>

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#include <nall/stdint.hpp>

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#include <nall/string.hpp>

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namespace nall {

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struct bpsmetadata {

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  inline bool load(const string &filename);

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  inline bool save(const string &filename, const string &metadata);

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  inline string metadata() const;

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protected:

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  file sourceFile;

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  string metadataString;

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};

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bool bpsmetadata::load(const string &filename) {

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  if(sourceFile.open(filename, file::mode::read) == false) return false;

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  auto read = [&]() -> uint8_t {

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    return sourceFile.read();

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  };

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  auto decode = [&]() -> uint64_t {

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    uint64_t data = 0, shift = 1;

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    while(true) {

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      uint8_t x = read();

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      data += (x & 0x7f) * shift;

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      if(x & 0x80) break;

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      shift <<= 7;

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      data += shift;

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    }

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    return data;

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  };

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  if(read() != 'B') return false;

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  if(read() != 'P') return false;

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  if(read() != 'S') return false;

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  if(read() != '1') return false;

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  decode();

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  decode();

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  unsigned metadataSize = decode();

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  char data[metadataSize + 1];

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  for(unsigned n = 0; n < metadataSize; n++) data[n] = read();

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  data[metadataSize] = 0;

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  metadataString = (const char*)data;

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  return true;

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}

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bool bpsmetadata::save(const string &filename, const string &metadata) {

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  file targetFile;

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  if(targetFile.open(filename, file::mode::write) == false) return false;

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  if(sourceFile.open() == false) return false;

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  sourceFile.seek(0);

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  auto read = [&]() -> uint8_t {

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    return sourceFile.read();

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  };

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  auto decode = [&]() -> uint64_t {

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    uint64_t data = 0, shift = 1;

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    while(true) {

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      uint8_t x = read();

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      data += (x & 0x7f) * shift;

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      if(x & 0x80) break;

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      shift <<= 7;

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      data += shift;

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    }

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    return data;

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  };

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  uint32_t checksum = ~0;

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  auto write = [&](uint8_t data) {

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    targetFile.write(data);

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    checksum = crc32_adjust(checksum, data);

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  };

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  auto encode = [&](uint64_t data) {

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    while(true) {

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      uint64_t x = data & 0x7f;

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      data >>= 7;

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      if(data == 0) {

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        write(0x80 | x);

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        break;

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      }

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      write(x);

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      data--;

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    }

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  };

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  for(unsigned n = 0; n < 4; n++) write(read());

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  encode(decode());

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  encode(decode());

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  unsigned sourceLength = decode();

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  unsigned targetLength = metadata.length();

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  encode(targetLength);

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  sourceFile.seek(sourceLength, file::index::relative);

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  for(unsigned n = 0; n < targetLength; n++) write(metadata[n]);

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  unsigned length = sourceFile.size() - sourceFile.offset() - 4;

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  for(unsigned n = 0; n < length; n++) write(read());

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  uint32_t outputChecksum = ~checksum;

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  for(unsigned n = 0; n < 32; n += 8) write(outputChecksum >> n);

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  targetFile.close();

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  return true;

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}

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string bpsmetadata::metadata() const {

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  return metadataString;

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}

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}

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#endif

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