chromium / chromiumos / platform / vboot_reference / refs/heads/factory-14778.B / . / firmware / 2lib / 2crc8.c

/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved. | |

* Use of this source code is governed by a BSD-style license that can be | |

* found in the LICENSE file. | |

* | |

* Very simple 8-bit CRC function. | |

*/ | |

#include "2crc8.h" | |

#include "2sysincludes.h" | |

/* Uses CRC-8 ITU version, with x^8 + x^2 + x + 1 polynomial. | |

Note that result will evaluate to zero for a buffer of all zeroes. */ | |

uint8_t vb2_crc8(const void *vptr, uint32_t size) | |

{ | |

const uint8_t *data = vptr; | |

unsigned crc = 0; | |

uint32_t i, j; | |

/* Calculate CRC-8 directly. A table-based algorithm would be faster, | |

but for only a few bytes it isn't worth the code size. */ | |

for (j = size; j; j--, data++) { | |

crc ^= (*data << 8); | |

for(i = 8; i; i--) { | |

if (crc & 0x8000) | |

crc ^= (0x1070 << 3); | |

crc <<= 1; | |

} | |

} | |

return (uint8_t)(crc >> 8); | |

} |