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      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ___FEC_ECC_H___
     18 #define ___FEC_ECC_H___
     19 
     20 #include <fec/io.h>
     21 
     22 #ifdef __cplusplus
     23 extern "C" {
     24 #endif
     25 
     26 /* ecc parameters */
     27 #define FEC_RSM 255
     28 
     29 /* parameters to init_rs_char */
     30 #define FEC_PARAMS(roots) \
     31     8,          /* symbol size in bits */ \
     32     0x11d,      /* field generator polynomial coefficients */ \
     33     0,          /* first root of the generator */ \
     34     1,          /* primitive element to generate polynomial roots */ \
     35     (roots),    /* polynomial degree (number of roots) */ \
     36     0           /* padding bytes at the front of shortened block */
     37 
     38 /* computes ceil(x / y) */
     39 inline uint64_t fec_div_round_up(uint64_t x, uint64_t y)
     40 {
     41     return (x / y) + (x % y > 0 ? 1 : 0);
     42 }
     43 
     44 /* rounds up x to the nearest multiple of y */
     45 inline uint64_t fec_round_up(uint64_t x, uint64_t y)
     46 {
     47     return fec_div_round_up(x, y) * y;
     48 }
     49 
     50 /* returns a physical offset for a byte in an RS block */
     51 inline uint64_t fec_ecc_interleave(uint64_t offset, int rsn, uint64_t rounds)
     52 {
     53     return (offset / rsn) + (offset % rsn) * rounds * FEC_BLOCKSIZE;
     54 }
     55 
     56 /* returns the size of ecc data given a file size and the number of roots */
     57 inline uint64_t fec_ecc_get_size(uint64_t file_size, int roots)
     58 {
     59     return fec_div_round_up(fec_div_round_up(file_size, FEC_BLOCKSIZE),
     60                 FEC_RSM - roots)
     61                     * roots * FEC_BLOCKSIZE
     62                 + FEC_BLOCKSIZE;
     63 }
     64 
     65 
     66 #ifdef __cplusplus
     67 } /* extern "C" */
     68 #endif
     69 
     70 #endif /* ___FEC_ECC_H___ */
     71