1 /* 2 // Copyright (c) 2022 Equinix, Inc. 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 #include "fru_reader.hpp" 18 19 #include <cstring> 20 21 ssize_t FRUReader::read(off_t start, size_t len, uint8_t* outbuf) 22 { 23 size_t done = 0; 24 size_t remaining = len; 25 size_t cursor = start; 26 while (done < len) 27 { 28 if (eof.has_value() && cursor >= eof.value()) 29 { 30 break; 31 } 32 33 const uint8_t* blkData = nullptr; 34 size_t available = 0; 35 size_t blk = cursor / cacheBlockSize; 36 size_t blkOffset = cursor % cacheBlockSize; 37 auto findBlk = cache.find(blk); 38 if (findBlk == cache.end()) 39 { 40 // miss, populate cache 41 uint8_t* newData = cache[blk].data(); 42 int64_t ret = 43 readFunc(blk * cacheBlockSize, cacheBlockSize, newData); 44 45 // if we've reached the end of the eeprom, record its size 46 if (ret >= 0 && static_cast<size_t>(ret) < cacheBlockSize) 47 { 48 eof = (blk * cacheBlockSize) + ret; 49 } 50 51 if (ret <= 0) 52 { 53 // don't leave empty blocks in the cache 54 cache.erase(blk); 55 return done != 0U ? done : ret; 56 } 57 58 blkData = newData; 59 available = ret; 60 } 61 else 62 { 63 // hit, use cached data 64 blkData = findBlk->second.data(); 65 66 // if the hit is to the block containing the (previously 67 // discovered on the miss that populated it) end of the eeprom, 68 // don't copy spurious bytes past the end 69 if (eof.has_value() && (eof.value() / cacheBlockSize == blk)) 70 { 71 available = eof.value() % cacheBlockSize; 72 } 73 else 74 { 75 available = cacheBlockSize; 76 } 77 } 78 79 size_t toCopy = (blkOffset >= available) 80 ? 0 81 : std::min(available - blkOffset, remaining); 82 83 // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-pointer-arithmetic) 84 memcpy(outbuf + done, blkData + blkOffset, toCopy); 85 cursor += toCopy; 86 done += toCopy; 87 remaining -= toCopy; 88 } 89 90 return done; 91 } 92