1 // SPDX-License-Identifier: Apache-2.0
2 // SPDX-FileCopyrightText: Copyright 2022 Equinix, Inc.
3
4 #include "fru_reader.hpp"
5
6 #include <cstring>
7
read(off_t start,size_t len,uint8_t * outbuf)8 ssize_t FRUReader::read(off_t start, size_t len, uint8_t* outbuf)
9 {
10 size_t done = 0;
11 size_t remaining = len;
12 size_t cursor = start;
13 while (done < len)
14 {
15 if (eof.has_value() && cursor >= eof.value())
16 {
17 break;
18 }
19
20 const uint8_t* blkData = nullptr;
21 size_t available = 0;
22 size_t blk = cursor / cacheBlockSize;
23 size_t blkOffset = cursor % cacheBlockSize;
24 auto findBlk = cache.find(blk);
25 if (findBlk == cache.end())
26 {
27 // miss, populate cache
28 uint8_t* newData = cache[blk].data();
29 int64_t ret =
30 readFunc(blk * cacheBlockSize, cacheBlockSize, newData);
31
32 // if we've reached the end of the eeprom, record its size
33 if (ret >= 0 && static_cast<size_t>(ret) < cacheBlockSize)
34 {
35 eof = (blk * cacheBlockSize) + ret;
36 }
37
38 if (ret <= 0)
39 {
40 // don't leave empty blocks in the cache
41 cache.erase(blk);
42 return done != 0U ? done : ret;
43 }
44
45 blkData = newData;
46 available = ret;
47 }
48 else
49 {
50 // hit, use cached data
51 blkData = findBlk->second.data();
52
53 // if the hit is to the block containing the (previously
54 // discovered on the miss that populated it) end of the eeprom,
55 // don't copy spurious bytes past the end
56 if (eof.has_value() && (eof.value() / cacheBlockSize == blk))
57 {
58 available = eof.value() % cacheBlockSize;
59 }
60 else
61 {
62 available = cacheBlockSize;
63 }
64 }
65
66 size_t toCopy = (blkOffset >= available)
67 ? 0
68 : std::min(available - blkOffset, remaining);
69
70 // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-pointer-arithmetic)
71 memcpy(outbuf + done, blkData + blkOffset, toCopy);
72 cursor += toCopy;
73 done += toCopy;
74 remaining -= toCopy;
75 }
76
77 return done;
78 }
79