StorageManager: remove unnecessary calculations on addr for next area

When writting or reading a block, if the block doesn't fit the area where it begins, the next base address is always zero. Thus the calculations to define the next value of addr are unnecessary.

Here's a quick validity proof using the previous calculations:
    First: Considering the case where the block doesn't fit it's first area:
        That means that (count + addr > length), what makes:
            count = length - addr; (1)
        So the following operations:
            addr += count;
            addr -= length;
        Are the same as doing:
            addr = addr + count - length; (2)
        Using (1) and (2) we have:
            addr = addr + length - addr - length = 0

    Second: When the block fits the area where it's at:
        That means that variable count is not changed,
        thus (n -= count) evaluates to 0, which makes the loop exit.

Another change was (b += count;) being moved after the condition to break the loop, since we just need to move the block pointer when it doesn't fit the first area.
This commit is contained in:
Gustavo Jose de Sousa 2015-03-19 10:04:13 -03:00 committed by Randy Mackay
parent 54b7a2db60
commit 6d89a8cf71
1 changed files with 10 additions and 10 deletions

View File

@ -150,15 +150,15 @@ bool StorageAccess::read_block(void *data, uint16_t addr, size_t n) const
} }
hal.storage->read_block(b, addr+offset, count); hal.storage->read_block(b, addr+offset, count);
n -= count; n -= count;
addr += count;
b += count;
// adjust addr for next area
addr -= length;
if (n == 0) { if (n == 0) {
break; break;
} }
// move pointer after written bytes
b += count;
// continue writing at the beginning of next valid area
addr = 0;
} }
return (n == 0); return (n == 0);
} }
@ -190,15 +190,15 @@ bool StorageAccess::write_block(uint16_t addr, const void *data, size_t n) const
} }
hal.storage->write_block(addr+offset, b, count); hal.storage->write_block(addr+offset, b, count);
n -= count; n -= count;
addr += count;
b += count;
// adjust addr for next area
addr -= length;
if (n == 0) { if (n == 0) {
break; break;
} }
// move pointer after written bytes
b += count;
// continue writing at the beginning of next valid area
addr = 0;
} }
return (n == 0); return (n == 0);
} }