August 10: Still trying to reduce the code. Tried to remove the int *success parameter of the expand_string() function. This parameter tells the calling function whether a new word was recognised. However, I had some problems in case of the line-continuation \.
for i in 1 2 3 \
4 5 6 # the space at the beginning of this line causes the problem
do
echo ${i}
done
seems to require some way to see that the \<newline> is not a new word.
August 11: Decided to try using the gen_stack for the arithmetic parser code. The benefits should include a simpler memory allocation strategy. The idea is to use an explicit stack to store the operands. When an operator is found, the top of the stack should contain the (evaluated) left operator. Then the right operator is evaluated, and pushed on the stack by recursive calls to the parsing function. Then the top two elements of the stack are popped, evaluated, and the result is pushed back. If at any time an error is found, the top-level function frees the stack. This frees up the other functions from having to free the temporary values.
August 13: Finally used the gen_stack for arith.c. Size check: After:
2276 8 16 2300 8fc bin/arith.o
Before
2172 0 16 2188 88c bin/arith.o
However, I had some problems with the branches and loops, so that doesn't work just yet. Have to fix it next. Also split the gen_stack commit out of the quoting patch.
August 14: Fixed up the branching and loop code. Using the new gen_stack code made me change a lot of things in the offset branch. Since I was focussing mostly on the arith.c changes, I just tried to make this part compile properly. So, today, I worked on fixing it up.
August 16: Okay, so it's the end of GSoC, and it's been an enjoyable time. To summarise the work done so far:
Features implemented:
- Quoting
- Arithmetic parser
- If-else branches
- Looping
- Return code
'Supporting' additions:
- Generic stack
- Simple automated testing of scripts, using qemu
Documentation of the features can be found here. The code can be found in the expt branch of my git repository. I'll be sending in the changes in a series of patches to the etherboot-developers mailing list. Size check: After:
159 0 0 159 9f bin/gen_stack.o 602 24 4 630 276 bin/shell.o 639 12 4 655 28f bin/exec.o 1079 0 0 1079 437 bin/parse.o 1855 160 24 2039 7f7 bin/if_cmd.o 2308 8 16 2332 91c bin/arith.o 87732 11528 139822 239082 3a5ea (TOTALS)
Compressed size: 59392
Before:
321 16 4 341 155 bin/shell.o 629 8 0 637 27d bin/exec.o 81979 11308 139774 233061 38e65 (TOTALS)
Compressed size: 55808
