Print Bigints in decimal format.

Print Bigints in decimal format.
Committed: https://code.google.com/p/dart/source/detail?r=1058

[siva, 2011-11-02 00:09:42]

lgtm

[cshapiro, 2011-11-02 00:19:01]

DBC

http://codereview.chromium.org/8351050/diff/2009/runtime/vm/bigint_operations.cc
File runtime/vm/bigint_operations.cc (right):

http://codereview.chromium.org/8351050/diff/2009/runtime/vm/bigint_operations...
runtime/vm/bigint_operations.cc:231: char* str = BN_bn2dec(bn);
BN has historically used an inefficient algorithm for binary to decimal
conversion.  Should we replace BN, a faster algorithm, such as the one used by
GMP, would be preferable.

http://www.gnu.org/software/gmp/manual/html_mono/gmp.html#Binary%20to%20Radix

[sra1, 2011-11-02 03:10:23]

DBC

http://codereview.chromium.org/8351050/diff/2009/runtime/vm/bigint_operations.cc
File runtime/vm/bigint_operations.cc (right):

http://codereview.chromium.org/8351050/diff/2009/runtime/vm/bigint_operations...
runtime/vm/bigint_operations.cc:231: char* str = BN_bn2dec(bn);
On 2011/11/02 00:19:01, cshapiro wrote:
> BN has historically used an inefficient algorithm for binary to decimal
> conversion.  Should we replace BN, a faster algorithm, such as the one used by
> GMP, would be preferable.
> 
>
http://www.gnu.org/software/gmp/manual/html_mono/gmp.html#Binary%2520to%2520R...

It might be fun to write the b^(n*2^i) algorithm in Dart, selecting n such that
b^n is a Smi.
You would need to have simple access to
(1) a Smi test
(2) some approximate comparison to tell if x*x > v without doing the
multiplication (number of bits/bytes/words).
(3) a divide producing both quotient and remainder

If the output is some kind of stream (.writeOn) instead of a string, you can
generate and the high digits before the low digits are ready.
If you are happy to over-allocate by 1 character, a string can be generated
without copying.