Hi Wolfgang
On Tue, Aug 30, 2011 at 3:17 PM, Wolfgang Denk wd@denx.de wrote:
Dear Graeme Russ,
In message CALButCJF1p+60WOLtiJqhcAed-71VxmP2mBqY2wdNURPk5=Q+g@mail.gmail.com you wrote:
it's fairly easy as well: #define CIRC_BUF_IDX(idx) ((idx) & (CONFIG_SYS_TMP_CON_BUF_SZ-1)) buffer[CIRC_BUF_IDX(gd->conf_buf_idx++)] = c;
But does that work for non power-of-two buffer sizes...
no, but not that big of a deal. so you get limited to the last 1KiB, 4KiB, 8KiB, 16KiB, etc... amount of data.
Until someone doesn't read the documentation and figures they can only squeeze 200 bytes out of their L1 cache after making room for gd and stack and then tries to print 201 bytes of debug info and trashes either the stack or gd and then things start to get a lot weirder than simply having their early debug messgaes clipped...
To be safe, CONFIG_SYS_TMP_CON_BUF_SZ would need to be checked for ^2 size and now we only get 128 bytes rather than 200 :( - Better to add another long in gd and get 196
Grrrgh.
If you want to support arbitrary buffer sizes, then just use
#define CIRC_BUF_IDX(idx) ((idx) % CONFIG_SYS_TMP_CON_BUF_SZ)
I know, but I was concerned that you wouldn't like the use of modulo arithmetic for every putc() - But I suppose thats cheaper than a compare plus branch...
If you prefer modulo over the 'must be a power of two' restriction, then I am happy to do it that way instead
Regards,
Graeme