On Mon, Sep 14, 2020 at 11:59:48AM +0200, Ahmad Fatoum wrote:
> Instead of storing pointers to 4-byte strings, we could just store the
> characters directly in the struct. Can save us up to 18 pointers worth
> of space. Additionally, the nul byte need not be stored explicitly for
> 3-byte strings, if we know those are the largest strings we have.
>
> The latter likely does not save us any space because of the usual
> alignment rules, but it will allow us to support sequences one byte
> bigger in future at no increase in size.
>
> Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
> ---
> lib/readkey.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/lib/readkey.c b/lib/readkey.c
> index c26e9d51aba9..551296de3eb6 100644
> --- a/lib/readkey.c
> +++ b/lib/readkey.c
> @@ -20,8 +20,10 @@
> #include <linux/ctype.h>
> #include <readkey.h>
>
> +#define MAX_ESC_LEN 3
> +
> struct esc_cmds {
> - const char *seq;
> + const char seq[MAX_ESC_LEN];
I would have expected that when this array is initialized with a static
initializer, the compiler would add a \0 at the end. Apparently this is
not the case, initializing this 3 byte array with "[6~" is perfectly
fine for the compiler.
> @@ -49,7 +51,7 @@ static const struct esc_cmds esccmds[] = {
> int read_key(void)
> {
> unsigned char c;
> - unsigned char esc[5];
> + unsigned char esc[MAX_ESC_LEN + 2];
> c = getchar();
>
> if (c == 27) {
> @@ -67,7 +69,7 @@ int read_key(void)
> }
> esc[i] = 0;
> for (i = 0; i < ARRAY_SIZE(esccmds); i++){
> - if (!strcmp(esc, esccmds[i].seq))
> + if (!strncmp(esc, esccmds[i].seq, MAX_ESC_LEN))
> return esccmds[i].val;
Anyway, I don't think we should play tricks with dropping string
termination characters just to squeeze some bytes out of the binary.
Sascha
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