Hello Sascha,
On 9/28/20 11:31 AM, Sascha Hauer wrote:
> 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.
Initializers are padded with zeroes if they are too short.
>> @@ -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.
I can define #define MAX_ESC_LEN 4 if you prefer that, but I consider
it superfluous.
Cheers,
Ahmad
>
> Sascha
>
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