On Fri, May 06, 2022 at 09:55:51PM +0100, Nikos Nikoleris wrote:
> This follows the typical format of:
>
> printf("%.Ns", *str);
>
> Where N might be a decimal digit string or '*'. This feature is used
> by a future change.
>
> See also: man 3 printf
>
> Signed-off-by: Nikos Nikoleris <nikos.nikoleris@xxxxxxx>
> ---
> lib/printf.c | 84 ++++++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 71 insertions(+), 13 deletions(-)
>
> diff --git a/lib/printf.c b/lib/printf.c
> index 1269723..724befa 100644
> --- a/lib/printf.c
> +++ b/lib/printf.c
> @@ -19,6 +19,7 @@ typedef struct strprops {
> char pad;
> int npad;
> bool alternate;
> + int precision;
> } strprops_t;
>
> static void addchar(pstream_t *p, char c)
> @@ -43,7 +44,7 @@ static void print_str(pstream_t *p, const char *s, strprops_t props)
> }
> }
>
> - while (*s)
> + while (*s && props.precision--)
> addchar(p, *s++);
>
> if (npad < 0) {
> @@ -147,9 +148,61 @@ static int fmtnum(const char **fmt)
> return num;
> }
>
> +static inline int isdigit(int c)
> +{
> + return '0' <= c && c <= '9';
> +}
We desperately need to add ctype to our library. We've already got
isblank, isalpha, and isalnum local to argv.c and I see later you
add isspace. I'll post a patch now that introduces ctype.[ch] with
the ones used by argv. Then, when you respin this series you can
add your ctype functions there.
> +
> +/*
> + * Adapted from drivers/firmware/efi/libstub/vsprintf.c
> + */
> +static int skip_atoi(const char **s)
> +{
> + int i = 0;
> +
> + do {
> + i = i*10 + *((*s)++) - '0';
> + } while (isdigit(**s));
> +
> + return i;
> +}
> +
> +/*
> + * Adapted from drivers/firmware/efi/libstub/vsprintf.c
> + */
> +static int get_int(const char **fmt, va_list *ap)
> +{
> + if (isdigit(**fmt)) {
> + return skip_atoi(fmt);
> + }
> + if (**fmt == '*') {
> + ++(*fmt);
> + /* it's the next argument */
> + return va_arg(*ap, int);
> + }
> + return 0;
> +}
> +
> int vsnprintf(char *buf, int size, const char *fmt, va_list va)
> {
> pstream_t s;
> + va_list args;
> +
> + /*
> + * We want to pass our input va_list to helper functions by reference,
> + * but there's an annoying edge case. If va_list was originally passed
> + * to us by value, we could just pass &ap down to the helpers. This is
> + * the case on, for example, X86_32.
> + * However, on X86_64 (and possibly others), va_list is actually a
> + * size-1 array containing a structure. Our function parameter ap has
> + * decayed from T[1] to T*, and &ap has type T** rather than T(*)[1],
> + * which is what will be expected by a function taking a va_list *
> + * parameter.
> + * One standard way to solve this mess is by creating a copy in a local
> + * variable of type va_list and then passing a pointer to that local
> + * copy instead, which is what we do here.
> + */
> + va_copy(args, va);
>
> s.buffer = buf;
> s.remain = size - 1;
> @@ -160,6 +213,7 @@ int vsnprintf(char *buf, int size, const char *fmt, va_list va)
> strprops_t props;
> memset(&props, 0, sizeof(props));
> props.pad = ' ';
> + props.precision = -1;
>
> if (f != '%') {
> addchar(&s, f);
> @@ -172,11 +226,14 @@ int vsnprintf(char *buf, int size, const char *fmt, va_list va)
> addchar(&s, '%');
> break;
> case 'c':
> - addchar(&s, va_arg(va, int));
> + addchar(&s, va_arg(args, int));
> break;
> case '\0':
> --fmt;
> break;
> + case '.':
> + props.precision = get_int(&fmt, &args);
> + goto morefmt;
> case '#':
> props.alternate = true;
> goto morefmt;
> @@ -204,54 +261,55 @@ int vsnprintf(char *buf, int size, const char *fmt, va_list va)
> case 'd':
> switch (nlong) {
> case 0:
> - print_int(&s, va_arg(va, int), 10, props);
> + print_int(&s, va_arg(args, int), 10, props);
> break;
> case 1:
> - print_int(&s, va_arg(va, long), 10, props);
> + print_int(&s, va_arg(args, long), 10, props);
> break;
> default:
> - print_int(&s, va_arg(va, long long), 10, props);
> + print_int(&s, va_arg(args, long long), 10, props);
> break;
> }
> break;
> case 'u':
> switch (nlong) {
> case 0:
> - print_unsigned(&s, va_arg(va, unsigned), 10, props);
> + print_unsigned(&s, va_arg(args, unsigned), 10, props);
> break;
> case 1:
> - print_unsigned(&s, va_arg(va, unsigned long), 10, props);
> + print_unsigned(&s, va_arg(args, unsigned long), 10, props);
> break;
> default:
> - print_unsigned(&s, va_arg(va, unsigned long long), 10, props);
> + print_unsigned(&s, va_arg(args, unsigned long long), 10, props);
> break;
> }
> break;
> case 'x':
> switch (nlong) {
> case 0:
> - print_unsigned(&s, va_arg(va, unsigned), 16, props);
> + print_unsigned(&s, va_arg(args, unsigned), 16, props);
> break;
> case 1:
> - print_unsigned(&s, va_arg(va, unsigned long), 16, props);
> + print_unsigned(&s, va_arg(args, unsigned long), 16, props);
> break;
> default:
> - print_unsigned(&s, va_arg(va, unsigned long long), 16, props);
> + print_unsigned(&s, va_arg(args, unsigned long long), 16, props);
> break;
> }
> break;
> case 'p':
> props.alternate = true;
> - print_unsigned(&s, (unsigned long)va_arg(va, void *), 16, props);
> + print_unsigned(&s, (unsigned long)va_arg(args, void *), 16, props);
> break;
> case 's':
> - print_str(&s, va_arg(va, const char *), props);
> + print_str(&s, va_arg(args, const char *), props);
> break;
> default:
> addchar(&s, f);
> break;
> }
> }
> + va_end(args);
> *s.buffer = 0;
> return s.added;
> }
> --
> 2.25.1
>
I think I should also post a patches that finally reformat these older
files. The tab+4spaces stuff must go!
When we get ctype we'll want to move out isdigit, but otherwise
Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
Thanks,
drew
