From patchwork Fri May 6 20:55:51 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nikos Nikoleris X-Patchwork-Id: 12841602 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C6F3C4332F for ; Fri, 6 May 2022 20:57:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1444267AbiEFVAu (ORCPT ); Fri, 6 May 2022 17:00:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1444260AbiEFVAr (ORCPT ); Fri, 6 May 2022 17:00:47 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C7A9C6EB07 for ; Fri, 6 May 2022 13:57:03 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A2D1F152B; Fri, 6 May 2022 13:57:03 -0700 (PDT) Received: from godel.lab.cambridge.arm.com (godel.lab.cambridge.arm.com [10.7.66.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CD6DB3F800; Fri, 6 May 2022 13:57:02 -0700 (PDT) From: Nikos Nikoleris To: kvm@vger.kernel.org Cc: drjones@redhat.com, pbonzini@redhat.com, jade.alglave@arm.com, alexandru.elisei@arm.com Subject: [kvm-unit-tests PATCH v2 09/23] lib/printf: Support for precision modifier in printing strings Date: Fri, 6 May 2022 21:55:51 +0100 Message-Id: <20220506205605.359830-10-nikos.nikoleris@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220506205605.359830-1-nikos.nikoleris@arm.com> References: <20220506205605.359830-1-nikos.nikoleris@arm.com> MIME-Version: 1.0 X-ARM-No-Footer: FoSSMail Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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 Reviewed-by: Andrew Jones --- 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'; +} + +/* + * 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; }