strutil: Locale independent sprintf() and vsprintf() functions

include/libsigrok/proto.h

@@ -248,6 +248,8 @@ SR_API uint64_t sr_parse_timestring(const char *timestring);
 SR_API gboolean sr_parse_boolstring(const char *boolstring);
 SR_API int sr_parse_period(const char *periodstr, uint64_t *p, uint64_t *q);
 SR_API int sr_parse_voltage(const char *voltstr, uint64_t *p, uint64_t *q);
+SR_API int sr_sprintf_ascii(char *buf, const char *format, ...);
+SR_API int sr_vsprintf_ascii(char *buf, const char *format, va_list args);
 SR_API int sr_snprintf_ascii(char *buf, size_t buf_size,
 		const char *format, ...);
 SR_API int sr_vsnprintf_ascii(char *buf, size_t buf_size,

src/strutil.c

@@ -259,6 +259,165 @@ SR_PRIV int sr_atof_ascii(const char *str, float *ret)
 	return SR_OK;
 }
 
+/**
+ * Compose a string with a format string in the buffer pointed to by buf.
+ *
+ * It is up to the caller to ensure that the allocated buffer is large enough
+ * to hold the formatted result.
+ *
+ * A terminating NUL character is automatically appended after the content
+ * written.
+ *
+ * After the format parameter, the function expects at least as many additional
+ * arguments as needed for format.
+ *
+ * This version ignores the current locale and uses the locale "C" for Linux,
+ * FreeBSD, OSX and Android.
+ *
+ * @param buf Pointer to a buffer where the resulting C string is stored.
+ * @param format C string that contains a format string (see printf).
+ * @param ... A sequence of additional arguments, each containing a value to be
+ *        used to replace a format specifier in the format string.
+ *
+ * @return On success, the number of characters that would have been written,
+ *         not counting the terminating NUL character.
+ *
+ * @since 0.6.0
+ */
+SR_API int sr_sprintf_ascii(char *buf, const char *format, ...)
+{
+	int ret;
+	va_list args;
+
+	va_start(args, format);
+	ret = sr_vsprintf_ascii(buf, format, args);
+	va_end(args);
+
+	return ret;
+}
+
+/**
+ * Compose a string with a format string in the buffer pointed to by buf.
+ *
+ * It is up to the caller to ensure that the allocated buffer is large enough
+ * to hold the formatted result.
+ *
+ * Internally, the function retrieves arguments from the list identified by
+ * args as if va_arg was used on it, and thus the state of args is likely to
+ * be altered by the call.
+ *
+ * In any case, args should have been initialized by va_start at some point
+ * before the call, and it is expected to be released by va_end at some point
+ * after the call.
+ *
+ * This version ignores the current locale and uses the locale "C" for Linux,
+ * FreeBSD, OSX and Android.
+ *
+ * @param buf Pointer to a buffer where the resulting C string is stored.
+ * @param format C string that contains a format string (see printf).
+ * @param args A value identifying a variable arguments list initialized with
+ *        va_start.
+ *
+ * @return On success, the number of characters that would have been written,
+ *         not counting the terminating NUL character.
+ *
+ * @since 0.6.0
+ */
+SR_API int sr_vsprintf_ascii(char *buf, const char *format, va_list args)
+{
+#if defined(_WIN32)
+	int ret;
+
+#if 0
+	/*
+	 * TODO: This part compiles with mingw-w64 but doesn't run with Win7.
+	 *       Doesn't start because of "Procedure entry point _create_locale
+	 *       not found in msvcrt.dll".
+	 *       mingw-w64 should link to msvcr100.dll not msvcrt.dll!
+	 * See: https://msdn.microsoft.com/en-us/en-en/library/1kt27hek.aspx
+	 */
+	_locale_t locale;
+
+	locale = _create_locale(LC_NUMERIC, "C");
+	ret = _vsprintf_l(buf, format, locale, args);
+	_free_locale(locale);
+#endif
+
+	/* vsprintf() uses the current locale, may not work correctly for floats. */
+	ret = vsprintf(buf, format, args);
+
+	return ret;
+#elif defined(__APPLE__)
+	/*
+	 * See:
+	 * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/printf_l.3.html
+	 * https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/xlocale.3.html
+	 */
+	int ret;
+	locale_t locale;
+
+	locale = newlocale(LC_NUMERIC_MASK, "C", NULL);
+	ret = vsprintf_l(buf, locale, format, args);
+	freelocale(locale);
+
+	return ret;
+#elif defined(__FreeBSD__) && __FreeBSD_version >= 901000
+	/*
+	 * See:
+	 * https://www.freebsd.org/cgi/man.cgi?query=printf_l&apropos=0&sektion=3&manpath=FreeBSD+9.1-RELEASE
+	 * https://www.freebsd.org/cgi/man.cgi?query=xlocale&apropos=0&sektion=3&manpath=FreeBSD+9.1-RELEASE
+	 */
+	int ret;
+	locale_t locale;
+
+	locale = newlocale(LC_NUMERIC_MASK, "C", NULL);
+	ret = vsprintf_l(buf, locale, format, args);
+	freelocale(locale);
+
+	return ret;
+#elif defined(__ANDROID__)
+	/*
+	 * The Bionic libc only has two locales ("C" aka "POSIX" and "C.UTF-8"
+	 * aka "en_US.UTF-8"). The decimal point is hard coded as "."
+	 * See: https://android.googlesource.com/platform/bionic/+/master/libc/bionic/locale.cpp
+	 */
+	int ret;
+
+	ret = vsprintf(buf, format, args);
+
+	return ret;
+#elif defined(__linux__)
+	int ret;
+	locale_t old_locale, temp_locale;
+
+	/* Switch to C locale for proper float/double conversion. */
+	temp_locale = newlocale(LC_NUMERIC, "C", NULL);
+	old_locale = uselocale(temp_locale);
+
+	ret = vsprintf(buf, format, args);
+
+	/* Switch back to original locale. */
+	uselocale(old_locale);
+	freelocale(temp_locale);
+
+	return ret;
+#elif defined(__unix__) || defined(__unix)
+	/*
+	 * This is a fallback for all other BSDs, *nix and FreeBSD <= 9.0, by
+	 * using the current locale for snprintf(). This may not work correctly
+	 * for floats!
+	 */
+	int ret;
+
+	ret = vsprintf(buf, format, args);
+
+	return ret;
+#else
+	/* No implementation for unknown systems! */
+	return -1;
+#endif
+}
+
 /**
  * Composes a string with a format string (like printf) in the buffer pointed
  * by buf (taking buf_size as the maximum buffer capacity to fill).
@@ -270,7 +429,7 @@ SR_PRIV int sr_atof_ascii(const char *str, float *ret)
  * After the format parameter, the function expects at least as many additional
  * arguments as needed for format.
  *
- * This version ignores the actual locale and uses the locale "C" for Linux,
+ * This version ignores the current locale and uses the locale "C" for Linux,
  * FreeBSD, OSX and Android.
  *
  * @param buf Pointer to a buffer where the resulting C string is stored.
@@ -317,7 +476,7 @@ SR_API int sr_snprintf_ascii(char *buf, size_t buf_size,
  * before the call, and it is expected to be released by va_end at some point
  * after the call.
  *
- * This version ignores the actual locale and uses the locale "C" for Linux,
+ * This version ignores the current locale and uses the locale "C" for Linux,
  * FreeBSD, OSX and Android.
  *
  * @param buf Pointer to a buffer where the resulting C string is stored.
@@ -348,6 +507,7 @@ SR_API int sr_vsnprintf_ascii(char *buf, size_t buf_size,
 	 *       Doesn't start because of "Procedure entry point _create_locale
 	 *       not found in msvcrt.dll".
 	 *       mingw-w64 should link to msvcr100.dll not msvcrt.dll!.
+	 * See: https://msdn.microsoft.com/en-us/en-en/library/1kt27hek.aspx
 	 */
 	_locale_t locale;