lib: cbprintf: add libc f/printf substitutes

This allows applications that may not use minimal libc avoid the cost
of a second printf-like formatting infrastructure by using printfcb()
instead of printf() for output.  It also helps make sure that the
formatting support (e.g. floats) is consistent between user-directed
output and the logging infrastructure.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>

doc/zephyr.doxyfile.in

@@ -1966,6 +1966,7 @@ PREDEFINED             = "CONFIG_ARCH_HAS_CUSTOM_BUSY_WAIT" \
                          "CONFIG_BT_USER_PHY_UPDATE" \
                          "CONFIG_BT_SMP" \
                          "CONFIG_BT_SMP_APP_PAIRING_ACCEPT" \
+                         "CONFIG_CBPRINTF_LIBC_SUBSTS" \
                          "CONFIG_ERRNO" \
                          "CONFIG_FLASH_JESD216_API" \
                          "CONFIG_FLASH_PAGE_LAYOUT" \

include/sys/cbprintf.h

@@ -11,6 +11,10 @@
 #include <stddef.h>
 #include <toolchain.h>
 
+#ifdef CONFIG_CBPRINTF_LIBC_SUBSTS
+#include <stdio.h>
+#endif /* CONFIG_CBPRINTF_LIBC_SUBSTS */
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -96,6 +100,84 @@ int cbprintf(cbprintf_cb out, void *ctx, const char *format, ...);
  */
 int cbvprintf(cbprintf_cb out, void *ctx, const char *format, va_list ap);
 
+#ifdef CONFIG_CBPRINTF_LIBC_SUBSTS
+
+/** @brief fprintf using Zephyrs cbprintf infrastructure.
+ *
+ * @note This function is available only when `CONFIG_CBPRINTF_LIBC_SUBSTS` is
+ * selected.
+ *
+ * @note The functionality of this function is significantly reduced
+ * when `CONFIG_CBPRINTF_NANO` is selected.
+ *
+ * @param stream the stream to which the output should be written.
+ *
+ * @param format a standard ISO C format string with characters and
+ * conversion specifications.
+ *
+ * @param ... arguments corresponding to the conversion specifications found
+ * within @p format.
+ *
+ * return The number of characters printed.
+ */
+__printf_like(2, 3)
+int fprintfcb(FILE * stream, const char *format, ...);
+
+/** @brief vfprintf using Zephyrs cbprintf infrastructure.
+ *
+ * @note This function is available only when `CONFIG_CBPRINTF_LIBC_SUBSTS` is
+ * selected.
+ *
+ * @note The functionality of this function is significantly reduced when
+ * `CONFIG_CBPRINTF_NANO` is selected.
+ *
+ * @param stream the stream to which the output should be written.
+ *
+ * @param format a standard ISO C format string with characters and conversion
+ * specifications.
+ *
+ * @param ap a reference to the values to be converted.
+ *
+ * @return The number of characters printed.
+ */
+int vfprintfcb(FILE *stream, const char *format, va_list ap);
+
+/** @brief printf using Zephyrs cbprintf infrastructure.
+ *
+ * @note This function is available only when `CONFIG_CBPRINTF_LIBC_SUBSTS` is
+ * selected.
+ *
+ * @note The functionality of this function is significantly reduced
+ * when `CONFIG_CBPRINTF_NANO` is selected.
+ *
+ * @param format a standard ISO C format string with characters and
+ * conversion specifications.
+ *
+ * @param ... arguments corresponding to the conversion specifications found
+ * within @p format.
+ *
+ * @return The number of characters printed.
+ */
+__printf_like(1, 2)
+int printfcb(const char *format, ...);
+
+/** @brief vprintf using Zephyrs cbprintf infrastructure.
+ *
+ * @note This function is available only when `CONFIG_CBPRINTF_LIBC_SUBSTS` is
+ * selected.
+ *
+ * @note The functionality of this function is significantly reduced when
+ * `CONFIG_CBPRINTF_NANO` is selected.
+ *
+ * @param format a standard ISO C format string with characters and conversion
+ * specifications.
+ *
+ * @param ap a reference to the values to be converted.
+ *
+ * @return The number of characters printed.
+ */
+int vprintfcb(const char *format, va_list ap);
+
 /** @brief snprintf using Zephyrs cbprintf infrastructure.
  *
  * @note This function is available only when `CONFIG_CBPRINTF_LIBC_SUBSTS` is
@@ -146,6 +228,8 @@ int snprintfcb(char *str, size_t size, const char *format, ...);
  */
 int vsnprintfcb(char *str, size_t size, const char *format, va_list ap);
 
+#endif /* CONFIG_CBPRINTF_LIBC_SUBSTS */
+
 /**
  * @}
  */

lib/os/cbprintf.c

@@ -22,6 +22,8 @@ int cbprintf(cbprintf_cb out, void *ctx, const char *format, ...)
 
 #if defined(CONFIG_CBPRINTF_LIBC_SUBSTS)
 
+#include <stdio.h>
+
 /* Context for sn* variants is the next space in the buffer, and the buffer
  * end.
  */
@@ -46,6 +48,40 @@ static int str_out(int c,
 	return c;
 }
 
+int fprintfcb(FILE *stream, const char *format, ...)
+{
+	va_list ap;
+	int rc;
+
+	va_start(ap, format);
+	rc = vfprintfcb(stream, format, ap);
+	va_end(ap);
+
+	return rc;
+}
+
+int vfprintfcb(FILE *stream, const char *format, va_list ap)
+{
+	return cbvprintf(fputc, stream, format, ap);
+}
+
+int printfcb(const char *format, ...)
+{
+	va_list ap;
+	int rc;
+
+	va_start(ap, format);
+	rc = vprintfcb(format, ap);
+	va_end(ap);
+
+	return rc;
+}
+
+int vprintfcb(const char *format, va_list ap)
+{
+	return cbvprintf(fputc, stdout, format, ap);
+}
+
 int snprintfcb(char *str, size_t size, const char *format, ...)
 {
 	va_list ap;