Introduce `tf_snprintf`
This is a reduced version of `snprintf` that only supports formats '%d',
'%i' and '%u'. It can be used when the full `snprintf` is not needed in
order to save memory. If it finds an unknown format specifier, it
prints an error message and panics.
Change-Id: I2cb06fcdf74cda2c43caf73ae0762a91499fc04e
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/common/tf_snprintf.c b/common/tf_snprintf.c
new file mode 100644
index 0000000..a99ab7a
--- /dev/null
+++ b/common/tf_snprintf.c
@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <debug.h>
+#include <platform.h>
+#include <stdarg.h>
+
+static void unsigned_dec_print(char **s, size_t n, size_t *chars_printed,
+ unsigned int unum)
+{
+ /* Enough for a 32-bit unsigned decimal integer (4294967295). */
+ unsigned char num_buf[10];
+ int i = 0, rem;
+
+ do {
+ rem = unum % 10;
+ num_buf[i++] = '0' + rem;
+ } while (unum /= 10);
+
+ while (--i >= 0) {
+ if (*chars_printed < n)
+ *(*s)++ = num_buf[i];
+ (*chars_printed)++;
+ }
+}
+
+/*******************************************************************
+ * Reduced snprintf to be used for Trusted firmware.
+ * The following type specifiers are supported:
+ *
+ * %d or %i - signed decimal format
+ * %u - unsigned decimal format
+ *
+ * The function panics on all other formats specifiers.
+ *
+ * It returns the number of characters that would be written if the
+ * buffer was big enough. If it returns a value lower than n, the
+ * whole string has been written.
+ *******************************************************************/
+int tf_snprintf(char *s, size_t n, const char *fmt, ...)
+{
+ va_list args;
+ int num;
+ unsigned int unum;
+ size_t chars_printed = 0;
+
+ if (n == 1) {
+ /* Buffer is too small to actually write anything else. */
+ *s = '\0';
+ n = 0;
+ } else if (n >= 2) {
+ /* Reserve space for the terminator character. */
+ n--;
+ }
+
+ va_start(args, fmt);
+ while (*fmt) {
+
+ if (*fmt == '%') {
+ fmt++;
+ /* Check the format specifier. */
+ switch (*fmt) {
+ case 'i':
+ case 'd':
+ num = va_arg(args, int);
+
+ if (num < 0) {
+ if (chars_printed < n)
+ *s++ = '-';
+ chars_printed++;
+
+ unum = (unsigned int)-num;
+ } else {
+ unum = (unsigned int)num;
+ }
+
+ unsigned_dec_print(&s, n, &chars_printed, unum);
+ break;
+ case 'u':
+ unum = va_arg(args, unsigned int);
+ unsigned_dec_print(&s, n, &chars_printed, unum);
+ break;
+ default:
+ /* Panic on any other format specifier. */
+ ERROR("tf_snprintf: specifier with ASCII code '%d' not supported.",
+ *fmt);
+ plat_panic_handler();
+ }
+ fmt++;
+ continue;
+ }
+
+ if (chars_printed < n)
+ *s++ = *fmt;
+ fmt++;
+ chars_printed++;
+ }
+
+ va_end(args);
+
+ if (n > 0)
+ *s = '\0';
+
+ return chars_printed;
+}