Add printf example

source/m3_api_libc.c

@@ -75,6 +75,97 @@ m3ApiRawFunction(m3_libc_print)
     m3ApiReturn(i_size);
 }
 
+static
+void internal_itoa(int n, char s[], int radix)
+{
+	static char const HEXDIGITS[0x10] = {
+		'0', '1', '2', '3', '4', '5', '6', '7',
+	    '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
+	};
+
+    int i, j, sign;
+    char c;
+
+    if ((sign = n) < 0) { n = -n; }
+    i = 0;
+    do {
+        s[i++] = HEXDIGITS[n % radix];
+    } while ((n /= radix) > 0);
+
+    if (sign < 0) { s[i++] = '-'; }
+    s[i] = '\0';
+
+    // reverse
+    for (i = 0, j = strlen(s)-1; i<j; i++, j--) {
+        c = s[i];
+        s[i] = s[j];
+        s[j] = c;
+    }
+}
+
+m3ApiRawFunction(m3_libc_printf)
+{
+    m3ApiReturnType (int32_t)
+
+	m3ApiGetArgMem  (const char*,	i_fmt)
+    m3ApiGetArgMem  (u32*,     		i_args)
+
+	m3ApiCheckMem(i_fmt, 1);
+
+	size_t fmt_len = strlen(i_fmt);
+	m3ApiCheckMem(i_fmt, fmt_len+1);
+
+	FILE* file = stdout;
+
+	int32_t length = 0;
+	char ch;
+    while ((ch = *i_fmt++)) {
+        if ( '%' != ch ) {
+            putc(ch, file);
+            length++;
+            continue;
+        }
+		ch = *i_fmt++;
+		switch (ch) {
+			case '%': {
+				fputc('%', file);
+				length++;
+				break;
+			}
+			case 'c': {
+				m3ApiCheckMem(i_args, sizeof(int));
+				char char_temp = *i_args++;
+				fputc(char_temp, file);
+				length++;
+				break;
+			}
+			case 'd':
+			case 'x': {
+				m3ApiCheckMem(i_args, sizeof(int));
+				int int_temp = *i_args++;
+				char buffer[32] = { 0, };
+				internal_itoa(int_temp, buffer, (ch == 'x') ? 16 : 10);
+				fputs(buffer, file);
+				length += strlen(buffer);
+				break;
+			}
+			case 's': {
+				m3ApiCheckMem(i_args, sizeof(int));
+				const char* string_temp = m3ApiOffsetToPtr(*i_args++);
+				size_t string_len = strlen(string_temp);
+
+				m3ApiCheckMem(string_temp, string_len+1);
+
+				fputs(string_temp, file);
+				length += string_len;
+				break;
+			}
+        }
+    }
+
+    m3ApiReturn(length);
+}
+
 m3ApiRawFunction(m3_libc_clock_ms)
 {
     m3ApiReturnType (uint32_t)
@@ -128,6 +219,7 @@ _   (SuppressLookupFailure (m3_LinkRawFunction (module, env, "_memcpy",
 _   (SuppressLookupFailure (m3_LinkRawFunction (module, env, "_abort",            "v()",     &m3_libc_abort)));
 _   (SuppressLookupFailure (m3_LinkRawFunction (module, env, "_exit",             "v(i)",    &m3_libc_exit)));
 _   (SuppressLookupFailure (m3_LinkRawFunction (module, env, "clock_ms",          "i()",     &m3_libc_clock_ms)));
+_   (SuppressLookupFailure (m3_LinkRawFunction (module, env, "printf",            "i(**)",   &m3_libc_printf)));
 
 _catch:
     return result;