libcatom: add sprintf

sw/lib/include/stdio.h

@@ -112,6 +112,14 @@ int	fprintf (FILE * file, const char * fmt, ...)
 int	printf (const char * fmt, ...)
         __attribute__((__format__ (__printf__, 1, 2)));
 
+/**
+ * @brief Writes formatted string to a char buffer
+ * @param str char buffer
+ * @param fmt format string
+ * @return int number of chars written
+ */
+int sprintf(char *str, const char *fmt, ...)
+    __attribute__((__format__ (__printf__, 2, 3)));
 
 // ========== Non Standard Functions ==========
 

sw/lib/libcatom/stdio.c

@@ -2,6 +2,7 @@
 #include <stdarg.h>
 #include <stdint.h>
 #include <stdbool.h>
+#include <assert.h>
 
 #define BACKSPACE 0x7f
 
@@ -355,6 +356,39 @@ int printf(const char *fmt, ...)
 }
 
 
+static char * __sstream_strbuf = NULL;
+static int __sstream_strbuf_writepos = -1;
+int __sstream_write(char * bf, uint32_t sz){
+    assert(__sstream_strbuf != NULL);
+    __sstream_strbuf[__sstream_strbuf_writepos++] = bf[0];
+    return 0;
+}
+
+int vsprintf(char *str, const char *fmt, va_list args) {
+    // setup a fake string stream that writes to a string buffer
+    FILE fake_sstream = {.read=NULL, .write=__sstream_write};
+    __sstream_strbuf = str;
+    __sstream_strbuf_writepos = 0;
+
+    int rv = vfprintf(&fake_sstream, fmt, args);
+
+    // terminate with nullchar
+    fake_sstream.write("\0", 1);
+
+    // cleanup after we're done
+    __sstream_strbuf = NULL;
+    __sstream_strbuf_writepos = -1;
+    return rv;
+}
+
+int sprintf(char *str, const char *fmt, ...) {
+    va_list args;
+    va_start(args, fmt);
+    int rv = vsprintf(str, fmt, args);
+    va_end(args);
+    return rv;
+}
+
 void dumphexbuf(char *buf, unsigned len, unsigned base_addr)
 {
     const int bpw = 4; // bytes per word