1 files changed, 98 insertions, 0 deletions
diff --git a/util/snprintf.c b/util/snprintf.c
new file mode 100644
index 0000000..1544a6c
--- /dev/null
+++ b/util/snprintf.c
@@ -0,0 +1,98 @@
+// See LICENSE for license details.
+
+#include <stdint.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdbool.h>
+
+int vsnprintf(char* out, size_t n, const char* s, va_list vl)
+{
+  bool format = false;
+  bool longarg = false;
+  size_t pos = 0;
+  for( ; *s; s++)
+  {
+    if(format)
+    {
+      switch(*s)
+      {
+        case 'l':
+          longarg = true;
+          break;
+        case 'p':
+          longarg = true;
+          if (++pos < n) out[pos-1] = '0';
+          if (++pos < n) out[pos-1] = 'x';
+        case 'x':
+        {
+          long num = longarg ? va_arg(vl, long) : va_arg(vl, int);
+          for(int i = 2*(longarg ? sizeof(long) : sizeof(int))-1; i >= 0; i--) {
+            int d = (num >> (4*i)) & 0xF;
+            if (++pos < n) out[pos-1] = (d < 10 ? '0'+d : 'a'+d-10);
+          }
+          longarg = false;
+          format = false;
+          break;
+        }
+        case 'd':
+        {
+          long num = longarg ? va_arg(vl, long) : va_arg(vl, int);
+          if (num < 0) {
+            num = -num;
+            if (++pos < n) out[pos-1] = '-';
+          }
+          long digits = 1;
+          for (long nn = num; nn /= 10; digits++)
+            ;
+          for (int i = digits-1; i >= 0; i--) {
+            if (pos + i + 1 < n) out[pos + i] = '0' + (num % 10);
+            num /= 10;
+          }
+          pos += digits;
+          longarg = false;
+          format = false;
+          break;
+        }
+        case 's':
+        {
+          const char* s2 = va_arg(vl, const char*);
+          while (*s2) {
+            if (++pos < n)
+              out[pos-1] = *s2;
+            s2++;
+          }
+          longarg = false;
+          format = false;
+          break;
+        }
+        case 'c':
+        {
+          if (++pos < n) out[pos-1] = (char)va_arg(vl,int);
+          longarg = false;
+          format = false;
+          break;
+        }
+        default:
+          break;
+      }
+    }
+    else if(*s == '%')
+      format = true;
+    else
+      if (++pos < n) out[pos-1] = *s;
+  }
+  if (pos < n)
+    out[pos] = 0;
+  else if (n)
+    out[n-1] = 0;
+  return pos;
+}
+
+int snprintf(char* out, size_t n, const char* s, ...)
+{
+  va_list vl;
+  va_start(vl, s);
+  int res = vsnprintf(out, n, s, vl);
+  va_end(vl);
+  return res;
+}