1 files changed, 33 insertions, 0 deletions
diff --git a/src/libstddjb/string_format.c b/src/libstddjb/string_format.c
new file mode 100644
index 0000000..f81b03d
--- /dev/null
+++ b/src/libstddjb/string_format.c
@@ -0,0 +1,33 @@
+/* ISC license. */
+
+#include <errno.h>
+#include <skalibs/bytestr.h>
+#include <skalibs/stralloc.h>
+
+int string_format (stralloc *sa, char const *vars, char const *format, char const *const *args)
+{
+  static unsigned char const tab[2][4] = { "1442", "4833" } ;
+  char class[256] = "3222222222222222222222222222222222222022222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222" ;
+  unsigned int varlen = str_len(vars) ;
+  unsigned int base = sa->len ;
+  int wasnull = !sa->s ;
+  unsigned int state = 0 ;
+
+  for (; state < varlen ; state++)
+    if (class[(unsigned char)vars[state]] == '2')
+      class[(unsigned char)vars[state]] = '1' ;
+    else return (errno = EINVAL, 0) ;
+
+  for (state = 0 ; state < 2 ; format++)
+  {
+    unsigned char c = tab[state][class[(unsigned char)(*format)] - '0'] ;
+    state = c & 3 ;
+    if (c & 4) if (!stralloc_catb(sa, format, 1)) goto err ;
+    if (c & 8) if (!stralloc_cats(sa, args[byte_chr(vars, varlen, *format)])) goto err ;
+  }
+  if (state == 2) return 1 ;
+  errno = EINVAL ;
+ err:
+  if (wasnull) stralloc_free(sa) ; else sa->len = base ;
+  return 0 ;
+}