Move everything into a new repo.

1 files changed, 42 insertions, 0 deletions

diff --git a/userland/libc/stdio/snprintf.c b/userland/libc/stdio/snprintf.c
new file mode 100644
index 0000000..328442a
--- /dev/null
+++ b/userland/libc/stdio/snprintf.c
@@ -0,0 +1,42 @@
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+struct sn_cookie {
+  char *s;
+  size_t n;
+};
+
+#define MIN(a, b) ((a) < (b) ? (a) : (b))
+
+size_t sn_write(FILE *f, const unsigned char *s, const size_t l) {
+  struct sn_cookie *c = f->cookie;
+  size_t k = MIN(l, c->n);
+  memcpy(c->s, s, k);
+  c->s += k;
+  c->n -= k;
+  *(c->s) = '\0';
+  // Upon successful completion, the snprintf() function shall return the number
+  // of bytes that would be written to s had n been sufficiently large excluding
+  // the terminating null byte.
+  return l;
+}
+
+int vsnprintf(char *str, size_t size, const char *format, va_list ap) {
+  char dummy[1];
+  struct sn_cookie c = {.s = (size ? str : dummy), .n = (size ? size - 1 : 0)};
+  FILE f = {
+      .write = sn_write,
+      .cookie = &c,
+  };
+  return vfprintf(&f, format, ap);
+}
+
+int snprintf(char *str, size_t size, const char *format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  int rc = vsnprintf(str, size, format, ap);
+  va_end(ap);
+  return rc;
+}