1 files changed, 92 insertions, 0 deletions
diff --git a/nss/buf.c b/nss/buf.c
new file mode 100644
index 0000000..75c62f9
--- /dev/null
+++ b/nss/buf.c
@@ -0,0 +1,92 @@
+#define _GNU_SOURCE
+#include <errno.h>
+#include <stdio.h>
+#include <syslog.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdlib.h>
+
+#include "cgen.h"
+#include "buf.h"
+
+#include "config/debug.h"
+
+
+int write_buf(char** buf, size_t * buflen, const char* val)
+{
+  /* write_buf will not write outside of (*buf)[0..(*buflen-1)]
+   * if *buflen > strlen(val), then write_buf will ensure that *buf points to a null-terminated string.
+   * on success, write_buf will advance *buf to the next free char,
+   *                            set *buflen to indicate the quantity of remaining space,
+   *                            and return 0.
+   * on error, write_buf will set errno, return 1, and will not modify *buf or *buflen.
+   * *buf and val should not overlap.
+   */
+
+  LET(size_t copy_amt = strlen(val) + 1, copy_amt == 0,
+      "Integer overflow.", out_err_overflow);
+
+  if (*buflen < copy_amt)
+    goto out_err_range;
+
+  memcpy(*buf, val, copy_amt);
+
+  *buf += copy_amt;
+  *buflen -= copy_amt;
+  return 0;
+
+out_err_overflow:
+  errno = EOVERFLOW;
+  return 1;
+
+out_err_range:
+  errno = ERANGE;
+  return 1;
+}
+
+int format_buf(char** buf, size_t* buflen, const char* fmt, ...)
+{
+  /* format_buf will not write outside of (*buf)[0..(*buflen-1)]
+   * if *buflen > 0, format_buf will ensure that *buf points to a null-terminated string.
+   * on success, format_buf will advance *buf to the next free char,
+   *                             set *buflen to indicate the quantity of remaining space,
+   *                             and return 0.
+   * on error, format_buf will set errno, return 1, and will not modify *buf or *buflen.
+   * *buf should not overlap with fmt or any optional arguments.
+   */
+  if (*buflen < 1)
+  {
+    errno = ERANGE;
+    return 1;
+  }
+
+  va_list ap;
+  va_start(ap, fmt);
+
+  int status = vsnprintf(*buf, *buflen, fmt, ap);
+  int err = errno;
+
+  va_end(ap);
+
+  if (status < 0)
+    goto out_err;
+
+  size_t written = (size_t) status;
+
+  err = ERANGE;
+  if (written >= *buflen)
+    goto out_err;
+
+  err = EOVERFLOW;
+  LET(written = written + 1, written == 0,
+      "Integer overflow.", out_err);
+
+  *buf += written;
+  *buflen -= written;
+  return 0;
+
+out_err:
+  (*buf)[*buflen-1] = '\0';
+  errno = err;
+  return 1;
+}