1 files changed, 100 insertions, 0 deletions
diff --git a/source/blender/io/wavefront_obj/importer/obj_import_string_utils.cc b/source/blender/io/wavefront_obj/importer/obj_import_string_utils.cc
new file mode 100644
index 00000000000..c8eaa046e68
--- /dev/null
+++ b/source/blender/io/wavefront_obj/importer/obj_import_string_utils.cc
@@ -0,0 +1,100 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "obj_import_string_utils.hh"
+
+/* NOTE: we could use C++17 <charconv> from_chars to parse
+ * floats, but even if some compilers claim full support,
+ * their standard libraries are not quite there yet.
+ * LLVM/libc++ only has a float parser since LLVM 14,
+ * and gcc/libstdc++ since 11.1. So until at least these are
+ * the minimum spec, use an external library. */
+#include "fast_float.h"
+#include <charconv>
+
+namespace blender::io::obj {
+
+StringRef read_next_line(StringRef &buffer)
+{
+  const char *start = buffer.begin();
+  const char *end = buffer.end();
+  size_t len = 0;
+  char prev = 0;
+  const char *ptr = start;
+  while (ptr < end) {
+    char c = *ptr++;
+    if (c == '\n' && prev != '\\') {
+      break;
+    }
+    prev = c;
+    ++len;
+  }
+
+  buffer = StringRef(ptr, end);
+  return StringRef(start, len);
+}
+
+static bool is_whitespace(char c)
+{
+  return c <= ' ' || c == '\\';
+}
+
+const char *drop_whitespace(const char *p, const char *end)
+{
+  while (p < end && is_whitespace(*p)) {
+    ++p;
+  }
+  return p;
+}
+
+const char *drop_non_whitespace(const char *p, const char *end)
+{
+  while (p < end && !is_whitespace(*p)) {
+    ++p;
+  }
+  return p;
+}
+
+static const char *drop_plus(const char *p, const char *end)
+{
+  if (p < end && *p == '+') {
+    ++p;
+  }
+  return p;
+}
+
+const char *parse_float(
+    const char *p, const char *end, float fallback, float &dst, bool skip_space)
+{
+  if (skip_space) {
+    p = drop_whitespace(p, end);
+  }
+  p = drop_plus(p, end);
+  fast_float::from_chars_result res = fast_float::from_chars(p, end, dst);
+  if (res.ec == std::errc::invalid_argument || res.ec == std::errc::result_out_of_range) {
+    dst = fallback;
+  }
+  return res.ptr;
+}
+
+const char *parse_floats(const char *p, const char *end, float fallback, float *dst, int count)
+{
+  for (int i = 0; i < count; ++i) {
+    p = parse_float(p, end, fallback, dst[i]);
+  }
+  return p;
+}
+
+const char *parse_int(const char *p, const char *end, int fallback, int &dst, bool skip_space)
+{
+  if (skip_space) {
+    p = drop_whitespace(p, end);
+  }
+  p = drop_plus(p, end);
+  std::from_chars_result res = std::from_chars(p, end, dst);
+  if (res.ec == std::errc::invalid_argument || res.ec == std::errc::result_out_of_range) {
+    dst = fallback;
+  }
+  return res.ptr;
+}
+
+}  // namespace blender::io::obj