1 files changed, 99 insertions, 0 deletions
diff --git a/source/blender/io/common/intern/string_utils.cc b/source/blender/io/common/intern/string_utils.cc
new file mode 100644
index 00000000000..01107b0866e
--- /dev/null
+++ b/source/blender/io/common/intern/string_utils.cc
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include "IO_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 mininum spec, use an external library. */
+#include "fast_float.h"
+#include <charconv>
+
+namespace blender::io {
+
+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 == '\\';
+}
+
+StringRef drop_whitespace(StringRef str)
+{
+  while (!str.is_empty() && is_whitespace(str[0])) {
+    str = str.drop_prefix(1);
+  }
+  return str;
+}
+
+StringRef drop_non_whitespace(StringRef str)
+{
+  while (!str.is_empty() && !is_whitespace(str[0])) {
+    str = str.drop_prefix(1);
+  }
+  return str;
+}
+
+static StringRef drop_plus(StringRef str)
+{
+  if (!str.is_empty() && str[0] == '+') {
+    str = str.drop_prefix(1);
+  }
+  return str;
+}
+
+StringRef parse_float(StringRef str, float fallback, float &dst, bool skip_space)
+{
+  if (skip_space) {
+    str = drop_whitespace(str);
+  }
+  str = drop_plus(str);
+  fast_float::from_chars_result res = fast_float::from_chars(str.begin(), str.end(), dst);
+  if (res.ec == std::errc::invalid_argument || res.ec == std::errc::result_out_of_range) {
+    dst = fallback;
+  }
+  return StringRef(res.ptr, str.end());
+}
+
+StringRef parse_floats(StringRef str, float fallback, float *dst, int count)
+{
+  for (int i = 0; i < count; ++i) {
+    str = parse_float(str, fallback, dst[i]);
+  }
+  return str;
+}
+
+StringRef parse_int(StringRef str, int fallback, int &dst, bool skip_space)
+{
+  if (skip_space) {
+    str = drop_whitespace(str);
+  }
+  str = drop_plus(str);
+  std::from_chars_result res = std::from_chars(str.begin(), str.end(), dst);
+  if (res.ec == std::errc::invalid_argument || res.ec == std::errc::result_out_of_range) {
+    dst = fallback;
+  }
+  return StringRef(res.ptr, str.end());
+}
+
+}  // namespace blender::io