[Glacier] Add a StringView class and StrSplit method.

lib/glacier/string/string_view.cpp

@@ -0,0 +1,73 @@
+#include "glacier/string/string_view.h"
+
+namespace glcr {
+namespace {
+
+uint64_t cstrlen(const char* ptr) {
+  uint64_t len = 0;
+  while (ptr[len] != '\0') {
+    len++;
+  }
+  return len;
+}
+
+}  // namespace
+
+StringView::StringView() {}
+StringView::StringView(const char* str) : value_(str), size_(cstrlen(str)) {}
+StringView::StringView(const char* str, uint64_t count)
+    : value_(str), size_(count) {}
+
+const char* StringView::data() const { return value_; }
+
+uint64_t StringView::size() const { return size_; }
+
+bool StringView::empty() const { return size_ == 0; }
+
+char StringView::at(uint64_t pos) const { return value_[pos]; }
+
+uint64_t StringView::find(char c, uint64_t pos) const {
+  for (uint64_t i = pos; i < size_; i++) {
+    if (value_[i] == c) {
+      return i;
+    }
+  }
+  return npos;
+}
+
+StringView StringView::substr(uint64_t start, uint64_t count) const {
+  // FIXME: Report an error here maybe.
+  if (start >= size_) {
+    return StringView{};
+  }
+  if (start + count > size_) {
+    count = size_ - start;
+  }
+  return StringView(value_ + start, count);
+}
+
+bool operator==(const StringView& str1, const StringView& str2) {
+  if (str1.empty() && str2.empty()) {
+    return true;
+  }
+  if (str1.size() != str2.size()) {
+    return false;
+  }
+  if (str1.data() == str2.data()) {
+    // Short circuit if they are the same exact string.
+    return true;
+  }
+  for (uint64_t i = 0; i < str1.size(); i++) {
+    if (str1.at(i) != str2.at(i)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool operator!=(const StringView& str1, const StringView& str2) {
+  return !(str1 == str2);
+}
+
+}  // namespace glcr