support: Define substr in terms of length rather than end index

This makes it more consistent with both Span and the C++ standard library.
yeetari · Mar 4, 2024 · 30a654e · 30a654e
1 parent 9ee543b
commit 30a654e
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Showing 4 changed files with 15 additions and 15 deletions.
diff --git a/engine/include/vull/support/string_view.hh b/engine/include/vull/support/string_view.hh
@@ -12,19 +12,19 @@ public:
     using Span::Span;
     constexpr StringView(const char *c_string) : Span(c_string, __builtin_strlen(c_string)) {}
 
-    constexpr StringView substr(size_t begin) const;
-    constexpr StringView substr(size_t begin, size_t end) const;
+    constexpr StringView substr(size_t offset) const;
+    constexpr StringView substr(size_t offset, size_t length) const;
     constexpr bool operator==(StringView other) const;
     constexpr size_t length() const { return size(); }
 };
 
-constexpr StringView StringView::substr(size_t begin) const {
-    return substr(begin, length());
+constexpr StringView StringView::substr(size_t offset) const {
+    return substr(offset, length() - offset);
 }
 
-constexpr StringView StringView::substr(size_t begin, size_t end) const {
-    VULL_ASSERT(begin + (end - begin) <= size());
-    return {data() + begin, end - begin};
+constexpr StringView StringView::substr(size_t offset, size_t length) const {
+    VULL_ASSERT(offset + length <= size());
+    return {data() + offset, length};
 }
 
 constexpr bool StringView::operator==(StringView other) const {

diff --git a/engine/sources/json/lexer.cc b/engine/sources/json/lexer.cc
@@ -28,7 +28,7 @@ Token Lexer::next_token() {
         if (m_head > m_source.length()) {
             return Token(TokenKind::Invalid);
         }
-        return Token(m_source.substr(begin + 1, m_head - 1));
+        return Token(m_source.substr(begin + 1, m_head - begin - 2));
     }
 
     if (ch == '-') {
@@ -49,15 +49,15 @@ Token Lexer::next_token() {
         return Token(static_cast<int64_t>(number.get<uint64_t>()));
     }
 
-    if (ch == 'n' && m_head + 3 <= m_source.length() && m_source.substr(m_head, m_head + 3) == "ull") {
+    if (ch == 'n' && m_head + 3 <= m_source.length() && m_source.substr(m_head, 3) == "ull") {
         m_head += 3;
         return Token(TokenKind::Null);
     }
-    if (ch == 't' && m_head + 3 <= m_source.length() && m_source.substr(m_head, m_head + 3) == "rue") {
+    if (ch == 't' && m_head + 3 <= m_source.length() && m_source.substr(m_head, 3) == "rue") {
         m_head += 3;
         return Token(TokenKind::True);
     }
-    if (ch == 'f' && m_head + 4 <= m_source.length() && m_source.substr(m_head, m_head + 4) == "alse") {
+    if (ch == 'f' && m_head + 4 <= m_source.length() && m_source.substr(m_head, 4) == "alse") {
         m_head += 4;
         return Token(TokenKind::False);
     }

diff --git a/engine/sources/script/lexer.cc b/engine/sources/script/lexer.cc
@@ -40,7 +40,7 @@ Token Lexer::next_token() {
         while (is_ident(m_source[m_head]) || is_digit(m_source[m_head])) {
             m_head++;
         }
-        auto string = m_source.view().substr(position, m_head);
+        auto string = m_source.view().substr(position, m_head - position);
         // TODO: Perfect hashing (http://0x80.pl/notesen/2023-04-30-lookup-in-strings.html) or trie switch.
         if (string == "elif") {
             return {TokenKind::KW_elif, position, m_line};
@@ -124,7 +124,7 @@ SourcePosition Lexer::recover_position(const Token &token) const {
         line_end++;
     }
 
-    const auto line_view = m_source.view().substr(line_head, line_end);
+    const auto line_view = m_source.view().substr(line_head, line_end - line_head);
     return {m_file_name, line_view, token.line(), token.position() - line_head + 1};
 }
 

diff --git a/engine/sources/shaderc/lexer.cc b/engine/sources/shaderc/lexer.cc
@@ -60,7 +60,7 @@ Token Lexer::next_token(bool in_comment) {
         while (is_ident(m_source[m_head]) || is_digit(m_source[m_head])) {
             m_head++;
         }
-        auto string = m_source.view().substr(position, m_head);
+        auto string = m_source.view().substr(position, m_head - position);
         if (string == "fn") {
             return MAKE_TOKEN(TokenKind::KW_fn);
         }
@@ -131,7 +131,7 @@ SourcePosition Lexer::recover_position(const Token &token) const {
         line_end++;
     }
 
-    const auto line_view = m_source.view().substr(line_head, line_end);
+    const auto line_view = m_source.view().substr(line_head, line_end - line_head);
     return {m_file_name, line_view, token.line(), token.position() - line_head + 1};
 }