AK: Add failable try_* functions to StringBuilder

These will allow us to start using TRY() with StringBuilder operations.

AK/StringBuilder.cpp

@@ -1,12 +1,11 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
 #include <AK/ByteBuffer.h>
 #include <AK/Checked.h>
-#include <AK/Memory.h>
 #include <AK/PrintfImplementation.h>
 #include <AK/StdLibExtras.h>
 #include <AK/String.h>
@@ -38,23 +37,40 @@ StringBuilder::StringBuilder(size_t initial_capacity)
     m_buffer.ensure_capacity(initial_capacity);
 }
 
-void StringBuilder::append(StringView str)
+ErrorOr<void> StringBuilder::try_append(StringView string)
 {
-    if (str.is_empty())
+    if (string.is_empty())
-        return;
+        return {};
-    MUST(will_append(str.length()));
+    TRY(will_append(string.length()));
-    MUST(m_buffer.try_append(str.characters_without_null_termination(), str.length()));
+    TRY(m_buffer.try_append(string.characters_without_null_termination(), string.length()));
+    return {};
+}
+
+ErrorOr<void> StringBuilder::try_append(char ch)
+{
+    TRY(will_append(1));
+    TRY(m_buffer.try_append(&ch, 1));
+    return {};
+}
+
+void StringBuilder::append(StringView string)
+{
+    MUST(try_append(string));
+}
+
+ErrorOr<void> StringBuilder::try_append(char const* characters, size_t length)
+{
+    return try_append(StringView { characters, length });
 }
 
 void StringBuilder::append(char const* characters, size_t length)
 {
-    append(StringView { characters, length });
+    MUST(try_append(characters, length));
 }
 
 void StringBuilder::append(char ch)
 {
-    MUST(will_append(1));
+    MUST(try_append(ch));
-    MUST(m_buffer.try_append(&ch, 1));
 }
 
 void StringBuilder::appendvf(char const* fmt, va_list ap)
@@ -93,32 +109,50 @@ void StringBuilder::clear()
     m_buffer.clear();
 }
 
-void StringBuilder::append_code_point(u32 code_point)
+ErrorOr<void> StringBuilder::try_append_code_point(u32 code_point)
 {
     auto nwritten = AK::UnicodeUtils::code_point_to_utf8(code_point, [this](char c) { append(c); });
     if (nwritten < 0) {
-        append(0xef);
+        TRY(try_append(0xef));
-        append(0xbf);
+        TRY(try_append(0xbf));
-        append(0xbd);
+        TRY(try_append(0xbd));
     }
+    return {};
+}
+
+void StringBuilder::append_code_point(u32 code_point)
+{
+    MUST(try_append_code_point(code_point));
+}
+
+ErrorOr<void> StringBuilder::try_append(Utf16View const& utf16_view)
+{
+    for (size_t i = 0; i < utf16_view.length_in_code_units();) {
+        auto code_point = utf16_view.code_point_at(i);
+        TRY(try_append_code_point(code_point));
+
+        i += (code_point > 0xffff ? 2 : 1);
+    }
+    return {};
 }
 
 void StringBuilder::append(Utf16View const& utf16_view)
 {
-    for (size_t i = 0; i < utf16_view.length_in_code_units();) {
+    MUST(try_append(utf16_view));
-        auto code_point = utf16_view.code_point_at(i);
-        append_code_point(code_point);
-
-        i += (code_point > 0xffff ? 2 : 1);
 }
+
+ErrorOr<void> StringBuilder::try_append(Utf32View const& utf32_view)
+{
+    for (size_t i = 0; i < utf32_view.length(); ++i) {
+        auto code_point = utf32_view.code_points()[i];
+        TRY(try_append_code_point(code_point));
+    }
+    return {};
 }
 
 void StringBuilder::append(Utf32View const& utf32_view)
 {
-    for (size_t i = 0; i < utf32_view.length(); ++i) {
+    MUST(try_append(utf32_view));
-        auto code_point = utf32_view.code_points()[i];
-        append_code_point(code_point);
-    }
 }
 
 void StringBuilder::append_as_lowercase(char ch)

AK/StringBuilder.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -21,6 +21,19 @@ public:
     explicit StringBuilder(size_t initial_capacity = inline_capacity);
     ~StringBuilder() = default;
 
+    ErrorOr<void> try_append(StringView);
+    ErrorOr<void> try_append(Utf16View const&);
+    ErrorOr<void> try_append(Utf32View const&);
+    ErrorOr<void> try_append_code_point(u32);
+    ErrorOr<void> try_append(char);
+    template<typename... Parameters>
+    ErrorOr<void> try_appendff(CheckedFormatString<Parameters...>&& fmtstr, Parameters const&... parameters)
+    {
+        VariadicFormatParams variadic_format_params { parameters... };
+        return vformat(*this, fmtstr.view(), variadic_format_params);
+    }
+    ErrorOr<void> try_append(char const*, size_t);
+
     void append(StringView);
     void append(Utf16View const&);
     void append(Utf32View const&);