AK: Add a GenericLexer and extend the JsonParser with it (#2696)

Author: https://github.com/benit8 🔰
Commit: https://github.com/SerenityOS/serenity/commit/7b356c33cb3
Pull-request: https://github.com/SerenityOS/serenity/pull/2696
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/Dexesttp
Reviewed-by: https://github.com/stelar7

AK/GenericLexer.cpp

@@ -0,0 +1,335 @@
+/*
+ * Copyright (c) 2020, Benoit Lormeau <blormeau@outlook.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/Assertions.h>
+#include <AK/GenericLexer.h>
+
+namespace AK {
+
+GenericLexer::GenericLexer(const StringView& input)
+    : m_input(input)
+{
+}
+
+GenericLexer::~GenericLexer()
+{
+}
+
+// Tells whether the parser's index has reached input's end
+bool GenericLexer::is_eof() const
+{
+    return m_index >= m_input.length();
+}
+
+// Returns the current character at the parser index, plus `offset` if specified
+char GenericLexer::peek(size_t offset) const
+{
+    return (m_index + offset < m_input.length()) ? m_input[m_index + offset] : '\0';
+}
+
+// Tests the next character in the input
+bool GenericLexer::next_is(char expected) const
+{
+    return peek() == expected;
+}
+
+// Tests if the `expected` string comes next in the input
+bool GenericLexer::next_is(const char* expected) const
+{
+    for (size_t i = 0; expected[i] != '\0'; ++i)
+        if (peek(i) != expected[i])
+            return false;
+    return true;
+}
+
+// Tests the next character against a Condition
+bool GenericLexer::next_is(Condition condition) const
+{
+    return condition(peek());
+}
+
+// Consume a character and advance the parser index
+char GenericLexer::consume()
+{
+    ASSERT(!is_eof());
+    return m_input[m_index++];
+}
+
+// Consume the given character if it is next in the input
+bool GenericLexer::consume_specific(char specific)
+{
+    if (peek() != specific)
+        return false;
+
+    ignore();
+    return true;
+}
+
+// Consume the given string if it is next in the input
+bool GenericLexer::consume_specific(const char* str)
+{
+    if (!next_is(str))
+        return false;
+
+    ignore(__builtin_strlen(str));
+    return true;
+}
+
+// Consume a number of characters
+StringView GenericLexer::consume(size_t count)
+{
+    if (count == 0)
+        return {};
+
+    size_t start = m_index;
+    size_t length = min(count, m_input.length() - m_index);
+    m_index += length;
+
+    return m_input.substring_view(start, length);
+}
+
+// Consume the rest of the input
+StringView GenericLexer::consume_all()
+{
+    if (is_eof())
+        return {};
+
+    auto rest = m_input.substring_view(m_index, m_input.length() - m_index);
+    m_index = m_input.length();
+    return rest;
+}
+
+// Consume until a new line is found
+StringView GenericLexer::consume_line()
+{
+    size_t start = m_index;
+    while (!is_eof() && peek() != '\r' && peek() != '\n')
+        m_index++;
+    size_t length = m_index - start;
+
+    consume_specific('\r');
+    consume_specific('\n');
+
+    if (length == 0)
+        return {};
+    return m_input.substring_view(start, length);
+}
+
+// Consume and return characters while `condition` returns true
+StringView GenericLexer::consume_while(Condition condition)
+{
+    size_t start = m_index;
+    while (!is_eof() && condition(peek()))
+        m_index++;
+    size_t length = m_index - start;
+
+    if (length == 0)
+        return {};
+    return m_input.substring_view(start, length);
+}
+
+// Consume and return characters until `stop` is peek'd
+// The `stop` character is ignored, as it is user-defined
+StringView GenericLexer::consume_until(char stop)
+{
+    size_t start = m_index;
+    while (!is_eof() && peek() != stop)
+        m_index++;
+    size_t length = m_index - start;
+
+    ignore();
+
+    if (length == 0)
+        return {};
+    return m_input.substring_view(start, length);
+}
+
+// Consume and return characters until the string `stop` is found
+// The `stop` string is ignored, as it is user-defined
+StringView GenericLexer::consume_until(const char* stop)
+{
+    size_t start = m_index;
+    while (!is_eof() && !next_is(stop))
+        m_index++;
+    size_t length = m_index - start;
+
+    ignore(__builtin_strlen(stop));
+
+    if (length == 0)
+        return {};
+    return m_input.substring_view(start, length);
+}
+
+// Consume and return characters until `condition` return true
+StringView GenericLexer::consume_until(Condition condition)
+{
+    size_t start = m_index;
+    while (!is_eof() && !condition(peek()))
+        m_index++;
+    size_t length = m_index - start;
+
+    if (length == 0)
+        return {};
+    return m_input.substring_view(start, length);
+}
+
+// Consume a string surrounded by single or double quotes
+// The returned StringView does not include the quotes
+StringView GenericLexer::consume_quoted_string()
+{
+    if (!is_quote(peek()))
+        return {};
+
+    char quote_char = consume();
+    size_t start = m_index;
+    while (!is_eof() && peek() != quote_char)
+        m_index++;
+    size_t length = m_index - start;
+
+    if (peek() != quote_char) {
+        m_index = start - 1; // Restore the index in case the string is unterminated
+        return {};
+    }
+
+    ignore();
+
+    return m_input.substring_view(start, length);
+}
+
+// Ignore a number of characters (1 by default)
+void GenericLexer::ignore(size_t count)
+{
+    count = min(count, m_input.length() - m_index);
+    m_index += count;
+}
+
+// Ignore characters while `condition` returns true
+void GenericLexer::ignore_while(Condition condition)
+{
+    while (!is_eof() && condition(peek()))
+        m_index++;
+}
+
+// Ignore characters until `stop` is peek'd
+// The `stop` character is ignored as it is user-defined
+void GenericLexer::ignore_until(char stop)
+{
+    while (!is_eof() && peek() != stop)
+        m_index++;
+
+    ignore();
+}
+
+// Ignore characters until the string `stop` is found
+// The `stop` string is ignored, as it is user-defined
+void GenericLexer::ignore_until(const char* stop)
+{
+    while (!is_eof() && !next_is(stop))
+        m_index++;
+
+    ignore(__builtin_strlen(stop));
+}
+
+// Ignore characters until `condition` return true
+// We don't skip the stop character as it may not be a single value
+void GenericLexer::ignore_until(Condition condition)
+{
+    while (!is_eof() && !condition(peek()))
+        m_index++;
+}
+
+
+bool is_control(char c)
+{
+    return (c >= 0 && c <= 31) || c == 127;
+}
+
+bool is_whitespace(char c)
+{
+    return (c >= '\t' && c <= '\r') || c == ' ';
+}
+
+bool is_lowercase(char c)
+{
+    return c >= 'a' && c <= 'z';
+}
+
+bool is_uppercase(char c)
+{
+    return c >= 'A' && c <= 'Z';
+}
+
+bool is_digit(char c)
+{
+    return c >= '0' && c <= '9';
+}
+
+bool is_punctuation(char c)
+{
+    return (c >= '!' && c <= '/')
+        || (c >= ':' && c <= '@')
+        || (c >= '[' && c <= '`')
+        || (c >= '{' && c <= '~');
+}
+
+bool is_printable(char c)
+{
+    return c >= ' ' && c <= '~';
+}
+
+bool is_graphic(char c)
+{
+    return c > ' ' && c <= '~';
+}
+
+bool is_alpha(char c)
+{
+    return is_lowercase(c) || is_uppercase(c);
+}
+
+bool is_alphanum(char c)
+{
+    return is_alpha(c) || is_digit(c);
+}
+
+bool is_hex_digit(char c)
+{
+    return is_digit(c)
+        || (c >= 'A' && c <= 'F')
+        || (c >= 'a' && c <= 'f');
+}
+
+bool is_quote(char c)
+{
+    return c == '\'' || c == '"';
+}
+
+bool is_path_separator(char c)
+{
+    return c == '/' || c == '\\';
+}
+
+}

AK/GenericLexer.h

@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2020, Benoit Lormeau <blormeau@outlook.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <AK/Function.h>
+#include <AK/StringView.h>
+
+namespace AK {
+
+class GenericLexer {
+public:
+    explicit GenericLexer(const StringView& input);
+    virtual ~GenericLexer();
+
+    using Condition = Function<bool(char)>;
+
+    size_t tell() const { return m_index; }
+    size_t tell_remaining() const { return m_input.length() - m_index; }
+
+    bool is_eof() const;
+
+    char peek(size_t offset = 0) const;
+
+    bool next_is(char expected) const;
+    bool next_is(const char* expected) const;
+    bool next_is(Condition) const;
+
+    char consume();
+    bool consume_specific(char specific);
+    bool consume_specific(const char* str);
+    StringView consume(size_t count);
+    StringView consume_all();
+    StringView consume_line();
+    StringView consume_while(Condition);
+    StringView consume_until(char stop);
+    StringView consume_until(const char* stop);
+    StringView consume_until(Condition);
+    // FIXME: provide an escape character
+    StringView consume_quoted_string();
+
+    void ignore(size_t count = 1);
+    void ignore_while(Condition);
+    void ignore_until(char stop);
+    void ignore_until(const char* stop);
+    void ignore_until(Condition);
+
+protected:
+    StringView m_input;
+    size_t m_index { 0 };
+};
+
+// ctype adaptors
+// FIXME: maybe put them in an another file?
+bool is_alpha(char);
+bool is_alphanum(char);
+bool is_control(char);
+bool is_digit(char);
+bool is_graphic(char);
+bool is_hex_digit(char);
+bool is_lowercase(char);
+bool is_path_separator(char);
+bool is_printable(char);
+bool is_punctuation(char);
+bool is_quote(char);
+bool is_uppercase(char);
+bool is_whitespace(char);
+
+}
+
+using AK::GenericLexer;
+
+using AK::is_alpha;
+using AK::is_alphanum;
+using AK::is_control;
+using AK::is_digit;
+using AK::is_graphic;
+using AK::is_hex_digit;
+using AK::is_lowercase;
+using AK::is_path_separator;
+using AK::is_printable;
+using AK::is_punctuation;
+using AK::is_quote;
+using AK::is_uppercase;
+using AK::is_whitespace;

AK/JsonParser.cpp

@@ -31,44 +31,7 @@
 
 namespace AK {
 
-static inline bool is_whitespace(char ch)
-{
-    return ch == ' ' || ch == '\n' || ch == '\t' || ch == '\v' || ch == '\r';
-}
-
-char JsonParser::peek() const
-{
-    if (m_index < m_input.length())
-        return m_input[m_index];
-    return '\0';
-}
-
-char JsonParser::consume()
-{
-    if (m_index < m_input.length())
-        return m_input[m_index++];
-    return '\0';
-}
-
-template<typename C>
-void JsonParser::consume_while(C condition)
-{
-    while (condition(peek()))
-        consume();
-}
-
-void JsonParser::consume_whitespace()
-{
-    consume_while([](char ch) { return is_whitespace(ch); });
-}
-
-bool JsonParser::consume_specific(char expected_ch)
-{
-    char consumed_ch = consume();
-    return consumed_ch == expected_ch;
-}
-
-String JsonParser::consume_quoted_string()
+String JsonParser::consume_and_unescape_string()
 {
     if (!consume_specific('"'))
         return {};
@@ -86,11 +49,9 @@ String JsonParser::consume_quoted_string()
             ++peek_index;
         }
 
-        if (peek_index != m_index) {
-            while (peek_index != m_index) {
-                final_sb.append(m_input.characters_without_null_termination()[m_index]);
-                m_index++;
-            }
+        while (peek_index != m_index) {
+            final_sb.append(m_input[m_index]);
+            m_index++;
         }
 
         if (m_index == m_input.length())
@@ -101,7 +62,7 @@ String JsonParser::consume_quoted_string()
             final_sb.append(consume());
             continue;
         }
-        consume();
+        ignore();
         char escaped_ch = consume();
         switch (escaped_ch) {
         case 'n':
@@ -120,18 +81,11 @@ String JsonParser::consume_quoted_string()
             final_sb.append('\f');
             break;
         case 'u': {
-            StringBuilder sb;
-            sb.append(consume());
-            sb.append(consume());
-            sb.append(consume());
-            sb.append(consume());
-
-            auto code_point = AK::StringUtils::convert_to_uint_from_hex(sb.to_string());
-            if (code_point.has_value()) {
+            auto code_point = AK::StringUtils::convert_to_uint_from_hex(consume(4));
+            if (code_point.has_value())
                 final_sb.append_code_point(code_point.value());
-            } else {
+            else
                 final_sb.append('?');
-            }
         } break;
         default:
             final_sb.append(escaped_ch);
@@ -150,27 +104,27 @@ Optional<JsonValue> JsonParser::parse_object()
     if (!consume_specific('{'))
         return {};
     for (;;) {
-        consume_whitespace();
+        ignore_while(is_whitespace);
         if (peek() == '}')
             break;
-        consume_whitespace();
-        auto name = consume_quoted_string();
+        ignore_while(is_whitespace);
+        auto name = consume_and_unescape_string();
         if (name.is_null())
             return {};
-        consume_whitespace();
+        ignore_while(is_whitespace);
         if (!consume_specific(':'))
             return {};
-        consume_whitespace();
+        ignore_while(is_whitespace);
         auto value = parse_helper();
         if (!value.has_value())
             return {};
         object.set(name, move(value.value()));
-        consume_whitespace();
+        ignore_while(is_whitespace);
         if (peek() == '}')
             break;
         if (!consume_specific(','))
             return {};
-        consume_whitespace();
+        ignore_while(is_whitespace);
         if (peek() == '}')
             return {};
     }
@@ -185,23 +139,23 @@ Optional<JsonValue> JsonParser::parse_array()
     if (!consume_specific('['))
         return {};
     for (;;) {
-        consume_whitespace();
+        ignore_while(is_whitespace);
         if (peek() == ']')
             break;
         auto element = parse_helper();
         if (!element.has_value())
             return {};
         array.append(element.value());
-        consume_whitespace();
+        ignore_while(is_whitespace);
         if (peek() == ']')
             break;
         if (!consume_specific(','))
             return {};
-        consume_whitespace();
+        ignore_while(is_whitespace);
         if (peek() == ']')
             return {};
     }
-    consume_whitespace();
+    ignore_while(is_whitespace);
     if (!consume_specific(']'))
         return {};
     return array;
@@ -209,7 +163,7 @@ Optional<JsonValue> JsonParser::parse_array()
 
 Optional<JsonValue> JsonParser::parse_string()
 {
-    auto result = consume_quoted_string();
+    auto result = consume_and_unescape_string();
     if (result.is_null())
         return {};
     return JsonValue(result);
@@ -283,39 +237,30 @@ Optional<JsonValue> JsonParser::parse_number()
     return value;
 }
 
-bool JsonParser::consume_string(const char* str)
-{
-    for (size_t i = 0, length = strlen(str); i < length; ++i) {
-        if (!consume_specific(str[i]))
-            return false;
-    }
-    return true;
-}
-
 Optional<JsonValue> JsonParser::parse_true()
 {
-    if (!consume_string("true"))
+    if (!consume_specific("true"))
         return {};
     return JsonValue(true);
 }
 
 Optional<JsonValue> JsonParser::parse_false()
 {
-    if (!consume_string("false"))
+    if (!consume_specific("false"))
         return {};
     return JsonValue(false);
 }
 
 Optional<JsonValue> JsonParser::parse_null()
 {
-    if (!consume_string("null"))
+    if (!consume_specific("null"))
         return {};
     return JsonValue(JsonValue::Type::Null);
 }
 
 Optional<JsonValue> JsonParser::parse_helper()
 {
-    consume_whitespace();
+    ignore_while(is_whitespace);
     auto type_hint = peek();
     switch (type_hint) {
     case '{':
@@ -347,12 +292,13 @@ Optional<JsonValue> JsonParser::parse_helper()
     return {};
 }
 
-Optional<JsonValue> JsonParser::parse() {
+Optional<JsonValue> JsonParser::parse()
+{
     auto result = parse_helper();
     if (!result.has_value())
         return {};
-    consume_whitespace();
-    if (m_index != m_input.length())
+    ignore_while(is_whitespace);
+    if (!is_eof())
         return {};
     return result;
 }

AK/JsonParser.h

@@ -27,13 +27,14 @@
 #pragma once
 
 #include <AK/JsonValue.h>
+#include <AK/GenericLexer.h>
 
 namespace AK {
 
-class JsonParser {
+class JsonParser : private GenericLexer {
 public:
     explicit JsonParser(const StringView& input)
-        : m_input(input)
+        : GenericLexer(input)
     {
     }
     ~JsonParser()
@@ -45,12 +46,7 @@ public:
 private:
     Optional<JsonValue> parse_helper();
 
-    char peek() const;
-    char consume();
-    void consume_whitespace();
-    bool consume_specific(char expected_ch);
-    bool consume_string(const char*);
-    String consume_quoted_string();
+    String consume_and_unescape_string();
     Optional<JsonValue> parse_array();
     Optional<JsonValue> parse_object();
     Optional<JsonValue> parse_number();
@@ -59,12 +55,6 @@ private:
     Optional<JsonValue> parse_true();
     Optional<JsonValue> parse_null();
 
-    template<typename C>
-    void consume_while(C);
-
-    StringView m_input;
-    size_t m_index { 0 };
-
     String m_last_string_starting_with_character[256];
 };
 

Kernel/CMakeLists.txt

@@ -193,6 +193,7 @@ set(KERNEL_SOURCES
 
 set(AK_SOURCES
     ../AK/FlyString.cpp
+    ../AK/GenericLexer.cpp
     ../AK/JsonParser.cpp
     ../AK/JsonValue.cpp
     ../AK/LexicalPath.cpp