AK: Add InputStream abstraction and InputMemoryStream implementation.

Author: https://github.com/asynts
Commit: https://github.com/SerenityOS/serenity/commit/5bfa7749c35
Pull-request: https://github.com/SerenityOS/serenity/pull/3007
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/nico

AK/Forward.h

@@ -48,6 +48,8 @@ class URL;
 class FlyString;
 class Utf32View;
 class Utf8View;
+class InputStream;
+class InputMemoryStream;
 
 template<typename T>
 class Span;
@@ -129,6 +131,8 @@ using AK::Function;
 using AK::HashMap;
 using AK::HashTable;
 using AK::InlineLinkedList;
+using AK::InputMemoryStream;
+using AK::InputStream;
 using AK::IPv4Address;
 using AK::JsonArray;
 using AK::JsonObject;

AK/Stream.h

@@ -0,0 +1,169 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * 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/Concepts.h>
+#include <AK/Forward.h>
+#include <AK/Span.h>
+#include <AK/StdLibExtras.h>
+
+namespace AK::Detail {
+
+class Stream {
+public:
+    virtual ~Stream()
+    {
+        ASSERT(!error() && !fatal());
+    }
+
+    bool error() const { return m_error; }
+    bool fatal() const { return m_fatal; }
+
+    bool handle_error() { return exchange(m_error, false); }
+
+    operator bool() const { return !m_error && !m_fatal; }
+
+protected:
+    mutable bool m_error { false };
+    mutable bool m_fatal { false };
+};
+
+}
+
+namespace AK {
+
+class InputStream : public AK::Detail::Stream {
+public:
+    virtual size_t read(Bytes) = 0;
+    virtual bool read_or_error(Bytes) = 0;
+    virtual bool eof() const = 0;
+    virtual bool discard_or_error(size_t count) = 0;
+};
+
+// clang-format off
+
+template<Concepts::Integral Integral>
+InputStream& operator>>(InputStream& stream, Integral& value)
+{
+    stream.read_or_error({ &value, sizeof(value) });
+    return stream;
+}
+
+#ifndef KERNEL
+template<Concepts::FloatingPoint FloatingPoint>
+InputStream& operator>>(InputStream& stream, FloatingPoint& value)
+{
+    stream.read_or_error({ &value, sizeof(value) });
+    return stream;
+}
+#endif
+
+// clang-format on
+
+inline InputStream& operator>>(InputStream& stream, bool& value)
+{
+    stream.read_or_error({ &value, sizeof(value) });
+    return stream;
+}
+
+inline InputStream& operator>>(InputStream& stream, Bytes bytes)
+{
+    stream.read_or_error(bytes);
+    return stream;
+}
+
+class InputMemoryStream final : public InputStream {
+    friend InputMemoryStream& operator>>(InputMemoryStream& stream, String& string);
+
+public:
+    InputMemoryStream(ReadonlyBytes bytes)
+        : m_bytes(bytes)
+    {
+    }
+
+    bool eof() const override { return m_offset >= m_bytes.size(); }
+
+    size_t read(Bytes bytes) override
+    {
+        const auto count = min(bytes.size(), remaining());
+        __builtin_memcpy(bytes.data(), m_bytes.data() + m_offset, count);
+        m_offset += count;
+        return count;
+    }
+
+    bool read_or_error(Bytes bytes) override
+    {
+        if (remaining() < bytes.size()) {
+            m_error = true;
+            return false;
+        }
+
+        __builtin_memcpy(bytes.data(), m_bytes.data() + m_offset, bytes.size());
+        m_offset += bytes.size();
+        return true;
+    }
+
+    bool discard_or_error(size_t count) override
+    {
+        if (remaining() < count) {
+            m_error = true;
+            return false;
+        }
+
+        m_offset += count;
+        return true;
+    }
+
+    void seek(size_t offset)
+    {
+        ASSERT(offset < m_bytes.size());
+        m_offset = offset;
+    }
+
+    u8 peek_or_error() const
+    {
+        if (remaining() == 0) {
+            m_error = true;
+            return 0;
+        }
+
+        return m_bytes[m_offset];
+    }
+
+    ReadonlyBytes bytes() const { return m_bytes; }
+    size_t offset() const { return m_offset; }
+    size_t remaining() const { return m_bytes.size() - m_offset; }
+
+private:
+    ReadonlyBytes m_bytes;
+    size_t m_offset { 0 };
+};
+
+}
+
+using AK::InputMemoryStream;
+using AK::InputStream;

AK/String.h

@@ -28,6 +28,7 @@
 
 #include <AK/Forward.h>
 #include <AK/RefPtr.h>
+#include <AK/Stream.h>
 #include <AK/StringImpl.h>
 #include <AK/StringUtils.h>
 #include <AK/Traits.h>
@@ -275,6 +276,28 @@ bool operator<=(const char*, const String&);
 
 String escape_html_entities(const StringView& html);
 
+inline InputMemoryStream& operator>>(InputMemoryStream& stream, String& string)
+{
+    // FIXME: There was some talking about a generic lexer class?
+
+    const auto start = stream.offset();
+
+    while (!stream.eof() && stream.m_bytes[stream.m_offset]) {
+        ++stream.m_offset;
+    }
+
+    if (stream.eof()) {
+        stream.m_error = true;
+        stream.m_offset = start;
+        string = nullptr;
+    } else {
+        string = String { stream.bytes().slice(start, stream.offset() - start) };
+        ++stream.m_offset;
+    }
+
+    return stream;
+}
+
 }
 
 using AK::CaseInsensitiveStringTraits;

AK/Tests/TestMemoryStream.cpp

@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ * 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/TestSuite.h>
+
+#include <AK/Stream.h>
+
+bool compare(ReadonlyBytes lhs, ReadonlyBytes rhs)
+{
+    if (lhs.size() != rhs.size())
+        return false;
+
+    for (size_t idx = 0; idx < lhs.size(); ++idx) {
+        if (lhs[idx] != rhs[idx])
+            return false;
+    }
+
+    return true;
+}
+
+TEST_CASE(read_an_integer)
+{
+    u32 expected = 0x01020304, actual;
+
+    InputMemoryStream stream { { &expected, sizeof(expected) } };
+    stream >> actual;
+
+    EXPECT(!stream.error() && !stream.fatal() && stream.eof());
+    EXPECT_EQ(expected, actual);
+}
+
+TEST_CASE(recoverable_error)
+{
+    u32 expected = 0x01020304, actual = 0;
+    u64 to_large_value = 0;
+
+    InputMemoryStream stream { { &expected, sizeof(expected) } };
+
+    EXPECT(!stream.error() && !stream.fatal() && !stream.eof());
+    stream >> to_large_value;
+    EXPECT(stream.error() && !stream.fatal() && !stream.eof());
+
+    EXPECT(stream.handle_error());
+    EXPECT(!stream.error() && !stream.fatal() && !stream.eof());
+
+    stream >> actual;
+    EXPECT(!stream.error() && !stream.fatal() && stream.eof());
+    EXPECT_EQ(expected, actual);
+}
+
+TEST_CASE(chain_stream_operator)
+{
+    u8 expected[] { 0, 1, 2, 3 }, actual[4];
+
+    InputMemoryStream stream { { expected, sizeof(expected) } };
+
+    stream >> actual[0] >> actual[1] >> actual[2] >> actual[3];
+    EXPECT(!stream.error() && !stream.fatal() && stream.eof());
+
+    EXPECT(compare({ expected, sizeof(expected) }, { actual, sizeof(actual) }));
+}
+
+TEST_CASE(seeking_slicing_offset)
+{
+    u8 input[] { 0, 1, 2, 3, 4, 5, 6, 7 },
+        expected0[] { 0, 1, 2, 3 },
+        expected1[] { 4, 5, 6, 7 },
+        expected2[] { 1, 2, 3, 4 },
+        actual0[4], actual1[4], actual2[4];
+
+    InputMemoryStream stream { { input, sizeof(input) } };
+
+    stream >> Bytes { actual0, sizeof(actual0) };
+    EXPECT(!stream.error() && !stream.fatal() && !stream.eof());
+    EXPECT(compare({ expected0, sizeof(expected0) }, { actual0, sizeof(actual0) }));
+
+    stream.seek(4);
+    stream >> Bytes { actual1, sizeof(actual1) };
+    EXPECT(!stream.error() && !stream.fatal() && stream.eof());
+    EXPECT(compare({ expected1, sizeof(expected1) }, { actual1, sizeof(actual1) }));
+
+    stream.seek(1);
+    stream >> Bytes { actual2, sizeof(actual2) };
+    EXPECT(!stream.error() && !stream.fatal() && !stream.eof());
+    EXPECT(compare({ expected2, sizeof(expected2) }, { actual2, sizeof(actual2) }));
+}
+
+TEST_MAIN(MemoryStream)