AK: Move bit streams from `LibCore`

2 files changed, 408 insertions, 0 deletions

diff --git a/AK/BitStream.h b/AK/BitStream.h
new file mode 100644
index 0000000000..922e86da17
--- /dev/null
+++ b/AK/BitStream.h
@@ -0,0 +1,400 @@
+/*
+ * Copyright (c) 2021, kleines Filmröllchen <filmroellchen@serenityos.org>.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/ByteBuffer.h>
+#include <AK/MaybeOwned.h>
+#include <AK/OwnPtr.h>
+#include <AK/Stream.h>
+
+namespace AK {
+
+/// A stream wrapper class that allows you to read arbitrary amounts of bits
+/// in big-endian order from another stream.
+class BigEndianInputBitStream : public Stream {
+public:
+    static ErrorOr<NonnullOwnPtr<BigEndianInputBitStream>> construct(MaybeOwned<Stream> stream)
+    {
+        return adopt_nonnull_own_or_enomem<BigEndianInputBitStream>(new BigEndianInputBitStream(move(stream)));
+    }
+
+    // ^Stream
+    virtual ErrorOr<Bytes> read(Bytes bytes) override
+    {
+        if (m_current_byte.has_value() && is_aligned_to_byte_boundary()) {
+            bytes[0] = m_current_byte.release_value();
+            return m_stream->read(bytes.slice(1));
+        }
+        align_to_byte_boundary();
+        return m_stream->read(bytes);
+    }
+    virtual ErrorOr<size_t> write(ReadonlyBytes bytes) override { return m_stream->write(bytes); }
+    virtual ErrorOr<void> write_entire_buffer(ReadonlyBytes bytes) override { return m_stream->write_entire_buffer(bytes); }
+    virtual bool is_eof() const override { return m_stream->is_eof() && !m_current_byte.has_value(); }
+    virtual bool is_open() const override { return m_stream->is_open(); }
+    virtual void close() override
+    {
+        m_stream->close();
+        align_to_byte_boundary();
+    }
+
+    ErrorOr<bool> read_bit()
+    {
+        return read_bits<bool>(1);
+    }
+    /// Depending on the number of bits to read, the return type can be chosen appropriately.
+    /// This avoids a bunch of static_cast<>'s for the user.
+    // TODO: Support u128, u256 etc. as well: The concepts would be quite complex.
+    template<Unsigned T = u64>
+    ErrorOr<T> read_bits(size_t count)
+    {
+        if constexpr (IsSame<bool, T>) {
+            VERIFY(count == 1);
+        }
+        T result = 0;
+
+        size_t nread = 0;
+        while (nread < count) {
+            if (m_current_byte.has_value()) {
+                if constexpr (!IsSame<bool, T> && !IsSame<u8, T>) {
+                    // read as many bytes as possible directly
+                    if (((count - nread) >= 8) && is_aligned_to_byte_boundary()) {
+                        // shift existing data over
+                        result <<= 8;
+                        result |= m_current_byte.value();
+                        nread += 8;
+                        m_current_byte.clear();
+                    } else {
+                        auto const bit = (m_current_byte.value() >> (7 - m_bit_offset)) & 1;
+                        result <<= 1;
+                        result |= bit;
+                        ++nread;
+                        if (m_bit_offset++ == 7)
+                            m_current_byte.clear();
+                    }
+                } else {
+                    // Always take this branch for booleans or u8: there's no purpose in reading more than a single bit
+                    auto const bit = (m_current_byte.value() >> (7 - m_bit_offset)) & 1;
+                    if constexpr (IsSame<bool, T>)
+                        result = bit;
+                    else {
+                        result <<= 1;
+                        result |= bit;
+                    }
+                    ++nread;
+                    if (m_bit_offset++ == 7)
+                        m_current_byte.clear();
+                }
+            } else {
+                auto temp_buffer = TRY(ByteBuffer::create_uninitialized(1));
+                TRY(m_stream->read(temp_buffer.bytes()));
+                m_current_byte = temp_buffer[0];
+                m_bit_offset = 0;
+            }
+        }
+
+        return result;
+    }
+
+    /// Discards any sub-byte stream positioning the input stream may be keeping track of.
+    /// Non-bitwise reads will implicitly call this.
+    void align_to_byte_boundary()
+    {
+        m_current_byte.clear();
+        m_bit_offset = 0;
+    }
+
+    /// Whether we are (accidentally or intentionally) at a byte boundary right now.
+    ALWAYS_INLINE bool is_aligned_to_byte_boundary() const { return m_bit_offset == 0; }
+
+private:
+    BigEndianInputBitStream(MaybeOwned<Stream> stream)
+        : m_stream(move(stream))
+    {
+    }
+
+    Optional<u8> m_current_byte;
+    size_t m_bit_offset { 0 };
+    MaybeOwned<Stream> m_stream;
+};
+
+/// A stream wrapper class that allows you to read arbitrary amounts of bits
+/// in little-endian order from another stream.
+class LittleEndianInputBitStream : public Stream {
+public:
+    static ErrorOr<NonnullOwnPtr<LittleEndianInputBitStream>> construct(MaybeOwned<Stream> stream)
+    {
+        return adopt_nonnull_own_or_enomem<LittleEndianInputBitStream>(new LittleEndianInputBitStream(move(stream)));
+    }
+
+    LittleEndianInputBitStream(MaybeOwned<Stream> stream)
+        : m_stream(move(stream))
+    {
+    }
+
+    // ^Stream
+    virtual ErrorOr<Bytes> read(Bytes bytes) override
+    {
+        if (m_current_byte.has_value() && is_aligned_to_byte_boundary()) {
+            bytes[0] = m_current_byte.release_value();
+            return m_stream->read(bytes.slice(1));
+        }
+        align_to_byte_boundary();
+        return m_stream->read(bytes);
+    }
+    virtual ErrorOr<size_t> write(ReadonlyBytes bytes) override { return m_stream->write(bytes); }
+    virtual ErrorOr<void> write_entire_buffer(ReadonlyBytes bytes) override { return m_stream->write_entire_buffer(bytes); }
+    virtual bool is_eof() const override { return m_stream->is_eof() && !m_current_byte.has_value(); }
+    virtual bool is_open() const override { return m_stream->is_open(); }
+    virtual void close() override
+    {
+        m_stream->close();
+        align_to_byte_boundary();
+    }
+
+    ErrorOr<bool> read_bit()
+    {
+        return read_bits<bool>(1);
+    }
+    /// Depending on the number of bits to read, the return type can be chosen appropriately.
+    /// This avoids a bunch of static_cast<>'s for the user.
+    // TODO: Support u128, u256 etc. as well: The concepts would be quite complex.
+    template<Unsigned T = u64>
+    ErrorOr<T> read_bits(size_t count)
+    {
+        if constexpr (IsSame<bool, T>) {
+            VERIFY(count == 1);
+        }
+        T result = 0;
+
+        size_t nread = 0;
+        while (nread < count) {
+            if (m_current_byte.has_value()) {
+                if constexpr (!IsSame<bool, T> && !IsSame<u8, T>) {
+                    // read as many bytes as possible directly
+                    if (((count - nread) >= 8) && is_aligned_to_byte_boundary()) {
+                        // shift existing data over
+                        result |= (m_current_byte.value() << nread);
+                        nread += 8;
+                        m_current_byte.clear();
+                    } else {
+                        auto const bit = (m_current_byte.value() >> m_bit_offset) & 1;
+                        result |= (bit << nread);
+                        ++nread;
+                        if (m_bit_offset++ == 7)
+                            m_current_byte.clear();
+                    }
+                } else {
+                    // Always take this branch for booleans or u8: there's no purpose in reading more than a single bit
+                    auto const bit = (m_current_byte.value() >> m_bit_offset) & 1;
+                    if constexpr (IsSame<bool, T>)
+                        result = bit;
+                    else
+                        result |= (bit << nread);
+                    ++nread;
+                    if (m_bit_offset++ == 7)
+                        m_current_byte.clear();
+                }
+            } else {
+                auto temp_buffer = TRY(ByteBuffer::create_uninitialized(1));
+                auto read_bytes = TRY(m_stream->read(temp_buffer.bytes()));
+                if (read_bytes.is_empty())
+                    return Error::from_string_literal("eof");
+                m_current_byte = temp_buffer[0];
+                m_bit_offset = 0;
+            }
+        }
+
+        return result;
+    }
+
+    /// Discards any sub-byte stream positioning the input stream may be keeping track of.
+    /// Non-bitwise reads will implicitly call this.
+    u8 align_to_byte_boundary()
+    {
+        u8 remaining_bits = m_current_byte.value_or(0) >> m_bit_offset;
+        m_current_byte.clear();
+        m_bit_offset = 0;
+        return remaining_bits;
+    }
+
+    /// Whether we are (accidentally or intentionally) at a byte boundary right now.
+    ALWAYS_INLINE bool is_aligned_to_byte_boundary() const { return m_bit_offset == 0; }
+
+private:
+    Optional<u8> m_current_byte;
+    size_t m_bit_offset { 0 };
+    MaybeOwned<Stream> m_stream;
+};
+
+/// A stream wrapper class that allows you to write arbitrary amounts of bits
+/// in big-endian order to another stream.
+class BigEndianOutputBitStream : public Stream {
+public:
+    static ErrorOr<NonnullOwnPtr<BigEndianOutputBitStream>> construct(MaybeOwned<Stream> stream)
+    {
+        return adopt_nonnull_own_or_enomem<BigEndianOutputBitStream>(new BigEndianOutputBitStream(move(stream)));
+    }
+
+    virtual ErrorOr<Bytes> read(Bytes) override
+    {
+        return Error::from_errno(EBADF);
+    }
+
+    virtual ErrorOr<size_t> write(ReadonlyBytes bytes) override
+    {
+        VERIFY(m_bit_offset == 0);
+        return m_stream->write(bytes);
+    }
+
+    template<Unsigned T>
+    ErrorOr<void> write_bits(T value, size_t bit_count)
+    {
+        VERIFY(m_bit_offset <= 7);
+
+        while (bit_count > 0) {
+            u8 next_bit = (value >> (bit_count - 1)) & 1;
+            bit_count--;
+
+            m_current_byte <<= 1;
+            m_current_byte |= next_bit;
+            m_bit_offset++;
+
+            if (m_bit_offset > 7) {
+                TRY(m_stream->write({ &m_current_byte, sizeof(m_current_byte) }));
+                m_bit_offset = 0;
+                m_current_byte = 0;
+            }
+        }
+
+        return {};
+    }
+
+    virtual bool is_eof() const override
+    {
+        return true;
+    }
+
+    virtual bool is_open() const override
+    {
+        return m_stream->is_open();
+    }
+
+    virtual void close() override
+    {
+    }
+
+    size_t bit_offset() const
+    {
+        return m_bit_offset;
+    }
+
+    ErrorOr<void> align_to_byte_boundary()
+    {
+        if (m_bit_offset == 0)
+            return {};
+
+        TRY(write_bits(0u, 8 - m_bit_offset));
+        VERIFY(m_bit_offset == 0);
+        return {};
+    }
+
+private:
+    BigEndianOutputBitStream(MaybeOwned<Stream> stream)
+        : m_stream(move(stream))
+    {
+    }
+
+    MaybeOwned<Stream> m_stream;
+    u8 m_current_byte { 0 };
+    size_t m_bit_offset { 0 };
+};
+
+/// A stream wrapper class that allows you to write arbitrary amounts of bits
+/// in little-endian order to another stream.
+class LittleEndianOutputBitStream : public Stream {
+public:
+    static ErrorOr<NonnullOwnPtr<LittleEndianOutputBitStream>> construct(MaybeOwned<Stream> stream)
+    {
+        return adopt_nonnull_own_or_enomem<LittleEndianOutputBitStream>(new LittleEndianOutputBitStream(move(stream)));
+    }
+
+    virtual ErrorOr<Bytes> read(Bytes) override
+    {
+        return Error::from_errno(EBADF);
+    }
+
+    virtual ErrorOr<size_t> write(ReadonlyBytes bytes) override
+    {
+        VERIFY(m_bit_offset == 0);
+        return m_stream->write(bytes);
+    }
+
+    template<Unsigned T>
+    ErrorOr<void> write_bits(T value, size_t bit_count)
+    {
+        VERIFY(m_bit_offset <= 7);
+
+        size_t input_offset = 0;
+        while (input_offset < bit_count) {
+            u8 next_bit = (value >> input_offset) & 1;
+            input_offset++;
+
+            m_current_byte |= next_bit << m_bit_offset;
+            m_bit_offset++;
+
+            if (m_bit_offset > 7) {
+                TRY(m_stream->write({ &m_current_byte, sizeof(m_current_byte) }));
+                m_bit_offset = 0;
+                m_current_byte = 0;
+            }
+        }
+
+        return {};
+    }
+
+    virtual bool is_eof() const override
+    {
+        return true;
+    }
+
+    virtual bool is_open() const override
+    {
+        return m_stream->is_open();
+    }
+
+    virtual void close() override
+    {
+    }
+
+    size_t bit_offset() const
+    {
+        return m_bit_offset;
+    }
+
+    ErrorOr<void> align_to_byte_boundary()
+    {
+        if (m_bit_offset == 0)
+            return {};
+
+        TRY(write_bits(0u, 8 - m_bit_offset));
+        VERIFY(m_bit_offset == 0);
+        return {};
+    }
+
+private:
+    LittleEndianOutputBitStream(MaybeOwned<Stream> stream)
+        : m_stream(move(stream))
+    {
+    }
+
+    MaybeOwned<Stream> m_stream;
+    u8 m_current_byte { 0 };
+    size_t m_bit_offset { 0 };
+};
+
+}
diff --git a/AK/Forward.h b/AK/Forward.h
index d94e7a6fd6..e258449ffd 100644
--- a/AK/Forward.h
+++ b/AK/Forward.h
@@ -18,6 +18,8 @@ class ByteBuffer;
 }
 
 class Bitmap;
+class BigEndianInputBitStream;
+class BigEndianOutputBitStream;
 using ByteBuffer = Detail::ByteBuffer<32>;
 class CircularBuffer;
 class DeprecatedInputStream;
@@ -31,6 +33,8 @@ class IPv4Address;
 class JsonArray;
 class JsonObject;
 class JsonValue;
+class LittleEndianInputBitStream;
+class LittleEndianOutputBitStream;
 class StackInfo;
 class DeprecatedFlyString;
 class DeprecatedString;
@@ -152,6 +156,8 @@ class [[nodiscard]] ErrorOr;
 using AK::Array;
 using AK::Atomic;
 using AK::Badge;
+using AK::BigEndianInputBitStream;
+using AK::BigEndianOutputBitStream;
 using AK::Bitmap;
 using AK::ByteBuffer;
 using AK::Bytes;
@@ -177,6 +183,8 @@ using AK::IPv4Address;
 using AK::JsonArray;
 using AK::JsonObject;
 using AK::JsonValue;
+using AK::LittleEndianInputBitStream;
+using AK::LittleEndianOutputBitStream;
 using AK::NonnullOwnPtr;
 using AK::NonnullOwnPtrVector;
 using AK::NonnullRefPtr;