feat: BitStream and Buffer classes

leia-uwu · leia-uwu · commit 31fe30efae1f · 2026-01-30T20:38:45.000-03:00
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -91,5 +91,6 @@ add_library(glimmerite::glimmerite ALIAS glimmerite_glimmerite)
 target_link_libraries(glimmerite_glimmerite
     INTERFACE
     glimmerite::math
+    glimerrite::misc
     glimmerite::client
 )
diff --git a/include/gmi/misc/BitStream.h b/include/gmi/misc/BitStream.h
@@ -0,0 +1,240 @@
+#pragma once
+
+#include <algorithm>
+#include <bit>
+#include <cassert>
+#include <cmath>
+#include <cstddef>
+#include <cstdint>
+#include <format>
+#include <stdexcept>
+#include <string_view>
+#include <type_traits>
+
+#include <gmi/misc/Buffer.h>
+
+namespace gmi {
+
+class BitStream {
+public:
+    BitStream(uint8_t* data, size_t size) : m_buff(data, size) { };
+    BitStream(const gmi::Uint8Buffer& buff) : m_buff(buff) { };
+
+    [[nodiscard]] size_t size() const {
+        return m_buff.size();
+    }
+
+    [[nodiscard]] size_t bitSize() const {
+        return m_buff.size() * 8;
+    }
+
+    [[nodiscard]] size_t index() const {
+        return std::ceil(m_bit_index / 8.0);
+    }
+
+    [[nodiscard]] size_t bitIndex() const {
+        return m_bit_index;
+    }
+
+    void setBitIndex(size_t index) {
+        if (index >= size()) {
+            throw std::out_of_range(
+                std::format(
+                    "setIndex: index out of range, size: {}, index: {}",
+                    size(),
+                    index
+                )
+            );
+        }
+        m_bit_index = index;
+    }
+
+    template<typename T>
+        requires(std::is_integral_v<T>)
+    [[nodiscard]] T readBits(uint8_t bitCount);
+
+    template<typename T>
+        requires(std::is_integral_v<T>)
+    void writeBits(T value, uint8_t bitCount);
+
+#define DECLARE_READ_WRITE_FNS(SIZE)                \
+    void writeUint##SIZE(uint##SIZE##_t value) {    \
+        writeBits<uint##SIZE##_t>(value, SIZE);     \
+    }                                               \
+    void writeInt##SIZE(int##SIZE##_t value) {      \
+        writeBits<int##SIZE##_t>(value, SIZE);      \
+    }                                               \
+    [[nodiscard]] uint##SIZE##_t readUint##SIZE() { \
+        return readBits<uint##SIZE##_t>(SIZE);      \
+    }                                               \
+    [[nodiscard]] int##SIZE##_t readInt##SIZE() {   \
+        return readBits<int##SIZE##_t>(SIZE);       \
+    }
+
+    DECLARE_READ_WRITE_FNS(8)
+    DECLARE_READ_WRITE_FNS(16)
+    DECLARE_READ_WRITE_FNS(32)
+    DECLARE_READ_WRITE_FNS(64)
+#undef DECLARE_READ_WRITE_FNS
+
+    void writeFloat32(float value) {
+        writeUint32(std::bit_cast<uint32_t>(value));
+    }
+
+    [[nodiscard]] float readFloat32() {
+        return std::bit_cast<float>(readUint32());
+    }
+
+    void writeFloat64(double value) {
+        writeUint64(std::bit_cast<uint64_t>(value));
+    }
+
+    [[nodiscard]] double readFloat64() {
+        return std::bit_cast<double>(readUint64());
+    }
+
+    void writeFloat(float value, float min, float max, uint8_t bitCount);
+
+    float readFloat(float min, float max, uint8_t bitCount);
+
+    void writeBool(bool value) {
+        writeBits<uint8_t>(value ? 1 : 0, 1);
+    }
+
+    [[nodiscard]] bool readBool() {
+        return readBits<uint8_t>(1) != 0;
+    }
+
+    void writeString(const std::string_view& view, size_t maxSize = 0);
+
+    [[nodiscard]] std::string readString(size_t maxSize = 0);
+
+private:
+    gmi::Uint8Buffer m_buff;
+
+    size_t m_bit_index = 0;
+};
+
+template<typename T>
+    requires(std::is_integral_v<T>)
+T BitStream::readBits(uint8_t bitCount) {
+    assert(bitCount <= (sizeof(T) * 8));
+
+    size_t byteIndex = this->index();
+    size_t bitIndex = this->bitIndex();
+    size_t byteCount = bitCount / 8;
+
+    size_t newIndex = (bitIndex + bitCount);
+    if (newIndex > this->bitSize()) {
+        throw std::out_of_range(
+            std::format(
+                "readBits: trying to read past the end of the buffer, buff size: {}, buff index: {}, bits to read: {}",
+                this->bitSize(),
+                bitIndex,
+                bitCount
+            )
+        );
+    }
+
+    T result = 0;
+
+    size_t offset = bitIndex;
+
+    // Ported from bitBuffer https://github.com/inolen/bit-buffer/blob/7b6ec454866090fac7c1b2e5d67f43ffe9ad6942/bit-buffer.js
+    // licensed under MIT
+    for (size_t i = 0; i < bitCount;) {
+        uint8_t remaining = bitCount - i;
+        uint8_t bitOffset = offset & 7;
+
+        // the max number of bits we can read from the current byte
+        uint8_t read = std::min<size_t>(remaining, 8 - bitOffset);
+
+        // create a mask with the correct bit width
+        uint8_t mask = (1 << read) - 1;
+
+        // shift the bits we want to the start of the byte and mask off the rest
+        T val = (m_buff[offset / 8] >> bitOffset) & mask;
+
+        result |= val << i;
+
+        offset += read;
+        i += read;
+    }
+
+    // if working with a signed number and the bit count is not the full type size
+    // we need to add the sign bit to the first bit
+    if (
+        std::is_signed_v<T>
+        && bitCount != (sizeof(T) * 8)
+        && result & (1 << (bitCount - 1))
+    ) {
+        result |= -1 ^ ((1 << bitCount) - 1);
+    }
+
+    m_bit_index = newIndex;
+
+    assert(offset == newIndex);
+
+    return result;
+}
+
+template<typename T>
+    requires(std::is_integral_v<T>)
+void BitStream::writeBits(T value, uint8_t bitCount) {
+    assert(bitCount <= (sizeof(T) * 8));
+
+    size_t byteIndex = this->index();
+    size_t bitIndex = this->bitIndex();
+    size_t byteCount = bitCount / 8;
+
+    size_t newIndex = (bitIndex + bitCount);
+    if (newIndex > this->bitSize()) {
+        throw std::out_of_range(
+            std::format(
+                "writeBits: trying to write past the end of the buffer, buff size: {}, buff index: {}, bits to write: {}",
+                this->bitSize(),
+                bitIndex,
+                bitCount
+            )
+        );
+    }
+
+    size_t offset = bitIndex;
+
+    // Ported from bitBuffer https://github.com/inolen/bit-buffer/blob/7b6ec454866090fac7c1b2e5d67f43ffe9ad6942/bit-buffer.js
+    // licensed under MIT
+    for (size_t i = 0; i < bitCount;) {
+        uint8_t wrote = 0;
+
+        // Write an entire byte if we can.
+        if (bitCount - i >= 8 && (offset & 7) == 0) {
+            m_buff[offset / 8] = value & 0xff;
+            wrote = 8;
+        } else {
+            uint8_t remaining = bitCount - i;
+            uint8_t bitOffset = offset & 7;
+            size_t byteOffset = offset / 8;
+            wrote = std::min<uint8_t>(remaining, 8 - bitOffset);
+
+            // create a mask with the correct bit width
+            uint8_t mask = ~(0xff << wrote);
+            // shift the bits we want to the start of the byte and mask off the rest
+            uint8_t writeBits = value & mask;
+
+            // destination mask to zero all the bits we're changing first
+            uint8_t destMask = ~(mask << bitOffset);
+
+            m_buff[byteOffset] = (m_buff[byteOffset] & destMask) | (writeBits << bitOffset);
+        }
+
+        offset += wrote;
+        i += wrote;
+        value = value >> wrote;
+    }
+
+    m_bit_index = newIndex;
+
+    assert(offset == newIndex);
+}
+
+}
diff --git a/include/gmi/misc/Buffer.h b/include/gmi/misc/Buffer.h
@@ -0,0 +1,36 @@
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+
+namespace gmi {
+
+template<typename T>
+class Buffer {
+public:
+    Buffer(T* data, size_t size) : m_data(data), m_size(size) { }
+
+    [[nodiscard]] size_t size() const {
+        return m_size;
+    }
+
+    [[nodiscard]] T* data() const {
+        return m_data;
+    }
+
+    [[nodiscard]] uint8_t operator[](size_t index) const {
+        assert(index < m_size);
+        return m_data[index];
+    }
+
+    [[nodiscard]] uint8_t& operator[](size_t index) {
+        assert(index < m_size);
+        return m_data[index];
+    }
+
+private:
+    T* m_data;
+    size_t m_size;
+};
+
+using Uint8Buffer = Buffer<uint8_t>;
+}
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
@@ -3,3 +3,4 @@ if (BUILD_CLIENT)
 endif()
 
 add_subdirectory(math)
+add_subdirectory(misc)
diff --git a/src/misc/BitStream.cpp b/src/misc/BitStream.cpp
@@ -0,0 +1,78 @@
+#include "gmi/misc/BitStream.h"
+#include <cmath>
+
+using gmi::BitStream;
+
+void BitStream::writeFloat(float value, float min, float max, uint8_t bitCount) {
+    assert(bitCount <= 32);
+
+    if (value < min || value > max) {
+        throw std::out_of_range(
+            std::format("writeFloat: value out of range: ${}, range: [{}, {}]", value, min, max)
+        );
+    }
+
+    uint32_t range = (1 << bitCount) - 1;
+    float t = (value - min) / (max - min);
+    uint32_t valueToWrite = std::round(t * range + 0.5);
+    writeBits<uint32_t>(valueToWrite, bitCount);
+}
+
+float BitStream::readFloat(float min, float max, uint8_t bitCount) {
+    assert(bitCount <= 32);
+
+    uint32_t range = (1 << bitCount) - 1;
+
+    float read = readBits<uint32_t>(bitCount);
+    float t = read / range;
+
+    return min + t * (max - min);
+}
+
+void BitStream::writeString(const std::string_view& view, size_t maxSize) {
+    bool noMaxSize = maxSize == 0;
+
+    size_t sizeToWrite = noMaxSize
+        ? view.size()
+        : std::min(view.size(), maxSize);
+
+    size_t i = 0;
+    for (; i < sizeToWrite; i++) {
+        writeUint8(view[i]);
+
+        if (view[i] == 0) {
+            return;
+        }
+    }
+
+    // add null terminator if:
+    // we have a max size and we wrote less than it
+    // or if we don't have a max size
+    if (i != maxSize || noMaxSize) {
+        writeUint8(0);
+    }
+}
+
+std::string BitStream::readString(size_t maxSize) {
+    std::string str;
+
+    size_t i = 0;
+    while (true) {
+        i++;
+
+        uint8_t val = readUint8();
+
+        // break if we found a null terminator
+        if (val == 0) {
+            break;
+        }
+
+        str.push_back(val);
+
+        if (maxSize != 0 && i >= maxSize) {
+            break;
+        }
+    }
+
+    return str;
+}
diff --git a/src/misc/CMakeLists.txt b/src/misc/CMakeLists.txt
@@ -0,0 +1,19 @@
+add_library(glimmerite_misc STATIC
+    BitStream.cpp
+)
+
+set(GMI_MISC_INCLUDE_DIR "${GMI_INCLUDE_DIR}/gmi/misc")
+target_sources(
+    glimmerite_misc
+    PUBLIC
+    FILE_SET HEADERS
+    TYPE HEADERS
+    BASE_DIRS ${GMI_INCLUDE_DIR}
+    FILES
+        ${GMI_MISC_INCLUDE_DIR}/BitStream.h
+        ${GMI_MISC_INCLUDE_DIR}/Buffer.h
+)
+
+set_target_properties(glimmerite_misc PROPERTIES LINKER_LANGUAGE CXX)
+
+add_library(glimmerite::misc ALIAS glimmerite_misc)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
diff --git a/tests/bitStreamTest.cpp b/tests/bitStreamTest.cpp

Original file line number	Diff line number	Diff line change
`@@ -91,5 +91,6 @@ add_library(glimmerite::glimmerite ALIAS glimmerite_glimmerite)`
`91`	`91`	`target_link_libraries(glimmerite_glimmerite`
`92`	`92`	`INTERFACE`
`93`	`93`	`glimmerite::math`
	`94`	`+ glimerrite::misc`
`94`	`95`	`glimmerite::client`
`95`	`96`	`)`
Original file line number	Diff line number	Diff line change
`@@ -3,3 +3,4 @@ if (BUILD_CLIENT)`
`3`	`3`	`endif()`
`4`	`4`
`5`	`5`	`add_subdirectory(math)`
	`6`	`+add_subdirectory(misc)`