// ------------------------------------------------------------------------------------------------
#include "Base/Buffer.hpp"
#include "sqrat/sqratUtil.h"
// ------------------------------------------------------------------------------------------------
#include <cstdlib>
#include <cstring>
#include <exception>
#include <stdexcept>
// ------------------------------------------------------------------------------------------------
namespace SqMod {
/* ------------------------------------------------------------------------------------------------
* Compute the next power of two for the specified number.
*/
inline unsigned int NextPow2(unsigned int num)
{
--num;
num |= num >> 1;
num |= num >> 2;
num |= num >> 4;
num |= num >> 8;
num |= num >> 16;
return ++num;
}
/* ------------------------------------------------------------------------------------------------
* Throw an memory exception.
*/
void ThrowMemExcept(const char * msg, ...)
{
// Exception messages should be concise
SQChar buffer[256];
// Variable arguments structure
va_list args;
// Get the specified arguments
va_start(args, msg);
// Run the specified format
int ret = std::vsnprintf(buffer, sizeof(buffer), msg, args);
// Check for formatting errors
if (ret < 0)
{
throw Sqrat::Exception(_SC("Unknown memory error"));
}
// Throw the actual exception
throw Sqrat::Exception(buffer);
}
/* ------------------------------------------------------------------------------------------------
* Allocate a memory buffer and return it.
*/
static Buffer::Pointer AllocMem(Buffer::SzType size)
{
// Attempt to allocate memory directly
Buffer::Pointer ptr = reinterpret_cast< Buffer::Pointer >(std::malloc(size));
// Validate the allocated memory
if (!ptr)
{
ThrowMemExcept("Unable to allocate (%u) bytes of memory", size);
}
// Return the allocated memory
return ptr;
}
/* ------------------------------------------------------------------------------------------------
* ...
*/
class MemCat
{
// --------------------------------------------------------------------------------------------
friend class Memory;
friend class Buffer;
public:
// --------------------------------------------------------------------------------------------
typedef Buffer::Value Value; // The type of value used to represent a byte.
// --------------------------------------------------------------------------------------------
typedef Buffer::Reference Reference; // A reference to the stored value type.
typedef Buffer::ConstRef ConstRef; // A const reference to the stored value type.
// --------------------------------------------------------------------------------------------
typedef Buffer::Pointer Pointer; // A pointer to the stored value type.
typedef Buffer::ConstPtr ConstPtr; // A const pointer to the stored value type.
// --------------------------------------------------------------------------------------------
typedef Buffer::SzType SzType; // The type used to represent size in general.
private:
/* --------------------------------------------------------------------------------------------
* Structure used to store a memory chunk in the linked list.
*/
struct Node
{
// ----------------------------------------------------------------------------------------
SzType mCap; // The size of the memory chunk.
Pointer mPtr; // Pointer to the memory chunk.
Node* mNext; // The next node in the list.
/* ----------------------------------------------------------------------------------------
* Base constructor.
*/
Node(Node * next)
: mCap(0)
, mPtr(nullptr)
, mNext(next)
{
/* ... */
}
};
// --------------------------------------------------------------------------------------------
static Node * s_Nodes; /* List of unused node instances. */
// --------------------------------------------------------------------------------------------
Node* m_Head; /* The head memory node. */
/* --------------------------------------------------------------------------------------------
* Default constructor.
*/
MemCat()
: m_Head(nullptr)
{
/* ... */
}
/* --------------------------------------------------------------------------------------------
* Destructor.
*/
~MemCat()
{
for (Node * node = m_Head, * next = nullptr; node; node = next)
{
// Free the memory (if any)
if (node->mPtr)
{
std::free(node->mPtr);
}
// Save the next node
next = node->mNext;
// Release the node instance
delete node;
}
// Explicitly set the head node to null
m_Head = nullptr;
}
/* --------------------------------------------------------------------------------------------
* Clear all memory buffers from the pool.
*/
void Clear()
{
for (Node * node = m_Head, * next = nullptr; node; node = next)
{
// Free the memory (if any)
if (node->mPtr)
{
free(node->mPtr);
}
// Save the next node
next = node->mNext;
// Release the node instance
Push(node);
}
// Explicitly set the head node to null
m_Head = nullptr;
}
/* --------------------------------------------------------------------------------------------
* Grab a memory buffer from the pool.
*/
void Grab(Pointer & ptr, SzType & size)
{
// NOTE: Function assumes (size > 0)
// Find a buffer large enough to satisfy the requested size
for (Node * node = m_Head, * prev = nullptr; node; prev = node, node = node->mNext)
{
// Is this buffer large enough?
if (node->mCap >= size)
{
// Was there a previous node?
if (prev)
{
prev->mNext = node->mNext;
}
// Probably this was the head
else
{
m_Head = node->mNext;
}
// Assign the memory
ptr = node->mPtr;
// Assign the size
size = node->mCap;
// Release the node instance
Push(node);
// Exit the function
return;
}
}
// Round up the size to a power of two number
size = (size & (size - 1)) ? NextPow2(size) : size;
// Allocate the memory directly
ptr = AllocMem(size);
// See if the memory could be allocated
// (shouldn't reach this point if allocation failed)
if (!ptr)
{
// Revert the size
size = 0;
// Throw the exception
ThrowMemExcept("Unable to allocate (%u) bytes of memory", size);
}
}
/* --------------------------------------------------------------------------------------------
* Return a memory buffer to the pool.
*/
void Drop(Pointer & ptr, SzType & size)
{
if (!ptr)
{
ThrowMemExcept("Cannot store invalid memory buffer");
}
// Request a node instance
Node * node = Pull();
// Assign the specified memory
node->mPtr = ptr;
// Assign the specified size
node->mCap = size;
// Demote the current head node
node->mNext = m_Head;
// Promote as the head node
m_Head = node;
}
/* --------------------------------------------------------------------------------------------
* Allocate a group of nodes and pool them for later use.
*/
static void Make()
{
for (SzType n = 16; n; --n)
{
// Create a new node instance
s_Nodes = new Node(s_Nodes);
// Validate the head node
if (!s_Nodes)
{
ThrowMemExcept("Unable to allocate memory nodes");
}
}
}
/* --------------------------------------------------------------------------------------------
* Retrieve an unused node from the free list.
*/
static Node * Pull()
{
// Are there any nodes available?
if (!s_Nodes)
{
Make(); // Make some!
}
// Grab the head node
Node * node = s_Nodes;
// Promote the next node as the head
s_Nodes = node->mNext;
// Return the node
return node;
}
/* --------------------------------------------------------------------------------------------
* Return a node to the free list.
*/
static void Push(Node * node)
{
// See if the node is even valid
if (!node)
{
ThrowMemExcept("Attempting to push invalid node");
}
// Demote the current head node
node->mNext = s_Nodes;
// Promote as the head node
s_Nodes = node;
}
};
// ------------------------------------------------------------------------------------------------
MemCat::Node * MemCat::s_Nodes = nullptr;
/* ------------------------------------------------------------------------------------------------
* Lightweight memory allocator to reduce the overhead of small allocations.
*/
class Memory
{
// --------------------------------------------------------------------------------------------
friend class Buffer; // Allow the buffer type to access the memory categories.
friend class MemRef; // Allow the memory manager reference to create new instances.
private:
/* --------------------------------------------------------------------------------------------
* Default constructor.
*/
Memory()
: m_Small()
, m_Medium()
, m_Large()
{
// Allocate several nodes for when memory starts pooling
MemCat::Make();
}
/* --------------------------------------------------------------------------------------------
* Destructor.
*/
~Memory()
{
for (MemCat::Node * node = MemCat::s_Nodes, * next = nullptr; node; node = next)
{
// Save the next node
next = node->mNext;
// Release the node instance
delete node;
}
// Explicitly set the head node to null
MemCat::s_Nodes = nullptr;
}
private:
// --------------------------------------------------------------------------------------------
MemCat m_Small; // Small memory allocations of <= 1024 bytes.
MemCat m_Medium; // Medium memory allocations of <= 4096 bytes.
MemCat m_Large; // Large memory allocations of <= 4096 bytes.
};
// ------------------------------------------------------------------------------------------------
MemRef MemRef::s_Mem;
// ------------------------------------------------------------------------------------------------
void MemRef::Grab()
{
if (m_Ptr)
{
++(*m_Ref);
}
}
// ------------------------------------------------------------------------------------------------
void MemRef::Drop()
{
if (m_Ptr && --(*m_Ref) == 0)
{
delete m_Ptr;
delete m_Ref;
m_Ptr = nullptr;
m_Ref = nullptr;
}
}
// ------------------------------------------------------------------------------------------------
const MemRef & MemRef::Get()
{
if (!s_Mem.m_Ptr)
{
s_Mem.m_Ptr = new Memory();
s_Mem.m_Ref = new Counter(1);
}
return s_Mem;
}
// ------------------------------------------------------------------------------------------------
Buffer::Buffer(const Buffer & o)
: m_Ptr(nullptr)
, m_Cap(o.m_Cap)
, m_Cur(o.m_Cur)
, m_Mem(o.m_Mem)
{
if (m_Cap)
{
Request(o.m_Cap);
std::memcpy(m_Ptr, o.m_Ptr, o.m_Cap);
}
}
// ------------------------------------------------------------------------------------------------
Buffer::~Buffer()
{
// Do we have a buffer?
if (m_Ptr)
{
Release(); // Release it!
}
}
// ------------------------------------------------------------------------------------------------
Buffer & Buffer::operator = (const Buffer & o)
{
if (m_Ptr != o.m_Ptr)
{
// Can we work in the current buffer?
if (m_Cap && o.m_Cap <= m_Cap)
{
// It's safe to copy the data
std::memcpy(m_Ptr, o.m_Ptr, o.m_Cap);
}
// Do we even have data to copy?
else if (!o.m_Cap)
{
// Do we have a buffer?
if (m_Ptr)
{
Release(); // Release it!
}
}
else
{
// Do we have a buffer?
if (m_Ptr)
{
Release(); // Release it!
}
// Request a larger buffer
Request(o.m_Cap);
// Now it's safe to copy the data
std::memcpy(m_Ptr, o.m_Ptr, o.m_Cap);
}
// Also copy the edit cursor
m_Cur = o.m_Cur;
}
return *this;
}
// ------------------------------------------------------------------------------------------------
void Buffer::Grow(SzType n)
{
// Backup the current memory
Buffer bkp(m_Ptr, m_Cap, m_Cur, m_Mem);
// Acquire a bigger buffer
Request(bkp.m_Cap + n);
// Copy the data from the old buffer
std::memcpy(m_Ptr, bkp.m_Ptr, bkp.m_Cap);
// Copy the previous edit cursor
m_Cur = bkp.m_Cur;
}
// ------------------------------------------------------------------------------------------------
void Buffer::Request(SzType n)
{
// NOTE: Function assumes (n > 0)
// Is there a memory manager available?
if (!m_Mem)
{
// Round up the size to a power of two number
n = (n & (n - 1)) ? NextPow2(n) : n;
// Allocate the memory directly
m_Ptr = AllocMem(n);
}
// Find out in which category does this buffer reside
else if (n <= 1024)
{
m_Mem->m_Small.Grab(m_Ptr, n);
}
else if (n <= 4096)
{
m_Mem->m_Medium.Grab(m_Ptr, n);
}
else
{
m_Mem->m_Large.Grab(m_Ptr, n);
}
// If no errors occurred then we can set the size
m_Cap = n;
}
// ------------------------------------------------------------------------------------------------
void Buffer::Release()
{
// TODO: Implement a limit on how much memory can actually be pooled.
// Is there a memory manager available?
if (!m_Mem)
{
std::free(m_Ptr); // Deallocate the memory directly
}
// Find out to which category does this buffer belong
else if (m_Cap <= 1024)
{
m_Mem->m_Small.Drop(m_Ptr, m_Cap);
}
else if (m_Cap <= 4096)
{
m_Mem->m_Medium.Drop(m_Ptr, m_Cap);
}
else
{
m_Mem->m_Large.Drop(m_Ptr, m_Cap);
}
// Explicitly reset the buffer
m_Ptr = nullptr;
m_Cap = 0;
m_Cur = 0;
}
// ------------------------------------------------------------------------------------------------
Buffer::SzType Buffer::Write(SzType pos, ConstPtr data, SzType size)
{
// Do we have what to write?
if (!data || !size)
{
return 0;
}
// See if the buffer size must be adjusted
else if ((pos + size) >= m_Cap)
{
// Acquire a larger buffer
Grow((pos + size) - m_Cap + 32);
}
// Copy the data into the internal buffer
std::memcpy(m_Ptr + pos, data, size);
// Return the amount of data written to the buffer
return size;
}
// ------------------------------------------------------------------------------------------------
Buffer::SzType Buffer::WriteF(SzType pos, const char * fmt, ...)
{
// Initialize the variable argument list
va_list args;
va_start(args, fmt);
// Call the function that takes the variable argument list
const SzType ret = WriteF(pos, fmt, args);
// Finalize the variable argument list
va_end(args);
// Return the result
return ret;
}
// ------------------------------------------------------------------------------------------------
Buffer::SzType Buffer::WriteF(SzType pos, const char * fmt, va_list args)
{
// Is the specified position within range?
if (pos >= m_Cap)
{
// Acquire a larger buffer
Grow(pos - m_Cap + 32);
}
// Backup the variable argument list
va_list args_cpy;
va_copy(args_cpy, args);
// Attempt to write to the current buffer
// (if empty, it should tell us the necessary size)
int ret = std::vsnprintf(m_Ptr + pos, m_Cap, fmt, args);
// Do we need a bigger buffer?
if ((pos + ret) >= m_Cap)
{
// Acquire a larger buffer
Grow((pos + ret) - m_Cap + 32);
// Retry writing the requested information
ret = std::vsnprintf(m_Ptr + pos, m_Cap, fmt, args_cpy);
}
// Return the value 0 if data could not be written
if (ret < 0)
{
return 0;
}
// Return the number of written characters
return static_cast< SzType >(ret);
}
// ------------------------------------------------------------------------------------------------
Buffer::SzType Buffer::WriteS(SzType pos, ConstPtr str)
{
// Is there any string to write?
if (str && *str != '\0')
{
// Forward this to the regular write function
return Write(pos, str, std::strlen(str));
}
// Nothing to write
return 0;
}
// ------------------------------------------------------------------------------------------------
void Buffer::AppendF(const char * fmt, ...)
{
// Initialize the variable argument list
va_list args;
va_start(args, fmt);
// Forward this to the regular write function
m_Cur += WriteF(m_Cur, fmt, args);
// Finalize the variable argument list
va_end(args);
}
// ------------------------------------------------------------------------------------------------
void Buffer::AppendS(const char * str)
{
// Is there any string to write?
if (str)
{
m_Cur += Write(m_Cur, str, std::strlen(str));
}
}
} // Namespace:: SqMod