// ------------------------------------------------------------------------------------------------
#include "Base/Buffer.hpp"
// ------------------------------------------------------------------------------------------------
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <exception>
#include <stdexcept>
// ------------------------------------------------------------------------------------------------
namespace SqMod {
/* ------------------------------------------------------------------------------------------------
* Compute the next power of two for the specified number.
*/
static inline unsigned int NPow2(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
char buffer[128];
// Variable arguments structure
va_list args;
// Get the specified arguments
va_start (args, msg);
// Run the specified format
int ret = vsnprintf(buffer, sizeof(buffer), msg, args);
// Check for formatting errors
if (ret < 0)
{
throw std::runtime_error("Unknown memory error");
}
// Throw the actual exception
throw std::runtime_error(buffer);
}
/* ------------------------------------------------------------------------------------------------
* Allocate a memory buffer and return it.
*/
static Buffer::Pointer AllocMem(Buffer::SzType size)
{
// Attempt to allocate memory directly
Buffer::Pointer ptr = (Buffer::Pointer)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;
// --------------------------------------------------------------------------------------------
typedef Buffer::Reference Reference;
typedef Buffer::ConstRef ConstRef;
// --------------------------------------------------------------------------------------------
typedef Buffer::Pointer Pointer;
typedef Buffer::ConstPtr ConstPtr;
// --------------------------------------------------------------------------------------------
typedef Buffer::SzType SzType;
private:
/* --------------------------------------------------------------------------------------------
*
*/
struct Node
{
// ----------------------------------------------------------------------------------------
SzType mCap;
Pointer mPtr;
Node* mNext;
/* ----------------------------------------------------------------------------------------
* Base constructor.
*/
Node(Node * next)
: mCap(0), mPtr(NULL), mNext(next)
{
/* ... */
}
};
// --------------------------------------------------------------------------------------------
static Node * s_Nodes; /* List of unused node instances. */
// --------------------------------------------------------------------------------------------
Node* m_Head; /* The head memory node. */
/* --------------------------------------------------------------------------------------------
* Default constructor.
*/
MemCat()
: m_Head(NULL)
{
/* ... */
}
/* --------------------------------------------------------------------------------------------
* Destructor.
*/
~MemCat()
{
for (Node * node = m_Head, * next = NULL; 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
delete node;
}
// Explicitly set the head node to null
m_Head = NULL;
}
/* --------------------------------------------------------------------------------------------
* Clear all memory buffers from the pool.
*/
void Clear()
{
for (Node * node = m_Head, * next = NULL; 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 = NULL;
}
/* --------------------------------------------------------------------------------------------
* 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 = NULL; 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)) ? NPow2(size) : size;
// Allocate the memory directly
ptr = AllocMem(size);
// See if the memory could be allocated
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()
{
if (!s_Nodes)
{
Make();
}
// 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 = NULL;
/* ------------------------------------------------------------------------------------------------
* Lightweight memory allocator to reduce the overhead of small allocations.
*/
class Memory
{
// --------------------------------------------------------------------------------------------
friend class Buffer;
friend class MemRef;
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 = NULL; 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 = NULL;
}
private:
// --------------------------------------------------------------------------------------------
MemCat m_Small, m_Medium, m_Large;
};
// ------------------------------------------------------------------------------------------------
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 = NULL;
m_Ref = NULL;
}
}
// ------------------------------------------------------------------------------------------------
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::Pointer Buffer::s_Ptr = NULL;
Buffer::SzType Buffer::s_Cap = 0;
// ------------------------------------------------------------------------------------------------
Buffer::Buffer(const Buffer & o)
: m_Ptr(NULL)
, m_Cap(0)
, m_Mem(o.m_Mem)
{
if (m_Cap)
{
Request(o.m_Cap);
memcpy(m_Ptr, o.m_Ptr, o.m_Cap);
}
}
// ------------------------------------------------------------------------------------------------
Buffer::~Buffer()
{
if (m_Ptr)
{
Release();
}
}
// ------------------------------------------------------------------------------------------------
Buffer & Buffer::operator = (const Buffer & o)
{
if (m_Ptr != o.m_Ptr)
{
if (m_Cap && o.m_Cap <= m_Cap)
{
memcpy(m_Ptr, o.m_Ptr, m_Cap);
}
else if (!o.m_Cap)
{
if (m_Ptr)
{
Release();
}
}
else
{
if (m_Ptr)
{
Release();
}
Request(o.m_Cap);
memcpy(m_Ptr, o.m_Ptr, o.m_Cap);
}
}
return *this;
}
// ------------------------------------------------------------------------------------------------
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)) ? NPow2(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 occured then we can set the size
m_Cap= n;
}
// ------------------------------------------------------------------------------------------------
void Buffer::Release()
{
// Is there a memory manager available?
if (!m_Mem)
{
// Deallocate the memory directly
free(m_Ptr);
}
// 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 = NULL;
m_Cap = 0;
}
// ------------------------------------------------------------------------------------------------
Buffer::SzType Buffer::Write(SzType pos, ConstPtr data, SzType size)
{
// Make sure the pos is not out of bounds
if (pos > m_Cap || !data || !size)
{
return 0;
}
// See if the buffer size must be adjusted
else if ((pos + size) >= m_Cap)
{
// Backup current data
Buffer bkp = Adjust< Value >(pos + size);
// Copy data back from the old buffer
memcpy(m_Ptr, bkp.m_Ptr, bkp.m_Cap);
}
// Copy the data into the internal buffer
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, ...)
{
// Make sure the pos is not out of bounds
if (pos > m_Cap)
{
return 0;
}
// Initialize the arguments list
va_list args;
va_start(args, fmt);
// Initial attempt to write to the current buffer
// (if empty, it should tell us the necessary size)
int ret = vsnprintf(m_Ptr + pos, m_Cap - pos, fmt, args);
// Do we need a bigger buffer?
if ((pos + ret) >= m_Cap)
{
// Backup current data
Buffer bkp = Adjust< Value >(pos + ret);
// Copy data back from the old buffer
memcpy(m_Ptr, bkp.m_Ptr, bkp.m_Cap);
// Argument list was modified during the initial format
va_end(args);
va_start(args, fmt);
// Resume writting the requested information
ret = vsnprintf(m_Ptr + pos, m_Cap - pos, fmt, args);
}
// Finalize the arguments list
va_end(args);
// Return the size of the written data in bytes
return (ret < 0) ? 0 : (SzType)ret;
}
// ------------------------------------------------------------------------------------------------
Buffer::SzType Buffer::WriteF(SzType pos, const char * fmt, va_list args)
{
// Make sure the pos is not out of bounds
if (pos > m_Cap)
{
return 0;
}
// Attempt to write to the current buffer
int ret = vsnprintf(m_Ptr + pos, m_Cap - pos, fmt, args);
// Return the size of the written data in bytes
return (ret < 0) ? 0 : (SzType)ret;
}
} // Namespace:: SQMod