barrier/io/CStreamBuffer.cpp

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2001-10-06 14:13:28 +00:00
#include "CStreamBuffer.h"
#include <assert.h>
//
// CStreamBuffer
//
const UInt32 CStreamBuffer::kChunkSize = 4096;
CStreamBuffer::CStreamBuffer() : m_size(0)
{
// do nothing
}
CStreamBuffer::~CStreamBuffer()
{
// do nothing
}
const void* CStreamBuffer::peek(UInt32 n) throw()
{
assert(n <= m_size);
// reserve space in first chunk
ChunkList::iterator head = m_chunks.begin();
head->reserve(n);
// consolidate chunks into the first chunk until it has n bytes
ChunkList::iterator scan = head;
++scan;
while (head->size() < n && scan != m_chunks.end()) {
head->insert(head->end(), scan->begin(), scan->end());
scan = m_chunks.erase(scan);
}
return reinterpret_cast<const void*>(head->begin());
}
void CStreamBuffer::pop(UInt32 n) throw()
{
m_size -= n;
// discard chunks until more than n bytes would've been discarded
ChunkList::iterator scan = m_chunks.begin();
while (scan->size() <= n && scan != m_chunks.end()) {
n -= scan->size();
scan = m_chunks.erase(scan);
}
// if there's anything left over then remove it from the head chunk.
// if there's no head chunk then we're already empty.
if (scan == m_chunks.end()) {
m_size = 0;
}
else if (n > 0) {
scan->erase(scan->begin(), scan->begin() + n);
}
}
void CStreamBuffer::write(
const void* vdata, UInt32 n) throw()
{
assert(vdata != NULL);
if (n == 0) {
return;
}
m_size += n;
// cast data to bytes
const UInt8* data = reinterpret_cast<const UInt8*>(vdata);
// point to last chunk if it has space, otherwise append an empty chunk
ChunkList::iterator scan = m_chunks.end();
if (scan != m_chunks.begin()) {
--scan;
if (scan->size() >= kChunkSize)
++scan;
}
if (scan == m_chunks.end()) {
scan = m_chunks.insert(scan);
}
// append data in chunks
while (n > 0) {
// choose number of bytes for next chunk
UInt32 count = kChunkSize - scan->size();
if (count > n)
count = n;
// transfer data
scan->insert(scan->end(), data, data + count);
n -= count;
data += count;
// append another empty chunk if we're not done yet
if (n > 0) {
scan = m_chunks.insert(scan);
}
}
}
UInt32 CStreamBuffer::getSize() const throw()
{
return m_size;
}