const void*
StreamBuffer::peek(UInt32 n)
{
assert(n <= m_size);
// if requesting no data then return NULL so we don't try to access
// an empty list.
if (n == 0) {
return NULL;
}
// reserve space in first chunk
ChunkList::iterator head = m_chunks.begin();
head->reserve(n + m_headUsed);
// consolidate chunks into the first chunk until it has n bytes
ChunkList::iterator scan = head;
++scan;
while (head->size() - m_headUsed < 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()[m_headUsed]));
}
void
StreamBuffer::write(const void* vdata, UInt32 n)
{
assert(vdata != NULL);
// ignore if no data, otherwise update size
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, Chunk());
}
// append data in chunks
while (n > 0) {
// choose number of bytes for next chunk
assert(scan->size() <= kChunkSize);
UInt32 count = kChunkSize - (UInt32)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;
scan = m_chunks.insert(scan, Chunk());
}
}
}