Labrador/Desktop_Interface/isobufferbuffer.cpp

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#include "isobufferbuffer.h"
#include <QDebug>
/* isoBufferBuffer is implemented as two consecutive, duplicate,
* ring buffers. the effect of this is that we are able to hand
* out pointers to pieces of contiguous memory representing the
* last N inserted elements (for some N <= capacity()) even
* when we looped back to the begining of the ring buffer less
* than N insertions ago
*
* There are some differences with the original implementation
* functionality-wise.
* Where the original implementation allowed queries half as
* long as the length passed in, and allocated a buffer 1.5 times
* the length passed in, this version allows queries of length up
* to the length passed into the constructor and allocates a
* buffer 2 times the length passed in.
* Overall, this means that in contrast to the original
* implementation which only allowed queries up to a third as
* long as the allocated buffer, we can now do queries as long as
* half of the allocated buffer, which is a notable improvement.
*/
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isoBufferBuffer::isoBufferBuffer(uint32_t length)
: m_data(std::make_unique<char[]>(length*2))
, m_capacity(length)
{
}
// Adds a character to the end of the buffer
void isoBufferBuffer::insert(char c)
{
char* dataPtr = m_data.get();
// Add character to first half of the buffer
dataPtr[m_top] = c;
// Then to the second
dataPtr[m_top+m_capacity] = c;
// Loop the buffer index if necessary and update size accordingly
m_top = (m_top + 1) % m_capacity;
m_size = std::min(m_size + 1, m_capacity);
}
void isoBufferBuffer::insert(char const * s)
{
while (*s != '\0')
insert(*s++);
}
void isoBufferBuffer::insert(std::string const & s)
{
for (char c : s)
insert(c);
}
void isoBufferBuffer::insert_hex(uint8_t x)
{
char str[5];
sprintf(str, "0x%02hhx", x);
insert((char const *)str);
}
char const* isoBufferBuffer::query(uint32_t count) const
{
if (count > m_capacity)
qFatal("isoBufferBuffer::query : you may not request more items than the capacity of the buffer");
if (count > m_size)
qFatal("isoBufferBuffer::query : you may not request more items than inserted");
return end() - count;
}
void isoBufferBuffer::clear()
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{
m_top = 0;
m_size = 0;
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}
char const * isoBufferBuffer::begin() const
{
return m_data.get() + m_top - m_size + m_capacity;
}
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char const * isoBufferBuffer::end() const
{
return m_data.get() + m_top + m_capacity;
}
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uint32_t isoBufferBuffer::size() const
{
return m_size;
}
uint32_t isoBufferBuffer::capacity() const
{
return m_capacity;
}