circularbuffer.c

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/*
 * COPYRIGHT:       See COPYING in the top level directory
 * PROJECT:         Serial port driver
 * FILE:            drivers/dd/serial/circularbuffer.c
 * PURPOSE:         Operations on a circular buffer
 *
 * PROGRAMMERS:     Hervé Poussineau (hpoussin@reactos.org)
 */
 
#include "serial.h"
 
#include <debug.h>
 
NTSTATUS
InitializeCircularBuffer(
    IN PCIRCULAR_BUFFER pBuffer,
    IN ULONG BufferSize)
{
    TRACE_(SERIAL, "InitializeCircularBuffer(pBuffer %p, BufferSize %lu)\n", pBuffer, BufferSize);
    ASSERT(pBuffer);
    pBuffer->Buffer = (PUCHAR)ExAllocatePoolWithTag(NonPagedPool, BufferSize * sizeof(UCHAR), SERIAL_TAG);
    if (!pBuffer->Buffer)
        return STATUS_INSUFFICIENT_RESOURCES;
    pBuffer->Length = BufferSize;
    pBuffer->ReadPosition = pBuffer->WritePosition = 0;
    return STATUS_SUCCESS;
}
 
NTSTATUS
FreeCircularBuffer(
    IN PCIRCULAR_BUFFER pBuffer)
{
    TRACE_(SERIAL, "FreeCircularBuffer(pBuffer %p)\n", pBuffer);
    ASSERT(pBuffer);
    if (pBuffer->Buffer != NULL)
        ExFreePoolWithTag(pBuffer->Buffer, SERIAL_TAG);
    return STATUS_SUCCESS;
}
 
BOOLEAN
IsCircularBufferEmpty(
    IN PCIRCULAR_BUFFER pBuffer)
{
    TRACE_(SERIAL, "IsCircularBufferEmpty(pBuffer %p)\n", pBuffer);
    ASSERT(pBuffer);
    return (pBuffer->ReadPosition == pBuffer->WritePosition);
}
 
ULONG
GetNumberOfElementsInCircularBuffer(
    IN PCIRCULAR_BUFFER pBuffer)
{
    TRACE_(SERIAL, "GetNumberOfElementsInCircularBuffer(pBuffer %p)\n", pBuffer);
    ASSERT(pBuffer);
    return (pBuffer->WritePosition + pBuffer->Length - pBuffer->ReadPosition) % pBuffer->Length;
}
 
NTSTATUS
PushCircularBufferEntry(
    IN PCIRCULAR_BUFFER pBuffer,
    IN UCHAR Entry)
{
    ULONG NextPosition;
    TRACE_(SERIAL, "PushCircularBufferEntry(pBuffer %p, Entry 0x%x)\n", pBuffer, Entry);
    ASSERT(pBuffer);
    ASSERT(pBuffer->Length);
    NextPosition = (pBuffer->WritePosition + 1) % pBuffer->Length;
    if (NextPosition == pBuffer->ReadPosition)
        return STATUS_BUFFER_TOO_SMALL;
    pBuffer->Buffer[pBuffer->WritePosition] = Entry;
    pBuffer->WritePosition = NextPosition;
    return STATUS_SUCCESS;
}
 
NTSTATUS
PopCircularBufferEntry(
    IN PCIRCULAR_BUFFER pBuffer,
    OUT PUCHAR Entry)
{
    TRACE_(SERIAL, "PopCircularBufferEntry(pBuffer %p)\n", pBuffer);
    ASSERT(pBuffer);
    ASSERT(pBuffer->Length);
    if (IsCircularBufferEmpty(pBuffer))
        return STATUS_ARRAY_BOUNDS_EXCEEDED;
    *Entry = pBuffer->Buffer[pBuffer->ReadPosition];
    pBuffer->ReadPosition = (pBuffer->ReadPosition + 1) % pBuffer->Length;
    return STATUS_SUCCESS;
}
 
NTSTATUS
IncreaseCircularBufferSize(
    IN PCIRCULAR_BUFFER pBuffer,
    IN ULONG NewBufferSize)
{
    PUCHAR NewBuffer;
 
    TRACE_(SERIAL, "IncreaseCircularBufferSize(pBuffer %p, NewBufferSize %lu)\n", pBuffer, NewBufferSize);
    ASSERT(pBuffer);
    ASSERT(pBuffer->Length);
    if (pBuffer->Length > NewBufferSize)
        return STATUS_INVALID_PARAMETER;
    else if (pBuffer->Length == NewBufferSize)
        return STATUS_SUCCESS;
 
    NewBuffer = (PUCHAR)ExAllocatePoolWithTag(NonPagedPool, NewBufferSize * sizeof(UCHAR), SERIAL_TAG);
    if (!NewBuffer)
        return STATUS_INSUFFICIENT_RESOURCES;
    RtlCopyMemory(NewBuffer, pBuffer->Buffer, pBuffer->Length * sizeof(UCHAR));
    ExFreePoolWithTag(pBuffer->Buffer, SERIAL_TAG);
    pBuffer->Buffer = NewBuffer;
    pBuffer->Length = NewBufferSize;
    return STATUS_SUCCESS;
}