// infinput.c

// Bitwise inputting for inflate (decompressor)

#include <stdio.h>
#include <crtdbg.h>
#include "inflate.h"
#include "infmacro.h"


void dumpBits(t_decoder_context *context, int n)
{
    context->bitbuf >>= n;
    context->bitcount -= n;
}


// retrieve n bits from the bit buffer, and dump them when done
// n can be up to 16
int getBits(t_decoder_context *context, int n)
{
    int result;

    context->bitcount -= n;
    result = (context->bitbuf & g_BitMask[n]);
    context->bitbuf >>= n;

    return result;
}



// Ensure that <num_bits> bits are in the bit buffer

// Returns FALSE if there are not and there was insufficient input to make this true

BOOL ensureBitsContext(t_decoder_context *context, int num_bits)
{
    if (context->bitcount + 16 < num_bits)
    {
        if (INPUT_EOF())
            return FALSE;

        context->bitbuf |= ((*context->input_curpos++) << (context->bitcount+16));
        context->bitcount += 8;

        if (context->bitcount + 16 < num_bits)
        {
            if (INPUT_EOF())
                return FALSE;

            context->bitbuf |= ((*context->input_curpos++) << (context->bitcount+16));
            context->bitcount += 8;
        }
    }

    return TRUE;
}


// initialise the bit buffer
BOOL initBitBuffer(t_decoder_context *context)
{
    if (context->input_curpos < context->end_input_buffer)
    {
        context->bitbuf = *context->input_curpos++;
        context->bitcount = -8;
        context->state = STATE_READING_BFINAL;
        return TRUE;
    }
    else
    {
        context->bitcount = -16;
        context->bitbuf = 0;
        return FALSE;
    }
}