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/* Copyright (C) 2005 Ole André Vadla Ravnås <oleavr@gmail.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "mimic-private.h"
/*
* _read_bits
*
* Internal helper-function used to read num_bits
* from stream.
*/
guint32 _read_bits(MimCtx *ctx, gint num_bits)
{
guint32 bits;
if (ctx->cur_chunk_len >= 16) {
guchar *input_buf = (guchar *) ctx->data_buffer + ctx->data_index;
if (!ctx->read_odd) {
ctx->read_odd = TRUE;
ctx->cur_chunk = (input_buf[3] << 24) |
(input_buf[2] << 16) |
(input_buf[1] << 8) |
input_buf[0];
} else {
ctx->read_odd = FALSE;
ctx->cur_chunk = (input_buf[1] << 24) |
(input_buf[0] << 16) |
(input_buf[7] << 8) |
input_buf[6];
ctx->data_index += 4;
}
ctx->cur_chunk_len -= 16;
}
bits = (ctx->cur_chunk << ctx->cur_chunk_len) >> (32 - num_bits);
ctx->cur_chunk_len += num_bits;
return bits;
}
/*
* _write_bits
*
* Internal helper-function used to write "length"
* bits of "bits" to stream.
*/
void _write_bits(MimCtx *ctx, guint32 bits, gint length)
{
/* Left-align the bit string within its 32-bit container. */
bits <<= (32 - length);
/* Append the bit string (one or more of the trailing bits might not fit, but that's ok). */
ctx->cur_chunk |= bits >> ctx->cur_chunk_len;
ctx->cur_chunk_len += length;
/* Is it full? */
if (ctx->cur_chunk_len >= 32) {
/* Add the full 32-bit chunk to the stream and update counter. */
ctx->chunk_ptr[0] = GUINT32_TO_LE(ctx->cur_chunk);
ctx->chunk_ptr++;
ctx->cur_chunk_len -= 32;
/* Add any trailing bits that didn't fit. */
ctx->cur_chunk = bits << (length - ctx->cur_chunk_len);
}
}
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