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