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66 lines
1.7 KiB
C
66 lines
1.7 KiB
C
/*
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* Copyright 2024 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "hdlc.h"
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#include "system/passert.h"
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void hdlc_streaming_decode_reset(HdlcStreamingContext *ctx) {
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ctx->escape = false;
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}
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bool hdlc_streaming_decode(HdlcStreamingContext *ctx, uint8_t *data, bool *should_store,
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bool *hdlc_error) {
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PBL_ASSERTN(data != NULL && should_store != NULL && hdlc_error != NULL);
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bool is_complete = false;
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*hdlc_error = false;
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*should_store = false;
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if (*data == HDLC_FLAG) {
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if (ctx->escape) {
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// extra escape character before flag
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ctx->escape = false;
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*hdlc_error = true;
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}
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// we've reached the end of the frame
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is_complete = true;
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} else if (*data == HDLC_ESCAPE) {
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if (ctx->escape) {
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// invalid sequence
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ctx->escape = false;
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*hdlc_error = true;
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} else {
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// ignore this character and escape the next one
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ctx->escape = true;
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}
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} else {
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if (ctx->escape) {
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*data ^= HDLC_ESCAPE_MASK;
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ctx->escape = false;
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}
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*should_store = true;
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}
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return is_complete;
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}
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bool hdlc_encode(uint8_t *data) {
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if (*data == HDLC_FLAG || *data == HDLC_ESCAPE) {
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*data ^= HDLC_ESCAPE_MASK;
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return true;
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}
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return false;
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}
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