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51 lines
1.6 KiB
C
51 lines
1.6 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 "cobs.h"
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size_t cobs_encode(void *dst_ptr, const void *src_ptr, size_t length) {
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const char *src = src_ptr;
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char *dst = dst_ptr;
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uint8_t code = 0x01;
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size_t code_idx = 0;
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size_t dst_idx = 1;
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for (size_t src_idx = 0; src_idx < length; ++src_idx) {
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if (src[src_idx] == '\0') {
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dst[code_idx] = code;
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code_idx = dst_idx++;
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code = 0x01;
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} else {
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dst[dst_idx++] = src[src_idx];
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code++;
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if (code == 0xff) {
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if (src_idx == length - 1) {
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// Special case: the final encoded block is 254 bytes long with no
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// zero after it. While it's technically a valid encoding if a
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// trailing zero is appended, it causes the output to be one byte
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// longer than it needs to be. This violates consistent overhead
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// contract and could overflow a carefully sized buffer.
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break;
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}
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dst[code_idx] = code;
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code_idx = dst_idx++;
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code = 0x01;
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}
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}
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}
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dst[code_idx] = code;
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return dst_idx;
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}
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